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Quantitative PCR (qPCR) has become a widely used technique for bacterial quantification. The affordability, ease of experimental design, reproducibility, and robustness of qPCR experiments contribute to its success. The establishment of guidelines for minimum information for publication of qPCR experiments, now more than 10 years ago, aimed to mitigate the publication of contradictory data. Unfortunately, there are still a significant number of recent research articles that do not consider the main pitfalls of qPCR for quantification of biological samples, which undoubtedly leads to biased experimental conclusions. qPCR experiments have two main issues that need to be properly tackled: those related to the extraction and purification of genomic DNA and those related to the thermal amplification process. This mini-review provides an updated literature survey that critically analyzes the following key aspects of bacterial quantification by qPCR: (i) the normalization of qPCR results by using exogenous controls, (ii) the construction of adequate calibration curves, and (iii) the determination of qPCR reaction efficiency. It is primarily focused on original papers published last year, where qPCR was applied to quantify bacterial species in different types of biological samples, including multi-species biofilms, human fluids, and water and soil samples., Christina A. Muzny, MD, MSPH, Christopher M. Taylor, PhD, Nuno Cerca, PhD and Ângela Lima, BSc, are currently funded by the National Institute of Allergy and Infectious Diseases (R01AI146065-01A1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation., info:eu-repo/semantics/publishedVersion

Trazodone (TZD) is a tetracyclic serotonin antagonist and reuptake inhibitor that is used as a second-generation phenylpiperazine antidepressant. However, the plasma concentrations of TZD have shown individual variations in clinical practice. Quantification of TZD plasma concentrations may be an effective and valuable method to balance the clinical efficacy and adverse reactions. This study aimed to establish a novel liquid chromatography coupled with mass spectrometry (LC-MS) assay for measuring TZD concentrations in human plasma for therapeutic drug monitoring (TDM).After protein precipitation with acetonitrile, LC-MS quantification of TZD was performed in the multiple reaction monitoring mode with chromatographic separation using a mobile phase of MeOH and 0.1% formic acid in water. This method validation intends to investigate specificity, sensitivity, linearity, precision, accuracy, recovery, matrix effect, and stability according to United states food and drug administration guidelines.This method showed good selectivity because no interfering peaks were observed in the plasma samples during the 2-minute run time. The range of the calibration curve was 1-3000 ng/mL. The detection and quantification limits were 0.3 and 1 ng/mL, respectively. The intraday and interday accuracies were 96.5%-103.4%, with precision relative SD% values of5%, except for the limit of quality. The mean TZD recovery from human plasma was 95.4%-104.5%. Finally, this method was successfully applied to TDM in 20 patients. The TZD plasma concentrations of the patients ranged between 21.5 and 2267.3 ng/mL.A novel analytical method was established to measure TZD by LC-MS coupled with an automatic 2-dimensional liquid chromatograph mass spectrometer coupler 9500 (LC-MS/MS-Mate 9500), which is superior to the ordinary LC-MS system in separation, transport, anti-interference, sensitivity, and quantitative analysis stability.

En este trabajo se realiza la determinación de la concentración de Cobre y Zinc en muestras de agua en un periodo de tiempo de 6 meses, entre julio y diciembre del 2022 con el fin de evaluar la calidad de la misma respecto a la resolución 0631 del 2015 del Ministerio de Ambiente, se realizó análisis de determinación de metales a un volumen aproximado de 800 muestras a través del método de referencia del Standar Methods 3030 B Ed. 23 / 2017 por plasma acoplado inductivamente - espectrometría de emisión óptica (ICP-OES) para luego confirmar si aplicaban dentro de los vertimientos establecidos en la resolución, y seguidamente, ordenarlos respecto a el tipo de vertimiento o actividad económica, estableciendo así, el análisis para vertimientos provenientes de actividades mineras y vertimientos provenientes de prestadores del servicio público de alcantarillado. Los resultados arrojaron que las muestras provenientes de vertimientos de actividad minera presentan una mayor concentración respecto a las provenientes de la prestadora del servicio de alcantarillado. Sin embargo, ninguna de las muestras analizadas sobrepasa el límite establecido por la resolución. In this work, the determination of the concentration of Copper and Zinc in water samples is carried out in a period of 6 months, between July and December 2022 in order to evaluate its quality with respect to resolution 0631 of 2015. of the Ministry of the Environment, metal determination analysis was carried out on an approximate volume of 800 samples through the reference method of Standard Methods 3030 B Ed. 23 / 2017 by inductively coupled plasma - optical emission spectrometry (ICP-OES) to then confirm if they applied within the discharges established in the resolution, and then order them with respect to the type of discharge or economic activity, thus establishing the analysis for discharges from mining activities and discharges from public sewerage service providers. The results showed that the samples from dumping of mining activity have a higher concentration than those from the sewage service provider. However, none of the samples analyzed exceeds the limit established by the resolution. Químico Ambiental http://www.ustabuca.edu.co/ustabmanga/presentacion Pregrado

Accurate and precise determination of plutonium and uranium in Fast Breeder Reactor (FBR) fuels is one of the most important steps in the chemical quality control of these fuels. Along with high precision, minimization of radioanalytical waste generated during measurements is of equal importance. Till date, routine wet radioanalytical techniques used for this purpose produce a lot of radioactive waste which needed an extensive recovery procedure. This paper describes a novel and simple micro-analytical method for determination of the Pu percentage with respect to uranium in fast reactor nuclear fuels, both carbide and oxide, using micro X-Ray Fluorescence (μ-XRF) spectrometry. The developed methodology requires ∼200 ng of sample for analysis and the radioactivity in such sample specimens is below 500 becquerel. Therefore, these sample specimens could be isolated with a layer of Scotch tape and analyzed. The detection limit for U and Pu, obtained using the developed methodology was ∼60–64 ng mL−1. Using a single calibration plot, the Pu percentage in fuel samples could be determined in the entire concentration range from 10 to 90% for both the fuels. The average precision obtained was 0.23% (1σ; n = 3) for samples having a (U/Pu) concentration of

The hydrophilic interaction chromatography (HILIC) technique outperforms other methods in terms of precision and sensitivity. The development and optimization of a HILIC method for validating a separation method for simvastatin estimation in pharmaceutical formulations necessitated determining the optimal mobile phase, buffer concentration, and pH value. The proposed HILIC methods using two columns demonstrated high precision (RSD less than 1%) and a robust linear relationship between the calibration graph and simvastatin concentration ranges of 0.05–4 µg mL−1 with a coefficient of determination (R2) of 0.9996 and 0.9994 for simvastatin. The HILIC methods provided excellent validated LOD (0.023 and 0.015 µg mL−1) and LOQ (0.069–0.045 µg mL−1) values for simvastatin. The HILIC approach was successfully used to estimate simvastatin in commercial pharmaceutical tablets, resulting in an excellent simvastatin recovery > 99%. Using statistical tests, the findings of the HILIC method were compared to the British pharmacopoeia protocol for simvastatin drug. There was no difference in accuracy between the methods.

A novel organic receptor based on isocyanate ions was developed and converted into its organic nanoparticles. The organic nanoparticles (ONPs) developed were of size 15–20 nm characterized via DLS and TEM. A recognition study was carried out to examine the response of ONPs towards different TBA salts of anions. Electrochemical studies were performed and from CV and DPV plots it was observed that among all the tested anions, ClO4- ions showed selective response. To confirm the selectivity, titration studies were carried out and a calibration curve was drawn which depicts the high sensitivity of ONPs towards ClO4- ions and 3 sigma method was utilized for calculating the detection limit and was obtained to be 7.9 nM. The real time applications of the synthesized sensor were explored and the accuracy of the analysis was found to be greater than 95%.

A simple and sensitive spectrophotometric method for the quantification of sulfite at trace level has been proposed. The method is based on the change in the intensity of the color developed on reaction of sulfite with Rhodamine-B Phenyl hydrazide (RBPH) in aqueous micellar medium. The experimental conditions such as pH, concentration of RBPH and Tween 80 have been optimized and calibration plot has been constructed. The proposed method offers a wide linearity in the concentration range 0–15 ppm of sulfite. The limit of detection and limit of quantification were found to be 0.006 and 1.5 ppm respectively, with the regression co-efficient R2 = 0.992. The proposed method has been successfully applied to measure the trace level sulfite in food samples such as tomato ketchup, jam, dry grapes, sugar and wine. Comparison of the developed method with standard protocol showed good recoveries.

This project was to study analytical technique foranti_thalassemia drug of deferasirox by glassy carbon electrode (GCE).The electrochemical performance of deferasirox was studied by cyclic voltammetry technique. The determination of deferasirox wasapplicate under Optimize condition in pH 13, scan rate 50 and 500mv/s,temperature 40 0Candinterference that have been studied. where found the resultsthat calibration curve ofdeferasiroxwas linear in the concentrations 2.6 × 10-4-2.6 × 10-2 M,the detection limits were9.227 × 10-4 M at 50mv/s and1.084 × 10-4 Mat 500mv/s while LOQ were 3.075 × 10-3 M and 3.613 × 10-4 M.The active area of electrode was calculated to be 0.314 cm2 and also the diffusion coefficientswere (2.294 × 10-4cm2sec-1)in scan rate 500 mv/s and (1.452 × 10-4cm2sec-1) in scan rate 50 mv/s.where RSD% for bulk, form and serum less than 0.5% while in urine less from 1.5% and recovery close to 99.8% in bulk, form and serum while in urine is 100.1. The voltammogram for deferasirox giveirreversible process with adsorption– controlled process. Finally, this technique was appliedfor deferasirox on pharmaceutical formulations and biological samples (serum and urine).

BACKGROUND In this study, development and validation of a simple, miniaturised and, environmentally friendly carrier mediated three phase hollow fibre liquid phase micro-extraction (HFLPME) technique was investigated for the enrichment of tetracycline residues in honey samples. The extracts were analyzed using UV/Vis spectrophotometry and the LC-Q-TOF/MS. Parameters affecting the extraction efficiency of HFLPME such as pH of the donor and acceptor solutions, salt addition, agitation speed and extraction time were optimized. RESULTS The calibration curves showed good linearity, in the range of 1-100 μg kg-1 with correlation coefficients ranging between 0.9943 and 0.9992, under the optimized conditions. Recoveries of blank honey samples at three spiking levels (1, 10 and 20 μg kg-1 ) ranged from 81.2% to 107.5%. RSDs for the precision of the method were less than 15.0%. LODs and LOQs were in the ranges of 0.0861 to 0.2628 μg kg-1 and 0.2610 to 0.7964 μg kg-1 , respectively. Finally, the proposed method was successfully applied in the extraction of five tetracyclines from honey samples. Doxycycline residue detected in one of the commercial honey samples was below the limit of quantification. CONCLUSION Due to the advantages offered by HFLPME, this method can be employed as an alternative to conventional extraction techniques for the clean-up and pre-concentration of antibiotics in complex matrices including food samples. This article is protected by copyright. All rights reserved.

In the present work, a novel, simple, and sensitive method for the direct determination of trace Sb in water samples was developed based on hydrogen-doped solution anode glow discharge-optical emission spectrometry (SAGD-OES). It was found that the vapor generation and excitation of Sb occurred simultaneously in the SAGD, contributing to the significant improvement in the sensitivity of Sb as compared with normal pure He-operated SAGD or solution cathode glow discharge. Besides, the proposed hydrogen-doped SAGD-OES could be operated even at pH = 14, which could reduce the interference of coexisting ions as many metal ions could be precipitated and removed. Our results demonstrated that the proposed method offered good tolerance to the interferences of Li, Na, Ca, Mg, Fe, Ni, Mn, and Zn ions even at a concentration of 50 mg L-1. Under optimized conditions, the limit of detection of Sb was 0.85 μg L-1, which was comparable to that of microplasma sources coupled with conventional hydride generation. The linearity of the Sb calibration curve reached R2 > 0.999 in the 5-5000 μg L-1 range. Finally, the accuracy of the proposed method was validated by the determination of certified reference materials [GSB 07-1376-2001 (1) and (2))] and real water samples. The proposed low-power (6 W), green, sensitive, rapid, and robust method provides a promising approach for on-site trace Sb analysis and may also be extended to other elements.

This study is focused mainly on impact of irrigation water quality in cultivated soil on distribution of essentials nutrients (Al, Mg, Ca, Fe, S, Si, Na, P, and K) and relatively toxic metals (As, Ba, Cr, Cu, Ti, Sn, Mn, Ni, and Zn) using an elegant Laser induced breakdown spectroscopy (LIBS) technique. A pulsed Nd:YAG laser operating at 1064 nm in conjunction with suitable detector was applied to record soil emission spectra. The abundance of these elements were evaluated via standard calibration curve Laser Induced Breakdown Spectroscopy (CC-LIBS) and calibration free Laser Induced Breakdown Spectroscopy (CF-LIBS) approaches. Quantitative analyses were accomplished under conjecture of local thermodynamic equilibrium (L.T.E) and optically thin plasma. The average electron temperatures were estimated by Boltzmann plot method for cultivated soil samples in 7800 to 9300 K range. The electron number density was ~ 1.11 × 1017 cm − 3 to 1.60 × 1017 cm − 3. Prior to application on soil samples, the experimental setup was optimized at the following parameters: pulsed energy = 60 mJpulse-1, sample to lens distance of 9.0 cm, and the gate delay of 3.5 μs. It is noteworthy that nutritional elements content of cultivated soils were found strongly dependent upon the irrigation water quality. The cultivated soil from industrial area was found rich of toxins while the cultivated land using tube well water contains toxins in least amount. Our LIBS findings were also validated by comparing its results with contents measured using a standard inductively coupled plasma optical emission spectroscopy (ICP-OES) method and both were found in excellent agreement. The present study could be highly beneficial for agricultural applications and for farmers to produce safe food products and higher crops yield.

In the present work, reusable magnetic molecularly imprinted polymers have been used for the first time as an adsorbent for the determination of chlorferon. Magnetic molecularly imprinted polymers have been used for the selective separation of chlorferon from the solution and sensitive fluorimetric determination has been performed using the native fluorescence of chlorferon. The developed method is rapid and determination of chlorferon was completed in an hour. Limit of detection (LOD) of the method was found to be 0.0027 mu M and the linearity of the calibration graph was observed within the range of 0.01-0.36 mu M (2.5 - 75 mu g L-1). Adsorption isotherms point out the multilayer adsorption and the heterogeneous distribution of binding sites for imprinted polymer and homogeneous binding site for non-imprinted polymer. The adsorption capacities of imprinted polymer and non-imprinted polymer were calculated as 2.03 mu mol g(-1) and 0.96 mu mol g(-1), respectively and the imprinting factor was found to be 2.11. The interference effects of some organic compounds and characterization studies were also evaluated. The method has been applied to honey and tap water samples and the recoveries were found to be in the range of 91.3 and 101.1 %., 18-EGEMATAL-003, 18-EGEMATAL-003.

The aim of this paper was to use chromatographic tools for validating an analytical method for the tacrolimus (TAC) determination in polymeric nanocapsules and for identifying the drug degradation products after alkaline stress. A rapid Ultra-High-Performance Liquid Chromatography coupled with photo-diode array (UHPLC-PDA) method was successfully performed using the following chromatographic conditions: the Shimadzu Shim-pack XR-ODS III C18 column (100 mm×2.00 mm, 2.2 μm), the mobile phase consisting of methanol and acidified ultrapure water (89:11 v/v), the flow rate of 0.55 mL·min−1, and the ultraviolet (UV) detection at 235 nm. This method was validated as per International Council for Harmonisation (ICH) guidelines. In addition, a TAC forced degradation assay was carried out after alkaline stress and its degradation products were investigated using Liquid Chromatography coupled tandem mass spectroscopy (LC-MS/MS). The calibration curve was linear in the range of 100.0–300.0 μg·mL−1 (r >0.9999). Accuracy was confirmed by the TAC recovery of 96.55 to 98.19%. Precision (intraday and interday) were demonstrated by relative standard deviation lower than 0.89% and 3.25%, respectively. Selectivity and robustness were also proved. The method developed it was successfully applied to quantify TAC from polymeric nanocapsules, showing a high loading efficiency rate (>96.47%). The main drug degradation product observed in a multiple reaction monitoring (MRM) experiment was m/z 844, confirming the susceptibility of TAC under alkaline conditions; this finding was first time described.

Показаны изложенные в текстах ГОСТ 12575 и ICUMSA GS2/3/9-5 отличия методики определения редуцирующих веществ Найта и Аллена. Продемонстрированы результаты экспериментальной отработки элементов данной методики. Установлено несовпадение практических результатов с приведёнными в документах. Применение данной методики в системе контроля производства сахара нецелесообразно., Differences between Knight and Allen’s method for determining reducing substances, as described in GOST 12575, and ICUMSA GS2/3/9-5, are shown. The results of experimental testing of the elements of this method are presented. A discrepancy between the practical results and those set out in the documents was established. The use of this method in the control system of sugar production is impractical.

UV-visible (UV-Vis) spectroscopy is a powerful instrument for qualitative investigation and quantitative detection of pollutants in water. UV-Vis spectrophotometry is an analytical method using the concept of transmission of light in UV and Visible wavenumber. Generally, compounds can be identified using UV-Vis Spectrophotometry, based on the concept of light absorption, specifically for compounds with a chromophore group and an auxochrome group. Although the utilization of UV-Vis spectrum analysis has been well-documented, no information regarding detailed step-by-step measurement for examining detailed quantitative analysis, particularly in determining the concentration of an analyte in an aqueous solution sample. Here, this study explores the idea and application of UV-Vis technology in water quality detection, including guidelines for determining the concentration of the sample in an aqueous solution. To support the analysis, we also added practical examples for understanding concentration during the organic decomposition. This paper is intended to be useful for researchers and students in understanding UV-Vis spectrophotometry when analyzing chemical composition during chemical decomposition, photocatalysis, phytoremediation, and adsorption analysis.

In this research, the effect of fine-grained microstructure on the friction coefficient compared to the coarse-grained one in the ring-compression test of copper samples is investigated. The equal channel angular pressing process was performed on annealed copper at room temperature and in the Bc route in three consecutive passes. Then, the ring-compression test was carried out on the ring-shaped samples at room temperature and in three conditions: dry, with Molybdenum disulfide, and graphite lubricants with deformation rates of 12.5, 25, 37.5, 50, and 62.5%. The calibration curves were provided using the finite element method and analysis of variance was employed to investigate the effect of parameters on friction coefficients. The results showed that the friction coefficients in ECAPed copper in the first and second passes while using graphite and Molybdenum disulfide lubricants are similar. ECAPed copper in the third pass and annealed copper, respectively have lower friction coefficients when being lubricated with graphite and Molybdenum disulfide lubricants compared to other copper samples. Additionally, in all copper samples, except for ECAPed copper in the third pass, the Molybdenum disulfide lubricant decreased the friction coefficient more compared to graphite lubricant.

Buckwheat has tremendous nutraceutical potential owing to its rutin and quercetin content. The aim of this study was to optimise and validate an analytical method for separating and quantifying these two flavonoids from it. Factors, such as range, linearity, precision, accuracy, limit of detection and limit of quantification, were evaluated for the two compounds using high performance liquid chromatography. On the basis of resolution and symmetry, mobile phase consisting of methanol and methanol:water:acetic acid in the ratio of (100:150:5), flow rate 1.3 ml/min and column temperature 30 °C were found to be optimal analytical conditions. Calibration curves exhibited good linearity with correlation coefficient of 0.995 & 0.9907 over the range 60–180 μg/ml & 2–10 μg/ml for rutin and quercetin respectively. LOD and LOQ values for rutin and quercetin were 6.36, 0.58 and 19.28, 1.77 μg/ml respectively. Recovery values of 96–100.8% confirmed that the method was accurate for rutin and quercetin analysis. This validated method was successfully used to analyse rutin and quercetin in leaves and seeds of buckwheat plant.

The adverse reactions caused by 6-thioguanine (6-TG) in anti-cancer treatment are closely related to the dose, leading to the urgent need for clinical monitoring of its concentration. In this work, a highly reproducible free-standing liquid membrane (FLM) surface-enhanced Raman spectroscopy (SERS) substrate was developed to detect 6-TG in human urine and serum quantitatively. Briefly, a prepared sample was adjusted to pH 2 and mixed with concentrated core–shell bimetallic nanoparticle (AgcoreAushell NP) suspension. The Au/Ag ratio of the AgcoreAushell NPs was optimized. Then the mixture was formed into an FLM using a custom mold. The relative standard deviation (RSD) of the experimental results can be stabilized below 10% (n ≥ 10). The R2 of the calibration curve in the range of 10 ~ 100 μg kg−1 was 0.988. In addition, the limit of detection (LOD) (3σ/k) of 6-TG was 5 μg kg−1. The FLM SERS platform has been successfully applied to the rapid and reliable analysis of 6-TG spiked in body fluids.

The application of polyaniline nanofibers doped with chloride and nitrate ions (PANINFs-Cl and PANINFs-NO3) in potentiometry was described. Both kinds of nanofibers were used as an ion-to-electron transducer in ion-selective electrodes with solid contact (SCISEs). Extensive research on the properties of the nanofibers themselves (SEM, UV–Vis spectroscopy, FTIR) and the constructed electrodes (potentiometric methods, electrochemical impedance spectroscopy) has been carried out. Basic analytical parameters of electrodes containing various nanofibers contents in the ion-selective membrane and with nanofibers as an intermediate layer were determined. It was found that application of PANI nanofibers resulted in improvement of electrode performance (among others, better stability and reversibility of the electrode potential). The obtained sensors were characterized by a high slope of the calibration curve, a wide measuring range and a fast response time. Moreover, they were insensitive to change of redox potential, as well as light and the presence of oxygen in the solution, what is important from a practical point of view. They were also successfully used for nitrate determination in real environmental samples.

In the present research, a blended polyacrylamide-chitosan hydrogel was synthesized. For the first time, the prepared sorbent was efficiently employed in a hydrogel-based spin-column setup as a promising format. The proposed method was applied for monitoring the trace amounts of ketoconazole, clotrimazole, and miconazole in blood samples. Effective adsorption and desorption parameters were optimized using a central composite design and the one-variable-at-a-time method. Under the optimal conditions, the calibration curves were linear in the range of 15.0-1000.0, 1.0-1000.0, and 2.0-1000.0 ng mL-1 for ketoconazole, clotrimazole, and miconazole, respectively, along with intra- and inter-day precision less than 8.4%. Limits of detection were obtained between 0.2-5.0 ng mL-1 . The preconcentration factors were found in the range of 5.9-7.8. The introduced method was successfully applied for micro solid-phase extraction of trace amounts of target antifungal drugs in blood samples, followed by liquid chromatography-tandem mass spectrometry. Satisfactory relative recoveries of 94.5%-103.5% were obtained, implying method reliability. Overall, the proposed method provides good accuracy and repeatability, high reusability, and good applicability to determine antifungal drugs in complex biological matrices. This article is protected by copyright. All rights reserved.

The direct current potential drop (DCPD) method is an important method for monitoring crack initiation and propagation in specimens. During fatigue crack growth monitoring, the load causes the potential drop (PD) signal to change and produces periodic fluctuations independent of crack growth, thereby affecting the measurement accuracy and resolution. This study proposes a novel calibration method to quantitatively evaluate and correct the measurement error due to the change in the PD signal caused by the load during fatigue crack growth monitoring. Tensile fatigue tests and DCPD monitoring tests were conducted to measure the PD signal fluctuation owing to the cyclic load before and after specimen cracking. Electrical–structural finite element analyses were used to simulate the test process, and a calibration function considering the influence of the load was obtained. The influence of the load on the measurement accuracy and resolution was quantitatively evaluated using the model and experimental data. The cyclic load caused the PD signal to deviate from the calibration curve when the deformation of the specimen was not considered; the PD signal exhibited periodic fluctuations as a result. Moreover, for a certain range of fatigue loads, the corresponding PD signal increased as the crack grew. The proposed calibration method can correct the measurement error due to cyclic load, thereby further improving the measurement accuracy and resolution, and providing a basis for high-precision crack growth measurement.

An analytical method using a porous polytetrafluoroethylene (PTFE) membrane that passes through gas while repelling water, and a needle-type extraction device was developed for purge-and-trap (PT) extraction followed by gas chromatography–mass spectrometric (GC–MS) determination of volatile organic compounds (VOCs) in water samples. The PTFE membrane was fixed in a solid-phase extraction glass cartridge, and 10 mL of water sample and sodium chloride were added. Then, a needle-type extraction device was inserted into the cartridge headspace, and the headspace gas was collected. Due to decompression on the inside of the cartridge, purge gas was introduced from the bottom side of the cartridge through the PTFE membrane. After the sample extraction, VOCs were thermally desorbed by inserting the needle into the heated GC injection port. The limit of quantification of the proposed method for 23 investigated VOCs was less than 0.5 μg/L, and the upper limit of the calibration curve was 500 μg/L for dichloromethane and 1000 μg/L for other compounds. The relative standard deviations of the relative peak area for 23 investigated VOCs were less than 15% (n = 5). The method was used to determine VOCs in tap water samples.

A straightforward in situ detection method for dengue infection was demonstrated through the molecular imprinting of a dengue nonstructural protein 1 (NS1) epitope into an electropolymerized molecularly imprinted polyterthiophene (E-MIP) film sensor. The key enabling step in the sensor fabrication is based on an epitope imprinting strategy, in which short peptide sequences derived from the original target molecules were employed as the main template for detection and analysis. The formation of the E-MIP sensor films was facilitated using cyclic voltammetry (CV) and monitored in situ by electrochemical quartz crystal microbalance (EC-QCM). Surface properties were analyzed using different techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and polarization modulation-infrared reflection-adsorption (PM-IRRAS). The standard calibration curve (R = 0.9830) was generated for the detection of the epitope, Ac-VHTWTEQYKFQ-NH2, with a linear range of 0.2 to 30 μg/mL and detection limit of 0.073 μg/mL. A separate calibration curve (R = 0.9786) was obtained using spiked buffered solutions of dengue NS1 protein, which resulted in a linear range of 0.2 to 10 μg/mL and a detection limit of 0.056 μg/mL. The fabricated E-MIP sensor exhibited long-term stability, high sensitivity, and good selectivity towards the targeted molecules. These results indicated that the formation of the exact and stable cavity imprints in terms of size, shape, and functionalities was successful. In our future work, we aim to use our E-MIP sensors for NS1 detection in real-life samples such as serum and blood.

A sensitive, selective and rapid liquid chromatography–electrospray ionization–tandem mass spectrometry (LC-ESI-MS/MS) method has been developed for the estimation of mesalamine in human plasma using a derivatization technique. Aliquid-liquid extraction technique with ethyl acetate was used for the extraction of mesalamine and mesalamine-D3 internal standard (IS). Mesalamine and mesalamine-D3 were analyzed on Thermo BetaBasic C8 (100 mm × 4.6 mm, 5 μm) column using acetonitrile and 10 mM ammonium formate in 70 : 30 v/v ratio under isocratic elution mode. The MS detection and quantitation were performed under multiple reaction monitoring using positive ESI for mesalamine (m/z, 210.1 → 191.9) and mesalamine D3 (m/z, 213.2 → 195.1). Main advantages of the proposed method include higher sensitivity (5.00 ng/mL), superior extraction efficiency (≥79%), and small volume (200 μL) of sample for processing. The calibration curve was linear in the concentration range of 5.00 – 2957.17 ng/mL with a good correlation coefficient (r2 ≥ 0.9980) for mesalamine. The intra-batch (within day) and inter-batch (between days) precision (% CV) and accuracy (% nominal) values varied from 2.09 to 4.44% and from 96.02 to 103.23%, respectively. The method was validated as per the US FDA guidelines and the results were found accurate and precise.

In this study, the recovery rates of the dissolution method for radioactivity analysis of expandable polystyrene (EPS) with a liquid scintillation counter (LSC) using tetrahydrofuran (THF), toluene, and acetone as solvents were estimated. The detection efficiency calibration curve for each solvent was derived. Two methods—the volumetric ratio method and the quenching agent method—were used to prepare quench source sets, and calibration curves were derived by linking the data from the two quench source sets. The R2 value of the calibration curve for THF was found to be 0.984. The relationship between the mass of dissolved EPS and the quench level was estimated: the quench level increased as the mass of dissolved EPS increased. Premix and postmix dissolution methods were tested. The recovery rates using THF with the premix method were 84.9 ± 0.9% and 96.5 ± 1.5% for 3H and 14C, respectively. Furthermore, the stability of the recovery rate over time when using THF was evaluated. The dissolution method with the premixed solution exhibited a more stable recovery rate over time. The dissolution methods were found to be applicable for analysis using LSC, and THF was found to be the most suitable solvent for the proposed method.

For understanding and assessing aerosol–cloud interactions and their impact on climate, reliable measurement data on aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to an existing differential mobility analyzer (DMA) with CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (Fact−Saerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under three different thermal gradient (dT) conditions (dT=6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: first, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on the particle size and κ to be investigated. To minimize the effect of multiply charged particles, a small geometric mean diameter (Dg) and geometric standard deviation (σg) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02 per 100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, intercomparison experiments between typical DMA-CCN and BS2-CCN measurements were performed with a laboratory-generated aerosol mixture and ambient aerosols. Good agreement of κ values between DMA-CCN and BS2-CCN measurements for both experiments shows that the BS2-CCN system can measure CCN activity well compared to the existing measurement method and can measure a broad range of hygroscopicity distributions with a high time resolution (∼1 s vs. a few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection and estimation of aerosol chemical composition.

Hydrogen fuel cells are among the promising energy sources worldwide, which could accomplish cyclic production of energy and avoid the emission of green-house or contaminative byproducts. However, sulfur compounds (SCs) even at trace level (nmol/mol) are usually involved in cell construction and further H2 production, which would cause degradation of the catalysts and shorten the lifetime of the fuel cells. Moreover, the highly reactive SCs could cause varied species and concentrations of them in complex matrices, so online rather than offline analysis of SCs in H2 would be preferred. In this context, we developed a new system combining online cryogenic preconcentration of nine SCs and subsequent determination by GC-SCD (sulfur chemiluminescent detector), with the correlation coefficients of the calibration curves higher than 0.999, calculated limits of detection no higher than 0.050 nmol/mol, analytical time around 30 min per sample, and satisfactory precision and accuracy (RSD

Nitrate determination in natural waters by spectrophotometry was described. Nitrate was converted to 4-nitroguaiacol by nitration of guaiacol (2-methoxyphenol) in concentrated sulfuric acid medium. The UV spectrum of nitro product presents a sensitive and reproducible band toward 329 nm with molar absorption coefficient of 2023 L mol−1 cm−1. The method gives a linear calibration curve ranging from 0.2 to 24 mg L−1 of $${\mathrm{NO}}_{3}^{-}$$ with a reproducibility (RSD) of 1.07% and a limit of detection of 0.05 mg L−1 of $${\mathrm{NO}}_{3}^{-}$$ . The application of paired-t-test between the present method and sodium salicylate method, commonly accepted as reference method for nitrate determination, shows there is no significative difference between them and having the same accuracy and exactitude. The method can be used to determine nitrate in ground and surface waters, using less chemicals and requiring less operating procedure time than those of the reference one.

Background Using a Symmetry C18 (4.6 × 150 mm, 3.5) column, a high-performance liquid chromatographic method for quantification of Rilpivirine and Cabotegravir in active pharmaceutical ingredients was developed and validated. The mobile phase is made up of buffer, acetonitrile, and 0.1 percent formic acid in a 20:80v/v ratio. The flow rate was kept constant at 1.0 ml/min, and detection was accomplished through absorption at 231 nm with a photodiode array detector. Results The calibration curve was linear, with a regression coefficient (R2) value of 0.999 and concentrations ranging from 30 to 450 g/ml of Rilpivirine and 20–300 g/ml of Cabotegravir. The method's LOD and LOQ were 0.375 g/ml, 1.238 g/ml, and 0.25 g/ml, 0.825 g/ml for Rilpivirine and Cabotegravir, respectively. Conclusions In the forced degradation studies, the degradants were characterized by using LCMS and FTIR. The current application was found to be simple, economical, and suitable, and validated according to ICH guidelines.

Introduction. In Russia, the current condition regarding water quality in the water bodies of the Russian Federation used for drinking purposes “continues to remain unfavourable according to the Strategy of the Environmental Safety of the Russian Federation until 2025. It takes place primarily due to the discharges of industrial and domestic wastewater.” Thus, 19% of wastewater is discharged into water bodies without purification, 70% – insufficiently purified, and only 11% – purified to the established acceptable discharge standards. Therefore, 30–40% of the country’s population regularly uses water that does not correspond to the hygienic standards, which leads to an increased risk of morbidity among the population. This study aims to execute chromatography-mass spectrometric determination of highly toxic and carcinogenic N-nitrosamines in drinking water. Materials and methods. Within the framework of the study, we reviewed standard samples of N-nitrosamines Mix, 1X1ML, 2000 ug/ml, methanol, experimental diagrams of solid-phase extraction. The practical charts of solid-phase extraction were tested with the help of a susceptible and accurate analytical mass-spectrometric method, a gas chromatograph with a mass selective detector (MSD). An internal laboratory control was carried out according to CIS standardization recommendations 76-2014 of the State System for Ensuring Uniform Measurement to ensure the reliability of the analytical results obtained to determine N-nitrosamines in water. The quality indicators for the analysis results were experimentally established: the accuracy, correctness, precision of the analysis technique, and the methods for their assessment according to GOST R ISO 5725-2002 standards. Results. In the course of the performed experimental studies, it was found that the degree of N-nitrosamines extraction from water samples of 100 ml volume, through scavenging analytes on a carbon cartridge (Coconut 6 cm 3 ) and using four optimal diagrams of solid-phase extraction – SPE for N-dimethyl nitrosamine, N-diethyl nitrosamine, N-dipropyl nitrosamine, N-piperidine nitrosamine was 73.9%, 90.8%, 100 and 95.4% respectively. Optimal elution scheme 4: stage 1 — conditioning the cartridge to activate it: 5 ml methylene chloride for 3 seconds, 5 ml ethyl acetate for 3 seconds, rinsing the cartridge with 5 ml water for 10 seconds. Stage 2 - adsorption of a 100 ml water sample on a 6 ml Coconut cartridge for 1 minute; stage 3 — rinsing the cartridge with 5% sodium chloride solution of 10 ml for 30 seconds; stage 4-elution of N-nitrosamines from the cartridge with methylene chloride of 3 ml for 3 min. into a test tube in position 1 of the carriage of the automatic TFE system. The method for the determination of N-nitrosamines in water is based on the concentration of the analyzed compounds of water samples on a carbon cartridge — solid-phase extraction (SPE), identification of substances by library mass spectra and retention time, quantitative determination according to the calibration graph on a high polarity capillary column HP-FFAP-50 m • 0.32 mm • 0.50 μm. Conclusion. The developed guidelines for measuring the N-nitrosamines content in the water of centralized water supply systems let us determine highly toxic compounds at the lower limit of 0.00004 μg/cm 3 with an error of not more than 35.0%. Contribution: Nurislamova T.V. — rationale, conclusion; Ulanova T.S. — concept, scientific advice; Maltseva O.A., Popova N.A. — materials and methods, results, discussion, conclusion; Subbotina D.Yu. — analytical and experimental part of the study. All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version. Conflict of interest. The authors declare no conflict of interest. Acknowledgement. The study had no sponsorship. Received: July 20, 2021 / Accepted: September 28, 2021 / Published: October 31, 2021

New, simple and economical high pressure liquid chromatography method has been developed for the simultaneous quantification of Pioglitazone and Rosiglitazone.By using Waters HPLC e-2695 quaternary pump with a PDA detector of 2998 instrument the chromatographic separation of Pioglitazone and Rosiglitazone was achieved on the column of Inertsil ODS (150x4.6mm, 3.5 µ) using an isocratic elution with a buffer containing 0.1percentformic acid and acetonitrile at a rate of 30:70 as a mobile phase with a flow rate of 1 ml/min at ambient temperature. A detector wavelength of 261 nm utilizing the PDA detector were given in the instrumental settings. The linearity was studied between the concentration range of 3-45 µg/ml of Pioglitazone and 1-15 µg/ml of Rosiglitazone were injected.The plotted calibration curves were linear with a regression coefficient of R2> 0.999, indicates that the linearity was with in the limit. As a part of method validation the parameters like specificity, linearity, accuracy, ruggedness, robustness were determined and the results were found to be within the allowable limit. The method developed was found to be applicable to routine analysis and to be used for the measurement of both active pharmaceutical ingredients (i.e, Pioglitazone and Rosiglitazone).Validation of the proposed method was carried out according to an International Conference on Harmonization (ICH) guidelines. Since, there is no HPLC method reported in the literature for the estimation of Pioglitazone and Rosiglitazone, there is a need to develop quantitative methods under different conditions to achieve improvement in specificity, selecivity etc.

Aim. To develop a new method, which has a good reproducibility of the experimental results, is fast, cheap and provides safe working conditions during the analysis, in order to determine the activity of cholinesterase.Experimental part. The light absorption of the test and control samples was measured using a CPhC-3-01 photoelectric photometer (420 nm, l = 3 cm). The reaction rate was characterized by the value of the optical density of the solution in 10 min (the fixed time method). Measurements were performed at +37 °C, the temperature of the reaction mixture was maintained by thermostatіng in water, the pH of the solutions was monitored potentiometrically using a glass electrode. The determination was repeated five times with each solution of a certain concentration of the enzyme. According to the average values obtained, the calibration graph of the specific activity of the enzyme (in international units – activity unit (AU/mg) – kmol/min to 1 mg of the substance) on the optical density of the solution was constructed. Using the mean value of five measurements of the optical density of the test solution the specific activity of the enzyme (U) was found by the calibration graph.Results and discussion. The essence of the method is the photometrical measurement of the rate of the enzymatic hydrolysis of acetylcholine in a buffer medium using 3,3′,5,5′-tetramethylbenzidine (TMB). The enzymatic hydrolysis reaction of the substrate was performed at pH 8.3, and in 10 min after the start the rate of enzymatic hydrolysis of acetylcholine was measured. The linear dependence of the optical density on the specific activity of the enzyme (U) was observed in the range of 3.5 – 28 AU/mg (activity unit/mg). The activity of the enzyme, according to the average results of 5 measurements, was 27.9 AU/mg. The declared activity the enzyme in accordance with the quality certificate was 28 AU/mg. The limit of quantification was 0.2 AU/mg. Metrological characteristics of the method were as follows: RSD = 1.8 % (n = 5; P = 0.95), accuracy – 0.45 %. These values indicate that the method proposed for determining the activity of cholinesterase is characterized by high sensitivity, reliability and reproducibility of the results. At the same time, it was proven that there was no systematic error in determining the activity of cholinesterase by the method developed.Conclusions. As a result of the research conducted a new method for determining the activity of the cholinesterase enzyme has been developed; it is characterized by high sensitivity, reliability and reproducibility of the results, and also provides safe working conditions during the analysis.

In the present study, an accurate, rapid, and simple chiral HPLC-UV method with amylose tris(3-chloro-5-methylphenylcarbamate) as stationary phase was developed and applied for enantiomeric determination of six nonsteroidal anti-inflammatory drugs (NSAIDs) in the commercial pharmaceutical formulations, including (R,S)-ibuprofen, S-ibuprofen, (R,S)-ketoprofen, S-ketoprofen, S-naproxen, and (R,S)-loxoprofen sodium. Experiments on the influence of mobile phase composition, proportion of organic modifier, percentage of acid additives, and column temperature on enantioseparation were conducted to obtain the best separation condition. It was indicated that one mobile phase simply composed of acetonitrile-water (0.1% formic acid, v/v) at the proportion of 50:50 (v/v) with a flow rate of 0.6 ml/min at 22°C could simultaneously provide the excellent enantiomeric resolutions for all selected NSAIDs, which made the enantioseparation process more applicable and operable. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Calibration curve of each enantiomer at the concentration of 5.0-100 ug/ml showed good linearity with the correlation coefficient above 0.9996. Satisfactory recovery (96.54-101.54%), good intra-day precision (RSD 0.52-1.46%), and inter-day precision (RSD 0.13-1.09%) were also obtained. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Quantitative results of the commercial capsules and tablets demonstrated that the difference between the declared and measured values did not exceed 1.52%.

In this research project, a selective and sensitive sensor was electrochemically designed to measure metformin hydrochloride (MET) based on molecularly imprinted polymer (MIP). To prepare the sensor, the polypyrrole was electrochemically synthesized on a pencil graphite electrode (PGE), which modified with silver nanoparticles (AgNPs). Cyclic voltammetry and differential pulse voltammetry techniques were performed to fabricate the sensor and quantitative measurements, respectively. To select the functional monomers, a computational method was used. Some critical factors controlling the performance of the MIP–AgNPs–PGE were optimized using Plackett–Burman design and central composite design methods. Under optimal conditions, a calibration curve was obtained in the range 0.1–1000 µM with a limit of detection of 6.8 nM (S/N = 3, n = 3) and limit of quantitation of 22.8 nM (S/N = 10, n = 3). RSD of 3.9 and 4.1% were obtained for repeatability and reproducibility of the system, respectively. Furthermore, the modified sensor was successfully used for the determination of MET concentration in some real samples.

This research, aimed to synthesis and functionalize of Fe3O4 magnetic nanoparticles (MNPs) using dialdehyde starch and modifying with arginine amino acid. The resulting MNPs were characterized by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Vibrating sample magnetometer (VSM). Synthesized MNPs were developed for preconcentration and determination of diclofenac in biological samples by UV- Vis Spectrophotometry. A Plackett–Burman experimental design was used to evaluate the influence of effective parameters. Significant parameters were further optimized by Central Composite Design (CCD). Sample volume, pH and salting effect had a main effect on extraction of diclofenac by the proposed method. Under the optimized conditions, the detection limit (3Sb, n = 7) was found to be 0.039 µg ml− 1.The calibration curve showed dynamic linear 0.05-10 µg ml− 1 with correlation coefficients (R2) of 0.987. The enrichment factor was found to be 148. The proposed method showed good results for preconcentration and determination of diclofenac in serum and pharmaceutical samples.

Quantitative calibration of analytes using chemical ionization mass spectrometers (CIMSs) has been hindered by the lack of commercially available standards of atmospheric oxidation products. To accurately calibrate analytes without standards, techniques have been recently developed to log-linearly correlate analyte sensitivity with instrument operating conditions. However, there is an inherent bias when applying log-linear calibration relationships that is typically ignored. In this study, we examine the bias in a log-linear-based calibration curve based on prior mathematical work. We quantify the potential bias within the context of a CIMS-relevant relationship between analyte sensitivity and instrument voltage differentials. Uncertainty in three parameters has the potential to contribute to the bias, specifically the inherent extent to which the nominal relationship can capture true sensitivity, the slope of the relationship, and the voltage differential below which maximum sensitivity is achieved. Using a prior published case study, we estimate an average bias of 30 %, with 1 order of magnitude for less sensitive compounds in some circumstances. A parameter-explicit solution is proposed in this work for completely removing the inherent bias generated in the log-linear calibration relationships. A simplified correction method is also suggested for cases where a comprehensive bias correction is not possible due to unknown uncertainties of calibration parameters, which is shown to eliminate the bias on average but not for each individual compound. Alfred P. Sloan FoundationAlfred P. Sloan Foundation [P-2018-11129] Published version This research has been supported by the Alfred P. Sloan Foundation (grant no. P-2018-11129).

The chemical derivatization of multiple lipid classes was developed using benzoyl chloride as a nonhazardous derivatization agent at ambient conditions. The derivatization procedure was optimized with standards for 4 nonpolar and 8 polar lipid classes and measured by reversed-phase ultrahigh-performance liquid chromatography-tandem mass spectrometry. The derivatization and nonderivatization approaches were compared on the basis of the calibration curves of 22 internal standards from 12 lipid classes. The new method decreased the limit of detection 9-fold for monoacylglycerols (0.9-1.0 nmol/mL), 6.5-fold for sphingoid base (0.2 nmol/mL), and 3-fold for diacylglycerols (0.9 nmol/mL). The sensitivity expressed by the ratio of calibration slopes was increased 2- to 10-fold for almost all investigated lipid classes and even more than 100-fold for monoacylglycerols. Moreover, the benzoylation reaction produces a more stable derivative of cholesterol in comparison to the easily in-source fragmented nonderivatized form and enabled the detection of fatty acids in a positive ion mode, which does not require polarity switching as for the nonderivatized form. The intralaboratory comparison with an additional operator without previous derivatization experiences shows the simplicity, robustness, and reproducibility. The stability of the derivatives was determined by periodical measurements during a one month period and five freeze/thaw cycles. The fully optimized derivatization method was applied to human plasma, which allows the detection of 169 lipid species from 11 lipid classes using the high confidence level of identification in reversed-phase (RP)-ultra high performance liquid chromatography (UHPLC)/mass spectrometry (MS). Generally, we detected more lipid species for monoacylglycerols, diacylglycerols, and sphingoid bases in comparison with previously reported papers without the derivatization.

For the determination of Galantamine Hydrobromide in bulk and produced extended formulation, a new sensitive and quick HPLC technique was developed and validated according to ICH guidelines. The HPLC analysis was carried out using a waters system with a Thermo Scientific C18 (steel column (5 µm, 250mm × 4.6 mm)) column and a mobile phase of 0.1M phosphate buffer: Acetonitrile (40:60V/V) pH adjusted to 4.5 with orthophosphoric acid, at a flow rate of 1.0 mL/min. The detection was done at a wavelength of 203 nm, and galantamine hydrobromide had a retention time of 8.0 minutes. Over the concentration range of 1-10 g/ml, the calibration plot revealed a linear relationship. The accuracy of the proposed method was determined by recovery studies and was found to be near to 100 and % RSD value was found less than 2. The repeatability testing for both standard and sample solutions showed that the method is precise within the acceptable limits. RSD % of the determination of precision was

Background Total gentamicin is a sum of five congeners C1, C1a, C2, C2a and minor C2b, which differ from each other in their methylation on the purpurosamine ring. Liquid chromatography with mass detection (LC-MS/MS) and specified calibration material enables the concentration of total gentamicin and its individual congeners to be analysed. Methods 50 µL serum was precipitated with acetonitrile in the presence of 0.5 mol/L formic acid. A RP BEH C18 1.7 µm 2.1x50 mm column maintained at 30 °C and tobramicin as the internal standard were used. Mass detection was performed in positive electrospray. The gentamicin results were compared with fluorescence polarization immunoassay (FPIA) and chemiluminiscent microparticle immunoassay (CMIA). Passing-Bablock regression analysis and Bland-Altman analysis were used. Results Calibration curves for individual gentamicin congeners were linear with correlation coefficients between 0.997 and 0.998. Recovery was 91.6–102.0% and the coefficients of variation 1.4–8.4%. The total gentamicin concentration was compared with immunoassay FPIA (LC-MSgen = 0.9798xPFIAgen) and CMIA (LC MSgen = 0.9835xCMIAgen) both with significant correlation (p Conclusion The LC-MS/MS method is fast and precise and can be applied to routine TDM in patients. Comparing it to immunoassays makes it possible to measure concentration of gentamicin congeners, which may be important in the case of their different pharmacokinetics.

Octreotide is a synthetic cyclic octapeptide analogue of somatostatin-14. It is mainly administered for the treatment of acromegaly, severe diarrhea, and neuroendocrine neoplasias. In this work, a hydrophilic interaction liquid chromatography (HILIC) method with fluorescence (FL) detection was developed and validated for the quantitation of octreotide in solutions for injection. Chromatographic separation was performed on an XBridge®-HILIC analytical column under isocratic elution with a short chromatographic run time of less than 10 min. The mobile phase consisted of ammonium bicarbonate 8.6 mM (pH 8.1)/acetonitrile 35/65 (v/v). The high sensitivity and selectivity of the fluorescence detection, with the excitation wavelength (λexcitation) set at 280 nm and the emission wavelength set at (λemission) 330 nm, enabled a simple sample preparation procedure that included only dilution steps. The calibration curve showed good linearity with a correlation coefficient greater than 0.998. The method was successfully applied to the analysis of commercially available octreotide injection forms.

Aerosols are a source of great uncertainty in radiative forcing predictions and have poorly understood health impacts. Most aerosol mass is formed in the atmosphere from reactive gas-phase organic precursors, forming secondary organic aerosol (SOA). Semivolatile organic compounds (SVOCs) (effective saturation concentration, C*, of 10−1–103 µg m−3) comprise a large fraction of organic aerosol, while intermediate-volatility organic compounds (IVOCs) (C* of 103–106 µg m−3) and volatile organic compounds (VOCs) (C* ≥ 106 µg m−3) are gas-phase precursors to SOA and ozone. The Comprehensive Thermal Desorption Aerosol Gas Chromatograph (cTAG) is the first single instrument simultaneously quantitative for a broad range of compound-specific VOCs, IVOCs and SVOCs. cTAG is a two-channel instrument which measures concentrations of C5–C16 alkane-equivalent-volatility VOCs and IVOCs on one channel and C14–C32 SVOCs on the other coupled to a single high-resolution time-of-flight mass spectrometer, achieving consistent quantification across 15 orders of magnitude of vapor pressure. cTAG obtains concentrations hourly and gas–particle partitioning for SVOCs every other hour, enabling observation of the evolution of these species through oxidation and partitioning into the particle phase. Online derivatization for the SVOC channel enables detection of more polar and oxidized species. In this work we present design details and data evaluating key parameters of instrument performance such as I/VOC collector design optimization, linearity and reproducibility of calibration curves obtained using a custom liquid evaporation system for I/VOCs and the effect of an ozone removal filter on instrument performance. Example timelines of precursors with secondary products are shown, and analysis of a subset of compounds detectable by cTAG demonstrates some of the analytical possibilities with this instrument.

Background Amine degradation products are very important for industrials not only leads to amine losses but also contribute to operational problems such as high corrosion effects. In this research, a new quantitative method has been developed for the analysis of 2-methylaminoethanol (MAE) and tris(2-hydroxyethylethyl)ethylenediamine (THEED) in the diethanolamine solution by cation-exchange chromatography. Methods The mobile phase was optimized for the interference-free determination of THEED and MAE. For THEED, the final composition was included 8 mmol L−1 HNO3 and 15% (v/v) acetonitrile. The linear range of the calibration curve was achieved in the range of 0.5 to 1000 ppm with the correlation coefficient of 0.9998. The relative standard deviation was 3.89%. Also, the mobile phase was optimized for MAE determination. The optimal composition was 1.45 mmol L−1 of HNO3, 0.15 mmol L−1 of 18-crown-6, and 3.4 mmol L−1 of dipicolinic acid. The mobile phase also was contained 0.75% (v/v) of acetonitrile. Significant Findings The linear range of the calibration curve was from 0.1 to 200 ppm with a correlation coefficient of 0.9999, and the relative standard deviation is 0.46%. Very low detection limits including 0.03 and 0.17 ppm were found for MAE and THEED respectively. Acceptable precisions, below the 3.89%, were accomplished by the method. The proposed method was used for the determination of desired compounds in the real natural gas sweetening solution.

The main focus of this study is to introduce and validate an electromembrane extraction (EME) method along with HPLC–UV analysis to determine theophylline in the plasma and urine. The main parameters affecting the extraction process such as type of supported liquid membrane organic solvent, donor and acceptor pH, extraction time and voltage were examined. Under optimal conditions, theophylline was extracted from the sample solution at pH = 9 to the acceptor solution at pH = 13, and as the extraction driving force, a voltage of 50 V was used for 10 min. Considering the main phenomena in EME, a computational model was used to predict the recovery ratio of EME systems. At this voltage and extraction time, the simulation was performed for various pH of the sample and acceptor solutions. Results revealed that the optimum working condition was computed to be when the sample and acceptor solution pH is around 9.5–10 and, 12.5–13, respectively, which are in acceptable agreement with experimental results. Under these conditions, the calibration curve is linear in the range of 50–500 ng/ml with a relative standard deviation of less than 7.0%. The limit of detection and limit of quantitation were 15 and 50 ng/ml, respectively. The enrichment factor and extraction recovery calculated for this method were 42 and 28%, respectively. The developed method was used for the plasma and urine with relative recovery of 95.1% and 69.2%, respectively. Moreover, the relative standard deviation of the biological samples was 4.4% and 3.9% for the plasma and urine, respectively.

NMR thermometers are a convenient way to determine the temperature inside the sample of an NMR spectrometer. They rely on signals with strongly temperature-dependent chemical shifts, often of OH groups; 99.8% perdeuterated methanol is an established example which is particularly well suited for modern, high-sensitivity spectrometers, but it is so far calibrated only in the range of 282 to 330 K. In this work, we extend this calibration to the entire liquid range of methanol, 175 to 338 K. Additionally, we use a temperature sensor calibrated traceably to the International Temperature Scale (ITS-90) and accounted for the magnetic field effect on the sensor, yielding a more accurate calibration curve with an uncertainty (2σ) varying between 25 and 190 mK.

Water pollution has been one of the major issues of the present time. It is essential to educate students regarding this issue and its possible solutions. In this article, a demonstration of a typical adsorption-based water cleaning process is presented. The removal of methylene blue (MB) and detergent from a aqueous solution is demonstrated using rice husk as the adsorbent. Quantification of the MB removal was achieved with the help of a smartphone-based colorimetry process. This demonstration would be helpful to students for understanding the adsorption process, calibration curves, and waste management. The kinetic study of adsorption will help students learn various kinetic models and their applications.

A possibility of determining antibacterial preparations of the tetracycline series (tetracycline, doxycycline, oxytetracycline, demeclocycline, methacycline and chlortetracycline) in waste water, natural waters, and milk by the sensitized fluorescence of europium on its hydroxide using digital colorimetry (smartphone) is studied. It is found that europium(III) forms complexes with tetracyclines in an alkaline medium, and the formation of the europium hydroxide precipitate does not change its fluorescence properties. The colorimetric parameters of the precipitate after centrifugation are measured using a smartphone. The limits of detection and determination are 0.001–0.004 and 0.005–0.01 µg/mL, respectively, for all analytes. The analytical ranges are 0.005 (0.08)–0.1 (1) µg/mL. The calibration curves are linear, R2 ≥ 0.98. A procedure for determining the total concentration of tetracyclines in waste water, natural waters, and milk is proposed. The duration of analysis is 20–30 min; the relative standard deviation of the results of analysis does not exceed 20%.

The application of sulfur and nitrogen co-doped carbon quantum dot−potassium permanganate chemiluminescence (CL) system for the determination of trace amounts of deltamethrin insecticide was investigated. The results showed that traces of deltamethrin significantly increased the CL of this system in the optimized conditions. This increase was proportional to the concentration of deltamethrin and was used for its determination. We prepared sulfur and nitrogen co-doped carbon quantum dots by hydrothermal method and characterized by fluorescence, X-ray and infrared spectra and transmission electron microscopy. In the optimum analytical conditions, the calibration graph was linear in the range of 1.8 to 20.0 µg/L with a detection limit of 0.3 µg/L. The new tested method has simple set up, high sensitivity and has been successfully applied to the determination of deltamethrin in water samples.

We demonstrate the suitability of a fast, green, easy-to-perform, and modified sample extraction procedure, i.e., dispersive liquid–liquid microextraction (DLLME) for the determination of efavirenz (EFV) in human plasma. Data acquisition was done by gas chromatography–mass spectrometry (GC–MS) in the selected ion monitoring (SIM) mode. The simplicity of the method lies in, among others, the avoidance of the use of large organic solvent volumes as mobile phases and non-volatile buffers that tend to block the plumbing in high-performance liquid chromatography (HPLC). Chromatographic and mass spectral parameters were optimized using bovine whole blood for matrix matching due to insufficient human plasma. Method validation was accomplished using the United States Food and Drug Administration (USFDA) 2018 guidelines. The calibration curve was linear with a dynamic range of 0.10–2.0 μg/mL and an R2 value of 0.9998. The within-run accuracy and precision were both less than 20% at the lower limit of quantification (LLOQ) spike level. The LLOQ was 0.027 μg/mL which compared well with some values but was also orders of magnitude better than others reported in the literature. The percent recovery was 91.5% at the LLOQ spike level. The DLLME technique was applied in human plasma samples from patients who were on treatment with EFV. The human plasma samples gave concentrations of EFV ranging between 0.14–1.00 μg/mL with three samples out of seven showing concentrations that fell within or close to the recommended therapeutic range.

A novel nitrogen-doped carbon quantum dots (N-CDs) were prepared by the microwave irradiation method. The fluorescence quenching effect of Co(II) on the N-CDs was studied in the sodium dodecyl sulfate (SDS) medium and the fluorescence quenching was sensitized in the SDS. The linear range of calibration curve for the determination of Co(II) was 0.17µg/mL-11.8µg/mL and the limit of detection was 0.052µg/mL. The method has been applied for the determination of Co(II) in samples with satisfactory results.

Introduction. Heavy metals are included in one of the significant groups of ecotoxicants. Determining heavy metals at low levels is one of the main problems in analytical chemistry, which depends on various factors. Ignoring the contribution of these factors to the total uncertainty can increase the probability of distortion of the results due to an erroneous decision on the compliance of the obtained data with a particular standard. The most significant influences include the purity of reagents, dishes, and air in laboratory rooms. Purpose of the work. Search for ways of reducing the listed influences provided that the expense of time, material and labour resources are minimized. Materials and methods. In the course of the work, many experiments were carried out, including the analysis of nitric acid for the content of metals before and after cleaning by distillation, the analysis of washes from new fluoroplastic laboratory glassware and glassware that had been cleaned by steaming, an assessment of the effect of air pollution in the laboratory room based on a study of calibration curves, which were constructed at the analysis of standard iron solutions prepared in the Clean Workplace and in a conventional fume hood. All measurements were performed by inductively coupled plasma mass spectrometry on Agilent 7800 ICP-MS mass spectrometer. Results. The efficiency of the proposed methods for eliminating interfering influences on the analysis has been experimentally proved. Conclusion. The technical and analytical problem, which consists of finding optimal conditions for preparation of reagents, glassware cleaning and decreasing the influence of laboratory air pollution, allows to increase reliability of the obtained results and prevent distortion of information about the observed degree of environmental pollution. Contribution: Egorova M.V. — the concept and design of the study, editing, approval of the final version of the article, responsibility for the integrity of all parts of the article; Rodionov A.S. — collection and processing of material, statistical analysis, writing the manuscript, collection of the literature data; Bogdanova Ju.J. — collection and processing of material. Conflict of interest. The authors declare no conflict of interest. Acknowledgment. The study had no sponsorship.