Coupling of size-exclusion chromatography to liquid chromatography/mass spectrometry for determination of trace levels of thifensulfuron-methyl and tribenuron-methyl in cottonseed and cotton gin trash

Size-exclusion chromatography (SEC) was coupled to reversed-phase liquid chromatography/mass spectrometry for the determination of thifensulfuron-methyl and tribenuron-methyl in cottonseed and cotton gin trash. The limit of quantitation was 20 parts per billion (ppb), and the limit of detection was 6 ppb. The analytes were extracted by homogenization in a buffer solution. The extracts underwent a solvent exchange into methanol and were injected onto an SEC column. As the analytes eluted from the SEC column, the eluate was diverted onto a reversed-phase column for additional separation of the analytes and their detection via mass spectrometry. This method is unique because the samples are not cleaned up before analysis, the analytes are injected in methanol, and the entire analysis is completed in 30 min. Average recoveries and standard deviations for thifensulfuronmethyl and tribenuron-methyl in cotton gin trash were 91 +/- 6% and 88 +/- 5%, respectively. Average recoveries and standard deviations for thifensulfuron-methyl and tribenuron-methyl in cottonseed were 91 +/- 11% and 99 +/- 12%, respectively. This is an effective method for the detection and determination of thifensulfuron-methyl and tribenuron-methyl in cotton.     

LC Determination of Thiols Derivatized with 4-(Aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole after SPE

Solid-phase extraction (SPE) coupled with high-performance liquid chromatography?Cfluorescence detection (LC?CFL) was developed for the determination of three thiol compounds including glutathione, cysteine and acetylcysteine. 4-(Aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole was used for derivatization of thiols. Factors affecting derivatization and extraction efficiency were optimized. Sample solution (2?mL) was extracted on a SPE column for 2?min and then eluted with 400???L methanol. The analytes were injected onto the LC system for separation on a C₁₈ column, and eluted with methanol?Cacetate buffer. The analytes were detected by fluorescence at an emission wavelength of 515?nm with excitation at 385?nm. The linearity of the method was in the range of 0.1?C60???M, with correlation coefficients ranging from 0.9979 to 0.9990. The detection limits of the method were in the range of 5?C20?nM. The proposed method was applied to the analysis of human plasma samples with recoveries of 86?C112.9%.     

Determination of Arbutin,Niacinamide, and Adenosine in Functional Cosmetic Products by High-Performance Liquid Chromatography

A reversed-phase high-performance liquid chromatography method using a diode array detector at 260 nm was developed and validated for the determination of arbutin, niacinamide, and adenosine in cosmetics. The analytes were extracted using methanol and deionized water. The separations were performed on a C₁₈ column with gradient elution. At the optimized conditions, the limits of detection for arbutin, niacinamide, and adenosine were 0.75, 0.12, and 0.01 µg/mL, respectively. The average recoveries were between 98.1% and 107.5%. The method was used to analyze thirty cosmetics.     

Development of a tandem thin-layer chromatography-high-performance liquid chromatography method for the identification and determination of corticosteroids in cosmetic products

A solid-phase extraction clean-up and and a liquid chromatographic method with ultraviolet detection were developed for the analysis of 51 corticosteroids in cosmetic samples in order to screen commercial samples for the presence of undeclared synthetic corticosteroids. A thin-layer chromatographic analysis was carried out on silica gel plates, using different eluants and detection reagents. When such a preliminary chromatographic separation gave some indications about the presence of steroid compounds, the methanol extracts from real samples were applied to a solid-phase extraction C₁₈ cartridge, and the analytes eluted with ethyl ether. The high-performance liquid chromatographic separation was then carried out for the identification and determination of the analytes using a Purospher RP-18 column, an isocratic or a gradient elution with a mixture acetonitrile-water and a photodiode-array detector. The accuracy of the method was determined by spiking experiments on home-made cosmetic samples. The analytical recoveries were satisfactory.     

超高效液相色谱-串联质谱法同时检测动物组织中15种保水功能药物

建立了超高效液相色谱-串联质谱检测动物组织中15种保水功能药物残留的分析方法。样品经含1.0%（v/v）甲酸的乙腈溶液提取和Oasis PRiME HLB SPE柱净化后,采用Acquity UPLC BEH C18色谱柱（50 mm×2.1 mm,1.7 μm）分离,以甲醇和0.1%（v/v）甲酸水溶液为流动相进行梯度洗脱,在电喷雾电离（ESI）源、正离子模式下,采用MRM监测模式进行数据采集。在1.0~50.0 μg/kg范围内,15种保水功能药物的线性关系良好,相关系数均≥0.9949;定量限均低于1.0 μg/kg。通过添加回收试验表明,动物组织中15种保水功能药物的平均回收率为60.0%~111.0%,批内RSD为0.56%~11.5%,批间RSD为2.31%~14.8%。该方法满足动物组织中该药物多残留的检测要求,为应对动物源性食品中筛查风险隐患和监控非法添加提供了新思路。     

Determination of Aflatoxins in Rice and Maize by Ultra-High Performance Liquid Chromatography–Tandem Mass Spectrometry with Accelerated Solvent Extraction and Solid-Phase Extraction

A fast and reliable ultra-high performance liquid chromatography–tandem mass spectrometry method was developed for the determination of aflatoxins B₁, B₂, G₁, and G₂ in cereal. The analytes were extracted by accelerated solvent extraction with methanol/water (80:20). A polymeric solid-phase extraction column was used for sample preparation. Under optimum conditions, the analyte recoveries for samples spiked at different concentration levels in rice and maize ranged from 71.2 to 94.0%, with relative standard deviations less than 16.4%. Limits of detection (signal-to-noise ratio, 3:1) for the aflatoxins ranged from 0.25 to 0.93 ng/g. The developed method was applied to the determination of aflatoxins in ten rice and maize samples. One maize sample tested positive with an aflatoxin B₁ concentration of 2.7 ng/g.     

固相萃取净化及超高效液相色谱-串联质谱法测定橡胶制品中的13种N-亚硝胺

建立了固相萃取(SPE)净化、超高效液相色谱-串联质谱(UHPLC-MS/MS)测定橡胶制品中13种N-亚硝胺的方法。样品于密闭萃取瓶中于60 ℃下用甲醇超声萃取30 min,C₁₈固相萃取小柱对萃取液进行净化,经C₁₈色谱柱分离,最后用电喷雾正离子(ESI⁺)和多重反应监测模式(MRM)对13种N-亚硝胺进行定性、定量测定。实验中对样品前处理、色谱分离条件和质谱检测条件进行了优化。在优化的实验条件下,橡胶样品中添加N-亚硝基二甲胺(NDMA)与N-亚硝基-二乙基胺(NDEA)为500 μg/kg、其他组分均为50 μg/kg时,各组分的相对标准偏差(RSD,n=7)小于10%;在实际样品中的加标回收率为70.7%~117.0%;方法的检出限(LOD,以10倍标准偏差计)为0.5~500 μg/kg。方法可应用于橡胶制品中13种N-亚硝胺的测定。     

Determination of olanzapine and desmethylolanzapine in the plasma of schizophrenic patients by means of an improved HPLC method with amperometric detection

Summary An improved HPLC method with electrochemical detection has been developed for the determination of olanzapine and its main metabolite, desmethylolanzapine, in human plasma. Chromatographic separation and analysis were performed on a C₈ reversed-phase column with a mixture of methanol, acetonitrile, and pH 3.7 phosphate buffer as mobile phase; 2-methylolanzapine was used as internal standard. Careful pretreatment of the plasma samples was implemented by means of solid phase extraction (SPE). Response was linearly dependent on concentration and precision was satisfactory over the concentration range 0.5–75.0 ng mL⁻¹ for both analytes. The limit of detection was 0.2 ng mL⁻¹ for both analytes. Application to plasma samples of patients treated with Zyprexa tablets gave good results. Because of its sensitivity and selectivity, and the need for small plasma samples, this method seems to be a useful tool for clinical monitoring.     

固相萃取-高效液相色谱-可变波长检测法同时测定调味品中甜味剂和人工合成色素

建立了同时测定调味品中糖精钠和合成色素的固相萃取-高效液相色谱(SPE-HPLC)分析方法。样品经石油醚低温去除油脂,聚酰胺固相萃取柱净化和富集,然后进行HPLC分析。采用反相C₁₈色谱柱,以甲醇和0.02 mol/L醋酸铵为流动相进行梯度洗脱,使用可变波长分别在230、510、484和510 nm进行检测。实验结果表明:糖精钠与合成色素的分离效果良好,回收率为88.6%～97.1%,相对标准偏差小于5%;方法检出限均可达到0.05 mg/kg。该方法操作简单,结果准确可靠,重现性好,适用于大批量调味品中甜味剂和人工合成色素的同时检测。     

Sensitive, selective and rapid determination of bupropion and its major active metabolite, hydroxybupropion, in human plasma by LC-MS/MS: application to a bioequivalence study in healthy Indian subjects

A sensitive, selective and rapid liquid chromatography tandem mass spectrometry (LC‐MS/MS) method was developed for the simultaneous determination of bupropion (BUP) and its major active metabolite hydroxybupropion (HBUP) in human plasma. Separation of both the analytes and venlafaxine as internal standard (IS) from 50 μL human plasma was carried out by solid‐phase extraction. The chromatographic separation of the analytes was achieved on a Zorbax Eclipse XDB C₁₈ (150 × 4.6 mm, 5 µm) analytical column using isocratic mobile phase consisting of 20 mm ammonium acetate–methanol (10:90, v/v), with a resolution factor of 3.5. The method was validated over a wide dynamic concentration range of 0.1–350 ng/mL for BUP and 0.1–600 ng/mL for HBUP. The matrix effect was assessed by post‐column infusion and the mean process efficiency was 96.08 and 94.40% for BUP and HBUP, respectively. The method was successfully applied to a bioequivalence study of 150 mg BUP (test and reference) extended release tablet formulation in 12 healthy Indian male subjects under fed conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Simple and rapid determination of N6‐(Δ2‐isopentenyl)adenine,zeatin, and dihydrozeatin in plants using on‐line cleanup liquid chromatography coupled with hybrid quadrupole‐Orbitrap high‐resolution mass spectrometry

A simple and rapid method was developed for the determination of three free cytokinins, namely, N⁶‐(Δ²‐isopentenyl)adenine, zeatin, and dihydrozeatin, in plants using TurboFlow on‐line cleanup liquid chromatography combined with hybrid quadrupole‐Orbitrap high‐resolution mass spectrometry. The samples were extracted using acetonitrile, and then the extract was purified on a C₁₈‐p column, in which the sample matrix was removed and the analytes were retained. Subsequently, the analytes were eluted from the extraction column onto the analytical column (Hypersil Gold C₁₈ column) prior to chromatographic separation and hybrid Q‐Orbitrap detection using the targeted‐MS² scan mode. The linearity was satisfactory with a correlation coefficient of >0.999 at concentrations ranging from 5–5000 pg/mL. The limits of quantification for the analytes ranged from 4.2–5.2 pg/mL. The intra‐ and inter‐day average recoveries of analytes fortified at three levels ranged from 85.4–108.2%, and the intra‐ and inter‐day relative standard deviations ranged from 4.04–8.57%. The method was successfully applied for the determination of free cytokinins in different tissue samples of Oryza sativa and Arabidopsis thaliana.     

High-Performance Liquid Chromatographic Method for the Simultaneous Determination of Four Flavonols in Food Supplements and Pharmaceutical Formulations

A method using high-performance liquid chromatography with diode array detection (HPLC-DAD) as a powerful separation technique has been developed for the simultaneous determination of the four flavonols rutin, quercetin, kaempferol and isorhamnetin in food supplements and pharmaceutical formulations. The chromatographic separation was achieved in 36?min using a Symmetry C₁₈ column (250?×?3?mm; 5?µm) as the stationary phase and a mixture of methanol, acetonitrile, and pH 2.5 aqueous acetic acid as the mobile phase in gradient elution mode. The analytical wavelengths were 256?nm for rutin, quercetin and isorhamnetin, and 368?nm for kaempferol. An ultrasound-assisted extraction protocol was performed using methanol as solvent. The detection and quantification limits were lower than 0.03?µg mL^?1 and 0.08?µg mL^?1, respectively. The inter-day and intra-day precisions were less than 4.8 and 5.1%, respectively, and the average recoveries were in the range from 96 to 107%. The method was applied for the determination of the studied flavonols in food supplements and pharmaceutical preparations. The satisfactory recovery values demonstrate the potential of the developed method for the determination of the analytes in these samples. In addition, the method is suitable for routine quality control due its ease of operation.     

Determination of metoserpate,buquinolate, and diclofenac in pork,eggs, and milk using liquid chromatography–tandem mass spectrometry

In this work, a method was developed for the simultaneous determination of residual metoserpate, buquinolate and diclofenac in pork, milk, and eggs. Samples were extracted with 0.1% formic acid in acetonitrile, defatted with n‐hexane, and filtered prior to analysis using liquid chromatography–tandem mass spectrometry. The analytes were separated on a C₁₈ column using 0.1% acetic acid and methanol as the mobile phase. The matrix‐matched calibration curves showed good linearity over a concentration range of 5–50 ng/g with coefficients of determination (R²) ≥0.991. The intra‐ and inter‐day accuracies (expressed as recovery percentage values) calculated using three spiking levels (5, 10, and 20 μg/kg) were 80–108.65 and 74.06–107.15%, respectively, and the precisions (expressed as relative standard deviation) were 2.86–13.67 and 0.05–11.74%, respectively, for the tested drugs determined in various matrices. The limits of quantification (1 and 2 μg/kg) were below the uniform residual level (0.01 mg/kg) set for compounds that have no specific maximum residue limit (MRL). The developed method was tested using market samples and none of the target analytes was detected in any of the samples. The validated method proved to be practicable for detection of the tested analytes in pork, milk, and eggs.     

Comparative pharmacokinetic study of four major bioactive components after oral administration of Zhi‐Zi‐Hou‐Po decoction in normal and corticosterone‐induced depressive rats

A highly selective and efficient LC–MS/MS method was developed to determine the plasma concentration of magnolol, hesperidin, neohesperidin and geniposide following oral administration of Zhi‐Zi‐Hou‐Po decoction in normal and depressed rats. Plasma samples were pretreated by protein precipitation with methanol. Chromatographic separation was performed on an XTerra^® MS C₁₈ column using a gradient elution with a mobile phase composed of acetonitrile–0.1% aqueous formic acid. The proposed method was validated to be specific, accurate and precise for the analytes determination in plasma samples. The calibration curves displayed good linearity over definite concentration ranges for the analytes. The intra‐ and inter‐day precision of the proposed method at three different levels were all within <11.13% and the relative errors ranged from ?8.46 to 8.93%. The recovery of the four compounds ranged from 82.72 to 89.08% and no apparent matrix effect was observed during sample analysis. After full validation, the established method was successfully applied for comparing the pharmacokinetics of four components between normal and depressed rats. The results showed that the AUC and C_max of four analytes in depressed rats were significantly different from those in normal rats and might provide helpful information to guide the clinical use of Zhi‐Zi‐Hou‐Po to treat depression.     

Simultaneous determination of rabeprazole and its two active metabolites in human urine by liquid chromatography with tandem mass spectrometry and its application in a urinary excretion study

A simple and rapid liquid chromatography with tandem mass spectrometry method has been developed and validated for the determination of rabeprazole and its two active metabolites, rabeprazole thioether and desmethyl rabeprazole thioether, in human urine using donepezil as the internal standard. The sample preparation procedure involved a simple dilution of urine sample with methanol (1:3, v/v). The chromatographic separation was achieved on a Hedera ODS‐2 C₁₈ column using a mixture of methanol/10 mmol/L ammonium acetate solution (containing 0.05% formic acid; 55:45, v/v) as the mobile phase. The method was validated over the concentration ranges of 0.15–100 ng/mL for rabeprazole, 0.30–400 ng/mL for rabeprazole thioether, and 0.05–100 ng/mL for desmethyl rabeprazole thioether. The established method was highly sensitive with a lower limit of quantification of 0.15 ng/mL for rabeprazole, 0.30 ng/mL for rabeprazole thioether, and 0.05 ng/mL for desmethyl rabeprazole thioether. The intra‐ and interbatch precision was <4.5% for the low, medium, and high quality control samples of all the analytes. The recovery of the analytes was in the range 95.4–99.0%. The method was successfully applied to a urinary excretion profiles after intravenous infusion administration of 20 mg rabeprazole sodium in healthy volunteers.     

Simultaneous determination and pharmacokinetic study of three flavonoid glycosides in rat plasma by LC–MS/MS after oral administration of Rubus chingii Hu extract

A simple and sensitive liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous determination of isoquercitrin, kaempferol‐3‐O‐rutinoside and tiliroside in rat plasma. Plasma samples were deproteinized with methanol and separated on a Hypersil Gold C₁₈ column (2.1 × 50 mm, i.d., 3.0 μm) using gradient elution with the mobile phase of water and methanol at a flow rate of 0.4 mL/min. Mass spectrometric detection was performed with negative ion electrospray ionization in selected reaction monitoring mode. All analytes showed good linearity over their investigated concentration ranges (r² > 0.99). The lower limit of quantification was 1.0 ng/mL for isoquercitrin and 2.0 ng/mL for kaempferol‐3‐O‐rutinoside and tiliroside, respectively. Intra‐ and inter‐day precisions were <8.2% and accuracy ranged from −11.5 to 9.7%. The mean extraction recoveries of analytes and IS from rat plasma were >80.4%. The assay was successfully applied to investigate the pharmacokinetic study of the three ingredients after oral administration of Rubus chingii Hu to rats.     

A Sorbent Extraction Procedure for the Preconcentration of Gold,Silver and Palladium on an Activated Carbon Column

ABSTRACT

A preconcentration method based on the use of an activated carbon column has been established for flame atomic absorption spectrometric determinations of gold, silver and palladium. The analytes were sorbed on the column as a complex of dithiophosphoric acid O, O-diethyl ester (DDTP). The sorbed analytes were eluted through the column with 2M NH₃ in acetone. Quantitative recoveries (≥95 %) for gold, silver and palladium were obtained from acidic solutions. The developing method was successfully applied to the determination of trace amounts of gold, silver and palladium in some samples with satisfactory results (relative standard deviation < 7 %; relative error < 3 %).     

Quantitation of 6-(pyridin-3-yl)quinolin-2(1H)-one, a cardiac stimulant, and its N-oxide metabolite in dog plasma by high-performance liquid chromatography.

A method is described for the determination of UK-57,400 (I), a 6-substituted quinoline cardiotonic, and its pyridyl-N-oxide in dog plasma. The analytes are selectively retained from plasma (1 ml) on a solid-phase extraction column and eluted with 1 ml of methanol. After evaporation to dryness, the residue is reconstituted in 100 microliters of the mobile phase. Chromatography is carried out on a Spherisorb 5 microns phenyl high-performance liquid chromatography column, with ultraviolet detection. Calibration curves are linear for concentrations from 10 to 100 ng ml-1. For I, the coefficients of variation at highest and lowest concentrations are 1 and 14%, respectively, while the corresponding figures for the pyridyl-N-oxide metabolite are 4 and 10%, respectively. Sample recovery from extraction is greater than 90%. The limit of detection is 4 ng ml-1 for both analytes.     

Simultaneous determination of cyadox and its metabolites in plasma by high‐performance liquid chromatography tandem mass spectrometry

Cyadox is a novel antimicrobial growth‐promoter of the quinoxalines. For food safety and pharmacokinetic studies, a convenient, sensitive and reproducible LC‐ESI‐MS/MS method was developed for the simultaneous determination of cyadox and its major metabolites, quinoxaline‐2‐carboxylic acid, 1,4‐bisdesoxycyadox, cyadox‐1‐monoxide and cyadox‐4‐monoxide in chicken plasma. Plasma sample was subjected to a simple deproteinisation with acetonitrile. Analysis was performed on a C₁₈ column by detection with mass spectrometry in multiple reaction monitoring mode. A gradient elution program with 0.2% formic acid, methanol and acetonitrile was performed at a flow rate of 0.2 mL/min. The decision limits (CCαs) of five analytes in plasma ranged from 1.0 to 4.0 μg/L, and the detection capabilities (CCβs) were <10 μg/L. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The extraction recoveries of five analytes were between 87.4 and 93.9% in plasma at the spiked levels of 5 (10)–200 μg/L with the relative standard deviations <10% for each analyte. The developed method demonstrated a satisfactory applicability in real plasma samples.