Enantioselective separation and determination of the dinotefuran enantiomers in rice,tomato and apple by HPLC

An effective chiral analytical method was developed for the resolution and determination of dinotefuran enantiomers in rice, tomato and apple samples. Dinotefuran enantiomers were baseline‐separated and determined on a novel chiral column, ChromegaChiral CCA, with n‐hexane–ethanol–methanol (85:5:10, v/v/v) as the mobile phase at a flow rate of 1.0 mL/min with UV detection at 270 nm. The resolution of dinotefuran enantiomers was about 1.8. The first eluted enantiomer was (+)‐dinotefuran and the second eluted one was (?)‐dinotefuran. The effects of mobile‐phase composition and column temperature on the enantioseparation were evaluated. The method was validated for linearity, repeatability, accuracy, LOD and LOQ. LOD was 0.15 mg/kg in rice and tomato, 0.05 mg/kg in apple, with an LOQ of 0.5 mg/kg in rice and tomato, 0.2 mg/kg in apple. The average recoveries of the pesticide from all matrices ranged from 75.8 to 92.9% for all fortification levels The precision values associated with the analytical method, expressed as RSD values, were <16.5% for the pesticide in all matrices. The methodology was successfully applied for the enantioselective analysis of dinotefuran enantiomers in real samples, indicating its efficiency in investigating the environmental stereochemistry of dinotefuran in food matrix.     

Determination of cyantraniliprole and its major metabolite residues in vegetable and soil using ultra-performance liquid chromatography/tandem mass spectrometry

A rapid, highly sensitive and selective method was developed for the determination of the cyantraniliprole and its major metabolite J9Z38 in cucumber, tomato and soil by ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS). Target compounds were extracted with acetonitrile and an aliquot cleaned with primary and secondary amine. Two pairs of precursor product ion transitions for cyantraniliprole and J9Z38 were measured and evaluated. Average recoveries for cucumber, tomato and soil at three levels (10, 50 and 100 µg/kg) ranged from 74.7 to 96.2% with intra‐day relative standard deviation (RSD) of 2.6–15.1% and inter‐day RSD of 3.4–13.3%. The limit of quantitation for cyantraniliprole and J9Z38 were determined to be 5 and 10 µg/kg in samples (cucumber, tomato and soil), respectively. This method was used to determine the cyantraniliprole and J9Z38 residues in real cucumber, tomato and soil samples for studies on their dissipation. The trial results showed that the half‐lives of cyantraniliprole obtained after treatments were 2.2, 2.8 and 9.5 days in cucumber, tomato and soil in Zhejiang, respectively, and that the average levels of cyantraniliprole and J9Z38 residues in cucumber and tomato were all <0.01 mg/kg with the interval of 10 days after treatment. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid selective accelerated solvent extraction and simultaneous determination of herbicide atrazine and its metabolites in fruit by ultra high performance liquid chromatography

A selective accelerated solvent extraction procedure achieved one step extraction and cleanup for analysis of herbicide atrazine and its metabolites in fruit. Using a BEH C18 analytical column and the gradient mode with 2 mM ammonium acetate aqueous solution/acetonitrile as a mobile phase achieved effective chromatographic separation of the five analytes within 4 min. The calibration curves were linear over two orders of magnitude of concentration with correlation coefficients (r) of 0.9996?0.9999. The method limit of quantification was 1, 2, 1.5, 3, and 2 μg/kg for atrazine, desethylatrazine, desisopropylatrazine, desethyldesisopropylatrazine, and hydroxyatrazine, respectively, in the case of atrazine it is at least two orders of magnitude lower than the maximum residue limit (0.25 mg/kg). The intra‐day and inter‐day precisions of the five analytes were in the range of 2.1–3.5 and 3.1–4.8 %, respectively. The recoveries of the five analytes at three spiked levels varied from 85.9 to 107% with a relative standard deviation of 1.8–4.9% for pear and apple samples. The ultra high performance liquid chromatography with diode array detection method was proved to be fast, inexpensive, selective, sensitive, and accurate for the quantification of the analytes in pear and apple samples.     

Enantioselective determination of carboxyl acid amide fungicide mandipropamid in vegetables and fruits by chiral LC coupled with MS/MS

An efficient enantioselective method for the determination of mandipropamid in vegetables and fruits was presented by LC coupled with MS/MS. The mandipropamid residues in samples (potato, pepper, grape, and watermelon) were extracted with acetonitrile containing 1% acetic acid. An aliquot was cleaned up with primary and secondary amine and C₁₈ sorbent. Complete enantioseparation of mandipropamid enantiomers in <4 min was obtained on a Lux Cellulose‐2 column at 25°C using methanol with 0.1% formic acid/0.1% aqueous formic acid solution (85:15, v/v) as mobile phase. Good linearity was obtained over the concentration range of 0.5–250 μg/L for each enantiomer in the standard solution and sample matrix calibration curves. Quantification was achieved using matrix‐matched standard calibration curves. The interday mean recoveries, intraday repeatability, and inter‐day reproducibility varied from 76.4 to 97.1%, 3.4 to 9.4%, and 3.5 to 11.4%, respectively. The limits of quantification for mandipropamid enantiomers in vegetables and fruits were both 1 μg/kg. Moreover, the absolute configuration of mandipropamid enantiomers was determined by the combination of experimental and predicted electronic circular dichroism spectra, and the first eluted enantiomer was confirmed as (R)‐mandipropamid on five chiral columns.     

Chiral determination of a novel acaricide cyflumetofen enantiomers in cucumber,tomato, and apple by HPLC

A simple chiral analytical method was developed for the enantiomeric determination of cyflumetofen in cucumber, tomato, and apple by normal‐phase HPLC. The effects of mobile phase composition and column temperature on the enantioseparation were evaluated. Excellent separation was achieved at 25°C on a Chiralpak AD‐H column, with a mixture of n‐hexane and 2‐propanol (95:5, v/v) as mobile phase at a flow rate of 1.0 mL/min detecting at 234 nm. The resolution of cyflumetofen enantiomers was up to 5.5. The elution order of the enantiomers was determined by an online OR‐2090 detector, which was performed under the same chromatographic conditions. The first eluted enantiomer was (–)‐cyflumetofen and the second eluted one was (+)‐cyflumetofen. The method was validated for linearity, repeatability, accuracy, LOD, and LOQ. LOD ranged from 0.1 to 0.15 mg/kg, with the LOD varying from 0.33 to 0.5 mg/kg for each enantiomer, respectively. The average recoveries of the pesticide ranged from 71.4 to 102.0% at all fortification levels. The precision values associated with the analytical method, expressed as RSD values, were below 14.8% in all matrices. The method was then successfully applied to detect cyflumetofen enantiomers in real samples.     

超高效液相色谱-串联质谱法测定蔬菜和水果中腈吡螨酯残留量

建立了蔬菜和水果中腈吡螨酯残留量的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法。样品经乙腈均质提取,混合使用乙二胺-N-丙基硅烷(PSA)和C18两种基质分散净化剂净化,净化液过膜后直接进行UPLC-MS/MS检测。通过考察腈吡螨酯在不同果蔬样品中的基质效应发现,采用UPLC-MS/MS检测蔬菜和水果中腈吡螨酯残留量时,腈吡螨酯在不同种类样品中存在不同程度的基质减弱效应,采用空白基质溶液稀释标准建立校正的标准曲线外标法定量以消除基质效应。结果表明,腈吡螨酯在0.05~10μg/L浓度范围内具有良好的线性关系,相关系数不低于0.999 6。在0.000 05~2 mg/kg范围内进行加标回收率实验,平均回收率为81.1%~99.3%,相对标准偏差为4.7%~9.3%,方法的定量下限为0.043μg/kg,检出限为0.013μg/kg。     

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.     

Enantioseparation and determination of dufulin enantiomers in cucumber and soil by chiral liquid chromatography–tandem mass spectrometry

A simple and rapid method for enantioselective determination of dufulin in cucumber and soil was developed by liquid chromatography with tandem mass spectrometry. The enantiomers were separated on a Superchiral S‐OD chiral cellulose tris(3,5‐dimethylphenylcarbamate) column at 20°C, with a mixture of acetonitrile and water (0.1% formic acid; 52:48, v/v) as mobile phase at a flow rate of 0.65 mL/min. The pretreatment conditions were optimized using an orthogonal test, and the optimized method showed good linearity and sensitivity. The limits of detection and limits of quantification of two dufulin enantiomers were 0.006 and 0.02 mg/kg, respectively. The average recoveries of S‐enantiomer and R‐enantiomer in cucumber and soil were 80.61–99.83% and 80.97–102.96%, respectively, with relative standard deviations of 1.30–9.72%. The method was successfully applied to determine dufulin in real cucumber and soil samples. The results demonstrate that the method could facilitate further research on the differences between individual dufulin enantiomers with respect to metabolites and environmental fate and finally help reveal the complex interactions that exist between dufulin, humans and the environment.     

Enantioselective determination of ketamine in dog plasma by chiral liquid chromatography–tandem mass spectrometry

Ketamine is an N‐methyl‐d ‐aspartate receptor antagonist that is usually used clinically as a racemic mixture. Its two enantiomers exhibit different pharmacological activities. To determine whether the enantiomers have different pharmacokinetic profiles, a chiral liquid chromatography–tandem mass spectrometry method was developed and validated for the determination of ketamine enantiomers in dog plasma. The enantiomers of ketamine were extracted from 50 μL of plasma by methyl tert‐butyl ether. Adequate chromatographic retention and baseline resolution of the enantiomers were achieved within a runtime of 5 min on a chiral column coated with polysaccharide derivatives, using a gradient mobile phase of acetonitrile and 10 mm ammonium bicarbonate aqueous solution. Ketamine enantiomers were detected by mass spectrometry with multiple reaction monitoring mode using the transitions of m/z 238.3 → 125.9 for the analytes and m/z 237.1 → 194.1 for carbamazepine (internal standard). The method was linear over the concentration range from 0.5 to 500 ng/mL for each enantiomer. The lower limit of quantification (LLOQ) for each enantiomer was 0.5 ng/mL. The intra‐ and inter‐day precision was <7.3% and 8.5% for R‐ and S‐ketamine, respectively. The accuracy was 92.9–110.4% for R‐ketamine and 99.8–102.4% for S‐ketamine. The method was successfully applied to characterize the stereoselective pharmacokinetic profiles of ketamine in beagle dogs.     

Enantioselective determination of acaricide etoxazole in orange pulp,peel, and whole orange by chiral liquid chromatography with tandem mass spectrometry

An efficient enantioselective method for the determination of etoxazole in orange pulp, peel, and whole orange was developed using liquid chromatography with tandem mass spectrometry. The enantioseparation was performed on a Chiralpak AD‐3R column at 30ºC using acetonitrile with 0.1% formic acid solution (80:20, v/v) as the mobile phase in less than 5 min. Quantification was achieved using matrix‐matched standard calibration curves. The overall mean recoveries for two enantiomers from orange pulp and whole orange were 91.0–99.6% and the orange peel was 92.6–103.1%, with relative standard deviations of 0.8–5.4% intraday and 2.0–4.8% interday at 1, 10, and 100 μg/kg levels, and 1.3–5.2% intraday and 3.5–4.3% interday at 5, 50, and 500 μg/kg levels, respectively. The limits of quantification for all enantiomers in three matrices did not exceed 5 μg/kg. Moreover, the absolute configuration of etoxazole enantiomers had been determined by the combination of experimental and predicted electronic circular dichroism spectra, and the first eluted enantiomer was confirmed as (S)‐etoxazole on a Chiralpak AD‐3R column while (R)‐etoxazole was first on three cellulose chiral columns. The application of the proposed method to real sample analysis suggests its potential use in enantioselective determination of etoxazole enantiomers in citrus.     

Simultaneous enantioselective determination of fenbuconazole and its main metabolites in soil and water by chiral liquid chromatography/tandem mass spectrometry

A novel and sensitive method was developed for the simultaneous determination of fenbuconazole and its main metabolites enantioselectively using chiral liquid chromatography coupled with tandem mass spectrometry. The separation and determination were performed using reversed-phase chromatography on a cellulose chiral stationary phase, a Chiralcel OD-RH (150 mm×4.6 mm) column, under isocratic conditions at 0.5 mL/min flow rate. The effects of three cellulose-based columns and three amylose-based columns on the separation were also investigated. The elution orders of the eluting enantiomers were identified by an optical rotation detector. The QuEChERS (acronym for Quick, Easy, Cheap, Effective, Rugged and Safe) method and solid-phase extraction (SPE) were used for the extraction and clean-up of the soil and water samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were evaluated. Under optimal conditions, the mean recoveries for all enantiomers from the soil samples were 82.5-104.1% with 2.7-9.5% intra-day relative standard deviations (RSD) and 5.7-11.2% inter-day RSD at 5, 25 and 50 μg/kg levels; the mean enantiomer recoveries from the water samples were 81.8-104.6% with 2.6-11.4% intra-day RSD and 5.3-10.4% inter-day RSD at 0.25, 0.5 and 2.5 μg/L levels. Coefficients of determination R2≥0.9991 were achieved for each enantiomer in the soil and water matrix calibration curves within the range of 1.0-125 μg/L. The limits of detection (LOD) for all enantiomers in the soil and water were less than 0.8 μg/kg, whereas the limit of quantification (LOQ) did not exceed 2.5 μg/kg. The results of the method validation confirm that this proposed method is convenient and reliable for the enantioselective determination of the enantiomers of fenbuconazole and its main metabolites in soil and water.     

HPLC enantioseparation of alkaloid malacitanine using fluorimetric/polarimetric detection

This work reports two methods developed for the separation and determination of the enantiomers of the new alkaloid malacitanine (MLC) and the determination of the enantiomeric purity in mixtures. First, the isomers were separated using a Chirex 3020 (250 mm × 4.6 mm, 5 μm) chiral column with a mobile phase of cyclohexane–1,2‐dichloroethane–ethanol–trifluoroacetic acid (64:30:6:0.6, v/v/v/v) at a flow rate of 1 mL/min and fluorimetric detection. Obtained retention times were 12.4 and 15.9 min (+ and ?) with a resolution Rs of 1.13. Relative standard deviations (RSDs) were 2.5 and 2.4% at the 0.5‐μg level (four determinations). Second, a nonenantioselective procedure for the determination of enantiomeric purity of MLC using a Lichrospher ® Si‐60 (250 mm × 5 mm, 5 μm) normal phase with a mobile phase of 100% ethanol at a flow rate of 0.9 mL/min coupled to two detectors in series, fluorimetric and polarimetric. RSD of 3.3% was obtained. Calculated enantiomeric purity by chiral chromatography gave 48.6% (?)‐MLC in the near racemic product. Using polarimetric signal of the nonseparated enantiomers and comparing the slopes of the calibration curves (enantiomers) from the racemic product gave 47.8% (?)‐MLC content. A study of accuracy of (?)‐MLC gave recoveries from 98.3 to 100.7%.     

Effective extraction and simultaneous determination of Sudan dyes from tomato sauce and chili‐containing foods using magnetite/reduced graphene oxide nanoparticles coupled with high‐performance liquid chromatography

A simple, effective, and robust magnetic solid‐phase extraction method was developed using magnetite/reduced graphene oxide nanoparticles as the adsorbent for the simultaneous determination of Sudan dyes (I, II, III, and IV) in foodstuffs. The magnetite/reduced graphene oxide nanoparticles were characterized by X‐ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The extraction parameters including extraction time, elution solution, and elution time and volume were investigated in detail. Such magnetite/reduced graphene oxide nanoparticles based magnetic solid‐phase extraction in combination with high‐performance liquid chromatography and variable wavelength detection gave the detection limits of 3–6 μg/kg for Sudan I–IV in chili sauce, tomato sauce, chili powder, and chili flake samples. The recoveries were 79.6–108% at three spiked levels with the intra‐ and inter‐day relative standard deviations of 1.2–8.6 and 4.5–9.6%, respectively. The feasibility was further performed by a comparison with commercial alumina‐N. This method is suitable for the routine analysis of Sudan dyes due to its sensitivity, simplicity, and low cost.     

Enantioselective LC‐ESI‐MS/MS determination of dropropizine enantiomers in rat plasma and application to a pharmacokinetic study

We developed and validated a simple, sensitive, selective and reliable LC–ESI‐MS/MS method for direct quantitation of dropropizine enantiomers namely levodropropizine (LDP) and dextrodropropizine (DDP) in rat plasma without the need for derivatization as per regulatory guidelines. Dropropizine enantiomers and carbamazepine (internal standard) were extracted from 50 μL rat plasma using ethyl acetate. LDP and DDP resolved with good baseline separation (R_s = 4.45) on a Chiralpak IG‐3 column. The mobile phase consisted of methanol with 0.05% diethylamine pumped at a flow rate of 0.5 mL/min. Detection and quantitation were done in multiple reaction monitoring mode following the transitions m/z 237 → 160 and 237 → 194 for dropropizine enantiomers and the internal standard, respectively, in the positive ionization mode. The proposed method provided accurate and reproducible results over the linearity range of 3.23–2022 ng/mL for each enantiomer. The intra‐ and inter‐day precisions were in the ranges of 3.38–13.6 and 5.11–13.8 for LDP and 4.19–11.8 and 8.89–10.1 for DDP. Both LDP and DDP were found to be stable under different stability conditions. The method was successfully used in a stereoselective pharmacokinetic study of dropropizine enantiomers in rats following oral administration of racemate dropropizine at 100 mg/kg. The pharmacokinetic results indicate that the disposition of dropropizine enantiomers is not stereoselective and chiral inversion does not occur in rats.     

A rapid MCM‐41 dispersive micro‐solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids

A rapid dispersive micro‐solid phase extraction (D‐μ‐SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM‐41 was used as sorbent in d ‐μ‐SPE of the azole compounds from biological fluids. Important D‐μ‐SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB‐C₁₈ column (2.1 × 100 mm, 3.5 μm), using a mobile phase of acetonitrile–0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v /v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1–10,000 μg/L with satisfactory limit of detection (≤0.06 μg/L) and limit of quantitation (≤0.3 μg/L). The proposed method also showed acceptable intra‐ and inter‐day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3–114.8%. The MCM‐41‐D‐μ‐SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 μL); thus it is advantageous for routine drug analysis.     

Stereoselective determination of dufulin in watermelon under field conditions using chiral ultra high performance liquid chromatography with high‐resolution mass spectrometry

An effective and sensitive chiral analytical method was established to investigate the stereoselective dissipation of rac‐dufulin in watermelon using ultra high performance liquid chromatography with a superchiral S‐OD chiral column (4.6 × 150 mm i.d., 5 μm) coupled with high‐resolution mass spectrometry. To optimize the pretreatment method for detecting rac‐dufulin in the three matrixes, different extraction solvents, extractant volumes, extraction times, and absorbents were investigated to improve extraction efficiency. Moreover, analysis of variance was used to perform method validation for determination of the two dufulin enantiomers in the three matrixes. Using the optimized method, good linearity was obtained (determination coefficient > 0.999). The limits of detection and quantification of the two dufulin enantiomers in soil, watermelon, and pulp were 0.15 and 0.5 μg/kg, respectively. The average recoveries of the two enantiomers in the three matrixes at four spiked levels ranged from 75.0 to 107.8%, with intra‐ and inter‐day relative standard deviations of 0.4–10.4%. In field trials, the R enantiomer was preferentially dissipated in watermelon. These method validation results confirmed that the developed method was convenient and reliable for the stereoselective determination of enantiomers of rac‐dufulin in watermelon.     

Quantitative determination of buprenorphine,naloxone and their metabolites in rat plasma using hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry

A rapid and sensitive LC–MS/MS method was developed and validated for the simultaneous determination of buprenorphine and its three metabolites (buprenorphine glucuronide, norbuprenorphine and norbuprenorphine glucuronide) as well as naloxone and its metabolite naloxone glucuronide in the rat plasma. A hydrophilic interaction chromatography column and a mobile phase containing acetonitrile and ammonium formate buffer (pH 3.5) were used for the chromatographic separation. Mass spectrometric detection was achieved by an electrospray ionization source in the positive mode coupled to a triple quadrupole mass analyzer. The calibration curves for the six analytes displayed good linearity over the concentration range 1.0 or 5.0–1000 ng/mL. The intra and inter‐day precision (CV) ranged from 2.68 to 16.4% and from 9.02 to 14.5%, respectively. The intra‐ and inter‐day accuracy (bias) ranged from −14.2 to 15.2% and from −9.00 to 4.80%, respectively. The extraction recoveries for all the analytes ranged from 55 to 86.9%. The LC–MS/MS method was successfully applied to a pharmacokinetic study of buprenorphine–naloxone combination in rats.     

Electromembrane extraction combined with cyclodextrin-modified capillary electrophoresis for the quantification of trimipramine enantiomers

A sensitive, simple and reproducible method was developed for preconcentration and determination of trimipramine (TPM) enantiomers in biological samples using electromembrane extraction combined with cyclodextrin‐modified capillary electrophoresis (CE). During the extraction, TPM enantiomers migrated from a 5 mL sample solution through a thin layer of 2‐nitrophenyl octyl ether NPOE immobilized in the pores of a hollow fiber, and into a 20 μL acidic aqueous acceptor phase presented inside the lumen of the fiber. A Box–Behnken design and the response surface methodology (RSM) were used for the optimization of different variables on extraction efficiency. Optimized extraction conditions were: NPOE as supported liquid membrane, inter‐electrode distance of 5 mm, stirring rate of 1000 rpm, 51 V potential difference, 34 min as the extraction time, acceptor phase pH 1.0 and donor phase pH 4.5. Then, the extract was analyzed using optimized cyclodextrin (CD)‐modified CE method for the separation of TPM enantiomers. Best results were achieved using 100 mM phosphate running buffer (pH 2.0) containing 10 mM α‐CD as the chiral selector, applied voltage of 18 kV and 20°C. The range of quantitation for both enantiomers was 20–500 ng/mL. The method was very reproducible so that intra‐ and interday RSDs (n=6) were <6%. The limits of quantitation and detection for both enantiomers were 20 and 7 ng/mL, respectively. Finally, this method was successfully applied to determine the concentration of TPM enantiomers in plasma and urine samples without any pre‐treatment.     

A chiral LC‐MS/MS method for the enantioselective determination of R‐(+)‐ and S‐(–)‐pantoprazole in human plasma and its application to a pharmacokinetic study of S‐(–)‐pantoprazole sodium injection

Pantoprazole, a proton pump inhibitor, is clinically used for the treatment of peptic diseases. An enantioselective LC‐MS/MS method was developed and validated for the simultaneous determination of pantoprazole enantiomers in human plasma. Pantoprazole enantiomers and the internal standard were extracted from plasma using acetonitrile. Chiral separation was carried on a Chiralpak IE column using the mobile phase consisted of 10 mm ammonium acetate solution containing 0.1% acetic acid–acetonitrile (28 : 72, v /v). MS analysis was performed on an API 4000 mass spectrometer. Multiple reactions monitoring transitions of m /z 384.1→200.1 and 390.1→206.0 were used to quantify pantoprazole enantiomers and internal standard, respectively. For each enantiomer, no apparent matrix effect was found, the calibration curve was linear over 5.00–10,000 ng/mL, the intra‐ and inter‐day precisions were below 10.0%, and the accuracy was within the range of –5.6% to 0.6%. This method was applied to the stereoselective pharmacokinetic studies in human after intravenous administration of S ‐(–)‐pantoprazole sodium injections. No chiral inversion was observed during sample storage, preparation procedure and analysis. While R ‐(+)‐pantoprazole was detected in human plasma with a slightly high concentration, which implied that S ‐(–)‐pantoprazole may convert to R ‐(+)‐pantoprazole in some subjects.     

Fast ultrasound‐assisted extraction followed by capillary gas chromatography combined with nitrogen–phosphorous selective detector for the trace determination of tebuconazole in garlic,soil and water samples

A fast and an efficient ultrasound‐assisted extraction technique using a lower density extraction solvent than water was developed for the trace‐level determination of tebuconazole in garlic, soil and water samples followed by capillary gas chromatography combined with nitrogen–phosphorous selective detector (GC–NPD). In this approach, ultrasound radiation was applied to accelerate the emulsification of the ethyl acetate in aqueous samples to enhance the extraction efficiency of tebuconazole without requiring extra partitioning or cleaning, and the use of capillary GC–NPD was a more sensitive detection technique for organonitrogen pesticides. The experimental results indicate an excellent linear relationship between peak area and concentration obtained in the range 1–50 μg/kg or μg/L. The limit of detection (S/N, 3 ± 0.5) and limit of quantification (S/N, 7.5 ± 2.5) were obtained in the range 0.2–3 and 1–10 μg/kg or μg/L. Good spiked recoveries were achieved from ranges 95.55–101.26%, 96.28–99.33% and 95.04–105.15% in garlic, Nanivaliyal soil and Par River water, respectively, at levels 5 and 20 μg/kg or μg/L, and the method precision (% RSD) was ≤5%. Our results demonstrate that the proposed technique is a viable alternative for the determination of tebuconazole in complex samples.