亲水作用液相色谱-串联质谱测定烟叶中马来酰肼及其糖苷

建立了一种基于亲水作用液相色谱-串联质谱的烟叶中马来酰肼及其糖苷的定量分析方法。方法采用乙腈-甲基叔丁基醚-水（7：10：13,体积比）超声波辅助提取烟叶中的马来酰肼及其糖苷,提取液经离心分相和溶剂置换后进行亲水作用液相色谱-串联质谱分析。马来酰肼及马来酰肼-O-β-D-葡萄糖苷的基质添加标准曲线的线性范围为5~150 mg/kg,相关系数（r²）为0.9971及0.9972,检出限分别为0.5 mg/kg和0.3 mg/kg,定量限分别为1.0 mg/kg和0.8 mg/kg。马来酰肼及马来酰肼-O-β-D-葡萄糖苷在10、40、80 mg/kg 3个加标水平下的回收率为83.1%~112.3%,在40 mg/kg加标水平下的日内重复性分别为2.7%和3.8%,日间重复性分别为8.3%和7.1%。应用该方法分析喷洒马来酰肼28天后烟叶中马来酰肼的分布情况,发现马来酰肼含量减少了80.8%,其中仅有7.6%转化成了马来酰肼糖苷,其他马来酰肼的去向有待进一步研究。     

Dissipation dynamics and final residues of flutriafol in tobacco and soil using ultrasound-assisted extraction before liquid chromatography/tandem mass spectrometry

The dissipation dynamics and final residues of flutriafol on tobacco plant and soil were studied under field conditions. The residues of flutriafol in soil, green tobacco leaves and cured tobacco leaves were extracted by ultrasound-assisted extraction, cleaned up by dispersive solid-phase extraction and detected by liquid chromatography with tandem mass spectrometry. The limits of detection of flutriafol in soil, green tobacco leaves and cured tobacco leaves were 0.006, 0.033 and 0.033 mg·kg^?1, respectively. The limits of quantification of flutriafol in soil, green tobacco leaves and cured tobacco leaves were 0.02, 0.1 and 0.1 mg·kg^?1, respectively. Recoveries were 72.9–102% with relative standard deviations of less than 12% in soil and tobacco matrix. For field experiments, the half-lives of flutriafol in soil and green tobacco leaves were 9.2–11.5 and 9.5–11.1 days, respectively. At harvest, the final residue levels of flutriafol in cured tobacco leaves collected 21 days after one application at the recommended dosage were below 2.0 mg/kg. The maximum residue limit maximum residue limit (MRL) for flutriafol in tobacco has not yet been established in any countries. The data could help the Chinese Government to establish the MRL of flutriafol in tobacco and provide guidance on the proper use of flutriafol.     

Simultaneous quantification of ten Amadori compounds in tobacco using liquid chromatography with tandem mass spectrometry

Amadori compounds are aroma precursors formed in the initial phase of the Maillard reaction. Based on their similar structures, simultaneous quantification of more than six Amadori compounds in tobacco has not been reported yet. In this study, a simple and rapid method was developed to simultaneously quantify ten Amadori compounds including the isomers of Fructose‐isoleucine and Fructose‐leucine in tobacco. The separation was performed on an Atlantis T₃ column (2.1 × 250 mm, 5 μm) by gradient elution using acetonitrile and water as the mobile phases. The quantification method was systematically evaluated and proven to be sensitive and accurate. The linearity was good, with correlation coefficients of 0.9977–0.9999. The limits of detection and quantitation were 1.354–2.532 and 4.516–8.444 ng/mL, respectively. The recoveries were 84.0–119.6%, and the relative standard deviations were 1.33–5.40%. The method was used to analyze the changes in the amounts of ten Amadori compounds in tobacco before and after tobacco primary processing. The analysis shows that the Maillard reaction occurs during the short processing period.     

Development and validation of a liquid chromatography with tandem mass spectrometry method for the determination of nitroimidazole residues in beeswax

In this study, a new method for the determination of 12 nitroimidazoles and their hydroxymetabolites (metronidazole, hydroxymetronidazole, dimetridazole, ronidazole, hydroxydimetridazole, ipronidazole, hydroxyipronidazole, carnidazole, ornidazole, secnidazole, ternidazole, tinidazole) in beeswax has been developed and validated. The optimized sample preparation procedure included melting and dilution of beeswax in a mixture of n‐hexane and isopropanol followed by extraction with 2% acetic acid. The extracts were purified on strong cation exchange based solid‐phase extraction cartridges and evaporated in a vacuum system with vortex motion. The separation and detection of the nitroimidazoles in the beeswax extracts were achieved within 12 min by liquid chromatography tandem mass spectrometry using a pentafluorophenyl analytical column and applying a gradient elution with acetonitrile and 0.01% acetic acid as mobile phases. The method performance characteristics were evaluated at three concentration levels (1, 2, and 5 μg/kg) and the method was found to be suitable for determination of all tested nitroimidazoles. The limits of detection and quantification were 0.2–0.5 and 0.5–1 μg/kg, respectively. The recoveries varied from 71.2 to 104.9% while the relative standard deviations were less than 13.8% under the intermediate precision conditions.     

Combination of liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry for the detection of 21 anabolic steroid residues in bovine urine

For the detection of anabolic steroid residues in bovine urine, a highly sensitive liquid chromatographic/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method was developed using both positive and negative ionization. For four compounds the ESI mode was not sensitive enough and gas chromatographic/mass spectrometric GC/MS detection was therefore still necessary as a complementary method. The sample clean-up consisted of solid-phase extraction (SPE) on a C(18) column followed by enzymatic hydrolysis and a second solid-phase extraction on a combination of a C(18) and a NH(2) column. After this last SPE clean-up, the eluate was split into two equal aliquots. One aliquot was further purified and after derivatization used for GC/MS analysis. The other aliquot was analyzed with LC/MS/MS in both ESI+ and ESI- modes. The method was validated according to the European Commission Decision 2002/657/EC. Decision limits (CCalpha) were between 0.16 and 1 ng ml(-1) for the compounds detected with the LC/MS/MS method. The developed method is used in routine analysis in our laboratory.     

Enantioseparation of nornicotine in tobacco by ultraperformance convergence chromatography with tandem mass spectrometry

Nornicotine, an alkaloid constituent of tobacco, is a precursor to the carcinogen N‐nitrosonornicotine that is produced during the curing and processing of tobacco. Accumulating evidence reveals that nornicotine enantiomers have different neurochemical and behavioral effects. In the present study, an accurate and rapid method was developed for the enantioseparation of (R )‐(+)‐nornicotine and (S )‐(−)‐nornicotine enantiomers in tobacco by ultra‐performance convergence chromatography with tandem mass spectrometry. Chromatographic conditions were investigated to achieve the optimal resolution of two enantiomers. Results indicated that (R )‐(+)‐nornicotine and (S )‐(−)‐nornicotine could be separated within 5 min when ammonium hydroxide was added into the cosolvent, and the best resolution (R _s = 4.76) was achieved on a immobilized cellulose tris‐(3,5‐dichlorophenylcarbamate) chiral stationary phase. The proposed method was validated and was finally applied to analyze the compositions of (R )‐(+)‐nornicotine and (S )‐(−)‐nornicotine in three typical types of tobaccos (flue‐cured, burley, and oriental). It was found that, enantiomer fraction of nornicotine (the proportion of (S )‐(−)‐nornicotine in the nornicotine pool) in burley tobacco samples was relatively high and constant compared with flue‐cured and oriental tobaccos. The effective and rapid enantioseparation of nornicotine may help the understanding of alkaloid metabolites in different tobacco varieties and may also benefit pharmacological studies of alkaloid enantiomers.     

超高压液相色谱质谱联用法同时测定牛肝中七种磺胺类药物

建立了牛肝中7种磺胺类药物残留量的超高压液相色谱质谱联用的测定方法.样品经乙腈提取后经过MCX阳离子交换小柱净化后,利用超高压液相色谱进行检测.方法检出限为0.02 μg/g.7种磺胺类药物的加标回收率为 70.6%～112.5% (添加水平为0.02,0.05,0.1,0.2 μg/g),相对标准偏差为 2.6%～14.3%.同时建立了阳性样品检测的质谱确证方法,能够满足国际上对药物残留的要求.     

Analysis of pesticide residues in tobacco with online size exclusion chromatography with gas chromatography and tandem mass spectrometry

An ultrasensitive method for the simultaneous analysis of pesticides residues in tobacco was developed with online size exclusion chromatography with gas chromatography and tandem mass spectrometry. Tobacco samples were extracted with the solvent mixture of cyclohexane and acetone (7:3, v/v) and centrifuged. Then, the supernatant liquors were injected directly into the online size exclusion chromatography with gas chromatography and tandem mass spectrometry without any other purification procedures after being filtered with a 0.22 μm organic phase filter. The matrix interferences were effectively removed and recoveries of most pesticides were in the range of 72–121%. Especially, for chlorothalonil, the analysis efficiency of this method was much more favorable than that of the general method, in which dispersive solid‐phase extraction was used as an additional purified procedure. In addition, the limits of quantitation of this method were from 1 to 50 μg/kg. Therefore, a rapid, cost‐effective, labor‐saving method was proposed in the present work, which was suitable for the analysis of 41 pesticide residues in tobacco.     

Simultaneous determination of residues of thiamethoxam and its metabolite clothianidin in tobacco leaf and soil using liquid chromatography‐tandem mass spectrometry

A simple analytical method was developed to simultaneously determine thiamethoxam and its metabolite, clothianidin, in fresh tobacco leaf, soil and cured tobacco leaf using liquid chromatography with tandem mass spectrometry. Thiamethoxam and clothianidin in tobacco and soil samples were extracted with acetonitrile containing 0.1% formic acid and purified using an NH₂‐SPE column. The optimized method provided good linearity with coefficients of determination R² ≥ 0.9981. The limits of detection and quantification were between 0.006–0.12 and 0.02–0.4 mg/kg, respectively. Intra‐ and inter‐day recovery assays were used to validate the established method. The average recoveries of thiamethoxam and clothianidin in fresh tobacco leaf, soil and cured tobacco leaf were 75.04–100.47%, 75.86–86.40% and 89.83–99.39%, respectively. The intra‐ and inter‐day relative standard deviations were all <9%. The developed method was successfully applied for the analysis of thiamethoxam and clothianidin residues in actual tobacco and soil samples. The results indicated that the established method met the requirements for the analysis of trace amounts of thiamethoxam and clothianidin in fresh tobacco leaf, soil and cured tobacco leaf.     

Determination of antimicrobial residues and metabolites in the aquatic environment by liquid chromatography tandem mass spectrometry

Antimicrobials are used in large quantities in human and veterinary medicine. Their environmental occurrence is of particular concern due to the potential spread and maintenance of bacterial resistance. After intake by the organisms, the unchanged drug and its metabolized forms are excreted and enter wastewater treatment plants where they are mostly incompletely eliminated, and are therefore eventually released into the aquatic environment. The reliable detection of several antimicrobials in different environmental aqueous compartments is the result of great improvements achieved in analytical chemistry. This article provides an overview of the more outstanding analytical methods based on liquid chromatography tandem mass spectrometry, developed and applied to determine antimicrobial residues and metabolites present in surface, waste, and ground waters.      

高效液相色谱串联质谱法测定牛奶中林可酰胺类和大环内酯类抗生素残留量的研究

建立了牛奶样品中洁霉素、氯洁霉素、红霉素、螺旋霉素、交沙霉素、泰乐菌素、竹桃霉素等7种林可酰胺类及大环内酯类药物残留量的确证方法。用乙腈萃取样品中7种林可酰胺类及大环内酯类抗生素,然后用正己烷脱脂,旋转蒸发仪浓缩,以Luna C18(2)色谱柱分离,在正离子模式下以电喷雾电离串联质谱仪进行测定。在20、50、200μg/kg 3个浓度水平进行验证试验,方法的线性范围为20~200μg/kg,总体平均回收率为74.5%~97.5%,相对标准偏差为2.7%~11.3%。该方法各项技术指标满足国内外法规的要求,可用于牛奶样品中林可酰胺类及大环内酯类抗生素残留量的确证检测。     

Determination of a metabolite of nifursol in foodstuffs of animal origin by liquid–liquid extraction and liquid chromatography with tandem mass spectrometry

An analytical method has been developed for the detection of a metabolite of nifursol, 3,5‐dinitrosalicylic acid hydrazide, in foodstuffs of animal origin (chicken liver, pork liver, lobster, shrimp, eel, sausage, and honey). The method combines liquid chromatography and tandem mass spectrometry with liquid–liquid extraction. Samples were hydrolyzed with hydrochloric acid and derivatized with 2‐nitrobenzaldehyde at 37°C for 16 h. The solutions of derivatives were adjusted to pH 7.0−7.5, and the metabolite was extracted with ethyl acetate. 3,5‐Dinitrosalicylic acid hydrazide determination was performed in the negative electrospray ionization method. Both isotope‐labeled internal standard and matrix‐matched calibration solutions were used to correct the matrix effects. Limits of quantification were 0.5 μg/kg for all samples. The average recoveries, measured at three concentration levels (0.5, 2.0, and 10 μg/kg) were in the range of 75.8–108.4% with relative standard deviations below 9.8%. The developed method exhibits a high sensitivity and selectivity for the routine determination and confirmation of the presence of a metabolite of nifursol in foodstuffs of animal origin.     

Quantitative determination of domperidone in human plasma by ultraperformance liquid chromatography with electrospray ionization tandem mass spectrometry

A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for determining domperidone in human plasma. The analyte and internal standard (IS; mosapride) were isolated from plasma samples by protein precipitation with methanol (containing 0.1% formic acid). The chromatographic separation was performed on an Xterra MS C(18) Column (2.1 x 150 mm, 5.0 microm) with a gradient programme mobile phase consisting of 0.1% formic acid and acetonitrile at a flow rate of 0.30 mL/min. The total run time was 4.0 min. The analyses were carried out by multiple reaction monitoring using the parent-to-daughter combinations m/z 426 --> 175 and m/z 422 --> 198 (IS). The areas of peaks from the analyte and IS were used for quantification of domperidone. The method was validated according to the FDA guidelines on bioanalytical method validation. Validation results indicated that the lower limit of quantification was 0.2 ng/mL, and the assay exhibited a linear range of 0.2-60.0 ng/mL and gave a correlation coefficient (r(2)) of 0.999 or better. Quality control samples (0.4, 0.8, 15 and 50 ng/mL) in six replicates from three different analytical runs demonstrated an intra-assay precision (RSD) 4.43-6.26%, an inter-assay precision 5.25-7.45% and an overall accuracy (relative error) of <6.92%. The method can be applied to pharmacokinetic and bioequivalence studies of domperidone.     

Analytical study on ethephon residue determination in water by ion-pairing liquid chromatography/tandem mass spectrometry

A detailed analytical study on ethephon residue determination in water, making use of ion-pairing liquid chromatography coupled to electrospray tandem mass spectrometry (LC/MS/MS), has been carried out. Ethephon is a plant growth regulator, highly polar, which is typically present in aqueous solution in anionic form due to its acid character. Both its extraction and pre-concentration from water samples and its chromatographic retention are difficult. Several approaches for sample pretreatment have been tested including direct injection into the chromatographic system, on-line solid phase extraction (SPE) and off-line SPE, with the best results being obtained after off-line SPE, using Oasis MAX cartridges (mixed-mode strong anion-exchange). After testing several ion-pairing reagents, tetrabuthylammonium acetate (TBA) was selected. This was added to the samples before LC/MS/MS analysis to facilitate ethephon chromatographic retention. The acquisition of several specific MS/MS transitions together with the evaluation of their relative intensity ratios allowed the reliable confirmation of the analyte in samples. The optimised approach was tested in low-salinity water spiked at 0.1?µg?L^?1 level with satisfactory recovery, and a limit of detection of 0.02?µg?L^?1. To this purpose, the water sample was partially de-ionised in an initial stage, in order to remove major ions that would have interfered in analyses. The application of this methodology to more saline/complex water samples, as surface or wastewater, was problematic and a thorough optimisation of the de-ionisation conditions would be required.     

Simultaneous enantioselective determination of six pesticides in aqueous environmental samples by chiral liquid chromatography with tandem mass spectrometry

A robust and sensitive method was developed for the enantiomeric analysis of six chiral pesticides (including metalaxyl, epoxiconazole, myclobutanil, hexaconazole, napropamide, and isocarbophos) in aquatic environmental samples. The optimized chromatographic conditions for the quantification of all the 12 enantiomers were performed with Chiralcel OD‐RH column using mobile phase consisting of 0.1% aqueous formic acid and acetonitrile operated under reversed‐phase conditions and then analyzed using liquid chromatography with tandem mass spectrometry. Twelve enantiomers were detected in multiple reaction monitoring mode. Solid‐phase extraction and dispersive liquid–liquid microextraction were employed in this study. Response surface methodology was applied to assist in the dispersive liquid–liquid microextraction optimization. Under the optimum conditions, recoveries of pesticides enantiomers varied from 83.0 to 103.2% at two spiked levels with relative standard deviation less than 11.5%. The concentration factors were up to 1000 times. Method detection and quantification limits varied from 0.11 to 0.48 ng/L and from 0.46 to 1.49 ng/L, respectively. Finally, this method was used to determination of the enantiomers composition of the six pesticides in environmental aqueous matrices, which will help better understand the behavior of individual enantiomer and make accurate risk assessment to ecosystems.     

Determination of spinetoram in leafy vegetable crops using liquid chromatography and confirmation via tandem mass spectrometry

Spinetoram is a second-generation member of the spinosyn class, all members of which have been shown to be effective in insect control via a novel mode of action. Spinetoram is a mixture of 3'-O-ethyl-5, 6-dihydro spinosyn J (XDE-175-J) and 3'-O-ethyl spinosyn L (XDE-175-L). In order to establish a determination method for the analysis of spinetoram residues in crops, commercial product (5% suspension concentrate spinetoram) was applied to two leafy vegetables (Garland chrysanthemum and Aster scaber) on different spraying schedules. The analytical method used herein was based on a reversed-phase separation on a C(18) column, isocratic elution and UV detection. The analytes were confirmed via tandem mass spectrometry. The method was linear over a concentration range of 0.05-10 ppm with a correlation coefficient in excess of 0.9998. The recoveries of XDE-175-J and XDE-175-L from the two vegetables ranged between 86.04 and 98.87% at spiking levels of 1 and 5 ppm. The relative standard deviations were no more than 7% for all recovery tests conducted herein. The calculated limits of detection and quantification were 0.01 and 0.03 ppm for both XDE-175-J and XDE-175-L. The levels of residues in two vegetables treated under a fixed schedule in the greenhouse were 6.21-0.55 ppm (maximum residue limit (MRL) = 7 ppm). In sum, this method constitutes an easy and reliable technique for the determination of spinetoram in leafy vegetables.     

高效液相色谱-串联质谱法测定动物源食品中粘杆菌素、多粘菌素B的残留量

建立了动物源食品中粘杆菌素和多粘菌素B残留的高效液相色谱-串联质谱(HPLC-MS/MS)测定方法。样品用V(10%三氯乙酸水溶液):V(乙腈)=30:70提取,Oasis WCX SPE柱净化,LC-MS/MS电喷雾正离子多反应监测模式(ESI+-MRM)检测。分析物在0～250μg/kg的浓度范围内呈良好线性,线性相关系数>0.995。方法的定量限为10μg/kg。方法在三个添加水平的平均回收率在71.6%～78.9%之间,相对标准偏差在6.2%～12%之间。方法适用于动物源食品中粘杆菌素和多粘菌素B的定量及确证检测。     

Separation and determination of homogenous fatty alcohol ethoxylates by liquid chromatography with mulitstage mass spectrometry

Alcohol ethoxylates (AEs) are a significant component of a stream of surfactants directed to the aquatic environment. The aim of this work was the investigation of the dependence of the analytical signals of homogeneous AE homologues on liquid chromatography with tandem mass spectrometry conditions, as well as the separation of AEs from the water matrix and, on this basis, the development of an analytical procedure suitable for the determination of AEs in environmental samples. Homogeneous homologues containing dodecyl moiety and 2–9 oxyethylene subunits were investigated. The analytical signals of the investigated homologues were optimized in terms of concentration of ammonium acetate in the mobile phase (optimum 5 mM) and a column temperature (optimum 35°C) of the liquid chromatography with tandem mass spectrometry system. A separation of AEs from the water matrix by liquid–liquid extraction (ethyl acetate, chloroform) or solid‐phase extraction (C₁₈, styrene divinylbenzene, H‐RX) was investigated. In a model investigation, the best recoveries (>90%) were obtained with a styrene divinylbenzene cartridge eluted with a 1:1 mixture of chloroform and methanol. However, much worse recoveries were obtained from the river water sample. Better results were obtained for liquid–liquid extraction with ethyl acetate. Recoveries of 62–80% were obtained for homologues having 4–9 oxyethylene subunits, at the lowest spike.     

Simultaneous determination of residues of metalaxyl,cyazofamid and a cyazofamid metabolite in tobacco leaves and soil by liquid chromatography with tandem mass spectrometry

A simple method was developed and validated for the simultaneous determination of metalaxyl, cyazofamid and the cyazofamid metabolite 4‐chloro‐5‐p‐tolylimidazole‐2‐carbonitrile (CCIM) by liquid chromatography with tandem mass spectrometry. The three target compounds were extracted from tobacco and soil with acetonitrile containing 0.1% acetic acid, and the extracts were purified using octadecylsilane. The proposed method showed satisfactory linearity (R² ≥ 0.9985) for the target compounds. The limits of detection for metalaxyl, cyazofamid and CCIM were 0.006, 0.06 and 0.06 mg/kg in soil and green tobacco leaves and 0.03, 0.3 and 0.3 mg/kg in cured tobacco leaves, respectively. The limits of quantification for metalaxyl, cyazofamid and CCIM were 0.02, 0.2 and 0.2 mg/kg in soil and green tobacco leaves and 0.1, 1 and 1 mg/kg in cured tobacco leaves, respectively. The average recoveries from soil and tobacco were 72.91–98.40% for metalaxyl, 76.73–105.80% for cyazofamid and 74.48–106.45% for CCIM. The relative standard deviation range was 1.23–6.99%. The developed method was successfully applied to analysis of residues of metalaxyl, cyazofamid and CCIM in real soil and tobacco samples. The results indicated that the established method could meet the requirement for the analysis of trace amounts of all three analytes in soil and tobacco.     

Simultaneous determination of benzene,toluene, ethylbenzene,and xylene metabolites in human urine using electromembrane extraction combined with liquid chromatography and tandem mass spectrometry

For the first time, electromembrane extraction combined with liquid chromatography and tandem mass spectrometry was applied for the determination of urinary benzene, toluene, ethylbenzene, and xylene metabolites. S‐Phenylmercapturic acid, hippuric acid, phenylglyoxylic acid, and methylhippuric acid isomers were extracted from human urine through a supported liquid membrane consisting of 1‐octanol into an alkaline acceptor solution filling the inside of a hollow fiber by application of an electric field. Various extraction factors were investigated and optimized using response surface methodology, the statistical method. The optimum conditions were established to be 300 V applied voltage, 15 min extraction time, 1500 rpm stirring speed, and 5 mM ammonium acetate (pH 10.2) acceptor solution. The method was validated with respect to selectivity, linearity, accuracy, precision, limit of detection, limit of quantification, recovery, and reproducibility. The results showed good linearity (r² > 0.995), precision, and accuracy. The extract recoveries were 52.8–79.0%. Finally, we applied this method to real samples and successfully measured benzene, toluene, ethylbenzene, and xylene metabolites.