Improved in‐tube electro‐membrane extraction followed by high‐performance liquid chromatography for simple and selective determination of ionic compounds: Optimization by central composite design

In this work, an efficient sample clean‐up method, named in‐tube electro‐membrane extraction, is modified to resolve the formation of bubbles in the extraction process. This modified method is applied for the extraction of two model analytes including tartrazine and sunset yellow from food samples. The method is based on the electro‐kinetic migration of ionized compounds by the application of an electrical potential difference, and on this basis the analytes under investigation, as anionic compounds, simply migrate from the donor phase and concentrate in the acceptor phase. A thin polypropylene sheet placed in the tube acts as a support for the membrane solvent, and it separates 30 μL of the aqueous acceptor from 1.2 mL of the aqueous donor. This setup can be used to solve the problem of extracting highly hydrophilic analytes. Response surface methodology is used for optimization of the experimental parameters so that under the optimized conditions, the method provides a good linearity in the range of 50–1000 ng/mL, low limits of detection (15–25 ng/mL), good extraction repeatabilities (relative standard deviations below 8.1%, n  = 5), and high extraction recoveries (54–76%).     

Simultaneous analysis of ten low‐molecular‐mass organic acids in the tricarboxylic acid cycle and photorespiration pathway in Thalassiosira pseudonana at different growth stages

A method using high‐performance liquid chromatography coupled with tandem mass spectrometry was developed for the simultaneous determination of organic acids in microalgae. o‐Benzylhydroxylamine was used to derivatize the analytes, and stable isotope‐labeled compounds were used as internal standards for precise quantification. The proposed method was evaluated in terms of linearity, recovery, matrix effect, sensitivity, and precision. Linear calibration curves with correlation coefficients >0.99 were obtained over the concentration range of 0.4–40 ng/mL for glycolic acid, 0.1–10 ng/mL for malic acid and oxaloacetic acid, 0.02–2 ng/mL for succinic acid and glyoxylic acid, 4–400 ng/mL for fumaric acid, 20–2000 ng/mL for isocitric acid, 2–200 ng mL⁻¹ for citric acid, 100–10000 ng mL⁻¹ for cis‐aconitic acid, and 1–100 ng mL⁻¹ for α‐ketoglutaric acid. Analyte recoveries were between 80.2 and 115.1%, and the matrix effect was minimal. Low limits of detection (0.003–1 ng/mL) and limits of quantification (0.01–5 ng/mL) were obtained except cis‐aconitic acid. Variations in reproducibility for standard solution at three different concentrations levels were <9%. This is the first report of the simultaneous analysis of ten organic acids in microalgae, which promotes better understanding of their growth state and provides reference value for high‐yield microalgae cultures.     

Phytic acid induced three‐dimensional graphene for the enrichment of phthalate esters from bottled water and sports beverage samples

A three‐dimensional graphene was synthesized through a hydrothermal reaction of graphene oxide with phytic acid. The microstructure and morphology of the phytic acid induced three‐dimensional graphene were investigated by nitrogen adsorption–desorption isotherms, scanning electron microscopy, and transmission electron microscopy. With a large surface area and three‐dimensional structure, the graphene was used as the solid‐phase extraction adsorbent for the extraction of phthalate esters from bottled water and sports beverage samples before high‐performance liquid chromatographic analysis. The results indicated that the graphene was efficient for the solid‐phase extraction of phthalate esters. The limits of detection (S/N = 3) of the method for the analytes were 0.02–0.03 ng/mL for the water samples and 0.03–0.15 ng/mL for the sports beverage sample. The limits of quantitation (S/N = 9) for the analytes were 0.06–0.09 ng/mL for water samples and 0.09–0.45 ng/mL for sports beverage sample. The calibration curves for the phthalate esters by the method had a good linearity from 0.1 to 80.0 ng/mL with correlation coefficients larger than 0.9997. The recoveries of the analytes for the method fell in the range of 86.7–116.2% with the relative standard deviations between 1.5 and 6.8%.     

Solid‐phase microextraction based on an agarose‐chitosan‐multiwalled carbon nanotube composite film combined with HPLC–UV for the determination of nonsteroidal anti‐inflammatory drugs in aqueous samples

We describe the preparation, characterization, and application of a composite film adsorbent based on blended agarose‐chitosan‐multiwalled carbon nanotubes for the preconcentration of selected nonsteroidal anti‐inflammatory drugs in aqueous samples before determination by high performance liquid chromatography with ultraviolet detection. The composite film showed a high surface area (4.0258 m²/g) and strong hydrogen bonding between the multiwalled carbon nanotubes and agarose/chitosan matrix, which prevent adsorbent deactivation and ensure long‐term stability. Several parameters, such as sample pH, addition of salt, extraction time, desorption solvent, and concentration of multiwalled carbon nanotubes in the composite film were optimized using a one‐factor‐at‐time approach. The optimum extraction conditions obtained were as follows: isopropanol as conditioning solvent, 10 mL of sample solution at pH 2, extraction time of 30 min, stirring speed of 600 rpm, 100 μL of isopropanol as desorption solvent, desorption time of 5 min under ultrasonication, and 0.4% w/v of composite film. Under the optimized conditions, the calibration curve showed good linearity in the range of 1–500 ng/mL (r² = 0.997–0.999), and good limits of detection (0.89–8.05 ng/mL) were obtained with good relative standard deviations of < 4.59% (n = 3) for the determination of naproxen, diclofenac sodium salt, and mefenamic acid drugs.     

Carbon molecular sieve based micro‐matrix‐solid‐phase dispersion for the extraction of polyphenols in pomegranate peel by UHPLC‐Q‐TOF/MS

A rapid, simple, and efficient sample extraction method based on micro‐matrix‐solid‐phase dispersion (micro‐MSPD) was applied to the extraction of polyphenols from pomegranate peel. Five target analytes were determined by ultra‐HPLC coupled with Q‐TOF/MS. Carbon molecular sieve (CMS) was firstly used as dispersant to improve extraction efficiency in micro‐MSPD. The major micro‐MSPD parameters, such as type of dispersant, amount of dispersant, grinding time, and the type and the volume of elution solvents, were studied and optimized. Under optimized conditions, 26 mg of pomegranate peel was dispersed with 32.5 mg of CMS, the grinding time was selected as 90 s, the dispersed sample was eluted with 100 μL of methanol. Results showed that the proposed method was of good linearity for concentrations of analytes against their peak areas (coefficient of determination r² > 0.990), the LOD was as low as 3.2 ng/mL, and the spiking recoveries were between 88.1 and 106%. Satisfactory results were obtained for the extraction of gallic acid, punicalagin A, punicalagin B, catechin, and ellagic acid from pomegranate peel sample, which demonstrated nice reliability and high sensitivity of this approach.     

Magnetic solid‐phase extraction of benzoylurea insecticides by Fe3O4 nanoparticles decorated with a hyper‐cross‐linked porous organic polymer

A magnetic polytriphenylamine porous organic polymer was prepared through simple self‐polycondensation of triphenylamine followed by coprecipitation with Fe²⁺ and Fe³⁺. It was applied as a magnetic adsorbent for the extraction of six benzoylurea insecticides from tomato, cucumber, and watermelon samples before their high‐performance liquid chromatography and mass spectral detection. Under the optimized experimental conditions, the established method gave a low limit of detection ranging from 0.05 to 0.1 ng/g and a good linear response ranging from 0.2 to 40 ng/g with coefficients of determination >0.99. The method recoveries for spiked analytes at the concentrations of 3 and 15 ng/g in real samples were in the range of 87.7–106.7% with the relative standard deviations <6.4%. The results indicated that it had a good adsorption capability toward the target analytes due to the π‐stacking and hydrogen bonding interactions. The polymer material showed great potential in the efficient extraction of organic compounds from real samples with complex matrixes.     

Microfunnel‐filter‐based emulsification microextraction followed by gas chromatography for simple determination of organophosphorus pesticides in environmental water samples

A simple and fast method named microfunnel‐filter‐based emulsification microextraction is introduced for an efficient determination of some organophosphorus pesticides including diazinon, malathion, and chlorpyrifos in the environmental samples including the river, sea, and well water. This method is based upon the dispersion of a low‐toxicity organic solvent (dihexyl ether), as the extractant, in a high volume of an aqueous sample solution (45 mL). It is implemented without a centrifugation step, and using a syringe filter and a micro‐funnel, the phase separation and transfer of the enriched analytes to the gas chromatograph are simply achieved. By filtration of the extractant phase, a suitable sample clean‐up is obtained, and the total extraction time is just a few minutes. The factors influencing the extraction efficiency are optimized, and under the optimal conditions, the proposed method provides a good linearity (in the range of 15–1500 ng/mL (R² > 0.996). A high enrichment factor is obtained (in the range of 306–342), and the method provides low limits of detection and quantification (in the ranges of 4–8 and 15–25 ng/mL, respectively).     

Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: A critical analysis of the 9‐fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies

The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption–desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9‐fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R² > 0.999) under optimized conditions for high‐performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R² > 0.97). K_f constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg^1‐1/n mL^1/n g^–1) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method.     

Comparison of three‐phase hollow fiber liquid‐phase microextraction based on reverse micelle with conventional two‐phase hollow fiber liquid‐phase microextraction and their applications for analysis of cinnamic acids in traditional Chinese medicines

A novel three‐phase hollow fiber liquid‐phase microextraction was developed based on reverse micelle as extraction solvent and acceptor phase, and compared with conventional two‐phase hollow fiber liquid‐phase microextraction. Both procedures were used in the extraction and concentration of four cinnamic acids (caffeic acid, p‐hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicines prior to high‐performance liquid chromatography analysis. Parameters affecting the two procedures were investigated and optimized to obtain the optimum enrichment factors. The mechanism of the developed procedure was explored and elucidated by comparison with conventional two‐phase hollow fiber liquid‐phase microextraction. Under the optimized conditions, the analytes’ enrichment factors were between 50 and 118 for the proposed procedure, and 31–96 for conventional two‐phase mode. Satisfactory linear ranges (r² ≥ 0.99), detection limits (0.1–0.6 ng/mL), precisions (<9.2%), and accuracies (recoveries: 80–123.1%) were observed for the two procedures. The results showed that the enrichment capacity of the proposed procedure for the cinnamic acids is better than that of conventional two‐phase procedure, and both are eco‐friendly, simple, and effective for the enrichment and detection of cinnamic acids in traditional Chinese medicines.     

Magnetic porous carbon derived from Co‐doped metal–organic frameworks for the magnetic solid‐phase extraction of endocrine disrupting chemicals

Metal–organic frameworks‐5 (MOF‐5) was explored as a template to prepare porous carbon due to its high surface area, large pore volume, and permanent nanoscale porosity. Magnetic porous carbon, Co@MOF‐5‐C, was fabricated by the one‐step direct carbonization of Co‐doped MOF‐5. After carbonization, the magnetic cobalt nanoparticles are well dispersed in the porous carbon matrix, and Co@MOF‐5‐C displays strong magnetism (with the saturation magnetization intensity of 70.17emu/g), high‐specific surface area, and large pore volume. To evaluate its extraction performance, the Co@MOF‐5‐C was applied as an adsorbent for the magnetic solid‐phase extraction of endocrine disrupting chemicals, followed by their analysis with high‐performance liquid chromatography. The developed method exhibits a good linear response in the range of 0.5–100 ng/mL for pond water and 1.0–100 ng/mL for juice samples. The limits of detection (S/N  = 3) for the analytes were in the range of 0.1–0.2 ng/mL.     

Simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone,and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma by liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study

A new liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran from Sophora tonkinensis in rat plasma using chlorpropamide as an internal standard. Plasma samples (50 μL) were prepared using a simple deproteinization procedure with 150 μL of acetonitrile containing 100 ng/mL of chlorpropamide. Chromatographic separation was carried out on an Acclaim RSLC120 C₁₈ column (2.1 × 100 mm, 2.2 μm) using a gradient elution consisting of 7.5 mM ammonium acetate and acetonitrile containing 0.1% formic acid (0.4 mL/min flow rate, 7.0 min total run time). The detection and quantitation of all analytes were performed in selected reaction monitoring mode under both positive and negative electrospray ionization. This assay was linear over concentration ranges of 50–5000 ng/mL (trifolirhizin), 25–2500 ng/mL ((–)‐maackiain), 5–250 ng/mL ((–)‐sophoranone), and 1–250 ng/mL 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran) with a lower limit of quantification of 50, 25, 5, and 1 ng/mL for trifolirhizin, (–)‐maackiain, (–)‐sophoranone, and 2‐(2,4‐dihydroxyphenyl)‐5,6‐methylenedioxybenzofuran, respectively. All the validation data, including the specificity, precision, accuracy, recovery, and stability conformed to the acceptance requirements. The results indicated that the developed method is sufficiently reliable for the pharmacokinetic study of the analytes following oral administration of Sophora tonkinensis extract in rats.     

Development of hollow fiber‐supported liquid‐phase microextraction and HPLC‐DAD method for the determination of pyrethroid metabolites in human and rat urine

A simple hollow fiber liquid‐phase microextraction method for the determination of synthetic pyrethroid metabolites, 3‐phenoxybenzoic acid and 4‐hydroxy‐3‐phenoxybenzoic acid, in human and rat urine was developed and validated. A polypropylene hollow fiber tightly fitted onto a Nylon rod and impregnated with organic solvent served as a disposable extraction device. Desorption of analytes was carried out in NaOH solution, analyzed further by gradient HPLC and diode array detection method. Important factors were identified using Taguchi OA16 (4⁵) orthogonal array design and further optimized using univariate approach. The optimum method performance was observed when 1 mL of urine hydrolyzed with 0.2 mL of concentrated HCl was further supplemented with 100 mg of NaCl and extracted for 120 min into dihexyl ether immobilized in the pores of the hollow fiber. Metabolites were desorbed into 0.1 mL of 0.1 M NaOH for another 120 min. Limits of detection and quantitation of 15 and 50 ng/mL were obtained for both analytes. Relative standard deviations of 1.6–12.6% over the linear range (50–10,000 ng/mL, r > 0.9906) were observed. Intra‐ and inter‐day accuracies of the method ranged from 98.3 to 109.5% and from 93.3 to 110.9%, respectively. The optimized method was applied to the analysis of real urine samples collected from rats exposed orally to cypermethrin. Copyright © 2013 John Wiley & Sons, Ltd.     

Surfactant‐assisted electromembrane extraction combined with cyclodextrin‐modified capillary electrophoresis for the separation and quantification of Tranylcypromine enantiomers in biological samples

Surfactant‐assisted electromembrane extraction coupled with cyclodextrin‐modified capillary electrophoresis was developed for the separation and determination of Tranylcypromine enantiomers in biological samples. This combination would provide a new strategy for selective and sensitive determination of target analytes. The addition of surfactant in the donor solution improved the analyte transport into the lumen of hollow fiber that resulted in an enhancement in the analytes migration into acceptor solution. Optimization of the variables, affecting proposed method, was carried out and best results were achieved with a 175 V potential as driving force of the electromembrane extraction, 2‐nitrophenyloctylether as the supported liquid membrane, donor solution containing 0.2 mM Triton X‐100 with pH 3 and 0.1 M HCl for acceptor solution. Then, the extract was analyzed using cyclodextrin‐modified capillary electrophoresis method for separation of Tranylcypromine enantiomers. The best results were obtained with a phosphate running buffer (100 mM, pH 2.0) containing 7% w/v hydroxypropyl‐α‐cyclodextrin. Under the optimum conditions, a low limit of detection (3.03 ng/mL), good linearity (R² > 0.9953), and relative standard deviations below 4.0% (n = 5) were obtained. Finally, this procedure was applied to determine the concentration of Tranylcypromine enantiomers in urine samples with satisfactory results.     

Quantitative determination of acidic hydrolysis products of Chemical Weapons Convention related chemicals from aqueous and soil samples using ion‐pair solid‐phase extraction and in situ butylation

Chemical warfare agents such as organophosphorus nerve agents, mustard agents, and psychotomimetic agent like 3‐quinuclidinylbenzilate degrade in the environment and form acidic degradation products, the analysis of which is difficult under normal analytical conditions. In the present work, a simultaneous extraction and derivatization method in which the analytes are butylated followed by gas chromatography and mass spectrometric identification of the analytes from aqueous and soil samples was carried out. The extraction was carried out using ion‐pair solid‐phase extraction with tetrabutylammonium hydroxide followed by gas chromatography with mass spectrometry in the electron ionization mode. Various parameters such as optimum concentration of the ion‐pair reagent, pH of the sample, extraction solvent, and type of ion‐pair reagent were optimized. The method was validated for various parameters such as linearity, accuracy, precision, and limit of detection and quantification. The method was observed to be linear from 1 to 1000 ng/mL range in selected ion monitoring mode. The extraction recoveries were in the range of 85–110% from the matrixes with the limit of quantification for alkyl phosphonic acids at 1 ng/mL, thiodiglycolic acid at 20 ng/mL, and benzilic acid at 50 ng/mL with intra‐ and interday precisions below 15%. The developed method was applied for the samples prepared in the scenario of challenging inspection.     

Determination of methyl methanesulfonate and ethyl methanesulfonate in methanesulfonic acid by derivatization followed by high‐performance liquid chromatography with ultraviolet detection

Methanesulfonic acid is routinely used in pharmaceuticals but can contain potentially genotoxic impurities such as methyl methanesulfonate and ethyl methanesulfonate. The aim of this study was to develop a simple high‐performance liquid chromatography with ultraviolet detection method for determining methyl methanesulfonate and ethyl methanesulfonate in methanesulfonic acid. Samples (250 mg) in water/acetonitrile (200 μL) were first combined with 10.0 mol/L sodium hydroxide solution (270 μL). Then they were mixed with 2.0 mg/mL N ,N‐diethyldithiocarbamate (500 μL), diluted to 5 mL with N ,N‐dimethylacetamide and allowed to react at 80°C for 1 h. The derivatives were analyzed using gradient high‐performance liquid chromatography with ultraviolet detection (277 nm) and structurally elucidated by liquid chromatography with mass spectrometry. With acetonitrile/5 mmol/L ammonium acetate solution as the eluent and 1 mL/min as the flow rate on a C18 column, the derivatives were eluted at 10.6 and 14.8 min. Good linearity (correlation coefficients > 0.999) and low limits of quantitation (0.6 ppm) were obtained. The recoveries were in the range of 80–115% with relative standard deviation < 5.0%. Finally, the established method was successfully used for the determination of methyl methanesulfonate and ethyl methanesulfonate in methanesulfonic acid.     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Hydrophobic deep eutectic solvent as a green extractant for high‐performance liquid chromatographic determination of tetracyclines in water samples

A green extractant, hydrophobic deep eutectic solvent was first introduced for extraction of tetracycline, oxytetracycline, and chlortetracycline from environmental water samples prior to high‐performance liquid chromatography determination. Deep eutectic solvents consist of methyltrioctylammonium chloride and various medium‐chain alcohols/acids, and are easy in preparation, low cost and toxicity, desirably biodegradable, and biocompatible. The overall time required for sample preparation was 6 min and the volume of organic solvent used for extraction was only 400 µL. Under the optimized extraction condition, the present method yielded low limit of detection (0.5–2.0 ng/mL), acceptable precision (relative standard deviations < 9.7%), good linearity from 2.0 to 500 ng/mL (r² ≥ 0.9991). This optimized procedure was applied for determination of tetracyclines in different water samples with desirable spiked recovery ranged from 77.5 to 87.6%. There is, therefore, a great potential to further expand application of the method for investigation of other ultra‐trace analyte(s) in environmental matrixes.     

Quantification of 3‐n‐butylphthalide in beagle plasma samples by supercritical fluid chromatography with triple quadruple mass spectrometry and its application to an oral bioavailability study

A high‐throughput, rapid, sensitive, environmentally friendly, and economical supercritical fluid chromatography with triple quadruple mass spectrometry method was established and validated for the first time to determine a cerebral stroke treatment drug named 3‐n‐butylphthalide in dog plasma. Plasma samples were prepared by protein precipitation with methanol and the analytes were eluted on an ACQUITY UPC^2TM HSS‐C₁₈ SB column (3 × 100 mm, 1.8 μm) maintained at 50°C. The mobile phase comprised supercritical carbon dioxide/methanol (90:10, v/v) at a flow rate of 1.5 mL/min, the compensation solvent was methanol at a flow rate of 0.2 mL/min and the total run time was 1.5 min per sample. The detection was carried out on a tandem mass spectrometer with an electrospray ionization source. Calibration curves were linear over the concentration range of 1.02–1021.00 ng/mL (r² ≥ 0.993) with the lower limit of quantification of 1.02 ng/mL. The intra‐ and inter‐day precision values were below 15% and the accuracy was from 97.90 to 103.70% at all quality control levels. The method was suitable for a pharmacokinetic study of 3‐n‐butylphthalide in beagle dogs.     

Trace determination of parabens in cosmetics and personal care products using fabric‐phase sorptive extraction and high‐performance liquid chromatography with UV detection

A simple, fast, and sensitive analytical protocol using fabric‐phase sorptive extraction followed by high performance liquid chromatography with ultraviolet detection has been developed and validated for the extraction of five parabens including methylparaben, ethylparaben, propylparaben, butylparaben, and benzylparaben. In the present work, sol‐gel polyethylene glycol coated fabric‐phase sorptive extraction membrane is used for the preconcentration of parabens (polar) from complex matrices. The use of fabric‐phase sorptive extraction membrane provides a high surface area which offers high sorbent loading, shortened equilibrium time, and overall decrease in the sample preparation time. Various factors affecting the performance of fabric‐phase sorptive extraction, including extraction time, eluting solvent, elution time, and pH of the sample matrix, were optimized. Separation was performed using a mobile phase consisting of water:acetonitrile (63:37; v/v) at an isocratic elution mode at a flow rate of 0.9 mL/min with wavelength at 254 nm. The calibration curves of the target analytes were prepared with good correlation coefficient values (r² > 0.9955). The limit of detection values range from 0.252 to 0.580 ng/mL. Finally, the method was successfully applied to various cosmetics and personal care product samples such as rose water, deodorant, hair serum, and cream with extraction recoveries ranged between 88 and 122% with relative standard deviation <5%.     

A highly sensitive capillary electrophoresis immunoassay strategy based on dual‐labeled gold nanoparticles enhancing chemiluminescence for the detection of prostate‐specific antigen

An enzyme and antibody dual labeled gold nanoparticles enhancing chemiluminescence strategy was developed for highly sensitive CE immunoassay (IA) of prostate‐specific antigen (PSA). In this work, gold nanoparticles were labeled with horseradish peroxidase and antiprostate specific antigen‐antibody, and used as the marker (Ab^*). After PSA (antigen, Ag) was added into the system, a noncompetitive immune reaction was happen between Ab^* and Ag to form an immune complex (Ag–Ab^*). Subsequently, the obtained Ag–Ab^* and unreacted Ab^* were separated by CE, and the chemiluminescence intensity of Ag‐Ab^* was used to estimate PSA concentration. The calibration curve showed a good linearity in the range of 0.25–10 ng/mL. Based on a S/N of 3, the detection limit for PAS was estimated to be 0.092 ng/mL. Proposed CE method was applied for PSA quantification in human serum samples from healthy volunteers and patients with prostate cancer. The obtained results demonstrated that the proposed CE method may serve as an alternative tool for clinical analysis of PSA.