Simplified Derivatization Method for Triclosan Determination in Personal Care Products by Gas Chromatography‐Mass Spectrometry

An efficient and eco‐friendly injection‐port tert‐butyldimethylsilylated (TBDMS) derivatization and gas chromatography‐mass spectrometry (GC‐MS) was developed to determine triclosan (TCS, an antibacterial agent) in the samples of toothpaste, liquid hand‐soap and facial cleansing cream. This on‐line derivatization coupled ultrasonic extraction provides sensitivity, fast and reproducible results for TCS analysis. The accuracy and precision of the method was evaluated. The developed method was successfully applied to determine the content of TCS in selected personal care products.     

Polymer monolith microextraction online coupled to hydrophilic interaction chromatography/mass spectrometry for analysis of β2‐agonist in human urine

An analytical method based on online combination of polymer monolith microextraction (PMME) technique with hydrophilic interaction LC (HILIC)/MS is presented. The extraction was performed with a poly(methacrylic acid‐co‐ethylene glycol dimethacrylate) monolithic column while the subsequent separation was carried out on a Luna silica column by HILIC. After 1:1 v/v dilution with 20 mM phosphate solution at pH 7.0 and centrifugation, urine sample was directly used for extraction. After optimization, 85% ACN (containing 0.3% formic acid v/v) was used for rapid online elution, which was also the mobile phase in HILIC to avoid band broadening during separation or carry‐over that was usually observed in PMME‐RP LC system. Online automation of extraction and separation procedures was realized under the control of a program in this study. The developed method was applied to rapid and sensitive monitoring of three β₂‐agonist traces in human urine. The LODs (S/N = 3) of the method were found to be 0.05–0.09 ng/mL of β₂‐agonists in urine. The recoveries of three β₂‐agonists spiked in five different urine samples ranged from 79.8 to 119.8%, with RSDs less than 18.0%.     

A sensitive non‐aqueous capillary electrophoresis‐mass spectrometric method for multiresidue analyses of β‐agonists in pork

Non‐aqueous capillary electrophoresis–mass spectrometry (NACE‐MS) was developed for trace analyses of β‐agonists (i.e. clenbuterol, salbutamol and terbutaline) in pork. The NACE was in 18 mM ammonium acetate in methanol–acetonitrile–glacial acetic acid (66 : 33 : 1, v/v/v) using a voltage of 28 kV. The hyphenation of CE with a time‐of‐flight MS was performed by electrospray ionization interface employing 5 mM ammonium acetate in methanol–water (80 : 20, v/v) as the sheath liquid at a flow rate of 2 μL/min. Method sensitivity was enhanced by a co‐injection technique (combination of hydrodynamic and electrokinetic injection) using a pressure of 50 mbar and a voltage of 10 kV for 12 s. The method was validated in comparison with HPLC–MS‐MS. The NACE‐MS procedure provided excellent detection limits of 0.3 ppb for all analytes. Method linearity was good (r² > 0.999, in a range of 0.8–1000 ppb for all analytes). Precision showed %RSDs of <17.7%. Sample pre‐treatment was carried out by solid‐phase extraction using mixed mode reversed phase/cation exchange cartridges yielding recoveries between 69 and 80%. The NACE‐MS could be successfully used for the analysis of β‐agonists in pork samples and results showed no statistical differences from the values reported by the Ministry of Public Health, Thailand using HPLC‐MS‐MS method. Copyright © 2009 John Wiley & Sons, Ltd.     

pCEC coupling with ESI‐MS for the analysis of β2‐agonists and narcotics using a poly‐(1‐hexadecene‐co‐TMPTMA) monolithic column

A pressure‐assisted CEC with ESI‐MS based on poly(1‐hexadecene‐co‐trimethylolpropane trimethacrylate) monolithic column for rapid analysis of two β₂‐agonists and three narcotics was established in this article. After the organic polymer‐based monolithic column was prepared by an in‐situ polymerization procedure, a systematic investigation of the pressure‐assisted CEC separation and ESI‐MS detection parameters was performed. Baseline separation of the studied analytes could be obtained using the solution containing 75% ACN v/v and 20 mmol/L ammonium acetate with pH 8.0 as running buffer, when applying separation voltage of 20 kV and assisted pressure of 5 bar. Under the optimized conditions, two β₂‐agonists and three narcotics could be completely resolved and accurately determined within 15 min. Finally, the proposed method was successfully used for real urine samples detection.     

A general gas‐assisted three‐liquid‐phase extraction method for separation and concentration of puerarin, 3′‐methoxydaidzin,puerarinxyloside, daidzin and daidzein from puerariae extract

In this work, a general and novel separation technique gas‐assisted three‐liquid‐phase extraction was established and applied in separating and concentrating isoflavonoids from the actual sample of puerariae extract by one step. For the gas‐assisted three‐liquid‐phase extraction method, optimal conditions were selected: polyethylene glycol 2000 and ethyl acetate as the flotation solvent, pH 5, (NH₄)₂SO₄ concentration 350 g/L in aqueous phase, N₂ flow rate 30 mL/min, flotation time 50 min, and flotation twice. Five isoflavonoids compounds puerarin, 3′‐methoxydaidzin, puerarinxyloside, daidzin and daidzein were separated with recoveries of 82, 84, 80, 88 and 89%, respectively. The separated products were purified by preparative high‐performance liquid chromatography, and the purity of the final products was >96%. The established general gas‐assisted three‐liquid‐phase extraction was used to separate anthraquinones from Cassiae Semen under the optimal conditions, and the recoveries were >75%. The experimental results showed that the established gas‐assisted three‐liquid‐phase extraction method is a general technique for separating active compounds from herb extract.     

Quantitative determination of amphetamine in plasma using negative ion chemical ionization GC‐MS of o‐(pentafluorobenzyl‐oxycarbonyl)‐2,3,4,5‐tetrafluorobenzoyl derivatives

Quantitative determination of amphetamine in plasma by the use of a novel electrophoric derivatization reagent, o‐(pentafluorobenzyloxycarbonyl)‐2,3,4,5‐tetrafluorobenzoyl chloride is described. Amphetamine can be quantitatively measured down to 49 pg/mL plasma using only 250 μL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionization MS. Plasma samples were made alkaline with carbonate buffer and treated with n‐hexane and reagent solution for 20 min, which, after concentration was measured by negative ion chemical ionization GC‐MS. The method is rapid as extraction and derivatization occur in one single step. [²H₅]‐Amphetamine was used as an internal standard. Validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, benchtop stability, freeze–thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.     

Development and validation of LC‐MS/MS method for the estimation of β‐hydroxy‐β‐methylbutyrate in rat plasma and its application to pharmacokinetic studies

A simple, sensitive and specific high‐performance liquid chromatography mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of β‐hydroxy‐β‐methyl butyrate (HMB) in small volumes of rat plasma using warfarin as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. A simple liquid–liquid extraction process was used to extract HMB and IS from rat plasma. The total run time was 3 min and the elution of HMB and IS occurred at 1.48 and 1.75 min respectively; this was achieved with a mobile phase consisting of 0.1% formic acid in a water–acetonitrile mixture (15:85, v/v) at a flow rate of 1.0 mL/min on a Agilent Eclipse XDB C₈ (150 × 4.6, 5 µm) column. The developed method was validated in rat plasma with a lower limit of quantitation of 30.0 ng/mL for HMB. A linear response function was established for the range of concentrations 30–4600 ng/mL (r > 0.998) for HMB. The intra‐ and inter‐day precision values for HMB were acceptable as per Food and Drug Administration guidelines. HMB was stable in the battery of stability studies, viz. bench‐top, autosampler freeze–thaw cycles and long‐term stability for 30 days in plasma. The developed assay method was applied to a bioavailability study in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel method for the rapid and specific extraction of multiple β2‐agonist residues in food by tailor‐made Monolith‐MIPs extraction disks and detection by gas chromatography with mass spectrometry

A quick and specific pretreatment method based on a series of extraction clean‐up disks, consisting of molecularly imprinted polymer monoliths and C₁₈ adsorbent, was developed for the specific enrichment of salbutamol and clenbuterol residues in food. The molecularly imprinted monolithic polymer disk was synthesized using salbutamol as a template through a one‐step synthesis process. It can simultaneously and specifically recognize salbutamol and clenbuterol. The monolithic polymer disk and series of C₁₈ disks were assembled with a syringe to form a set of tailor‐made devices for the extraction of target molecules. In a single run, salbutamol and clenbuterol can be specifically extracted, cleaned, and eluted by methanol/acetic acid/H₂O. The target molecules, after a silylation derivatization reaction were detected by gas chromatography‐mass spectrometry. The parameters including solvent desorption, sample pH, and the cycles of reloading were investigated and discussed. Under the optimized extraction and clean‐up conditions, the limits of detection and quantitation were determined as 0.018–0.022 and 0.042–0.049 ng/g for salbutamol and clenbuterol, respectively. The assay described was convenient, rapid, and specific; thereby potentially efficient in the high‐throughput analysis of β₂‐agonists residues in real food samples.     

Rapid determination of bisphenol A in drinking water using dispersive liquid‐phase microextraction with in situ derivatization prior to GC‐MS

This paper described a novel approach for the determination of bisphenol A by dispersive liquid‐phase microextraction with in situ acetylation prior to GC‐MS. In this derivatization/extraction method, 500 μL acetone (disperser solvent) containing 30.0 μL chlorobenzene (extraction solvent) and 30.0 μL acetic anhydride (derivatization reagent) was rapidly injected into 5.00 mL aqueous sample containing bisphenol A and K₂CO₃ (0.5% w/v). Within a few seconds the analyte was derivatized and extracted at the same time. After centrifugation, 1.0 μL of sedimented phase containing enriched analyte was determined by GC‐MS. Some important parameters, such as type and volume of extraction and disperser solvent, volume of acetic anhydride, derivatization and extraction time, amount of K₂CO₃, and salt addition were studied and optimized. Under the optimum conditions, the LOD and the LOQ were 0.01, 0.1 μg/L, respectively. The experimental results indicated that there was linearity over the range 0.1–50 μg/L with coefficient of correlation 0.9997, and good reproducibility with RSD 3.8% (n = 5). The proposed method has been applied for the analysis of drinking water samples, and satisfactory results were achieved.     

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME–SFO) was for the first time combined with field‐amplified sample injection (FASI) in CE to determine four β₂‐agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting‐out extraction, β₂‐agonists were extracted into ACN that was then used as the disperser solvent in DLLME–SFO. Optimum DLLME–SFO conditions were: 1.0 mL ACN, 50 μL 1‐undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β₂‐agonists into CE. Compared to conventional CZE, DLLME–SFO–FASI–CE achieved sensitivity enhancement factors of 41–1046 resulting in LODs in the range of 1.80–37.0 μg L^?1. Linear dynamic ranges of 0.15–10.0 mg L^?1 for cimbuterol and 15–1000 μg L^?1 for the other analytes were obtained with coefficients of determination (R²) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β₂‐agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.     

Development of an ASE‐GC‐MS/MS method for detecting dinitolmide and its metabolite 3‐ANOT in eggs

An accelerated solvent extraction coupled with gas chromatography‐tandem mass spectrometry (ASE‐GC‐MS/MS) method for detecting dinitolmide residue and its metabolite (3‐amino‐2‐methyl‐5‐nitrobenzamide, 3‐ANOT) in eggs was developed and optimized. The samples were extracted using ASE with acetonitrile as the extractant and were purified by passage through a neutral alumina solid‐phase extraction column. Then, the samples were analyzed using the GC‐MS/MS method. The optimized method parameters were validated according to the requirements set forth by the European Union and the Food and Drug Administration. The average recoveries of dinitolmide and 3‐ANOT from eggs (egg white, egg yolk, and whole egg) at the limit of quantification (LOQ), 0.5 maximum residue limit (MRL), 1 MRL, and 2 MRL were 82.74% to 87.49%, the relative standard deviations (RSDs) were less than 4.63%, and the intra‐day RSDs and the inter‐day RSDs were 2.96% to 5.21% and 3.94% to 6.34%, respectively. The limits of detection and the LOQ were 0.8 to 2.8 μg/kg and 3.0 to 10.0 μg/kg, respectively. The decision limits (CC_α) were 3001.69 to 3006.48 μg/kg, and the detection capabilities (CC_β) were 3001.74 to 3005.22 μg/kg. Finally, the new method was successfully applied to the quantitative determination of dinitolmide and 3‐ANOT in 50 commercial eggs from local supermarkets.     

Quantitative determination of β,β‐dimethylacrylshikonin (DASK) in rat whole blood by liquid chromatography–tandem mass spectrometry with pre‐column derivation and its pharmacokinetic application

A sensitive and selective liquid chromatography–tandem mass spectrometric (LC‐MS/MS) method was developed and validated for the determination of β,β‐dimethylacrylshikonin (DASK) in rat whole blood. DASK was pretreated using pre‐column derivatization with 2‐mercaptoethanol followed by liquid–liquid extraction with cyclohexane. Detection was performed on Thermo Finnigan TSQ Quantum triple quadrupole mass spectrometer by selected reaction monitoring mode via electrospray ionization source. The linear range for the determination of DASK spiked in rat whole blood (0.25 mL) was 3–3000 ng/mL. The accuracy was within 9%. Intra‐ and inter‐day precisions were no more than 16.1 and 13.3%, respectively. The validated LC‐MS/MS method was successfully applied to the preliminary pharmacokinetic study in rats. After DASK administration (60 mg/kg, p.o.) in rats, pharmacokinetic parameters were obtained, where the area under the drug concentration–time curve was 2393.7 ± 224.4 ng h/mL and the elimination half‐life was 27.6 ± 5.3 h. Copyright © 2008 John Wiley & Sons, Ltd.     

Two‐phase electromembrane extraction followed by gas chromatography‐mass spectrometry analysis

A two‐phase electromembrane extraction (EME) was developed and directly coupled with gas chromatography mass spectrometry (GC‐MS) analysis. The proposed method was successfully applied to the simultaneous determination of imipramine, desipramine, citalopram and sertraline. The model compounds were extracted from neutral aqueous sample solutions into the organic phase filled in the lumen of the hollow fiber. This method was accomplished with 1‐heptanol as organic phase, by means of 60 V applied voltage and with the extraction time of 15 min. Experiments reported recoveries in the range of 69–87% from 1.2 mL neutral sample solution. The compounds were quantified by GC‐MS instrument, with acceptable linearity ranging from 1 to 500 ng mL^?1 (R² in the range of 0.989 to 0.998), and repeatability (RSD) ranging between 7.5 and 11.5% (n = 5). The estimated detection limits (S/N ratio of 3:1) were less than 0.25 ng mL^?1. This novel approach based on two‐phase EME brought advantages such as simplicity, low‐costing, low detection limit and fast extraction with a total analysis time less than 25 min. These experimental findings were highly interesting and demonstrated the possibility of solving ionic species in the organic phase at the presence of electrical potential.     

Analysis of β‐blockers in groundwater using large‐volume injection coupled‐column reversed‐phase liquid chromatography with fluorescence detection and liquid chromatography time‐of‐flight mass spectrometry

Atenolol, nadolol, metoprolol, bisoprolol and betaxolol were simultaneously determined in groundwater samples by large‐volume injection coupled‐column reversed‐phase liquid chromatography with fluorescence detection (LVI‐LC‐LC‐FD) and liquid chromatography‐time‐of‐flight mass spectrometry (LC‐TOF‐MS). The LVI‐LC‐LC‐FD method combines analyte isolation, preconcentration and determination into a single step. Significant reductions in costs for sample pre‐treatment (solvent and solid phases for clean up) and method development times are also achieved. Using LC‐TOF‐MS, accurate mass measurements within 3 ppm error were obtained for all of the β‐blockers studied. Empirical formula information can be obtained by this method, allowing the unequivocal identification of the target compounds in the samples. To increase the sensitivity, a solid‐phase extraction step with Oasis MCX cartridge was carried out yielding recoveries of 79–114% (n=5) with RSD 2–7% for the LC‐TOF‐MS method. SPE gives a high purification of β‐blockers compared with the existing methods. A 100% methanol wash was allowed for these compounds with no loss of analytes. Limit of quantification was 1–7 ng/L for LVI‐LC‐LC‐FD and 0.25–5 ng/L for LC‐TOF‐MS. As a result of selective extraction and effective removal of coextractives, no matrix effect was observed in LVI‐LC‐LC‐FD and LC‐TOF‐MS analyses. The methods were applied to detect and quantify β‐blockers in groundwater samples of Almería (Spain).     

An LC–MS/MS method for simultaneous determination of 1,5‐dicaffeoylquinic acid and 1‐O‐acetylbritannilactone in rat plasma and its application to a pharmacokinetic study

A selective and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous quantitative determination of 1,5‐dicaffeoylquinic acid (1,5‐DCQA) and 1‐O‐ acetylbritannilactone (1‐O‐ ABL) in rat plasma. Chromatographic separation was performed on a Zorbax Eclipse XDB‐C₁₈ column using isocratic mobile phase consisting of methanol–water–formic acid (70:30:0.1, v /v/v) at a flow rate of 0.25 mL/min. The detection was achieved using a triple‐quadrupole tandem MS in selected reaction monitoring mode. The calibration curves of all analytes in plasma showed good linearity over the concentration ranges of 0.850–213 ng/mL for 1,5‐DCQA, and 0.520–130 ng/mL for 1‐O‐ ABL, respectively. The extraction recoveries were ≥78.5%, and the matrix effect ranged from 91.4 to 102.7% in all the plasma samples. The method was successfully applied for the pharmacokinetic study of the two active components in the collected plasma following oral administration of Inula britannica extract in rats.     

Development and validation of a UPLC‐MS/MS method for the determination of 7‐hydroxymitragynine,a μ‐opioid agonist,in rat plasma and its application to a pharmacokinetic study

A simple, sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated to determine the concentrations of 7‐hydroxymitragynine in rat plasma. Following a single‐step liquid–liquid extraction of plasma samples using chloroform, 7‐hydroxymitragynine and the internal standard (tryptoline) were separated on an Acquity UPLC^TM BEH C₁₈ (1.7 µm, 2.1 × 50 mm) column using an isocratic elution at a flow rate of 0.2 mL/min. The mobile phase consisted of 0.1% acetic acid in water and 0.1% acetic acid in acetonitrile (10:90, v/v). The run time was 2.5 min. The analysis was carried out under the multiple reaction‐monitoring mode using positive electrospray ionization. Protonated ions [M + H]⁺ and their respective product ions were monitored at the following transitions: 415 → 190 for 7‐hydroxymitragynine and 173 → 144 for the internal standard. The calibration curve was linear over the range of 10–4000 ng/mL (r² = 0.999) with a lower limit of quantification of 10 ng/mL. The extraction recoveries ranged from 62.0 to 67.3% at concentrations of 20, 600 and 3200 ng/mL). Intra‐ and inter‐day assay precisions (relative standard deviation) were <15% and the accuracy was within 96.5–104.0%. This validated method was successfully applied to quantify 7‐hydroxymitragynine in rat plasma following intravenous administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction combined with magnetic solid‐phase extraction for the determination of aflatoxins B1, B2, G1, and G2 in animal feeds by high‐performance liquid chromatography with fluorescence detection

A novel two‐step extraction technique combining ionic‐liquid‐based dispersive liquid–liquid microextraction with magnetic solid‐phase extraction was developed for the preconcentration and separation of aflatoxins in animal feedstuffs before high‐performance liquid chromatography coupled with fluorescence detection. In this work, ionic liquid 1‐octyl‐3‐methylimidazolium hexafluorophosphate was used as the extractant in dispersive liquid–liquid microextraction, and hydrophobic pelargonic acid modified Fe₃O₄ magnetic nanoparticles as an efficient adsorbent were applied to retrieve the aflatoxins‐containing ionic liquid. Notably, the target of magnetic nanoparticles was the ionic liquid rather than the aflatoxins. Because of the rapid mass transfer associated with the dispersive liquid–liquid microextraction and magnetic solid phase steps, fast extraction could be achieved. The main parameters affecting the extraction recoveries of aflatoxins were investigated and optimized. Under the optimum conditions, vortexing at 2500 rpm for 1 min in the dispersive liquid–liquid microextraction and magnetic solid‐phase extraction and then desorption by sonication for 2 min with acetonitrile as eluent. The recoveries were 90.3–103.7% with relative standard deviations of 3.2–6.4%. Good linearity was observed with correlation coefficients ranged from 0.9986 to 0.9995. The detection limits were 0.632, 0.087, 0.422 and 0.146 ng/mL for aflatoxins B₁, B2, G1, and G2, respectively. The results were also compared with the pretreatment method carried out by conventional immunoaffinity columns.     

Solid‐phase Extraction Coupled Simple On‐line Derivatization Gas Chromatography – Tandem Mass Spectrometry for the Determination of Benzophenone‐type UV Filters in Aqueous Samples

The rapid determination of three benzophenone‐type UV filters: 2‐hydroxy‐4‐methoxy‐benzophenone (BP‐3), 2,4‐dihydroxybenzophenone (BP‐1) and 2,2′‐dihydroxy‐4‐methoxy‐benzophenone (BP‐8), in aqueous samples is described. The method involved the extraction of an aqueous sample using an Oasis HLB solid‐phase extraction (SPE) cartridge, followed by on‐line derivatization gas chromatography ‐ tandem mass spectrometry (GC‐MS/MS) with a trimethylsilylating (TMS) reagent. This eco‐friendly, injection‐port derivatization method, is sensitive, rapid, and provides reproducible results for these hydroxylated benzophenones in aqueous samples. The limits of quantitation (LOQs) were determined to be 1.0 to 2.5 ng/L for samples in 100 mL of water. The precision for these analytes, as indicated by relative standard deviations (RSDs), proved to be less than 11% for both intra‐ and inter‐day analysis. Accuracy, expressed as the mean extraction yield, was between 80 and 106%. The method was then applied to some environmental water samples, river water and samples of effluents from a wastewater treatment plant (WWTP), having the potential to contain BP‐3 and BP‐1.     

Determination of thiol compounds by HPLC and fluorescence detection with 1,3,5,7‐tetramethyl‐8‐bromomethyl‐difluoroboradiaza‐s‐indacene

Altered levels of thiols in biological fluids are considered to be an important indicator for several diseases. In this article, 1,3,5,7‐tetramethyl‐8‐bromomethyl‐difluoroboradiaza‐s‐indacene is proposed as a fluorescent derivatization reagent for the determination of thiols including glutathione, cysteine, N‐acetylcysteine, and homocysteine by HPLC. Under the optimized derivatization and separation conditions, a baseline separation of all the four derivatives has been achieved using isocratic elution on an RP C₈ column within 26 min. With fluorescence detection at 505 and 525 nm for the excitation and emission, respectively, the LODs (S/N = 3) are from 0.2 nM (glutathione) to 0.8 nM (cysteine). The feasibility of this method in real samples has been evaluated by the determination of thiols in human plasma from the healthy persons and hypertensive patients with recoveries of 92–105.3%.