Simultaneous determination of four trace estrogens in feces,leachate, tap and groundwater using solid–liquid extraction/auto solid‐phase extraction and high‐performance liquid chromatography with fluorescence detection

A simple and selective high‐performance liquid chromatography method coupled with fluorescence detection was developed for the simultaneous measurement of trace levels of four estrogens (estrone, estradiol, estriol and 17α‐ethynyl estradiol) in environmental matrices. For feces samples, solid–liquid extraction was applied with a 1:1 v/v mixture of acetonitrile and ethyl acetate as the extraction solvent. For liquid samples (e.g., leachate and groundwater), hydrophobic/lipophilic balanced automated solid‐phase extraction disks were selected due to their high recoveries compared to conventional C₁₈ disks. Chromatographic separations were performed on a reversed‐phase C₁₈ column gradient‐eluted with a 45:55 v/v mixture of acetonitrile and water. The detection limits were down to 1.1 × 10^?2 (estrone), 4.11 × 10^?4 (estradiol), 5.2 × 10^?3 (estriol) and 7.18 × 10^?3 μg/L (17α‐ethynyl estradiol) at excitation/emission wavelengths of 288/310 nm, with recoveries in the range of 96.9 ± 3.2–105.4 ± 3.2% (n = 3). The method was successfully applied to determine estrogens in feces and water samples collected at livestock farms and a major river in Northeast China. We observed relatively high abundance and widespread distribution of all four estrogens in our sample collections, implying the urgency for a comprehensive and intricate investigation of estrogenic fate and contamination in our researched area.     

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid‐phase extraction combined with dispersive liquid–liquid microextraction and high‐performance liquid chromatography

Solid‐phase extraction coupled with dispersive liquid–liquid microextraction was developed as an ultra‐preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion‐methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid‐phase extraction coupled with dispersive liquid–liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid‐phase extraction coupled with dispersive liquid–liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9–6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.     

Electrospun titania sol–gel‐based ceramic composite nanofibers for online micro‐ solid‐phase extraction with high‐performance liquid chromatography

Titanium(IV) tetraisopropoxide was employed as a metal oxide sol–gel precursor to prepare ceramic composite nanofibers by the electrospinning system. To facilitate this process and obtain the desired nanofibers with higher aspect ratios and surface area, poly(vinylpyrrolidone) was added to the sol of titania. Four ceramic nanofibers sheets based on titania were prepared while each sheet contained different transition metals such as Fe‐Mn, Fe‐Ni, Fe‐Co, and Fe‐Mn‐Co‐Ni. The scanning electron microscope images showed good homogeneity for all the prepared ceramic composites with a diameter range of 100–250 nm. The sorption efficiency was investigated by a micro‐solid‐phase extraction setup in online combination with high‐performance liquid chromatography for the determination of naproxen and clobetasol. All the prepared composites exhibited comparable efficiencies for the desired analytes and the type of metal showed insignificant effect. For the selected composite with Fe‐Mn, the linearity of the analytes was in the range of 1–1000 μg/L and the limit of detection values were found to be 2 and 0.3 μg/L for naproxen and clobetasol, respectively. The developed method was extended to the analysis of urine and blood plasma samples and acceptable relative standard deviations were obtained at two concentration levels.     

Online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry for the determination of five tannins in traditional Chinese medicine injections

A rapid analytical method based on online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry has been established and applied to the determination of tannin compounds that may cause adverse effects in traditional Chinese medicine injections. Different solid‐phase extraction sorbents have been compared and the elution buffer was optimized. The performance of the method was verified by evaluation of recovery (≥40%), repeatability (RSD ≤ 6%), linearity (r² ≥ 0.993), and limit of quantification (≤0.35 μg/mL). Five tannin compounds, gallic acid, cianidanol, gallocatechin gallate, ellagic acid, and penta‐O‐galloylglucose, were identified with concentrations ranging from 3.1–37.4 μg/mL in the analyzed traditional Chinese medicine injections.     

Determination of phthalate esters from environmental water samples by micro‐solid‐phase extraction using TiO2 nanotube arrays before high‐performance liquid chromatography

We describe a highly sensitive micro‐solid‐phase extraction method for the pre‐concentration of six phthalate esters utilizing a TiO₂ nanotube array coupled to high‐performance liquid chromatography with a variable‐wavelength ultraviolet visible detector. The selected phthalate esters included dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, bis(2‐ethylhexyl)phthalate and dioctyl phthalate. The factors that would affect the enrichment, such as desorption solvent, sample pH, salting‐out effect, extraction time and desorption time, were optimized. Under the optimum conditions, the linear range of the proposed method was 0.3–200 μg/L. The limits of detection were 0.04–0.2 μg/L (S/N = 3). The proposed method was successfully applied to the determination of six phthalate esters in water samples and satisfied spiked recoveries were achieved. These results indicated that the proposed method was appropriate for the determination of trace phthalate esters in environmental water samples.     

Determination of chloramphenicol in biological matrices by solid‐phase membrane micro‐tip extraction and capillary electrophoresis

Solid‐phase membrane micro‐tip extraction (SPMMTE) and capillary electrophoresis (CE) methods were developed and validated for analysis of chloramphenicol in human plasma and urine samples. Iron composite nanoparticles were prepared using green technology. CE was carried out using a silica capillary (60 cm × 50 μm i.d.), phosphate buffer (50 mm , 8.0 pH)–acetonitrile (95:5, v/v) as the background electrolyte, 10 kV voltage, 280 nm detection, 20 s injection time and 27 ± 1°C temperature. Frusemide was used as an internal standard. The values of migration time, electrophoretic mobility, electrophoretic velocity and theoretical plates of chloramphenicol were 12.254 min, 4.44 × 10, 7.41 × 10 and 11,227. The limits of detection and quantitation of chloramphenicol were 0.1 and 1.0 μg/mL. Recovery of chloramphenicol in the standard solution was 95%. Solid‐phase membrane micro‐tip extraction and capillary electrophoresis methods may be used to analyze chloramphenicol in human plasma and urine samples of any patient.     

Evaluation of solid‐phase extraction procedures for the quantitation of venlafaxine in human saliva by high‐performance liquid chromatography

In recent years, the use of human saliva for diagnostic purposes has evoked great interest. Thus, the aim of this study was to choose the optimal solid‐phase extraction cartridges and extraction solvents for the quantitation of venlafaxine in saliva. Blank saliva samples spiked with venlafaxine concentrations between 25 and 750 ng/mL were analyzed using five solid‐phase extraction columns (C18, C8, Strata‐X, Strata‐X‐C, and Strata‐X‐AW), washing solvents (deionized water, phosphate buffer at pH 5.5, and their mixtures with methanol), and elution solvents (methanol, acetonitrile, and their mixtures with 25% ammonia). A high‐performance liquid chromatography system was used to quantify venlafaxine in saliva. The results of this study revealed that nine of 25 procedures enabled quantitation of venlafaxine in the tested concentration range. The procedure that used a C18 cartridge, a mixture of methanol and deionized water as the washing solvent, and methanol as the elution solvent was the most effective and allowed quantitation of all venlafaxine concentrations with an acceptable recovery. In contrast, the Strata‐X‐C cartridge could not detect venlafaxine at the lowest concentration (25 ng/mL). The data acquired from the high‐performance liquid chromatography system were confirmed by a multivariate data analysis.     

Ionic‐liquid‐functionalized zinc oxide nanoparticles for the solid‐phase extraction of triazine herbicides in corn prior to high‐performance liquid chromatography analysis

Zinc oxide nanoparticles have recently been used as effective adsorbent materials for sample pretreatment in analytical chemistry because of their excellent properties, such as high specific surface area, high effective porosity, non‐toxicity, and ease of fabrication. In this study, the zinc oxide nanoparticles functionalized by an ionic liquid, 1‐carboxyethyl‐3‐methylimidazolium chloride, were fabricated and used as the adsorbent for the solid phase extraction of five triazine herbicides in corn for the first time. High‐performance liquid chromatography was employed for the determination of these triazine herbicides. Several experimental parameters affecting the extraction efficiency were investigated, including the volume of extraction solvent, the extraction time, the type of extraction solvent and elution solvent, the amount of absorbent, and the volume of elution solvent. By using the proposed method, low limits of detection and quantification for all the five triazine herbicides were obtained between 0.71–1.08 and 2.67–3.64 ng/g, respectively. Recoveries of the proposed method range from 89.05 to 100.33% with intra‐ and inter‐day relative standard deviations lower than 8.45%. The calibration curves are linear in the concentration range of 0.005–1.00 μg/g with the correlation coefficient higher than 0.9954.     

Application of zein‐modified magnetite nanoparticles in dispersive magnetic micro‐solid‐phase extraction of synthetic food dyes in foodstuffs

A simple method for the simultaneous and trace analysis of four synthetic food azo dyes including carmoisine, ponceau 4R, sunset yellow, and allura red from some foodstuff samples was developed by combining dispersive μ‐solid‐phase extraction and high‐performance liquid chromatography with diode array detection. Zein‐modified magnetic Fe₃O₄ nanoparticles were prepared and used for μ‐solid‐phase extraction of trace amounts of mentioned food dyes. The prepared modified magnetic nanoparticles were characterized by scanning electron microscopy and FTIR spectroscopy. The factors affecting the extraction of the target analytes such as pH, amount of sorbent, extraction time, type and volume of the desorption eluent, and desorption time were investigated. Under the optimized conditions, the method provided good repeatability with relative standard deviations lower than 5.8% (n = 9). Limit of detection values ranged between 0.3 and 0.9 ng/mL with relatively high enrichment factors (224–441). Comparing the obtained results indicated that Fe₃O₄ nanoparticles modified by zein biopolymer show better analytical application than bare magnetic nanoparticles. The proposed method was also applied for the determination of target synthetic food dyes in foodstuff samples such as carbonated beverage, snack, and candy samples.     

Computational design and fabrication of core–shell magnetic molecularly imprinted polymer for dispersive micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the determination of rhodamine 6G

A novel core–shell magnetic nano‐adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro‐solid‐phase extraction followed by determination of rhodamine 6G using high‐performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m‐aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA₉ (3⁴) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid‐base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano‐adsorbent was successfully applied to dispersive micro‐solid‐phase extraction coupled to high‐performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0–99.1, 89.5–92.7, and 86.9–105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%.     

Graphene‐based pipette tip solid‐phase extraction with ultra‐high performance liquid chromatography and tandem mass spectrometry for the analysis of carbamate pesticide residues in fruit juice

Graphene‐based pipette tip solid‐phase extraction was combined with ultra‐high performance liquid chromatography and tandem mass spectrometry for the determination of carbamate pesticide residues in fruit juice samples. Four milligrams of graphene was used as sorbent material to pack a 1000 μL pipette tip for the extraction of pirimicarb, propoxur, isoprocarb, fenobucarb, and diethofencarb from 3 mL of fruit juice sample. The whole extraction process was finished in 12 min, and the volume of eluent used was only 1.5 mL. Under the optimized conditions, good linear relationship (R > 0.999) and lower limits of detection (0.0022–0.033 ng/mL) were achieved. The recoveries at three spiked levels ranged from 80.90 to 124.60% with relative standard deviations less than 4.88%. Compared with commercially available sorbents including propylsulfonic acid silica, graphitized carbon black, and C₁₈, graphene was superior in extraction efficiency. The proposed method is simple, rapid, sensitive, selective, and solvent saving.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Imatinib assay by high‐performance liquid chromatography in tandem mass spectrometry with solid‐phase extraction in human plasma

We have developed a method of liquid chromatography in tandem with mass spectrometry to monitor therapeutic levels of imatinib in plasma, a selective inhibitor of protein tyrosine kinase. After solid‐phase extraction of plasma samples, imatinib and its internal standard, imatinib‐D8, were eluted with Zorbax SB‐C₁₈ at 60 °C, under isocratic conditions through a mobile phase consisting of 4 mm ammonium formate, pH: 3.2 (solution A) and acetonitrile solution B. The flow rate was 0.8 mL/min with 55% solution A + 45% solution B. Imatinib was detected and quantified by mass spectrometry with electrospray ionization operating in selected‐reaction monitoring mode. The calibration curve was linear in the range 10–5000 ng/mL, the lower limit of quantitation being 10 ng/mL. The method was validated according to the recommendations of the Food and Drug Administration, including tests of matrix effect (bias < 10%) and recovery efficiency (>80 and <120%). The method is precise (coefficient of variance intra‐day <2% and inter‐day <7%), accurate (95–108%), sensitive and specific. It is a simple method with very fast recording time (1.2 min) that is applicable to clinical practice. This will permit improvement of the pharmacological treatment of patients. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods for the rapid analysis of triazine herbicides in real waters

Novel, fast, selective, eco‐friendly and reproducible solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods were developed and validated for the analysis of triazine herbicides (atrazine and secbumeton) in stream and lake waters. The retention times of atrazine and secbumeton were 7.48 and 8.51 min. The solid‐phase membrane tip extraction was carried out in semiautomated dynamic mode on multiwall carbon nanotubes enclosed in a cone‐shaped polypropylene membrane cartridge. Acetone and methanol were found as the best preconditioning and desorption solvents, respectively. The extraction and desorption times for these herbicides were 15.0 and 10.0 min, respectively. The percentage recoveries of atrazine and secbumeton were 88.0 and 99.0%. The linearity range was 0.50–80.0 μg/L (r² > 0.994), with detection limits (<0.47 μg/L, S/N = 3) and good reproducibility (<8.0%). The ease of operation, eco‐friendly nature, and low cost of solid‐phase membrane tip extraction made these methods novel. The Solid‐phase membrane tip extraction method was optimized by considering the effect of extraction time, desorbing solvents and time.     

Determination of Doxepin in human plasma using cloud‐point extraction with high‐performance liquid chromatography and ultraviolet detection

A new straightforward method based on cloud‐point extraction has been developed, optimized, and validated for the determination of doxepin in human plasma by high‐performance liquid chromatography separation and UV detection. The nonionic surfactant Triton X‐114 was chosen as the extraction solvent. Chromatography separation was performed on a μBondapak^R C₁₈ column (4.6 mm id × 300 mm, 3 μm particle size), which was used for isocratic elution at a detection wavelength of 289 nm. Under the optimum conditions, the linear range of doxepin in human plasma was 0.1–0.9 μg/mL. Also, the detection limit, preconcentration factor, and enrichment factor were 0.08 μg/mL, 50, and 49.0, respectively.     

Determination of atenolol in human plasma using ionic‐liquid‐based ultrasound‐assisted in situ solvent formation microextraction followed by high‐performance liquid chromatography

An efficient analytical method called ionic‐liquid‐based ultrasound‐assisted in situ solvent formation microextraction followed by high‐performance liquid chromatography was developed for the determination of atenolol in human plasma. A hydrophobic ionic liquid (1‐butyl‐3‐methylimidazolium hexafluorophosphate) was formed by the addition of a hydrophilic ionic liquid (1‐butyl‐3‐methylimidazolium tetrafluoroborate) to a sample solution containing an ion‐pairing agent during microextraction. The analyte was extracted into the ionic liquid phase while the microextraction solvent was dispersed throughout the sample by utilizing ultrasound. The sample was then centrifuged, and the extracting phase retracted into the microsyringe and injected to liquid chromatography. After optimization, the calibration curve showed linearity in the range of 2–750 ng/mL with the regression coefficient corresponding to 0.998. The limits of detection (S/N = 3) and quantification (S/N = 10) were 0.5 and 2 ng/mL, respectively. A reasonable relative recovery range of 90–96.7% and satisfactory intra‐assay (4.8–5.1%, n = 6) and interassay (5.0–5.6%, n = 9) precision along with a substantial sample clean‐up demonstrated good performance of the procedure. It was applied for the determination of atenolol in human plasma after oral administration and some pharmacokinetic data were obtained.     

Analysis of lignans in Magnoliae Flos by turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry

In this study, a method coupling turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry was developed for analyzing the lignans in Magnoliae Flos. By the online pretreatment of turbulent flow chromatography solid‐phase extraction, the impurities removal and analytes concentration were automatically processed, and the lignans were separated rapidly and well. Seven lignans of Magnoliae Flos including epieudesmin, magnolin, 1‐irioresinol‐B‐dimethyl ether, epi‐magnolin, fargesin aschantin, and demethoxyaschantin were identified by comparing their retention behavior, UV spectra, and mass spectra with those of reference substances or literature data. The developed method was validated, and the good results showed that the method was not only automatic and rapid, but also accurate and reliable. The turbulent flow chromatography with online solid‐phase extraction and high‐performance liquid chromatography with tandem mass spectrometry method holds a high potential to become an effective method for the quality control of lignans in Magnoliae Flos and a useful tool for the analysis of other complex mixtures.     

Extraction and preconcentration of formaldehyde in water by polypyrrole‐coated magnetic nanoparticles and determination by high‐performance liquid chromatography

In this study, a simple and rapid extraction method based on the application of polypyrrole‐coated Fe₃O₄ nanoparticles as a magnetic solid‐phase extraction sorbent was successfully developed for the extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4‐dinitrophenylhydrazine. The analyses were performed by high‐performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 μL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10–500 μg/L), correlation coefficient (R² ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 μg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.     

Monodisperse silica nanoparticles coated with gold nanoparticles as a sorbent for the extraction of phenol and dihydroxybenzenes from water samples based on dispersive micro‐solid‐phase extraction: Response surface methodology

A selective and sensitive method was developed based on dispersive micro‐solid‐phase extraction for the extraction of hydroquinone, resorcinol, pyrocatechol and phenol from water samples prior to high‐performance liquid chromatography with UV detection. SiO₂, SiO₂@MPTES, and SiO₂@MPTES@Au nanoparticles (MPTES = 3‐mercaptopropyltriethoxysilane) were synthesized and characterized by scanning electronic microscopy, thermogravimetric analysis, differential thermogravimetric analysis, and infrared spectroscopy. Variables such as the amount of sorbent (mg), pH and ionic strength of sample the solution, the volume of eluent solvent (μL), vortex and ultrasonic times (min) were investigated by Plackett–Burman design. The significant variables optimized by a Box–Behnken design were combined by a desirability function. Under optimized conditions, the calibration graphs of phenol and dihydroxybenzenes were linear in a concentration range of 1–500 μg/L, and with correlation coefficients more than 0.995. The limits of detection for hydroquinone, resorcinol, pyrocatechol, and phenol were 0.54, 0.58, 0.46, and 1.24 μg/L, and the limits of quantification were 1.81, 1.93, 1.54, and 4.23 μg/L, respectively. This procedure was successfully employed to determine target analytes in spiked water samples; the relative mean recoveries ranged from 93.5 to 98.9%.     

Graphene oxide reinforced polymeric ionic liquid monolith solid‐phase microextraction sorbent for high‐performance liquid chromatography analysis of phenolic compounds in aqueous environmental samples

A graphene oxide reinforced polymeric ionic liquids monolith was obtained by copolymerization of graphene oxide doped 1‐(3‐aminopropyl)‐3‐(4‐vinylbenzyl)imidazolium 4‐styrenesulfonate monomer and 1,6‐di‐(3‐vinylimidazolium) hexane bihexafluorophosphate cross‐linking agent. Coupled to high‐performance liquid chromatography, the monolith was used as a solid‐phase microextraction sorbent to analyze several phenolic compounds in aqueous samples. Under the optimized extraction and desorption conditions, linear ranges were 5–400 μg/L for 3‐nitrophenol, 2‐nitrophenol, and 2,5‐dichlorophenol and 2–400 μg/L for 4‐chlorophenol, 2‐methylphenol, and 2,4,6‐trichlorophenol (R² = 0.9973–0.9988). The limits of detection were 0.5 μg/L for 3‐nitrophenol and 2‐nitrophenol and 0.2 μg/L for the rest of the analytes. The proposed method was used to determine target analytes in groundwater from an industrial park and river water. None of the analytes was detected. Relative recoveries were in the range of 75.5–113%.