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In present study, we developed a highly sensitive, electrochemical immunosensor based on fullerene C60-modified disposable graphite paper (GP) electrode for determination of Suppression of Tumorigenicity 2 (ST2) in human serum. The synthesis of the ST2 immunosensor was monitored with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques and single frequency impedance (SFI) technique which is utilized for the specific interaction between anti-ST2 and ST2 antigen. Moreover, the morphological alteration of each GP surface was examined by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). All parameters such as fullerene C60 concentration, antibody concentration and antibody incubation time were optimized. Analytical characteristics such as linear determination range, repeatability, reproducibility, regeneration and surface coverage were determined for the immunosensor. The ST2 electrochemical immunosensor had excellent repeatability, reproducibility and a wide detection range (from 0.1 fg mL−1 to 100 fg mL−1). The proposed immunosensor also had low limit of detection (LOD) and limit of quantification (LOQ) values of 0.124 fg mL−1 and 0.414 fg mL−1, respectively. The proposed immunosensor was applied to real samples to test applicability in clinical practice.

A certified reference seawater material (CRM), UME CRM 1206 which was sampled from the Marmara Sea (40 31,423 N; 027 11, 333 E) with 27 psu of salinity is about to be released by Inorganic Analysis Laboratory of TUBITAK National Metrology Institute (UME). This paper represents the characterization measurements of Cd, Cr, Cu, Ni, Pb and Zn in this CRM. The use of a reference method by a single laboratory is one of the options for the characterization of a candidate CRM according to ISO 17034 [ 39 ]. This approach is used throughout this study with an introduction of a primary reference method. For this purpose, combination of triethylamine assisted Mg(OH)2 co-precipitation and triple isotope dilution mass spectrometry (TEA/Mg(OH)2-ID3MS) were developed and validated. This optimized co-precipitation protocol provided the recovery of target analytes within the range of 72%–92% which was the main advantage of TEA/Mg(OH)2 method especially for Cd, Ni, Cu and Zn compared to NH4OH assisted co-precipitation. Analytical performance of TEA/Mg(OH)2-ID3MS were investigated under the optimum conditions. The results for matrix certified reference material were found to be not significantly different from the certified values based on the comparison of the results and certified values within their combined uncertainties. On the other hand, intermediate precision and repeatability of the developed method were found to be in the range of 0.34%–0.90% and 0.09%–0.49%, respectively. This study reports characterization measurements with their expanded uncertainties (k = 2) as 0.4327 ± 0.0071 ng/g for Cd, 2.442 ± 0.033 ng/g for Cr, 1.018 ± 0.012 ng/g for Cu, 4.568 ± 0.037 ng/g for Ni, 1.068 ± 0.016 ng/g for Pb and 8.521 ± 0.075 ng/g for Zn where the intermediate precision was found to be the main contributor to measurement uncertainty budget of TEA/Mg(OH)2-ID3MS method for each analyte.

Amoxicillin is an antibiotic that can accumulate in aquatic environments and lead to the development of resistant bacteria; thus, its determination is of great importance. In this study, a glassy carbon electrode modified with reduced graphene oxide and Nafion was used as a sensor in a square-wave voltammetry method for determination of amoxicillin in river water samples from Guarapuava city, Brazil. The method was validated, using parameters and statistical tools recommended by the validation guidelines, in the range of 1.8–5.4 μmol L−1 (r = 0.922 and R2 = 85.1%). The analytical curve was constructed using external standard calibration in pure electrolyte, since the matrix effect was not significant. Results of linear regression analysis, lack of fit test and analysis of the residual plots pointed that the linear regression was significant, without lack of fit of linear model and that the variances had homoscedastic distribution. Both coefficients of regression curve were significant and, thus, they were included in the regression equation: Response = 7.0 + 3.5CAMX. The limits of detection and quantification were 0.36 and 1.2 μmol L−1, respectively. The method was selective towards interferents such as humic acids and benzylpenicillin. The relative standard deviations for repeatability and intermediate precision were adequate according to the limits established in literature. The mean recoveries were statistically equal to those obtained through a comparative chromatography method, so, the accuracy of the method was also adequate. Therefore, the method can be applied to the voltammetric determination of amoxicillin in river water, affording reliable and consistent measurements.

Dust analysis provides a means to assess the degree of exposure of humans in an indoor environment to various contaminant classes such as flame retardants, pesticides and others. There is increasing interest in non-targeted acquisitions using high resolution mass spectrometry (HRMS) to better capture the contaminant profile. However, these studies are confronted with the challenge of assessing confidence in proposed identifications, particularly when authentic standards are not available. Here, we demonstrate the analysis of dust extracts representing various indoor environments (industrial e-waste processing and domestic) for high-abundance environmental contaminants using a data-independent LC-HRMS approach, incorporating ion mobility spectrometry (IMS) to provide additional characterization capability for the complex samples. Twenty-nine xenobiotic compound identifications were made based on both targeted and non-targeted processing approaches using accurate mass precursor and product ion measurement combined with an ion mobility derived collision-cross section (TWCCSN2) determination. Characterization of the repeatability of TWCCSN2 value measurements and their average relative error to compared authentic standards of 0.38% were consistent with various published studies and represent a robust measurement property. TWCCSN2 values were particularly useful in cases where confirmation after the initial dust analysis was performed using a different chromatographic method, due to the gas-phase measurement being unaffected by such changes. Observed compound TWCCSN2 values were then compared to predicted CCSN2 values obtained using two different machine-learning based predictive techniques. Results from one of the predictive programs indicates a promising avenue for use of these models for supporting compound identification in non-targeted analyses.

Exhaled hydrogen cyanide (HCN) has been extensively investigated as a promising biomarker of the presence of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) disease. Its concentration profile for exhalation can provide useful information for medical disease diagnosis and therapeutic procedures. However, the complexity of breath gas, like high humidity, carbon dioxide (CO2) and trace organic compounds, usually leads to quantitative error, poor selectivity and sensitivity for HCN with some of existing analytical techniques. In this work, acetone-assisted negative photoionization (AANP) based on a vacuum ultraviolet (VUV) lamp with a time-of- flight mass spectrometer (AANP-TOFMS) was firstly proposed for online measurement of trace HCN in human breath. In-source collision-induced dissociation (CID) was adopted for sensitivity improvement and the signal response of the characteristic ion CN− (m/z 26) was improved by about 24-fold. For accurate and reliable analysis of the exhaled HCN, matrix influences in the human breath including humidity and CO2 were investigated, respectively. A Nafion tube was used for online dehumidification of breath samples. Matrix-adapted calibration in the concentration range of 0.5–50 ppbv with satisfactory dynamic linearity and repeatability was obtained. The limit of quantitation (LOQ) for HCN at 0.5 ppbv was achieved in the presence of 100% relative humidity and 4% CO2. Finally, the method was successfully applied for online determination of human mouth- and nose-exhaled HCN, and the nose-exhaled HCN were proved to be reliable for assessing systemic HCN levels for individuals. The results are encouraging and highlight the potential of AANP-TOFMS with in-source CID as a selective, accurate, sensitive and noninvasive technique for determination of the exhaled HCN for CF clinical diagnosis and HCN poisoning assessment.

MoS2 and nitrogen doped active carbon composite (MoS2/ANC) is fabricated to detect taxifolin and exhibits superior redox current response and decreased redox potential difference. Further investigation reveals that the kinetic process of the redox reaction of taxifolin on MoS2/ANC electrode is controlled by both adsorption and diffusion process. Under the optimum conditions, the redox peak currents linearly relate with the concentration of taxifolin in the range of 1 × 10−9–1 × 10−6 mol L−1, accompanied by the low detection limit (3 × 10−10 mol L−1). Meanwhile, outstanding selectivity, stability and repeatability are also obtained at MoS2/ANC electrode. At last, the proposed method is applied to quantitatively detect taxifolin in fructus polygoni orientalis and satisfactory results have been achieved.

We report the on-line coupling of a monolithic molecularly imprinted polymer to nano-liquid chromatography for the selective analysis of cocaine and its main metabolite, benzoylecgonine, in complex biological samples. After the screening of different synthesis conditions, a monolithic molecularly imprinted polymer was in situ synthesized into a 100 μm internal diameter fused-silica capillary using cocaine as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. Scanning electron microscopy was used to assess the homogeneous morphology of the molecularly imprinted polymer and its permeability was measured. Its selectivity was evaluated by nano-liquid chromatography-ultraviolet, leading to imprinting factors of 3.2 ± 0.5 and 2.2 ± 0.3 for cocaine and benzoylecgonine, respectively, on polymers resulting from three independent syntheses, showing the high selectivity and the repeatability of the synthesis. After optimizing the extraction protocol to promote selectivity, the monolithic molecularly imprinted polymer was successfully on-line coupled with nano-liquid chromatography-ultraviolet for the direct extraction and analysis of cocaine present in spiked human plasma and saliva samples. The repeatability of the obtained extraction recovery, between 85.4 and 98.7% for a plasma sample spiked at 100 ng mL−1, was high with relative standard deviation values lower than 5.8% for triplicate analyses on each of the three independently synthesized molecularly imprinted polymers. A linear calibration range was achieved between 100 and 2000 ng mL−1 (R2 = 0.999). Limits of quantification of 14.5 ng mL−1 and 6.1 ng mL−1 were achieved in plasma and urine samples, respectively. The very clean-baseline of the resulting chromatogram illustrated the high selectivity brought by the monolithic molecularly imprinted polymer that allows the removal of a huge peak corresponding to the elution of interfering compounds and the easy determination of the target analyte in these complex biological samples.

The pregnancy-associated glycoproteins (PAGs) have been widely used as biomarkers for the early diagnosis of pregnancy in cattle and sheep. This study aimed to obtain the single-stranded DNA aptamers that specifically bound to ovine pregnancy-associated glycoprotein 7 (ovPAG7) with high affinity (Kd = 9.8–32.4 nM) using real serum sample–assisted FluMag-systematic evolution of ligands by exponential enrichment (SELEX). Subsequently, the selected aptamers were applied to fabricate an ultrasensitive colorimetric aptasensor for ovPAG7 detection based on functionalized magnetic microparticles and hybridization chain reaction. Under the optimized conditions, the colorimetric aptasensor exhibited a broad linear range (0.2–500 ng mL−1), low detection limit (0.081 ng mL−1), good recovery rate (94.5–109.1%), and high repeatability (relative standard deviation of 4.02–8.16%) in ovPAG7-spiked serum. Furthermore, this aptasensor was applied to measure the ovPAG7 in serum samples of ewes for pregnancy diagnosis. Blood samples were collected from Chinese Merino ewes on days 22, 28 after artificial insemination (AI) for ovPAG7 detection, respectively. Transrectal ultrasonography diagnosis of pregnancy 45 days after AI was the reference (gold) standard for all PAG tests. Diagnostic sensitivity, specificity, and accuracy of the proposed aptasensor were 95.8, 87.5, and 92.5% at day 22 and 95.8, 90.6, and 93.7% at day 28, respectively. The degree of agreement (Kappa) between developed aptasensor and ultrasonography diagnosis 22 and 28 day after AI were higher than 0.8. These results illustrated that the aptasensor was proved to be a sensitive, reliable and cost-effective way of measuring PAG and might be a useful means of pregnancy detection in ewes.

Glutathione is an essential intra- and extracellular antioxidant. The level of glutathione in the body is highly related to different disease states and is a useful indicator of disease risk and oxidative stress status. We have developed a sensitive, selective, and comprehensive LC-MS/MS method for the absolute quantification and 13C-tracer analysis of total glutathione using dithiothreitol for the reduction of glutathione disulfide. The limit of detection (LOD) was 0.01 μM, while the lower limit of quantification (LLOQ) was 0.78 μM, with the linear (R = 0.9997) range extending up to 100 μM. The intra-run and inter-run coefficients of variation of 2.49% and 2.04%, respectively, attest to high repeatability. Mean (±SD) recoveries of three different concentrations (low, medium, high) of GSH spiked into aliquots of HCT116 cells prior to cell extraction were 108.9% (±2.1), 100.8% (±8.3), and 99.9% (±7.1), respectively. Finally, using a 20 Da wide Q1 window in MRM mode, we were able to detect and relatively quantify all isotopic labeling states of GSH extracted from HCT116 cells fed with either 13C-labeled glucose or glutamine.

A new determination method for total bromine in electronic devices was developed by using ultrasound assisted extraction, copper-catalyzed reductive debromination and ion chromatography (UAE-RD-IC). It was found that all the added brominated flame retardants (polybrominateddiphenyl ethers, polybrominated biphenyls, tetrabromobisphenol A, and hexabromocyclododecane) could be completely debrominated by using copper-based catalysts and reducing agent N2H4•H2O. The complete debromination of brominated flame retardants released all of their bromine in the form of bromide ions, which could be determined by ion chromatography. After the extraction parameters were optimized by achieving the maximum IC signal in the certified reference material GBW(E) 082725, the UAE-RD-IC method was established for the determination of total bromine in solid samples. By analyzing the certified reference material, the Br content was obtained as 695.3 ± 16.0 mg kg−1, being well consistent with its standard value (694.54 ± 30.63 mg kg−1). The relative standard deviation (RSD) of five parallel determinations was 1.7%, indicating the good repeatability of the developed method. The proposed method was further applied to analyze the samples of cables and computer mouse shells. For all these practical samples, the Br contents obtained by the UAE-RD-IC method were in good agreement with that obtained by the standard oxygen bomb combustion-IC method. It was noted that the new method has a detection limit of Br of about 20 mg kg−1, being much lower than that (75 mg kg−1) of the traditional oxygen bomb combustion-IC method for total bromine detection. Therefore, the proposed method was qualified as a practical method to measure total bromine content in actual electronic devices with good analytical performances of accuracy, precision and sensitivity.

In this study, a sensitive immunosensor was developed for the first time for p21-activated kinase 2 (PAK 2) detection. In the design of the immunosensor, 3-glycidoxypropyltrimethoxysilane (GPTMS) was utilized as an ITO electrode modification material for anti-PAK 2 antibody immobilization. This molecule had epoxy group, which was reactive to amino groups of antibodies. Anti-PAK 2 antibodies were also used as biomolecules for sensitive interaction for PAK 2 antigen. In the presence of PAK 2 antigens, high impedance signal was observed when the process followed by using Electrochemical Impedance Spectroscopy technique (EIS). Apart from EIS technique, Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV) and Single Frequency Impedance (SFI) techniques were utilized. Microscopic surface characterizations of immunosensor fabrication steps were performed by using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The immunosensor exhibited good sensitivity and selectivity for PAK 2 antigen detection. A linear calibration curve between EIS response and PAK 2 concentration was obtained in the range of 0.005–0.075 pg/mL with the detection limit of 1.5 fg/mL. It had good repeatability, excellent reproducibility and high stability. Additionally, this immunosensor can be reused by simple application protocol. Furthermore, it had good recovery for PAK 2 antigen detection in human serum samples. The good recovery illustrated that the developed immunosensor was a promising tool for PAK 2 detection in practical applications.

Plasticizers and other plastics additives have been extensively used as ingredients of plastics and are as a result thereof easily released in the aquatic environment, due to different physical diffusion processes. In this context, a dedicated method was developed for the simultaneous quantification of 27 known and a virtually unlimited number of unknown alkylphenols, Bisphenol A and phthalates in 2 aquatic matrices, i.e. sea- and freshwater. To this extent, a novel instrumental HESI-UHPLC-HRMS (heated electro-spray ionization ultra-high performance liquid chromatographic high resolution mass spectrometric) method was devised for the simultaneous analysis of 7 phenols (i.e. 6 alkylphenols and Bisphenol A) and 20 phthalates within 10 min. Thereafter, a solid-phase extraction protocol was statistically (95% confidence interval, p > 0.05) optimized based on experimental designs. The method was proven fit-for-purpose through a successful validation at environmentally relevant nanomolar concentrations. Analytical precautions were taken for minimizing false-positive results to suppress in-house contamination. The method demonstrated an excellent analytical performance across all known plasticizers and plastics additives for sea- and freshwater, revealing good linearity (R2 > 0.99, n = 39), stable recoveries (98.5–105.8%), satisfactory repeatability (RSD

The preparation of the metal-organic frameworks (MOFs)@silica core-shell microspheres as the stationary phases mainly relied on the method of electrostatic interaction between the metal ions of MOFs and the silanol groups. Herein, the ligands of MOFs were preferentially modified to the surface of silica as connection points and seed crystals to connect or form the MOFs. In this way, the evenness of the MOFs particles on the silica surface was effectively improved, and the prepared composites possessed excellent reproducibility and stability, including acid-base stability. The relative standard deviation of the retention time for repeatability ranged from 0.1% to 0.26% and for stability retention time from 0.3% to 0.6%. Compared with commercial columns, the prepared stationary phase showed enhanced separation selectivity for separation of both hydrophilic and hydrophobic compounds containing alkaloids, nucleosides, antibiotics and alkylbenzenes, etc. The obtained column was used as a matrix for fast separation and analysis of antibiotics in actual samples. In short, the composites showed superior reproducibility, stability and satisfactory separation performance towards a variety of compounds in the studied conditions. It also provided another way to improve the evenness of MOFs particles on the surface of silica and enhance the stability of them under polar conditions.

Chemical vapor generation (CVG) of cadmium was optimized based on response from atomic absorption spectrometry (AAS) with a heated quartz tube atomizer (QTA). Effect of several modifiers on analytical performance was studied. These additives were: inorganic salts of Cr3+, Ti4+ and Co2+ and their on-line synthesized complexes with KCN and thiourea, respectively. The use of these additives resulted in sensitivity enhancement, better repeatability and correspondingly in improvement of overall CVG efficiency. The latter was quantified by two independent approaches: a) by means of 115mCd radioactive indicator, b) from comparison of sensitivities obtained with conventional solution nebulization and with CVG, both coupled simultaneously to inductively coupled plasma mass spectrometry. Both approaches provided comparable results. The highest efficiency, between 60 and 70%, was reached in the presence of Cr3+/KCN and Ti4+/KCN while 19% was achieved in Co2+/ascorbic acid/thiourea environment. Highly irreproducible results with low CVG efficiency ranging from 2.5 to 15% were reached in the absence of any additives. The generated cadmium species were identified to be mostly free atoms regardless of the additives presence or their absence. Cr3+/KCN environment was selected as the most robust for CVG of Cd reaching sensitivity of 6.6 s ng−1 Cd and limit of detection of 60 pg mL−1 Cd (9 pg Cd absolute) with detection by QTA-AAS.

Practical biological and environmental samples always contain both acidic and basic substances, and the samples are always precious. Thus, separation of analytes with different nature from the same sample was of great significance. Successive liquid phase microextraction (sLPME) of acidic and basic analytes under optimal extraction conditions was therefore proposed for the first time. The concept of sLPME was proved by using three acidic analytes (naproxen, flurbiprofen and diclofenac) and three basic analytes (haloperidol, fluoxetine and sertraline) as model analytes, and using polypropylene glycol with an average molecular weight of 4000 (PPG4000) as SLM. The recoveries of all target analytes by sLPME were similar to that by individual LPME due to good affinity of PPG4000 to both acidic and basic analytes. Under optimal extraction conditions, the recoveries for all analytes by sLPME from urine samples were in the range of 62%–95%. Moreover, combined with LC-MS/MS, such sLPME approach was also evaluated with urine samples. The matrix effect of sLPME-LC-MS/MS at different levels for all analytes ranged from −14.1%-13.2%. The linear ranges with R2 > 0.996 were 5–1000 ng mL−1 for basic analytes, and 20–1000 ng mL−1 for acidic analytes except diclofenac (1–1000 ng mL−1). The repeatability and accuracy at four levels were in the range of 3%–10% and 86%–120%, respectively. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) were found to be 0.07–0.49 ng mL−1 and 0.25–1.63 ng mL−1, respectively. Finally, the strategy for constructing a sLPME system was further confirmed with urine, plasma and saliva using another two versatile SLM solvents possessing high affinity to both acidic and basic analytes. Successive LPME enabled separation of acidic and basic analytes from the same sample under optimum extraction conditions for all target analytes. Thus, we believe that the sLPME system will become a potent platform for forensic toxicology analysis, food science, environmental analysis and epidemiology study.

Halogen bonding (XB), a highly energetic and directional interaction, is here proposed as a new mechanism to increase solute solubilisation in solvent extractions. The approach is illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in soils and sediments using supramolecular solvents (SUPRAS) containing XB donors in their structure. SUPRAS consisting of inverted hexagonal aggregates of decanoic acid, synthesized by water-induced coacervation of the amphiphile in tetrahydrofuran (THF), were explored for this purpose. Sample treatment involved the extraction of 400 mg of soil or sediment with 250 μL of SUPRAS for 5 min and then centrifugation for 10 min. SUPRAS extracts were directly analyzed by chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) and quantification was carried out using isotopically labelled internal standards. Quantitative recoveries (93–102%) were obtained for the six HBCD enantiomers in both fresh and aged spiked samples. The mild experimental conditions required for extraction (room temperature and atmospheric pressure), the low SUPRAS volume/sample amount ratio needed (0.6 mL g─1), the short time required for sample treatment (15 min), and the simplicity of the procedure (use of conventional equipment and the possibility of treating several samples simultaneously), makes this method clearly superior to those previously reported. Method quantitation limits were in the intervals 0.58–2.23 ng g─1, and the relative standard deviations (n = 18, HBCD stereoisomer concentration = 50 ng g─1) obtained under repeatability and reproducibility conditions varied within the ranges 1.0–4% and 2.5–5%, respectively. The approach here described could be easily extended to the extraction of brominated flame retardants in different types of matrices.

Near infrared emission spectroscopy (NIRES) has been investigated to yield a new analytical method for determination of CaO, SiO2, Al2O3, Fe2O3, MgO, and SO3 in Portland cement samples. The analyses were accomplished by correlation of the second derivative NIRES spectra with reference elemental analyses made by X-ray Fluorescence (XRF), using Partial Least Square (PLS) regression models. Four different types of cements (type II, III, IV and V) were included in the models. The results show RMSEP from 0.18 to 1.67% (m/m) (which represents 8.6 to 2.8% of the mean value parameters, respectively) and precision (repeatability) from 0.12 to 1.49% (m/m). The worse performance of prediction [RMSEP = 0.18% (m/m), r2 = 0.63] was found for Fe2O3 determination due its low variability in the samples employed in the calibration and validation set, usual low content in cements, and high correlation with the weak emitting C4AF phase. However, the paired t-test at 95% confidence level demonstrated that the analytical results obtained by NIRES multivariate models are equivalent to measurements performed by XRF for all oxides analyzed. The cost, speed and safety aspects are improved in comparison with the XRF method. The method based on NIRES requires no sample preparation and speed up the cement analysis (6 min) about 5 times when compared with the method based on XRF presently employed by cement industries.

A literature criticism is given on methods currently using gas chromatography mass spectrometry (GC-MS) to determine plant cannabinoids (p-CBDs). In this study, trialkylsilylation of seven p-CBDs (including their transformation products formed in the drug user's body) was compared applying various alkylsilyl reagents 1 and the mass fragmentation properties of the corresponding derivatives were characterized. Derivatization, mass fragmentation and quantitation related model investigations were optimized as a function of the reaction times and conditions. Special emphasis was put (i) on the maximum responses of species, (ii) on the proportions of formed stable products, suitable for selective quantitation of all seven p-CBDs simultaneously. Results, as novel to the field confirmed that HMDS + TFA, for p-CBDs never applied reagent before, serves as their derivatization reagent of choice. These species were characterized by their retention, mass fragmentation and analytical performance characteristics. In model solutions with injected amounts in the range of 20 pg–2000 pg, repeatability (average 4.98% RSD, varying between 2.98 and 6.2% RSD), linearity (R2, 0.9956–0.9995), LOQ (20–80 pg/μL injected species) and recovery (95.2–104%) values were defined. The practical utility of this proposal, along with method development validation, was shown in a particularly unique manner and supported by the novel, extraction free, direct sample preparation working strategy. For this purpose, two Cannabis-type ruderalis (C-trd) plant tissues (C-trd1, C-trd2) were directly derivatized in the presence of the matrix. This process, which approaches green chemistry, performed without the use of organic solvents, was associated with the quantitation of self p-CBD contents of C-trd plant tissues. Applying 0.5–2.0 mg dried tissues, adding standards, the following self p-CBDs contents were confirmed: in C-trd1 6.6 μg/mg CBD, 4.4 μg/mg CBN and 1.3 μg/mg CBC, while in C-trd2 0.46 μg/mg CBD, 0.27 μg/mg CBC and 0.19 μg/mg CBG were found. The latter results were characterized by repeatability (2.52–4.99% RSD), linearity (R2, 0.9640–0.9997) and recovery (87.9–109%) data.

Systematic variation of the instrument's response both within- and between-batches is frequently observed in untarget LC-MS metabolomics involving the analysis of a large number of samples. The so-called batch effect decreases the statistical power and has a negative impact on repeatability and reproducibility of the results. As there is no standard way of assessing or correcting LC-MS batch effects and there is no single method providing optimal results in all situations, the selection of the optimal approach is not trivial. This work explores the effectiveness of a set of tools for batch effect assessment. Qualitative tools include the monitoring of spiked internal standards, principal component analysis and hierarchical cluster analysis. Quantitative tools comprise the distribution of RSDQC values, the median Pearson correlation coefficient in QCs, the ratio of random features in QCs using the runs test, as well as multivariate tools such as the d-statistic, Silhouette plots, Principal Variance Component Analysis and the expected technical variation in the prediction. Results show that qualitative and quantitative approaches are complementary and that by limiting the analysis to QCs the power to detect and evaluate both within and between batch effects is increased. Besides, the graphical integration of outputs from multiple quantitative tools facilitates the evaluation of batch effects and it is proposed as a straightforward way for comparing and tailoring batch effect elimination approaches. (c) 2018 Elsevier B.V. All rights reserved.

Manual handling of microliter volumes of samples and reagents is usually prone to errors and may have direct consequence on the overall performance of microextraction process. Direct connection of a syringe pump and a disposable microextraction unit using flexible polymeric tubing was employed for semi-automated liquid handling in micro-electromembrane extraction (μ-EME). A three-phase μ-EME system was formed by consecutive withdrawal of microliter volumes of donor solution, free liquid membrane (FLM) and acceptor solution into the unit. Excellent repeatability and accuracy of the withdrawal sequence was achieved for solution volumes typically used in μ-EME (1–5 μL) as well as excellent correlation between the initially withdrawn and the finally collected solution volumes. μ-EMEs were initiated by application of d.c. electric potential to the terminal aqueous solutions and specific μ-EME parameters were optimized in order to ensure complete transfer of model analytes from donor to acceptor solution. Exhaustive μ-EMEs of three basic drugs, nortriptyline, papaverine and haloperidol, were achieved from 1.3 μL of acidified donor solution (10 mM HCl) across 2.5 μL of FLM (1-ethyl-2-nitrobenzene) into 1.3 μL of acidified acceptor solution (25 mM HCl) in 10 min at 150 V. The three drugs were also exhaustively extracted from salt- and protein-containing standard solutions, human urine and human plasma with extraction recoveries ranging from 79 to 102%. Resulting acceptor solutions were analysed by capillary electrophoresis with ultraviolet detection (CE-UV) and the μ-EME-CE-UV method was characterized by good linearity (coefficients of determination ≥ 0.992), high repeatability (RSD values ≤ 6.5%) and limits of detection ≤ 0.15 mg/L.

9-Xanthydrol was introduced as an assisted-extraction-reagent to quantify ethyl carbamate (EC) in wines by heart-cutting multidimensional gas chromatography coupled with mass spectrometry (MDGC-MS). 9-Xanthydrol could help to increase the extraction efficiency, because it could react with ethyl carbamate to form the low-polar product, which facilitated the transfer of ethyl carbamate into organic phase. Then the reaction product was decomposed in high temperature, so ethyl carbamate could be obtained again in injector port. Heart-cutting multidimensional gas chromatography coupled with mass spectrometry was used not only for avoiding 9-xanthydrol interference but also for getting a larger volume injector, higher sensitivity and lower limit of detection. The method was optimized and validated in terms of sample volume, sodium chloride, the acid concentration, the 9-xanthydrol concentration and the reaction time. Good linear relationship (R2 = 0.9998) over the concentration range of 2.00 μg L−1 - 200.00 μg L−1 was obtained. The limit of detection (LOD, 0.02 μg L−1) and quantification (LOQ, 0.10 μg L−1) were lower than previously reported. The RSDs of precision (repeatability and reproducibility) were lower than 8.15%, and the recovery (96.17–99.25%) and accuracy (99.21–110.93%) were validated as well. This methodology was applied to the quantification of ethyl carbamate in several different fermented wines with values ranging from 13.05 to 155.20 μg L−1.

Several species are simultaneously used for internal standardization to improve accuracy in inductively coupled plasma optical emission spectrometry (ICP-OES). In multi-internal standard calibration (MISC), signal ratios between the analyte and each of several internal standard species are used for calibration. A single calibration solution is required, and the MISC graph is built with intensity ratios calculated with analytical signals recorded for the sample (IA,sam) on the y-axis, while those recorded for the calibration standard (IA,std) are plot on the x-axis (i.e. IA,sam/IIS(i) vs. IA,std/IIS(i), where IIS(i) represents the signal intensity for a given internal standard species). Nine analytes (As, Cd, Cr, Cu, Fe, Mg, Mn, Pb and Zn), and two sets of internal standard species (i.e. Bi, Ge, In, Rh, Sc, Te, Tl and Y in solution, or eighteen emission lines from plasma naturally occurring Ar) were evaluated in this proof-of-concept study. The MISC method's efficiency was evaluated by analyte addition and recovery experiments and by analyzing two certified reference materials. Figures of merit for MISC (limit of detection, repeatability and trueness) were comparable to those obtained for the traditional external standard calibration (EC) and internal standard (IS) methods. Different from IS, MISC requires no time-consuming study to identify an ideal internal standard species, and signal biases are minimized by an averaged, more encompassing internal standardization effect.

The thin films used in headspace thin-film microextraction (HS-TFME) enable higher sensitivity and superior extraction rates compared to other microextraction approaches, largely due to their greater surface area-to-volume ratio and extraction-phase volume. Nonetheless, analytes exhibiting a low affinity for the headspace and/or large partitioning between the extraction phase and headspace will still require more time to reach equilibrium. In this paper, we detail the development of a new method, termed as vacuum-assisted HS-TFME (Vac-HS-TFME), and we demonstrate how its use of vacuum conditions can accelerate the extraction kinetics of analytes with long equilibration times. The pressure-dependence of the extraction process was formulated and related to improvements in gas-phase diffusivity when lowering the total pressure. Four low-molecular-weight polycyclic aromatic hydrocarbons (PAHs) were used to experimentally verify the improvements in extraction efficiencies enabled by Vac-HS-TFME (vs. HS-TFME). To this end, the effects of temperature and extraction time on Vac-HS-TFME were investigated, with the results being compared to those obtained via regular HS-TFME. Furthermore, the use of a high-capacity sorbent in TFME allowed the positive effects of temperature and vacuum conditions to be combined successfully. Extraction-time profiles constructed at 30 and 50 °C revealed substantial acceleration in the overall extraction kinetics when sampling under vacuum conditions. At 50 °C, all of the analytes extracted via Vac-HS-TFME reached equilibrium within 45 min, whereas only two reached this state under atmospheric pressure. Vac-HS-TFME's analytical performance was evaluated under optimized conditions, and the results were compared to those obtained with regular HS-TFME. The findings revealed that for the two lighter PAHs, the performance of the two methods was similar since they were extracted close or at equilibrium. However, the calibration models for the two heavier PAHs tested here were linear over a wider concentration range (50–10000 ng L−1) when using Vac-HS-TFME, had superior intra-day repeatability (7.4% and 6.7% vs. 11% and 9.3% with regular HS-TFME), and the limits of detection were lower compared to regular HS-TFME (15 and 11 ng L−1 compared to 136 to 100 ng L−1 with regular HS-TFME). Finally, the analysis of spiked wastewater effluent samples showed that the matrix did not affect extraction. The proposed Vac-HS-TFME approach combines the advantages of low-pressure sampling and high-capacity sorbent, and has a great potential for future applications in food, flavour, environmental, and biological analyses.

Made available in DSpace on 2018-12-11T17:34:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-02 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this paper, we describe a validated paper-based microfluidic analytical device for the simultaneous quantification of two important biomarkers of renal function in urine. This paper platform provides an inexpensive, simple, and easy to use colorimetric method for the quantification of creatinine (CRN) and uric acid (UA) in urine samples. The microfluidic paper-based analytical device (μPAD) consists of a main channel with three identical arms, each containing a circular testing zone and a circular uptake zone. Creatinine detection is based on the Jaffé reaction, in which CRN reacts with picrate to form an orange-red product. Uric acid quantification is based on the reduction of Fe3+ to Fe2+ by UA, which is detected in a colorimetric reaction using 1,10-phenanthroline. Under optimum conditions, obtained through chemometrics, the concentrations of the analytes showed good linear correlations with the effective intensities, and the method presented satisfactory repeatability. The limits of detection and the linear ranges, respectively, were 15.7 mg L−1 and 50–600 mg L−1 for CRN and 16.5 mg L−1 and 50–500 mg L−1 for UA. There were no statistically significant differences between the results obtained using the μPAD and a chromatographic comparative method (Student's t-test at 95% confidence level). Instituto de Química Universidade Estadual Paulista “Julio de Mesquita Filho”- UNESP, R. Prof. Francisco Degni 55, P.O. Box 355 Instituto de Química de São Carlos Universidade de São Paulo, Av. Trabalhador São-carlense, 400 Instituto de Química Universidade Estadual Paulista “Julio de Mesquita Filho”- UNESP, R. Prof. Francisco Degni 55, P.O. Box 355 CNPq: 132646/2014-5 CAPES: 2014/17749-7 FAPESP: 2015/21733-1 CNPq: 308788/2015-0

Accurate quantification of multiple miRNAs biomarkers in body fluid is still a challenge for early screening of cancer. Herein, by catalytic hairpin assembly as a signal amplification strategy, we designed a novel surface-enhanced Raman scattering (SERS)-lateral flow assay (LFA) strip for ultrasensitive detection of miR-21 and miR-196a-5p in non-small cell lung cancer (NSCLC) urine on a single test (T) line. 4-mercaptobenzoic acid or 5,5′-dithiobis-2-nitrobenzoic acid as Raman molecules was labeled and two hairpin DNA sequence was modified gold nanocages (GNCs) were designed as two SERS tags. Through target miRNA-triggered catalytic hairpin assembly (CHA), the double-stranded DNAs (H1–H2 complex) formed by SERS tags and the related hairpin-structured DNA sequence 2 (H2) were immobilized on a single T line of SERS-LFA strip. This generated abundant “hot spots” because of the formation of numerous H1–H2 complex thus facilitated the SERS measurement. Through this method, two kinds of miRNAs were analyzed, resulting in limits of detection of 2.08 pM and 3.31 pM for miR-21 in PBS buffer and human urine, 1.77 pM and 2.18 pM for miR-196a-5p in PBS buffer and human urine. Significantly, the SERS-LFA strip exhibited high specificity and good repeatability toward miRNAs. The whole detection time was only 30 min, which means that the high detection efficiency of the strip. The clinical feasibility of the proposed method was also evaluated by detecting the levels of miR-21 and miR-196a-5p in urine samples from NSCLC patients and healthy subjects. The developed SERS-LFA strip has wide application prospect in biomedical research, drug development and early clinical diagnosis.

An open tubular (OT) column (25 μm i.d.) was prepared by in situ ring-opening polymerization of octaglycidyldimethylsilyl polyhedral oligomeric silsesquioxanes (POSS-epoxy) with 4-aminophenyl disulfide (APDS) in a binary porogenic system of ethanol/H2O. It was found that porogenic composition played an important role in the formation of OT stationary phases. The ratio of ethanol/H2O at 6/1 (v/v) would lead to the fabrication of hybrid monoliths, while the ratio of ethanol/H2O at 13/1 (v/v) would result in the synthesis of OT phases. In addition, the effects of precursor content and reaction duration on the thickness of OT stationary phases were investigated. Either lower precursor content or shorter reaction duration would produce thinner layer of OT column. The repeatability of OT columns was evaluated through relative standard deviation (RSD%) with benzene as the analyte. The run-to-run, column-to-column and batch-to-batch repeatabilities were 1.7%, 4.8% and 5.6%, respectively, exhibiting satisfactory repeatability of the OT column. Then tryptic digest of mouse liver proteins was used to evaluate the performance of the resulting OT columns (25 μm i.d. × 2.5 m in length) by cLC-MS/MS analysis, demonstrating their potential in proteome analysis.

With the aim of contributing to the development and improvement of microextraction techniques, a novel approach combining the principles and advantages of stir bar sorptive extraction (SBSE) and dispersive liquid-liquid microextraction (DLLME) is presented. This new approach, termed stir bar dispersive liquid microextraction (SBDLME), involves the addition of a magnetic ionic liquid (MIL) and a neodymium-core magnetic stir bar into the sample allowing the MIL coat the stir bar due to physical forces (i.e., magnetism). As long as the stirring rate is maintained at low speed, the MIL resists rotational (centrifugal) forces and remains on the stir bar surface in a manner closely resembling SBSE. By increasing the stirring rate, the rotational forces surpass the magnetic field and the MIL disperses into the sample solution in a similar manner to DLLME. After extraction, the stirring is stopped and the MIL returns to the stir bar without the requirement of an additional external magnetic field. The MIL-coated stir bar containing the preconcentrated analytes is thermally desorbed directly into a gas chromatographic system coupled to a mass spectrometric detector (TD-GC-MS). This novel approach opens new insights into the microextraction field, by using the benefits provided by SBSE and DLLME simultaneously, such as automated thermal desorption and high surface contact area, respectively, but most importantly, it enables the use of tailor-made solvents (i.e., MILs). To prove its utility, SBDLME has been used in the extraction of lipophilic organic UV filters from environmental water samples as model analytical application with excellent analytical features in terms of linearity, enrichment factors (67-791), limits of detection (low ng L-1), intra- and inter-day repeatability (RSD

Increasing metabolite coverage by combining data from different platforms or methods can improve understanding of related metabolic mechanisms and the identification of biomarkers. However, no one method can obtain metabolomic and lipidomic information in a single analysis. In this work, aiming at collecting comprehensive information on metabolome and lipidome in a single analytical run, we developed an on-line heart-cutting two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) method. Complex metabolites from biological samples are divided into two fractions by using a precolumn. The first fraction is directly transferred and subjected to metabolomics analysis. Most lipids are retained on the precolumn until the mobile phases for lipidomics flow through; then they are subjected to lipidomics analysis. Up to 447 and 289 metabolites in plasma, including amino acids, carnitines, bile acids, free fatty acids, lyso-phospholipids, phospholipids, sphingomyelins etc. were identified within 30 min in the positive mode and negative mode, respectively. A comparison of the newly developed method with the conventional metabolomic and lipidomic approaches showed that approximately 99% features obtained by the two conventional methods can be covered with this 2D-LC method. Analytical characteristics evaluation showed the method had a wide linearity range, high sensitivity, satisfactory recovery and repeatability. These results demonstrate that this method is reliable, stable and well qualified in metabolomics analysis, particularly for large-scale metabolomics studies with small amount of samples.

In the present work, we propose a safe, simple, and relatively rapid procedure for the efficient clean-up and pre-concentration of ultra-trace calcium channel blockers (CCBs) from the human plasma and urine samples followed by high performance liquid chromatography-ultraviolet detection. The proposed sample preparation method is a combination of two microextraction methods termed as ultrasound-assisted dispersive micro solid-phase extraction coupled with air-agitated liquid-liquid microextraction based on solidification of a floating organic droplet (UA-dμSPE-AA-LLME-SFO). A superior clean-up and a higher pre-concentration factor are two valuable outcomes of the mentioned procedure, leading to an accurate measurement of the therapeutically low concentrations in the biological samples. The basis of the first dispersive micro solid-phase extraction is an effective nano-adsorbent named the PANI-DBSNa/TiO2 nano-composite. It was easily synthesized sonochemically by the in situ chemical oxidative polymerization method as core-sell structures, and subsequently, characterized by different techniques including FESEM, XRD, and TGA. The optimum conditions enriched via the response surface methodology (RSM) consisted of pH 12.1, 23 mg of the PANI-DBSNa/TiO2 nano-composite, a sonication time of 4.3 min, 225 μL of methanol, and 78 μL of 1-undecanol. Under the optimum experimental conditions, the good linear ranges of 4.0-4000, 8.0-10000, and 7.0-8000 ng mL-1 were obtainable for diltiazem, amlodipine, and verapamil, respectively, with the correlation of determinations (R2s) higher than 0.99 and the low limits of detection (LODs) of 1.5-3.0 ng mL-1. The relative standard deviations (%RSDs) were in the span of 5.5-6.5% (n = 3); implying on the satisfactory repeatability (or reproducibility). The enrichment factor (EF) and extraction recovery percentage (%ER) values were found to be 68 and 65% for diltiazem, 80 and 75% for amlodipine, and 46 and 45% for verapamil, respectively.

The primary goal of the present study is the inter-laboratory evaluation of a thin film microextraction (TFME) technique to be used as an alternative approach to liquid-liquid extraction (LLE). Polydimethylsiloxane/divinylbenzene (PDMS/DVB) and PDMS/DVB-carbon mesh supported membranes were used for the extraction of 23 targeted pesticides, while a thermal desorption unit (TDU) was employed to transfer these analytes to a GC/MS instrument for separation and detection. After optimization of the most critical parameters, both membranes were capable of achieving limits of detection (LOD) in the low ng L−1 range while demonstrating excellent robustness, withstanding up to 100 extractions/desorption cycles. Furthermore, limits of quantification (LOQ) between 0.025 and 0.50 μg L−1 were achieved for the 23 compounds selected from several classes of pesticides with a wide range of polarities. A wide linear range of 0.025–10.0 μg L−1 with strong correlation to response (R2 > 0.99) was attained for most of the studied analytes. Both membranes showed good accuracy and repeatability at three levels of concentration. Moreover, the method was also validated through blind split analyses of 18 surface water samples, collected within 3 months, using TFME at the University of Waterloo and LLE at Maxxam Analytics (Mississauga, ON) which is an accredited commercial analytical laboratory. Good agreement between the two methods was achieved with accuracy values ranging from 70 to 130%, for the majority of analytes in the samples collected. At the concentration levels investigated, 90% of the analytes were quantifiable by TFME, whereas only 53% of the compounds were reportable using the LLE method particularly at concentrations lower than 1 μg L−1. The comparison of TFME and LLE from several analytical aspects demonstrated that the novel TFME method gave similar accuracy to LLE, while providing additional advantages including higher sensitivity, lower sample volume, thus reduced waste production, and faster analytical throughput. Given the sensitivity, simplicity, low cost, accuracy, greenness and relatively fast procedure of TFME, it shows great potential for adoption in analytical laboratories as an alternative to LLE.

Label-free biosensors which can be integrated into lab-on-a-chip platforms have the advantage of using small volumes for rapid and inexpensive measurements contrary to label-based technologies which are often more costly and time-consuming. in this study, graphene oxide screen printed electrodes (GPHOXE) were modified by deactivated Cas9 (dCas9) proteins and synthetic guide RNA (sgRNA) as the biorecognition receptor for label-free detection of circulating tumor DNAs (ctDNA). This was achieved by detection of a tumor related mutation (PIK3CA exon 9 mutation) via sequence-specific recognition followed by electrochemical impedance spectroscopy (EIS) analysis. the biosensor showed high specificity as there was no impedance signal for other ctDNA sequences, even the single nucleotide mismatch. dCas9-sgRNA modified biosensor demonstrated linear detection limits between 2 and 20 nM for 120 bp ctDNA's in 40 s. the calibration curve showed good linearity, LOD was calculated as 0.65 nM and LOQ was calculated as 1.92 nM. Selectivity and repeatability studies were carried out in real blood samples and the recovery was higher than 96%. in conclusion, dCas9-sgRNAwas effectively immobilized and optimized on GPHOXE as the selective biorecognition receptor of this ultrafast impedimetric biosensor. the CRISPRd-Cas9 powered impedimetric system showed good selectivity, high repeatability and good recovery properties. This is the first literature to report the use of CRISPR/Cas technology as a label-free tool that can be used in an impedimetric system for detection of ctDNA's. (C) 2020 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK-1001, 217S353], This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK-1001) with the project number of 217S353.

In this fundamental work, tributyl phosphate (TBP) with zero hydrogen-bond acidity was for the first time discovered as an efficient supported liquid membrane (SLM) for EME of acidic drugs (barbiturates) due to its high polarity-polarizability. This discovery indicated that strong dipole-dipole interaction induced by high polarity-polarizability played an important role for efficient EME of acidic drugs. In addition, three barbiturates were successfully extracted for the first time from human whole blood and urine samples by EME with recoveries up to 90%. Interestingly, efficient EME of barbiturates from biological samples required much lower extraction voltage than that from buffer samples. This was due to the significant contribution from LPME during the EME process, when EME was conducted from the samples with just partially ionized analytes. EME combined with HPLC-UV and LC-MS were validated using whole blood and urine, respectively. In all cases, the linearity (R2) was > 0.99 within the reported linear range. Repeatability at three concentrations was satisfactory (

In this research, the advantages of molecularly imprinted polymer (MIP) materials have been used to develop a new electrochemical sensor for determination of quetiapine (QTP) drug. MIP nanoparticles were synthesized by precipitation polymerization method and used as QTP recognition elements in the composition of modified carbon paste electrode (CPE) for selective and sensitive assay of this drug. Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used for electrochemical analysis. Some parameters affecting the sensor performance were optimized and under optimal conditions, the proposed sensor showed linear responses with QTP concentration in the range of 1.6 × 10−8 to 2.5 × 10−6 M (R2 = 0.9964). The limits of detection (LOD) and quantification (LOQ) were calculated 5.04 × 10−9 M and 1.68 × 10−8 M respectively. Also, the amounts of %RSD for evaluation of repeatability and reproducibility of the proposed sensors were respectively obtained 2.19 and 3.02%. The method was successfully applied to determination of QTP in its pharmaceutical formulation and human urine samples.

Perchlorate is an environmental contaminant that originates from anthropogenic as well as natural sources. The health effects of perchlorate with respect to the thyroid function are well known. The capabilities of the inductively coupled plasma mass spectrometry (ICPMS) has been recently expanded by coupling with tandem mass spectrometry. The advantages of HPLC-ICPMS/MS has not yet been thoroughly assessed for chlorine speciation analysis. We report a rapid and simple method for perchlorate determination in ground, tap, and river water and we show that the ICPMS/MS offers as a chromatographic detector at least 10-fold improvement in the detection limit relative to single quadrupole ICPMS. The achieved limit of detection was 0.3 μg Cl L−1 perchlorate and could be yet improved by simple freeze-drying (down to ca. 50 ng Cl L−1, based on the river water matrix), which is comparable with HPLC-ESIMS/MS, with the advantage of eliminating the need for the 18O-perchlorate isotopically labeled internal standard. The method was validated in the various water matrices in terms of recovery at levels 5.0–250 μg Cl L−1 (±10%), repeatability (RSD

Sample preparation for non-target analysis is challenging due to the difficulty in the extraction of polar and non-polar analytes simultaneously. Most commercial solid sorbents lack the proper comprehensiveness for extraction of analytes with different physiochemical properties. A possible key is the combination of hydrophobic polymer and hydrophilic surface functional groups in solid based extraction methods in order to generate the susceptibility for retaining both polar and non-polar analytes. To pursue this goal, in this study, four polar groups including NH2, NO2, COOH, and COCH3 were chemically bound to Amberlite XAD-4 substrate in order to prepare a generic extraction platform. To validate the applicability of extractive phases, 22 analytes possessing wide range of polarities (LogP range between −2 and +7) were chosen for extraction using the synthesized polymers by online micro solid phase extraction (μ-SPE) and further analyzed with high-performance liquid chromatography and UV–Vis detection (HPLC-UV). The recovery data were compared with commercial sorbents by t-test, principal component analysis (PCA) and hierarchical cluster analysis (HCA). Amberlite XAD-4 modified with COOH group (XAD-COOH) revealed extraction efficiencies statistically better than commercially available sorbents including LiChrolut® EN, Oasis® HLB and Amberlite® XAD-4®. The reproducibility and repeatability of XAD-COOH were also studied and acceptable results were obtained. Furthermore, the swellability of polymers was also measured and the results were comparable with commercial ones. To evaluate the extraction ability of XAD-COOH in real sample matrix, water sample near a heavy crude oil spill, urine and hospital wastewater were analyzed. Comparison of the data with LiChrolut® EN corroborates the dominance of XAD-COOH for screening analysis.

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn’t require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010–0.036 μg L−1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13–7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73–6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

With rapid advances in gut microbiome research, fecal bile acids are increasingly being monitored as potential biomarkers of diet related disease susceptibility. As such, rapid, robust and reliable methods for their analysis are of increasing importance. Herein is described a simple extraction method for the analysis of bile acids in feces suitable for subsequent quantification by liquid chromatography and tandem mass spectrometry. A C18 column separated the analytes with excellent peak shape and retention time repeatability maintained across 800 injections. The intra-day and inter-day precision and accuracy was greater than 80%. Recoveries ranged from 83.58 to 122.41%. The limit of detection and limit of quantification were in the range 2.5–15 nM, respectively. The optimized method involved extracting bile acids from wet feces with minimal clean up. A second aliquot of fecal material was dried and weighed to correct for water content. Extracting from dried feces showed reduced recovery that could be corrected for by spiking the feces with deuterated standards prior to drying. Storage of the extracts and standards in a refrigerated autosampler prior to analysis on the LC-MS is necessary. Multiple freeze-thaws of both extracts and standards lead to poor recoveries for some bile acids. The method was successfully applied to 100 human fecal samples.

This article focuses on the data evaluation of non-target high-resolution LC-MS profiles of water samples. Taking into account multiple technical replicates, the difficulties in peak recognition and the related problems of false positive and false negative findings are systematically demonstrated. On the basis of a combinatorial approach, different models involving sophisticated workflows are evaluated, particularly with regard to the repeatability. In addition, the improvement resulting from data processing was systematically taken into consideration where the recovery of spiked standards emphasized that real peaks of interest were barely or not removed by the derived filter criteria. The comprehensive evaluation included different matrix types spiked with up to 263 analytical standards which were analyzed repeatedly leading to a total number of more than 250 injections that were incorporated in the assessment of different models of data processing. It was found that the analysis of multiple replicates is the key factor as, on the one hand, it provides the option of integrating valuable filters in order to minimize the false positive rate and, on the other hand, allows correcting partially false negative findings occurring during the peak recognition. The developed processing strategies including replicates clearly point to an enhanced data quality since both the repeatability as well as the peak recognition could be considerably improved. As proof of concept, four different matrix types, including a wastewater treatment plant (WWTP) effluent, were spiked with 130 isotopically labeled standards at different concentration levels. Despite the stringent filter criteria, at 100 ng L(-1) recovery rates of up to 93% were reached in the positive ionization mode. The proposed model, comprising three technical replicates, filters less than 5% and 2% of the standards recognized at 100 and 500 ng L(-1), respectively and thus indicates the general applicability of the presented strategies.

In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation–Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability.

Pseudotargeted metabolomics is a novel strategy integrating the advantages of both untargeted and targeted methods. The conventional pseudotargeted metabolomics required two MS instruments, i.e., ultra-high performance liquid chromatography/quadrupole-time- of-flight mass spectrometry (UHPLC/Q-TOF MS) and UHPLC/triple quadrupole mass spectrometry (UHPLC/QQQ-MS), which makes method transformation inevitable. Furthermore, the picking of ion pairs from thousands of candidates and the swapping of the data between two instruments are the most labor-intensive steps, which greatly limit its application in metabolomic analysis. In the present study, we proposed an improved pseudotargeted metabolomics method that could be achieved on an UHPLC/Q-TOF/MS instrument operated in the multiple ion monitoring (MIM) mode with time-staggered ion lists (tsMIM). Full scan-based untargeted analysis was applied to extract the target ions. After peak alignment and ion fusion, a stepwise ion picking procedure was used to generate the ion lists for subsequent single MIM and tsMIM. The UHPLC/Q-TOF tsMIM MS-based pseudotargeted approach exhibited better repeatability and a wider linear range than the UHPLC/Q-TOF MS-based untargeted metabolomics method. Compared to the single MIM mode, the tsMIM significantly increased the coverage of the metabolites detected. The newly developed method was successfully applied to discover plasma biomarkers for alcohol-induced liver injury in mice, which indicated its practicability and great potential in future metabolomics studies.

A low cost, disposable and easy to use microfluidic paper-based analytical device (μPAD) was developed for simple and non-invasive determination of total aldehydes in saliva with a potential to be used in epidemiological studies to assess oral cancer risk. The μPAD is based on the colour reaction between aldehydes (e.g. acetaldehyde, formaldehyde), 3-methyl-2-benzothiazolinone hydrazone (MBTH) and iron(III) to form an intense blue coloured formazan dye. The newly developed μPAD has a 3D design with two overlapping paper layers. The first layer comprises 15 circular detection zones (8 mm in diameter), each impregnated with 8 μL of MBTH, while the second layer contains 15 reagent zones (4 mm in diameter). Two μL of iron(III) chloride are added to each one of the second layer zones after the addition of sample to the detection zones in the first layer. All hydrophilic zones of the μPAD are defined by wax printing using a commercial wax printer. Due to the 2-step nature of the analytical reaction, the two paper layers are separated by a cellulose acetate interleaving sheet to allow for the reaction between the aldehydes in the saliva sample with MBTH to proceed first with the formation of an azine, followed by a blue coloured reaction between the azine and the oxidized by iron(III) form of MBTH, produced after the removal of the interleaving sheet. After obtaining a high resolution image of the detection side zone of the device using a flatbed scanner, the intensity of the blue colour within each detection zone is measured with Image J software. Under optimal conditions, the μPAD is characterised by a working range of 20.4-114.0 μM, limit of detection of 6.1 μM, and repeatability, expressed as RSD, of less than 12.7% (n = 5). There is no statistically significant difference at the 95% confidence level between the results obtained by the μPAD and the reference method (Student's t-test: 0.090

The analysis of bacterial volatile organic compounds has gained attraction as a non-invasive way to identify disease-causing organisms, given that bacteria have unique metabolisms and volatile metabolic byproducts. In the present research, different adsorbent materials (Carbopack Y, X, B, Carboxen 1000 and Tenax TA), packed singularly or in combination, were compared in terms of sampling performance (sensitivity, repeatability and selectivity) for the extraction of standards and bacterial volatile metabolites in vitro (from Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli). After extraction, bacterial volatile organic compounds were desorbed and analyzed in a comprehensive two-dimensional gas chromatography system coupled to a time-of-flight mass spectrometer (GC × GC-ToF MS). The results show that Tenax has the greater ability to extract the standard mix as well as volatile organic compounds with better repeatability (4–26 RSD%), higher sensitivity (on average ∼24 fold) compared to Carbopack Y, X and Carboxen 1000 tube, which followed in terms of performance. In addition, Tenax confirmed the best sensitivity and discriminatory power with no misclassification in the untargeted and unsupervised analysis for the differentiation of the bacterial species.

An effective analytical method for bromine and iodine determination in human hair using interference-free inductively coupled plasma mass spectrometry (ICP-MS) was developed. Human hair was digested based on combustion reaction to obtain compatible solutions with ICP-MS analysis. Using microwave-induced combustion (MIC), masses of human hair ranging from 50 to 300 mg were efficiently digested. Only a diluted alkaline solution (100 mmol L−1 NH4OH) was used for the absorption of both analytes, which was fully compatible with ICP-MS analysis. Using these conditions low limits of detection were obtained (LOD of 0.01 μg g−1 for Br and 0.004 μg g−1 for I). Recovery tests at two levels (50% and 100%) using a standard solution or mixtures of the sample with certified reference materials (CRMs) were carried out to evaluate the suitability of proposed method and recoveries between 94% and 102% were always obtained. Accuracy was evaluated by analysis of a human hair CRM, and the Br and I concentrations obtained by the proposed method did not differ significantly from those described in the certificate. Repeatability (RSDs ≤ 4%) and reproducibility (RSDs ≤ 7%) of the results using proposed method were always very suitable. The digests obtained using the MIC method were fully compatible with ICP-MS and the interferences currently found using conventional digestion methods were completely eliminated. Ultra-trace concentrations of Br and I were determined in human hair, demonstrating that the proposed method is a suitable strategy, and it presents several advantages compared to others published in the literature.

The significant advance of delivering high value multi-species data from sub-1 mL ice core sample volumes allows higher temporal resolution in deposition records of inorganic and low molecular weight organic anions and cations. The determination of these species is a fundamental strategic requirement in modern paleoclimate studies. Herein, for the first time, a dual capillary ion chromatography (Cap-IC) based method for the simultaneous separation of 17 organic and inorganic anions and cations in low volume Antarctic ice core samples is presented. The total amount of sample required for direct injection has been reduced to 190 μL, which is 35 times lower than the amount of sample required by standard ion chromatography methods. A dual Cap-IC system configured for the simultaneous determination of cations and anions was used throughout. A range of chromatographic parameters was optimised for both anion and cation systems to obtain baseline separations of all target analytes in a suitable run time and to minimise the amount of sample required. Baseline separation of matrix and trace ‘marker’ ions were achieved in less than 35 min, after injecting only 40 μL of sample in each IC system. Limits of detection (LODs) for all analytes determined were within a range similar to that achieved by previously published standard bore IC-based methods. Intra- and inter-day repeatability were evaluated, with both parameters being typically below 3% for peak area. In further validation of the method, a comparative analysis of a set of 420 ice core samples from Aurora Basin North site, Antarctica, previously analysed by standard IC, established that the proposed low sample volume technique was applicable as a routine measurement approach in ice core analysis projects.

Microcystins (MCs), which are produced by eruptive cyanobacteria, seriously threaten the health of humans for their poisonousness. Herein, a facile strategy was introduced to synthesize the magnetic γ-cyclodextrin polymer (Fe3O4@PDA@γ-CDP) composite and set it as a novel adsorbent with excellent properties for the magnetic solid-phase extraction (MSPE) of MCs. The prepared Fe3O4@PDA@γ-CDP microspheres exhibit good aqueous dispersibility and highly affinity for MCs, thus contribute to an excellent extraction performance for trace MCs in water samples. Combined with HPLC–MS/MS, a handy, sensitive and efficient method was developed for detection of MCs in water samples, which shows good linearity (R2 ≥ 0.9992) in the range of 1.0–1000 pg mL−1, low limits of detection (0.8–2.0 pg mL−1, S/N = 3), satisfactory repeatability with the relative standard deviations (RSDs) lower than 6.2% (n = 5). At last, the proposed method was successfully applied for the extraction and detection of MCs in fresh water and sea water samples, which provides great potential of trace-level MCs determination in lake and sea water.