Search

A hollow-fiber liquid-phase microextraction (HF-LPME) method was established for purification and enrichment of glutathione (GSH) in human saliva followed by a miniaturized capillary electrophoresis with amperometric detection system (mini-CE-AD). Based on regulating isoelectric point and increasing salt effect to modify donor phase, HF-LPME could provide high enrichment efficiency for GSH up to 471 times, and the extract was directly injected for mini-CE-AD analysis. The salt-effect enhanced HF-LPME/mini-CE-AD method has been successfully applied to saliva analysis, and acceptable LOD (0.46 ng/mL, S/N = 3) and recoveries (92.7-101.3%) could be obtained in saliva matrix. The sample pretreatment of this developed method was simple and required no derivatization, providing a potential alternative for non-invasive fluid analysis using portable instrument.

Novel open-tubular (OT) columns were prepared for the first time based on zeolite silica nanoparticles (SiO2NPs) as the nano coating materials. The main immobilization factors, including the size and concentration of zeolite SiO2NPs, the content of bovine serum albumin (BSA), heat temperature and time, were investigated to obtain OT columns with good stability and repeatability. Then, the separation performance of the prepared OT columns with/without BSA modifier was explored using capillary electrochromatography with an amperometric detection system. Under the optimum conditions, eight groups of model molecules, including homologues, structural isomers, epimers and enantiomers, underwent baseline separation in the prepared OT columns. The zeolite SiO2NPs-OT columns provided an efficiency of up to 108 200 plates m−1 for 4-chloro-2-methylaniline, and the OT column modified with BSA accomplished the separation and analysis of ephedrine and pseudoephedrine in ephedra herbs. The relative standard deviations of the migration time, peak area and resolution of the selected model analytes were within 8.4% for run-to-run, day-to-day, and column-to-column repeatability. Furthermore, the prepared OT columns could provide acceptable separation performance in a simple running buffer without any organic additives or surfactants, indicating their promising potential for isomer separation.

A novel kind of chiral open-tubular (OT) column was established with homochiral zeolitic imidazolate framework-8 nanomaterials using L-histidine as the chiral carbon center (L-His-ZIF-8). The morphologies of L-His-ZIF-8 nanoparticles and chiral OT column were characterized by scanning electron microscopy. The effects of L-His-ZIF-8 concentrations, pH values, and concentrations of the running buffer on the resolution of the selected chiral compounds were investigated based on miniaturized capillary electrochromatography with amperometric detection system (mini-CEC-AD), respectively. The separation performances of the prepared L-His-ZIF-8@OT chiral columns were explored under the optimal conditions, and the RSDs of run-to-run, day-to-day, and column-to-column reproducibility were less than 6.7% using salbutamol raceme as the model enantiomers. The prepared chiral OT columns have been successfully applied to the enantioseparation of one pair of amino acid enantiomers, two pairs of racemic drugs, and three pairs of neurotransmitter enantiomers. Under the optimum conditions, the prepared OT columns were applied to real-world sample analysis of salbutamol aerosol. The limits of detection of salbutamol raceme were 0.90 μg·mL-1 (S/N = 3), and the recovery was 80.4-82.7%. The assay results indicated that this kind of chiral OT column modified with homochiral L-His-ZIF-8 possesses good reproducibility and stability. This developed mini-OT-CEC-AD system has some attractive characteristics of sensitivity and low cost, providing a potential way for the separation of chiral compounds.

In this work, novel stationary phase coatings by zeolite SiO2NPs coupled with β-cyclodextrin (β-CD) or β-CD/L-phenylalanine were developed for chiral open-tubular capillary electrochromatography (OT-CEC). The OT columns were prepared taking advantage of the strong adhesion of polydopamine in one-step method. Scanning electron micrography and electroosmotic flow were used to characterize the prepared single/dual-selector OT columns. Chiral separation of four chiral analytes (catechin/epicatechin, ephedrine/pseudoephedrine, ritodrine and salbutamol) was carried out in order to evaluate the performance of the prepared columns in OT-CEC with amperometric detection system. In terms of migration time, peak area, resolution, and selectivity factor of catechin/epicatechin and salbutamol, the run-to-run, day-to-day, and column-to-column repeatability were within 8.9%. Under the optimum conditions, the developed methods were applied for the analyses of Chinese herbal medicine Catechu herbs and salbutamol aerosol samples.

In this work, a class of novel and eco-friendly open-tubular (OT) chiral column was presented for the first time by one step preparation with zeolite imidazolate framework-8 (ZIF-8) and bovine serum album (BSA) based on electrostatic adsorption and adsorption affinity. This stationary phase materials combined the features of large surface areas and adsorption affinity of ZIF-8, and also the multiple chiral binding sites of BSA, which contributes to the π-interaction and hydrophobic interaction with the analytes. The separation performance of BSA@ZIF-8-OT chiral columns was evaluated with a miniaturized capillary electrochromatography and amperometric detection (mini-CEC-AD) system; in particular, nine groups of model molecules, including homologues, structural isomers, and chiral compounds, were baseline separated under the certain optimum conditions. The RSDs of run-to-run, day-to-day, column-to-column, and batch-to-batch reproducibility were less than 13.8 %. Furthermore, the prepared OT columns were successfully applied to fast analysis of ephedrine isomers in Chinese herb ephedra, and the LODs achieved 1.5-2.0 ng mL-1 (S/N=3) by an electrophoretic stacking technique of moving chemical reaction boundary. This mini-CEC-AD system with BSA@ZIF-8-OT chiral columns provides a promising potential in pharmaceutical analysis due to its fast, sensitive, enantioselective, and low-cost characteristics.

The whole grain intake is closely associated with human health. In this work, three-phase dynamic hollow-fiber liquid-phase microextraction reinforced with 0.10 mg/mL 30 nm zeolitic imidazolate framework-8 nanoparticles was introduced for purification and enrichment of free urinary metabolite biomarkers of whole grain intake. Eight milliliters of HCl (pH 3.00) and 8 μL of 300 mM NaOH solutions were used as the donor and acceptor phases, respectively. The temperature and stirring rate were kept at 25℃ and 500 rpm, and the extraction time was 40 min. The extraction process required no further desorption, and the resultant extract was directly used for electrophoretic analysis without derivatization. Based on the synergistic effect of hollow-fiber liquid-phase microextraction and the electrophoretic stacking, the enrichment factors of 3,5-dihydroxybenzoic acid and 3-(3,5-dihydroxyphenyl)-1-propionic acid reached 1018-1034 times, and their limits of detection achieved 0.33-0.67 ng/mL (S/N = 3) in urine matrix. The developed method has been successfully used for urine analysis, and the sample recovery data were in the range of 97.0-103.5%. This developed method provided an attractive alternative for the determination of urinary metabolite biomarkers of whole grain intake due to its sensitive, fast, low-cost, and environmental-friendly features.

A novel capillary electrophoresis with laser-induced fluorescence detection method has been developed for the analysis of aldehyde metabolism biomarkers for oxidative stress in exhaled breath condensate (EBC), and fluorescein 5-thiosemicarbazide was used as a derivatization reagent. In a simple capillary zone electrophoresis mode, ten low molecular weight aldehydes (LMWAs) could be well separated within 30 min. The reaction efficiency was doubled by increasing sample solution pH and magnetic stirring, and the LODs of this method reached 0.16-3.4 nM (S/N = 3). Acceptable recoveries (82.1-115%) were obtained for EBC samples, and the RSD data were within 7.9%. This developed method has been applied for the analyses of EBC samples and evaluation of the correlation between smoking and the contents of aldehyde metabolites in EBC. Due to no need of buffer additives and sample preconcentration, this proposed method may provide an appealing alternative for the trace analyses of LMWAs in noninvasive biofluids. Graphical abstract ᅟ.

A tributyl phosphate assisted hollow-fiber liquid-phase microextraction coupled with capillary electrophoresis-contactless coupled conductivity detection (HF-LPME/CE-C4D) method has been developed for trace analysis of common short-chain fatty acids (SCFAs) without derivatization. Under the optimum conditions, ten SCFAs including a pair of isomers were well separated from their homologous FAs and the main coexisting inorganic anions within 40 min. Tributyl phosphate assisted HF-LPME produced excellent purification and enrichment for the model sample with high-salt matrix, microbial degradation fluid, and the limits of detection could reach 0.072–0.67 ng/mL (S/N = 3). Owing to its high sensitivity, good linearity, and acceptable recovery, this proposed method provided a sensitive and environment-friendly alternative for trace analysis of SCFAs in complicated samples.

The primary clinical diagnosis of Alzheimer’s disease is mainly based on medical history and neuropsychiatric inventory. It is urgent to seek biological indicators with better sensitivity and higher specificity to clinically diagnose and evaluate Alzheimer’s disease. In this work, an electrophoretic method based on 2-thiobarbituric acid derivatization and amperometric detection was developed to determine formaldehyde as a urinary biomarker of Alzheimer’s disease. Under the optimum conditions, the formaldehyde derivative was well separated from the coexisting interferences in urine sample. The limit of detection for formaldehyde was 80.0 nM (2.4 ng/ mL) based on an electrophoretic stacking technology. The average recovery values were in the range of 91.7–110%, and the relative standard deviation values were less than 4.1%. This method has been applied to analyze human urine samples from healthy volunteers and patients with different degrees of Alzheimer’s disease. The assay results showed that the ...

Synergistic stacking technique by combining field-amplified sample injection with moving chemical reaction boundary was developed for the sensitive determination of two major sialic acids, N-acetylneuraminic acid (NANA) and N-glycolylneuraminic acid (NGNA) based on capillary electrophoresis with capacitively coupled contactless conductivity detection. A series of experimental parameters affecting electrophoretic separation, detection sensitivity, and hydrolysis efficiency of sialic acids were investigated. Under the optimum conditions, NANA and NGNA could be well separated from the common monosaccharides and disaccharides as well as other potential coexisting inorganic and organic anions in a running buffer of 30 mmol L−1 NaOH–10 mmol L−1 Na2HPO4/0.8 mmol L−1 CTAB. This developed method has been applied to determine the target analytes in dairy products. In terms of its high sensitivity (LODs 1.7–2.2 ng mL−1, namely, 5.5–7.2 nmol L−1), good linearity (r > 0.999), acceptable recovery (93–107%), and reliability of acid hydrolysis step, this proposed method provides a simple, rapid, sensitive, and environmentally friendly alternative for the analyses of the main sialic acids in dairy products without derivatization.

Low-molecular-weight thiols are widely present in human fluids, and are regarded as a kind of potential broad-spectrum evaluation indicators for some clinical diseases. In this work, gold nanoparticles capped with Tween 20 were used for purification and microextraction of the main free thiols (cysteine, homocysteine, glutathione and methionine) in saliva based on Au-S bond formation. Ultrasound further sped up the releasing of the target analytes, and the releasing time needed was only 10 min, and the required sample volume was only 40 µL. The desorption solution could be directly injected for electrophoretic analysis without derivatization, and field-amplified sample stacking of electrophoretic online enrichment technology further improved the detection sensitivity. The synergistic enrichment effect made the enrichment factors of four analytes reach 1119–2067 times. This developed method was applied for the analyses of saliva samples of healthy volunteers. Acceptable sensitivity (LODs: 0.15–1.5 ng mL−1) and recoveries (97.6–116%) were obtained in the saliva sample matrix. This proposed method provides an alternative for the sensitive detection of low-molecular-weight thiols in noninvasive body fluids, which has potential application prospect in the preliminary noninvasive diagnosis of diabetes, cardiovascular diseases, etc.

Ethane-1,2-diamine (EA) and hexane-1,6-diamine (HA) are two important plastic restricted substances commonly existing in food contact materials. A capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C 4 D) method has been developed for direct determination of above analytes, and the detection sensitivity has been significantly improved based on electromembrane extraction (EME). Under the optimum conditions, EA and HA could be well separated from their aliphatic diamine homologs as well as the common inorganic cations within 25 min. The limits of detection could reach sub-ng/mL level, and good linearity ( r > 0.998) between peak area and analyte concentration could be obtained at three orders of magnitude. This EME/CE-C 4 D method provided a novel application for determining these plastic restricted substances in different bottled soft drinks, providing an alternative for the sensitive analyses of diamine substances.

Background Cyromazine (CYR) and its main degradation product melamine (MEL) are attracting wide attention due to their potential hazards to the environment and humans. In this work, double surfactants-assisted electromembrane extraction (DS-EME) by Tween 20 and alkylated phosphate was firstly used for purification and extraction of CYR and MEL, and the extract was directly analyzed by capillary electrophoresis with capacitively coupled contactless conductivity detection. Results Under the optimum conditions, two targets could be well separated from the main interferences, including common biogenic amines and inorganic cations within 14 min. This developed method was successfully applied to the analyses of surface water, soil and cucumber samples, and the average recoveries were in the range 93.3-112%. DS-EME provided a synergistic purification and enrichment effect for CYR and MEL by adding Tween 20 and alkylated phosphate into donor phase and supporting liquid membrane, respectively. Satisfactory limits of detection [0.2-1.5 ng mL-1 , signal-to-noise ratio (S/N) = 3] could be obtained in the tested sample matrices, and the corresponding enrichment factors were up to 115∼123 times. Conclusion This developed method provides an alternative for the simultaneous analysis of CYR and MEL in complex real-world samples. © 2019 Society of Chemical Industry.

Due to their important biological role as markers for different pathologies, sialic acid (SA) analyses are important for clinical research. In this work, a miniaturized capillary electrophoresis with amperometric detection (mini-CE-AD) was developed for the determination of N-acetylneuraminic acid (NANA), which is the most widespread form of SAs. NANA was first oxidized by periodic acid in an acidic solution, and then the oxidation product β-formyl pyruvic acid was derivatized with electroactive 2-thiobarbituric acid (TBA) to form an electroactive NANA-TBA adduct, which could be readily determined by mini-CE-AD. The limit of detection (LOD) of NANA-TBA could achieve 0.50 µg/mL (1.6 µmol·L−1, S/N=3) based on an online enrichment approach of moving chemical reaction boundary. The proposed method was successfully applied to the analysis of NANA in human saliva, and the recoveries were in the range of 91.8% –109% with RSDs of 1.8% –3.9%. Due to its simple design and construction, low cost and portability, the mini-CE-AD device will possess more practicability in more field work as an alternative to conventional and microchip CE approaches.

A CE combined with amperometric detection method has been developed for simultaneous determination of nine environmental endocrine disruptors, including bisphenol A, methylparaben, ethylparaben, propylparaben, 4-tert-butylphenol, diethylstilbestrol, 17α-ethinylestradiol, β-estradiol and estriol. In this work, various experimental parameters affecting enrichment factors, electrophoretic separation and detection were investigated in detail. And poly(sodium 4-styrenesulfonate) was selected as the buffer modifier, resulting in considerable improvement of the resolution of the target analytes. Under the optimum conditions, nine analytes could be well separated within 30 min in a 10 g/L poly(sodium 4-styrenesulfonate) modified 60 mmol/L Na2B4O7–H3BO3 buffer (pH 7.60). For each analyte good linear correlation between electrochemical response and its concentration at two or three grades was obtained, the method detection limits reached 0.047–13 ng/mL (S/N = 3) with the assistance of hollow-fiber liquid-phase microextraction, and the highest enrichment factor was up to 255-fold. This proposed method has been applied for the direct analyses of real environmental water and tap water samples without need of derivatization, the average recoveries were in the range of 81.4–117 %, and the corresponding relative standard deviations were lower than 6.2 %.

A capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of inorganic metabolites (thiocyanate, nitrite and nitrate) in human saliva. Field amplified sample injection, as a simple sample stacking technique, was used in conjunction for online preconcentration of above inorganic anions. A selective separation for the target anions from other coexisting constituents present in saliva could be obtained within 14min in a 10mmol/L His-90mmol/L HAc buffer (pH 3.70) at the separation voltage of -18kV. The limits of detection and limits of quantification of the three analytes were within the range of 3.1-4.9ng/mL (S/N=3) and 10-16ng/mL (S/N=10), respectively. The average recovery data were in the range of 81-108% at three different concentrations. This method provides a simple, rapid and direct approach for metabolite analyses of nitric oxide and cyanide based on noninvasive saliva sample, which presents a potential fast screening tool for clinical test.

In this work, citrate-capped gold-nanoparticles (citrate-AuNPs) have been firstly used for selective extraction of trace polyamines, putrescine (Put) and cadaverine (Cad), followed by field-amplified sample stacking (FASS) coupled with capillary electrophoresis and capacitively coupled contactless conductivity detection (FASS-CE-C4D). Put and Cad were extracted by electrostatic attractions between the amine group of the polyamines and the citrate ligands adsorbed on the surfaces of AuNPs. AuNPs microextraction (AuNPs-ME) effectively shortened preparation time (50 min) by introducing ultrasound, and the required sample extraction volume was only 1 mL. Furthermore, a synergistic enrichment strategy based on off-line AuNPs-ME and on-line FASS significantly improved the detection sensitivity, making the enrichment factors up to 1726–1887 times. Under the optimum conditions, Put and Cad could be well separated from the potential coexisting substances and then directly determined by CE-C4D without derivatization. Due to its low sample consumption, high sensitivity (LODs: 0.070–0.17 ng mL−1), and acceptable recoveries (90–105%), this AuNPs-ME/FASS-CE-C4D method provides a rapid, economical and eco-friendly approach for direct determination of polyamines in human exhaled breath condensate, and has potential application prospects in preliminary noninvasive diagnosis of oral and respiratory inflammation.

An environmentally friendly method for the trace analysis of four aliphatic aldehydes as water disinfection byproducts has been developed based on hollow-fiber liquid-phase microextraction followed by miniature capillary electrophoresis with amperometric detection. After derivatization with 2-thiobarbituric acid, four aliphatic aldehydes (formaldehyde, acetaldehyde, propylaldehyde, and butyraldehyde) became detectable by the amperometric detector. Under the optimum conditions, four aliphatic aldehydes can be well separated from the coexisting interferents as well as their homologs (pentanal, glyoxal, and methyl-glyoxal), and the limits of detection (S/N = 3) could reach sub-nanogram-per-milliliter level based on hollow-fiber liquid-phase microextraction. The proposed method has been applied for the analyses of above four aliphatic aldehydes in different water samples such as drinking water, tap water, and river water, and the average recoveries were in the range of 90-113%, providing an alternative to conventional and microchip capillary electrophoresis approaches.

Electromembrane extraction (EME) as a novel sample preparation technique was firstly applied for the purification and enrichment of bromate (BrO3 −) in drinking water prior to capillary zone electrophoresis with capacitively coupled contactless conductivity detection (CZE-C4D). BrO3 −, as the primary disinfection by-product of ozonation, could be well separated with the major inorganic anions coexisting in water samples using a 300 mmol L−1 acetic acid solution as the running buffer. Under the optimum conditions, the calibration curve showed good linearity (r 2 = 0.996), and the limit of detection was down to 0.12 ng mL−1 with the enrichment factor at 267. The relative standard deviation (RSD) values for peak area and migration time at a spiked concentration of 10 ng mL−1 of bromate were below 8.8 and 2.5 %, respectively. This proposed EME-CZE-C4D method has been successfully applied to analyze bottled drinking water and tap water samples with recoveries in the range of 85~98 %, providing an alternative to the determination of bromate in drinking water.

A method for sensitive determination of five priority haloacetic acids in drinking water has been developed for the first time based on electromembrane extraction (EME) prior to CZE with capacitively coupled contactless conductivity detection (CZE-C4D). The target analytes were extracted from 10 mL of the sample solution (donor phase), through the supported liquid membrane (using a polypropylene membrane supporting 1-octanol), and into 10 µL of 50 mmol/L NaAc solution (acceptor phase). The extracted solution was directly analyzed by CZE-C4D without derivatization. Several factors that affect separation, detection and extraction efficiency were investigated. Under the optimum conditions, five haloacetic acids (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid) could be well separated from other components coexisting in water samples within 23 min, exhibiting a linear calibration over two orders of magnitude (r⪖0.9943); the enrichment factors at 430–671 were obtained in a 30 min of extraction, and the limits of detection were in the range of 0.17–0.61 ng/mL. The intraday relative standard deviations for peak areas investigated at 10 ng/mL were between 1.2% and 9.7% for the combined EME-CZE-C4D procedure. This approach offers an attractive alternative to the officially proposed method for purified drinking water analysis, which requires derivatization procedure prior to gas chromatography analysis.

A hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the purification and preconcentration of biogenic polyamines and their precursor amino acids in human saliva. Putrescine (Put), cadaverine (Cad), spermidine (Spe), ornithine (Orn), lysine (Lys), and arginine (Arg) were determined by the CE-LIF detection after microextraction. Several factors that affect extraction efficiency, separation, and detection were investigated. Under the optimum conditions, six analytes could achieve baseline separation within 30 min, exhibiting a linear calibration at three orders of magnitude ( r 2 > 0.998); the obtained enrichment factors of HF-LPME were between 19 (for Orn) and 218 (for Cad), and the LODs were in the range of 0.0072–0.26 nmol/L. The proposed HF-LPME/CE-LIF method has been successfully applied for the sensitive analyses of the real-world saliva samples collected from healthy volunteers and different patients with oral diseases, providing a potential method for primary non-invasive diagnosis of some oral diseases.

The objective of this work was to develop a high-performance capillary electrophoresis with amperometric detection (CE-AD) method for the determination of pharmacologically active ingredients in extracts of Valeriana medicinal plants. The method was validated for linearity, repeatability, limits of detection (LODs) and limits of quantification (LOQs), etc. The LODs and LOQs of eight compounds were found to be in the range from 1.0 × 10−8 to 1.2 × 10−7 and 3.3 × 10−8 to 4.0 × 10−7 g/mL, respectively. The proposed method was successfully applied for the analyses and comparison of bioactive components in Valeriana samples after a relatively simple extraction procedure, and the resultant “electrochemical profiles” can intuitively demonstrate the content diversity of each electrochemically active ingredient in Valeriana samples from different places and plant parts. It was found the content of bioactive ingredients may vary by an order of magnitude depending on natural conditions, e.g. soil, climate, humidity etc.

A hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the preconcentration of trace sulfonamides in water samples. Six commonly used sulfonamides including sulfamethazine (SMZ), sulfamerazine (SMR), sulfadiazine (SDZ), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and sulfathiazole (STZ) were determined by CE with electrochemical detection (CE-ED) after microextraction. Several factors that affect extraction efficiency, separation, and detection were investigated. Under the optimum conditions, above sulfonamide compounds could achieve baseline separation within 35min, exhibiting a linear calibration over three orders of magnitude (r(2)≥0.998); the obtained enrichment factors were between 121 (for SDZ) and 996 (for SDM), and the LODs were in the range of 0.033-0.44ng/mL. The proposed HF-LPME/CE-ED method has been applied for the sensitive analyses of the real-world water samples with recoveries in the range of 75.1-109%.

A novel method has been developed for simultaneous determination of eight typical biogenic amines (BAs) based on CZE with capacitively coupled contactless conductivity detection (CZE–C4D). On-column C4D was used for direct quantification of these nonUV-absorbing amine compounds without derivatization. The effects of various experimental factors on separation and detection were investigated. Under the optimum conditions, spermine, spermidine, histamine, putrescine, cadaver, β-phenylethylamine, tyramine, and tryptamine can be well separated within 24 min at the separation voltage of 16 kV in 150 mmol L−1 18-crown-6/500 mmol L−1 acetic acid running buffer, and the excitation voltage and frequency of C4D were 60 V and 550 kHz, respectively. A good linear relationship could be obtained between the peak area and the concentration of each BA at three orders of magnitude; the limits of detection were in the range of 44.3–149 ng mL−1. This proposed method has been successfully applied for the analysis of BAs in water and hard liquor samples.

A novel miniaturized CE with amperometric detection (mini-CE-AD) method has been developed for fast determination of aliphatic aldehyde preservatives, namely formaldehyde and glyoxal, in commodities. After derivatization with an electroactive compound 2-thiobarbituric acid, these two nonelectroactive aldehydes were converted to electroactive adducts, therefore detectable by mini-CE-AD approach. Under the optimum conditions, two aldehydes can be well-separated with the coexisting interferents as well as their homologs (acetaldehyde and methyl-glyoxal), and the LODs (S/N = 3) were achieved at nanogram-per-milliliter level (1.64-2.80 ng/mL) based on the online enrichment method of transient moving chemical reaction boundary. The proposed method has been applied for the analyses of above aldehyde preservatives in different real commodity samples including skincare products, baby lotion, and toothpaste, and the average recoveries were in the range of 94-105%, which should find a wide range of analytical applications as an alternative to conventional and microchip CE approaches.

An electrophoretic method was developed for the determination of several important catecholamine markers, namely norepinephrine, epinephrine, dopamine, metanephrine, vanillylmandelic acid and homovanillic acid in urine samples. Under the optimum conditions, the six marker compounds could be well separated with the major coexisting interference compound uric acid within 24 min at a separation voltage of 16 kV in a borate running buffer(80 mmol/L, pH=9.48). Highly linear response can be obtained over three orders of magnitude for the above markers with the low limits of detection ranging from 1.0 ng/mL to 5.0 ng/mL(S/N=3). The proposed capillary electrophoresis with amperometric detection(CE-AD) method has been used to simultaneously determine the six catecholamine markers in urine samples of healthy volunteers and patients suffering from different diseases avoiding redundant measurements and high assay cost; and the electrochemical profiles can suggest more diagnostic information of multiple diseases, which provides a promising and convenient entry into primary diagnoses of several clinical diseases.

Newborn screening in urine is important for the diagnosis of many inborn errors of metabolism (IEM). Capillary electrophoresis with laser-induced fluorescence detection (CE–LIF) is a major technological advance in screening IEM. It has the advantage of sensitive and simultaneous multiple disease screening with minimal sample requirement. The analytes were derivatized with fluorescein isothiocyanate (FITC) prior to CE–LIF analysis. In urine samples, free amino acids (AAs) were well separated from other coexisting components, exhibiting a linear calibration over the concentration range 0.01–5.0 μmol/L with the limits of detection (LODs) ranging from 0.005 to 0.010 μmol/L. The relative standard deviations (RSDs) were in the range 0.1–1.0% for peak area, and 0.2–1.0% for migration time, respectively. Under optimized conditions, the method presented here has been successfully used for the simultaneous and sensitive analysis of seven AAs in urine samples of newborn babies, and evaluating the effect of therapy as well.

A novel method for fast determination of ethylendiamine (EDA) in Aminophylline Tablets has been developed by small-sized capillary electrophoresis with amperometric detection (small-CE-AD) coupled with field-amplified sample injection (FASI). Under the optimum conditions, EDA and four aliphatic diamine homologs (1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane and 1,6-diaminohexane) could be well separated within 6 min at a separation voltage of 2.0 kV in an acetate buffer solution of pH 3.8 with low limit of detection (LOD) of 1.3×10−11 g/mL for EDA (S/N=3). The proposed method has been successfully applied to direct determination of EDA content in different batches of Aminophylline Tablets. The method does not require off-line preconcentration and derivatization steps, which should find wide application fields including pharmaceuticals as an alternative to conventional and microchip CE approaches.

A hollow fiber-based liquid-phase microextraction method has been developed for enrichment of trace chloroanilines in water samples. Target analytes including aniline, three mono-chlorinated aniline isomers (o-chloroaniline, m-chloroaniline, and p-chloroaniline) and four mono-chlorinated methylaniline isomers (2-chloro-4-methylaniline, 3-chloro-4-methylaniline, 4-chloro-2-methylaniline, and 5-chloro-2-methylaniline) were determined by CE with amperometric detection after microextraction. Several factors that affect separation, detection, and extraction efficiency were investigated. Under the optimum conditions, eight aniline compounds could be well separated from other components coexisting in water samples within 25 min, exhibiting a linear calibration over three orders of magnitude (r > 0.998); the obtained enrichment factors were between 51 and 239, and the LODs were in the range of 0.01-0.1 ng/mL. The proposed method has been applied for the analyses of real environmental water and sewage samples with relative recoveries in the range of 83-108%.

We report on a method for the determination of the biogenic amines (BAs) spermine, spermidine, histamine, cadaverine, β-phenylethylamine, tyramine and tryptamine. It is based on capillary zone electrophoresis in the presence of 18-crown-6 (180 mM), and is making use of amperometric detection. Under optimized conditions, seven BAs could be well separated within 29 min at a separation voltage of 14 kV in a buffer solution of pH 3.6. The limits of detection for seven BAs are around 10 ng.mL−1 for standard mixtures. The method does not require preconcentration and derivatization steps, and thus provides an attractive alternative to quantitative multi-analysis of BAs in water samples.

A sensitive and low-cost analytical method has been developed to determine 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-nitroguanine (8-NO(2)Gua) based on capillary electrophoresis with amperometric detection (CE-AD) after solid phase extraction (SPE). Under optimized condition, these two markers were well separated from other components coexisting in urine, exhibiting a linear calibration over the concentration range of 0.1-50.0 μg/mL with the detection limits ranging from 0.02 to 0.06 μg/mL. The relative standard deviations (RSDs) were in the range of 0.1-2.1% for peak area, 0.1-1.5% for migration time, respectively. The average recovery and RSD were within the range of 100.0-108.0% and 0.1-1.7%, respectively. It was found that the urinary contents of 8-OHdG and 8-NO(2)Gua in cancer patients were significantly higher than those in healthy ones.

A novel miniaturised capillary electrophoresis with electrochemical detection (mini-CE-ED) method has been developed for fast determination of formaldehyde (FA) and acetaldehyde (AA) in several food products without preconcentration. Because FA and AA usually exist as uncharged molecules with zero electrophoretic mobility, plus the fact that these two compounds lack of chromophore for sensitive ultraviolet (UV) detection, effective and sensitive determination of FA and AA in real samples is often a challenging task. In this work, an electroactive compound 2-thiobarbituric acid (TBA) was selected as the ideal derivatisation reagent to facilitate the electrochemical determination of FA and AA. Under the optimum conditions, FA-TBA and AA-TBA adducts can be well separated by mini-CE-ED with low detection limit of 9.10 × 10 −9 g/mL (13.2 fg) for FA (S/N = 3). The proposed method should find a wide range of analytical applications in food products as an alternative to conventional and microchip CE approaches.

An indirect high-performance capillary electrophoresis with amperometric detection (CE-AD) method has been developed for determination of lactic acid (LA) in body fluids of lactating postpartum women. Several important factors such as the running buffer additive and concentration, the working electrode potential, the pH value and concentration of the running buffer, the separation voltage and injection time were investigated. Under the optimum conditions, LA could be well separated with co-existing interferences including uric acid (UA) in real samples in a 90-cm-length capillary at separation voltage of 12 kV in 4.0 × 10−6 g mL−1 3,4-dihydroxybenzylamine (DHBA)/40 mmol L−1 H3BO3–Na2B4O7 buffer (pH 7.8). The linearity between peak current and concentration of LA was over three orders of magnitude with detection limit of 5.00 × 10−7 g mL−1 (S/N = 3). This proposed method has been successfully used to study the effects of moderate exercise on LA content in breast milk and urine samples of lactating postpartum women, and assay results showed that LA content in breast milk can return to normal level through 60 min rest without decreasing acceptance by breast-feeding infants, although the LA level did increase by 4–6 times in both breast milk and urine samples at 10 min after moderate exercise.

The urinary metabolic marker compounds, namely phenylpyruvic acid (PPA), 2-hydroxyphenylacetic acid (oOPAA), 4-hydroxyphenylacetic acid (pOPAA), phenyllactic acid (PLA) and phenylacetic acid (PAA) of phenylketonuric individuals were detected by a novel method of micellar electrokinetic capillary chromatography with capacitively coupled contactless conductivity detection and amperometric detection (MECC-C 4 D/AD). Electrophoretic runs were performed in a 35 mmol L −1 SDS/60 mmol L −1 H 3 BO 3 –Na 2 B 4 O 7 running buffer (pH 8.2) at a separation voltage of 16 kV, and five marker compounds and the major coexisting compound uric acid (UA) could be well separated within 23 min. Highly linear response was obtained for five marker compounds over three orders of magnitude with detection limits ranging from 6.6 × 10 −6 to 6.4 × 10 −8 g mL −1 (S/N = 3). The proposed method has been used to detect the marker compounds simultaneously in urine samples with the advantages of obtaining more information about target analytes and avoiding redundant measurements and high assay cost. Urinary patterns in phenylketonuric babies were distinct and easily distinguished from those of healthy newborns. The proposed MECC-C 4 D/AD method could find clinical application in early noninvasive diagnosis of phenylketonuria (PKU), as significant differences could be found in the urinary content of five marker compounds among the phenylketonuric babies without or with dietotherapy and the healthy babies.

A high-performance capillary zone electrophoresis with amperometric detection (CZE-AD) method has been developed for the separation and sensitive determination of the preservatives methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in soy sauce samples. The effects of several factors such as the pH and concentration of running buffer, the separation voltage, the applied potential and the injection time on CZE-AD were investigated. Under the optimum conditions, four preservatives can be well separated within 16 min at the separation voltage of 16 kV in a 80 mmol/L borax running buffer (pH 9.94), and adequate extraction was obtained with ethanol for the determination of the above four parabens. Satisfactory recovery (95.0–102.0%), repeatability of the peak current (≤2.4%) and migration time (≤0.5%) of four analytes, as well as detection limits (5.7 × 10−8–4.4 × 10−8 g/mL) for the method, were achieved. This proposed procedure has been successfully used for the analysis of paraben preservatives in soy sauce samples, and the content of EP was from 0.08 to 0.14 mg/mL in the tested samples.

Numerous disinfection products are widely used in daily life to kill pathogenic microorganisms. However, most disinfectants are organic compounds that might be hazardous to the environment and humans when used excessively. Phenolic disinfectants in disinfection products are investigated using a high-performance capillary electrophoresis-amperometric detection method. Under the optimum conditions, five commonly used disinfectants can be well-separated within 19 min at the separation voltage of 18 kV in a 80 mmol/L borax running buffer (pH 9.2), and adequate extraction was obtained with ethanol for the determination of the five compounds. Satisfactory recovery (93.5-106.0%), intra-day repeatability of the peak current (< 2.9%), and detection limits (1.6 × 10 -7 - 3.8 x 10 -8 g/ml) for the method are achieved. This proposed procedure is successfully used to analyze different samples of disinfection products.

Two non-electroactive biomarkers methylglyoxal (MGo) and glyoxal (Go) in urine and environmental water samples were determined for the first time by capillary electrophoresis with amperometric detection (CE-AD) after derivatizing with an electroactive compound 2-thiobarbituric acid. Experimental conditions of derivatization and CE-AD detection were optimized. Highly linear response was obtained for these two biomarkers over three orders of magnitude with good correlation (r(2)>0.999). The limits of detection (LODs) and limits of quantitation (LOQs) of MGo and Go were 0.2microgL(-1) and 1.0microgL(-1), 0.5microgL(-1) and 2.0microgL(-1), respectively. The average recovery and relative standard deviation (RSD) were within the range of 90.9-101.3% and 0.7-2.2%, respectively. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation of MGo and Go in real sample matrices by employing relatively simple and inexpensive instrument.

A high-performance micellar electrokinetic capillary chromatography with amperometric detection (MECC–AD) method for the fast determination of melamine (MM), occasionally used to increase the apparent protein content of milk products, has been developed. Method development involved optimisation of the working electrode, the running buffer system and acidity, the concentration of sodium dodecyl sulphate (SDS), the separation voltage, the applied potential and the sample injection time. Under the optimum conditions, MM can be well separated from its co-existing interferences in real-world samples within 9 min at the separation voltage of 20 kV in a 8 mmol/L SDS/20 mmol/L H 3 BO 3 –Na 2 B 4 O 7 running buffer (pH 7.4). Satisfactory recovery (83.3–105.5%), repeatability of the peak current (3.2%) and migration time (3.8%), and the limit of detection (2.1 × 10 −6 g/mL) for the method were achieved. This proposed procedure has been successfully used for the determination of MM in milk products.

A micellar electrokinetic capillary chromatography method with electrochemical detection (MECC-ED) has been developed for the simultaneous determination of eight phenolic additives, including propyl gallate (PG), tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) in cosmetic products. Method development involved optimization of the working electrode, the pH value of running buffer, the concentration of sodium dodecyl sulfate (SDS), the separation voltage, and the sample injection time. Under the optimum conditions, all analytes can be well separated within 26 min at the separation voltage of 18 kV in a 9 mmol·L−1 sodium dodecyl sulfate (SDS) −60 mmol·L−1 borate running buffer (pH 8.0). A 300 μm diameter carbon disk electrode generated good response at +0.90 V (vs. SCE) for all analytes. Linearity of the present method was over three orders of magnitude of analyte concentration with detection limits (S/N=3) ranging from 1.1×10−7 to 1.2×10−6 g·mL−1 for all analytes. This proposed method has been successfully applied to the simultaneous determination of the above additives in commercial cosmetics, and the assay results were satisfactory.

BACKGROUND: The objective of this study was to adapt and improve previously published analysis methods aimed at the simultaneous determination of sulfonamide residues in edible animal tissues by capillary zone electrophoresis with electrochemical detection. RESULTS: The effects of several factors such as the acidity and concentration of running buffer, the separation voltage, the applied potential and the injection time on CZE-ED were investigated. Complete separation of six sulfonamides was achieved within 17 min by using 40 mmol L−1 Na2B4O7/25 mmol L−1 KH2PO4 (pH 6.2) at an applied voltage of 18 kV. Excellent linearity was obtained over two orders of magnitude with the improved detection limits (S/N = 3) ranged from 1.7 × 10−7 to 4.4 × 10−9 g mL−1 for all six sulfonamides in comparison with previous reports. A solvent extraction/centrifuge/evaporation procedure was used to extract sulfonamides from animal tissues, sample clean-up and pre-concentration of sulfonamides prior to CZE-ED analysis. Good recoveries from 81% to 92% were achieved. CONCLUSION: Results obtained in this work indicated that the proposed CZE-ED method was sensitive, rapid and simple for the simultaneous determination of sulfonamides in edible animal tissues. Therefore, the new faster and easy handling procedure provides an additional powerful tool that can be employed for the analysis of sulfonamide residues in foodstuff. Copyright © 2009 Society of Chemical Industry

Valeriana officinalis var. latifolia is a common medicinal and fragrant plant in China. The plant’s essential oil plays an important role in its sedative and hypnotic action. In this work, supercritical fluid extraction and headspace solid phase micro-extraction, with gas chromatography–mass spectrometry, were used for analysis of the volatile components of the roots of V. officinalis var. latifolia. The results were compared with those obtained by hydrodistillation. Seventy-two compounds were isolated and identified by GC–MS. The results showed that the major volatile components of V. officinalis var. latifolia were significantly different from those of V. officinalis, and varied with different extraction methods. SFE co-extracted high-molecular-weight compounds that do not contribute to the aroma. Hydrodistillation extraction resulted in loss of some highly volatile fragrant components. The conditions (extraction temperature and pressure) used for SFE affected the extraction yield and the composition of the oil.

Capability of fast analysis of a novel miniaturized capillary electrophoresis with carbon disk electrode amperometric detection (mini-CE-AD) system was demonstrated by determining acetaminophen and p-aminophenol in dosage forms. Factors influencing the separation and detection processes were examined and optimized. Under the optimum conditions, the end-capillary 300 microm carbon disc electrode amperometric detector offered favorable signal-to-noise characteristics at a relatively low potential (+600 mV versus Ag/AgCl) for detecting acetaminophen and p-aminophenol. Two analytes can been separated within 150 s in a 8.5 cm length capillary at a separation voltage of 2000V using a Na2B4O7-KH2PO4 running buffer (pH 7.2). Acetaminophen and p-aminophenol could be detected down to the 1.4 x 10(-6)-5.9 x 10(-7) molL(-1) level with linearity up to the 1.0 x 10(-3) molL(-1) level examined. The inter-day repeatability for analytes in peak current (R.S.D.< or =2.3%) and migration times (R.S.D.< or =1.3%) were excellent. The proposed mini-CE-AD system should find a wide range of analytical applications in pharmaceutical formulations as an alternative to conventional CE and mu-CE.

Capillary electrophoresis with amperometric detection (CE-AD) has been used for the determination of catechin, rutin, ferulic acid, o-dihydroxybenzene, chlorogenic acid, caffeic acid, gallic acid, and protocatechuic acid in coffee. Comparison of extraction efficiency of antioxidants using different polar solvents was also conducted by this method. Effects of several important factors including the acidity and concentration of running buffer, separation voltage, and working electrode potential, were evaluated to obtain the optimum analysis conditions. The working electrode was a 300 um carbon disc electrode at an applied potential of +0.95 V (vs. saturated calomel reference electrode). Under the optimum conditions, the analytes can be well separated within 26 min in a 75 cm length fused-silica capillary (i.d. 2.5 × 10−5 m). The current response was linear over three orders of magnitude with detection limits (S/N = 3) ranging from 6.0 × 10−8 to 3.6 × 10−7 g/mL for all analytes.

An improved method based on a novel miniaturized capillary electrophoresis with amperometric detection (CE-AD) system was described to study the correlation between the trace amount of uric acid (UA) in human saliva and urine samples for patients suffering from gout disease. Under the optimum conditions, UA can been well separated from its co-existing potential interferences, namely xanthine, hypoxanthine, and ascorbic acid, within 170 s with estimated separation efficiency of 111,210 TP m−1. The proposed miniaturized CE-AD system has been successfully applied for the analysis of UA in less invasive biological samples, which could provide potential application in fast diagnosis of gout.

A high-performance capillary electrophoresis with amperometric detection (CE–AD) method has been developed for the determination of the pharmacologically active ingredients in different parts of Morus alba L. after a relatively simple extraction procedure. This method was also used in the comparison of bioactive constituent difference in the five parts, based on their electropherograms or characteristic “CE–AD profiles”. The effects of several factors such as the acidity and concentration of running buffer, separation voltage, applied potential and injection time were investigated to find the optimum conditions. Method detection limits (S/N = 3) ranged from 1.5 × 10−7 to 1.4 × 10−8 g/mL for all 10 analytes, and the assay results were satisfactory.

A novel miniaturized analytical system for fast separation and detection of bioactive amines, based on the coupling of a micromachined capillary electrophoresis (CE) system with a Cu amperometric detector (CE‐AD) is described. Tryptamine, tryptophan, and tyramine could be detected down to the 1.5×10−6∼5.8×10−7 M level with linearity up to the 2.0×10−4 M level examined. The injection‐to‐injection reproducibility for analytes in peak current (RSD

A new and efficient method for the determination of synthetic phenolic antioxidants (SPAs) has been developed by using micellar electrokinetic capillary chromatography (MECC) with electrochemical detection. Under the optimum conditions, all analytes were successfully separated within 13 min at the separation voltage of 18 kV in a 20 mmol/L borate running buffer (pH 7.4) containing 25 mmol/L sodium dodecyl sulfate. The excellent linearity was obtained in the concentration range from 5.0 × 10 −4 to 2.0 × 10 −6 mol/L and the detection limits ( S / N = 3) of propyl gallate (PG), tert -butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) range from 2.9 × 10 −7 to 2.7 × 10 −6 mol/L. This method has been proved to be effective and successfully applied for the determination of SPA in food products, providing a promising and convenient entry to monitor the superscale use of phenolic antioxidants.

A high-performance capillary electrophoresis with electrochemical detection method has been developed for the determination of the pharmacologically active ingredients, acacetin, rutin, umbelliferone, kaempferol, apigenin, luteolin and quercetin, in Herba Saussureae Involucratae. Under optimum conditions, the seven analytes could be completely separated within 19 min in a 75 cm length capillary at a separation voltage of 16 kV in a 50 mm borax running buffer (pH 9.2). A 300 µm diameter carbon disk electrode, positioned opposite the outlet of the capillary in a wall-jet configuration at a potential of +950 mV (vs a saturated calomel electrode) was used as the working electrode. A good linear relationship was established between peak current and concentration of the analytes over two orders of magnitude with detection limits (signal-to-noise ratio = 3) ranging from 1.2 × 10–7 to 4.1 × 10–8 g/mL for all analytes. The proposed method has been successfully applied to the analyses of bio-active components of Herba Saussureae Involucratae samples after a relatively simple extraction procedure. The assay results show that the resultant electrochemical profiles are indicative of the content diversity of each electrochemically active ingredient in the various samples, and may also offer some evidence for phytotaxonomy. Copyright © 2006 John Wiley & Sons, Ltd.

A new and efficient method for the determination of antioxidants [Propyl gallate (PG), tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT)] in cosmetics has been established by using micellar electrokinetic capillary chromatography with electrochemical detection (MECC-ED). Under the optimum conditions of the method, all analytes were successfully separated within 13 min at the separation voltage of 18 kV in a 20 mmol/L borate running buffer (pH 7.4) containing 25 mmol/L sodium dodecyl sulfate. The excellent linearity was obtained in the concentration range from 5.0 x 10(-4) to 2.0 x 10(-6) mol/L and the detection limits (S/N = 3) of PG, TBHQ, BHA, and BHT range from 3 x 10(-7) to 3 x 10(-6) mol/L.

The fast separation capability of a novel miniaturized capillary electrophoresis with amperometric detection (CE-AD) system was demonstrated by determining sugar contents in Coke and diet Coke with an estimated separation efficiency of 60,000 TP/m. Factors influencing the separation and detection processes were examined and optimized. The end-capillary 300 microm Cu wire amperometric detector offers favorable signal-to-noise characteristics at a relatively low potential (+0.50 V vs. Ag/AgCl) for detecting sugars. Three sugars (sucrose, glucose, and fructose) have been separated within 330 s in a 8.5 cm length capillary at a separation voltage of 1000 V using a 50 mM NaOH running buffer (pH 12.7). Highly linear response is obtained for the above compounds over the range of 5.0 to 2.0 x 10(2) microg/mL with low detection limit, down to 0.8 microg/mL for glucose (S/N = 3). The injection-to-injection repeatability for analytes in peak current (RSD < 3.6%) and for migration times (RSD < 1.4%) was excellent. The new miniaturized CE-AD system should find a wide range of analytical applications involving assays of carbohydrates as an alternative to conventional CE and micro-CE.