Determination of Veterinary Drug Residues in Animal-derived Foods by Liquid Chromatography-Mass Spectrometry

[Objectives]This study was conducted to establish a rapid and effective method for simultaneous extraction of 54 kinds of veterinary drug residues in animal-derived food, including sulfonamides, quinolones, tetracyclines, malachite greens, penicillins, nitroimidazoles, tranquilizers and macrolides, by HPLC-MS. [Methods] The samples were extracted with 80% acetonitrile water(containing 0.1% formic acid), combined with QuEChERS extraction technology and C18 and PSA purification, analyzed by high performance liquid chromatography-mass spectrometry, and quantified by external standard method. The target substances were analyzed on ZORBAX Eclipse C18 chromatographic column using 0.2% formic acid water and 0.2% methanol as mobile phases. The gradient elution mode was used for chromatographic separation and multiple reaction detection. [Results] In the linear range of 0.5-50.0 ng/ml, the linear relationship of the 54 kinds of veterinary drug residues was good, with correlation coefficients(r~2) greater than 0.995, and the detection limits ranged from 0.30 to 1.00 μg/kg. The results showed that the recovery ranged from 75.4% to 118.2% when different matrixes were added for recovery. [Conclusions] This method is simple, efficient, accurate, stable, and highly operable. It is applicable to simultaneous batch screening of veterinary drug residues in animal-derived food, and has high practical application value.

CO₂Absorption Solvent Degradation Compound Identification Using Liquid Chromatography-Mass Spectrometry Quadrapole-Time of Flight (LCMSQTOF)

The degradation of the alkanolamine solvent used in the removal of acid gases from natural gas streams due to exposure to contaminants, thermal degradation and presence of oxygen or oxygen containing compounds will change the solvent properties, such as heat transfer coefficient, diffusion coefficient, and mass transfer coefficient of the solvent. Therefore, characterization and quantification of amine degradation product becomes one of the important analyses to determine alkanolamine solvent’s health. In order to identify degradation products of alkanolamine solvent, analytical strategies by using mass spectrometry (MS) as detector have been studied extensively. In this work, due to the low concentration of the amine degradation product, a method was developed for identification of alkanolamine degradation products using LCMS-QTOF technique. A strategy for identification of trace degradation products has been identified. Six (6) alkanolamine degradation products had been identified by using LCMS-QTOF targeted analysis in the blended alkanolamine solvent used in natural gas processing plant. Another fifteen (15) molecular formulas having similarity in chemical structure to alkanolamine degradation products were identified using untargeted analysis strategy, as possible compounds related to degradation products. Using LCMS-QTOF via targeted and untargeted analysis strategy, without tedious column separation and reference standard, enables laboratory to provide a quick and indicative information for alkanolamine solvent’s organic degradation compounds identification in CO2 adsorption, within reasonable analysis time.

Liquid Chromatography-mass Spectrometry Analysis on Effect of Roughage Types on Liver Metabolic in Dairy Cows

The major objective of this study was to determine the effect of corn straw or mixed diet on the small molecule metabolites of liver and milk production of healthy Chinese Holstein cows during lactation.In this study,metabolomic methods based on ultra performance liquid chromatography-mass spectrometry(LC-MS)were used to study the liver metabolites of dairy cows fed on corn straw diet or mixed diet.Ten healthy Chinese Holstein cows were randomly assigned to two groups,under the same management condition,fed different diets respectively,corn straw group(CS)or a mixture of alfalfa hay and Chinese wild rye hay mixed forage group(MF).All the cows were fed for 8 weeks and recorded body weight,dry matter intake,body condition score,fat,protein,lactose,milk yield and the total solids.Livers were sampled from each cow through a liver puncture needle for analysis of a significant difference in small molecule metabolites in cow liver samples from the two different diets.The results suggested that different diet types had significant effects on liver metabolism and milk components in dairy cows.The contents of milk fat,the total solids,milk protein,lactose,dry matter intake(DMI),milk yield,milk protein(%),lactose(%)and milk fat(%)of the corn straw group were significantly lower than those of the mixed forage group(p<0.05);the contents of phosphatidylcholine(PC),histidine,hypoxanthine and mridine in liver tissues of the corn straw group were significantly lower than those in the mixed forage group(p<0.05);acetylcarnitine,uric acid,triacylglycerol(TG),acetal phosphatidylcholine(plasmenyl-PC),acetalphosphatidylethanolamine(plasmenyl-PE)and sphingomyelin(SM)of the corn straw group were significantly higher than those in the mixed forage group(p<0.05).In summary,cows fed on mixed forage diet significantly improved milk yield and lactation performance clearly.

Chemical Components of Achyranthes bidentata Leaves by Ultra High Performance Liquid Chromatography-Mass Spectrometry

[Objectives] To study the chemical components and relative content of Achyranthes bidentata leaves and provide a scientific basis for further development and utilization of A. bidentata leaves.[Methods] The chemical components of A. bidentata leaves were rapidly analyzed using the ultra high performance liquid chromatography-time of flight-high resolution mass spectrometry (UHPLC-TOF-MS).[Results] Thirty eight chemical compounds were identified in samples of A. bidentata leaves collected from Wen County of Henan Province, in which seven chemical compounds had the relative content higher than 5%, linoleic acid reached 25.7% and inokosterone A reached 13.8%.[Conclusions] A. bidentata leaves contain many kinds of chemical compounds. This study is expected to provide a certain basis for further extraction of linoleic acid and inokosterone A.

A Validated Liquid Chromatography-Mass Spectrometry Method for the Detection and Quantification of Oxidative Metabolites of 2,2',4,4'-Tetrabromodiphenyl Ether in Rat Hepatic Microsomes

In the present study, we developed and validated an analytical method using ultra performance liquid chromatography-mass spectrometry (UPLC/MS) for the quantitative determination of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) metabolism by rat hepatic microsomes. BDE-47 is a brominated flame retardant that was widely used in a variety of consumer products and has subsequently been identified as a ubiquitous environmental contaminant. Hydroxy-bromodiphenyl ethers (OH-BDEs) were isolated from rat hepatic microsomes by liquid-liquid extraction. Chromatographic separation was achieved by UPLC on a C18 column with gradient elution using a mobile phase consisting of methanol and water, each containing 0.1% formic acid, at a flow rate of 0.2 mL/min. Detection and quantification were performed using a mass spectrometer in single ion recording mode with negative electrospray ionization. The UPLC/MS method was validated for linearity, limit of quantification (LOQ), accuracy, precision and recovery. The weighted calibration curves (1/X2) were linear over a concentration range of 5 - 250 nM with LOQ values between 5 nM and 50 nM for the individual OH-BDEs. Intra- and inter- day accuracy (%DEV) and precision (%RSD) values ranged from –11.7% to 9.5% and 5.9% to 16.5%, respectively. Recovery values of 70% to 90% were obtained for all OH-BDEs. The validated method allowed us to successfully analyze metabolite formation following incubation of BDE-47 with hepatic microsomes prepared from phenobarbital-treated rats. Results demonstrate that the UPLC/MS method has sufficient sensitivity and reproducibility to fully characterize the in vitro metabolism of BDE-47 and possibly other PBDEs.

Novelties Filtration Theory of Liquid Chromatography-Mass Spectrometry in Volume Nanotube of Cotton Filament of Layers Woven Fabrics

Objectives of the research to present a modern theory of water purification for multiple purposes entitled “a novelties filtration theory of liquid chromatography-mass spectrometry” is an exceedingly sensitive and specific analytical technique in volume layers woven fabrics that can precisely determine the identities and quantities of compounds within volume Nanotube of cotton filament of layers woven fabrics. The problems are that the filters in the local and international markets have increased complications in configuration, installation and cost without reaching the efficiency that humanity hopes. Throw materials and methods the chromatography-mass spectrometry in layers woven fabrics, and throw the nanotube of cotton filament for purification of water dyes and smells. Industry, in which mass spectrometry is a convenient, versatile method for characterization and identification of process throw the Nanotube of cotton filament for purification of water dyes and smells. Results came up with a theme “innovations in textiles”, and also, for characterization of fibers and contaminants of the fabrics. Additive manufacturing in layers woven fabrics, are the processes used to synthesize a volume object under computer control with successive material layers that have been used and highlighted. The conclusions has included chromatography-mass spectrometry drop, physico-chemical, biological, combined physical-biological and chemical-biological treatment processes recently being developed to meet Jet-filtration, the strict discharging limits set by ASTM standards. Some important aspects of both qualitative and quantitative data analysis have been described and the power of using mass profiles to enhance selectivity and sensitivity has been demonstrated.

Determination of 14 Organophosphorus Pesticide Residues in Mutton by Gel Permeation Chromatography-Gas Chromatography-Mass Spectrometry(GPC-GC-MS)

[Objectives]This study was conducted to purify mutton samples by gel permeation chromatography(GPC).[Methods]Fourteen organophosphorus pesticide residues in samples were qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry(GC-MS)in selective ion scanning mode(SIM).[Results]The organophosphorus pesticide standard solutions showed good linearity in the mass concentration range of 0.1-10.0μg/ml with correlation coefficients(r)not lower than 0.999,and the detection limits(S=3 N)ranged from 0.01 to 0.05 mg/kg.The average recovery values were in the range of 80.2%-99.7%,with relative standard deviations(RSDs,n=3)in the range of 1.8%-6.3%,at the addition levels of 0.5,1.0 and 2.0 mg/kg.[Conclusions]The method is simple,sensitive and accurate,and can be used for the determination of organophosphorus pesticide residues in mutton.

Insight into chemical basis of traditional Chinese medicine based on the state-of-the-art techniques of liquid chromatography-mass spectrometry

Traditional Chinese medicine(TCM) has been an indispensable source of drugs for curing various human diseases.However,the inherent chemical diversity and complexity of TCM restricted the safety and efficacy of its usage.Over the past few decades,the combination of liquid chromatography with mass spectrometry has contributed greatly to the TCM qualitative analysis.And novel approaches have been continuously introduced to improve the analytical performance,including both the data acquisition methods to generate a large and informative dataset,and the data post-processing tools to extract the structure-related MS information.Furthermore,the fast-developing computer techniques and big data analytics have markedly enriched the data processing tools,bringing benefits of high efficiency and accuracy.To provide an up-to-date review of the latest techniques on the TCM qualitative analysis,multiple data-independent acquisition methods and data-dependent acquisition methods(precursor ion list,dynamic exclusion,mass tag,precursor ion scan,neutral loss scan,and multiple reaction monitoring)and post-processing techniques(mass defect filtering,diagnostic ion filtering,neutral loss filtering,mass spectral trees similarity filter,molecular networking,statistical analysis,database matching,etc.) were summarized and categorized.Applications of each technique and integrated analytical strategies were highlighted,discussion and future perspectives were proposed as well.

Study of Differential Serum Metabolites in Patients with Adenomatous Polyps of Colon and Yang-Deficiency Constitution Based on Ultra-Performance Liquid Chromatography-Mass Spectrometry

Objective:To study the differences between the serum metabolites in patients with adenomatous polyps of the colon and yang-deficiency constitution and those without colon polyps and with balanced constitution,and look for biomarkers that can be used to distinguish between the two groups.Methods:General patient information was gathered,and Chinese medicine constitutions were collected in 940 patients who underwent electronic colonoscopy.A total of 119 patients with adenomatous polyps of the colon and yang-deficiency constitution were included in the experimental group,and 150 patients without colon polyps and with balanced constitution were included in the control group.Metabolomics analysis was performed on the fasting venous blood obtained from each patient in both groups.Principal component analysis and orthogonal partial least squares discriminant analysis were performed on the detection results,potential biomarkers were screened,metabolic pathway changes were determined,and the metabolic processes involved were discussed.Results:A total of 59 differential biomarkers between the experimental group and the control group were identified.The differential metabolites were found mainly in the glycerophospholipid metabolism pathway,and the bile acid 3-oxo-4,6-choladienoic acid was the biomarker that distinguished the experimental group from the control group.Conclusions:With the help of metabolomics analysis,the differential metabolites in patients with adenomatous polyps of the colon and yang-deficiency constitution and those in patients without colon polyps and with balanced constitution could be identified.The biomarker 3-oxo-4,6-choladienoic acid may have potential diagnostic value in patients with adenomatous polyp of the colon and yang-deficiency constitution.(Trial Registration No.NCT02986308)

Recent progress in polar metabolite quantification in plants using liquid chromatography-mass spectrometry

Metabolite analysis or metabolomics is an important component of systems biology in the post-genomic era.Although separate liquid chromatography（LC） methods for quantification of the major classes of polar metabolites of plants have been available for decades,a single method that enables simultaneous determination of hundreds of polar metabolites is possible only with gas chromatography-mass spectrometry（GC-MS） techniques.The rapid expansion of new LC stationary phases in the market and the ready access of mass spectrometry in many laboratories provides an excellent opportunity for developing LC-MS based methods for multitarget quantification of polar metabolites.Although various LC-MS methods have been developed over the last 10 years with the aim to quantify one or more classes of polar compounds in different matrices,currently there is no consensus LC-MS method that is widely used in plant metabolomics studies.The most promising methods applicable to plant metabolite analysis will be reviewed in this paper and the major problems encountered highlighted.The aim of this review is to provide plant scientists,with limited to moderate experience in analytical chemistry,with up-to-date and simplified information regarding the current status of polar metabolite analysis using LC-MS techniques.

Simultaneous Determination and Pharmacokinetics of Tetrandrine,Fangchinoline,and Cyclanoline in Rat Plasma by Ultra-High Performance Liquid Chromatography-Mass Spectrometry after Oral Administration of Stephaniae Tetrandrae Radix Extract

Objective:The objective of the study was to develop a rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometric method for the determination of tetrandrine,fangchinoline,and cyclanoline in rat plasma and to investigate their pharmacokinetics after oral administration of Stephaniae Tetrandrae Radix extracts.Methods:Sample pretreatment involved methanol pretreatment and liquid–liquid extraction of ethyl acetate from plasma with methanol.Tramadol was used as the internal standard.The analysis was performed using an high strength silica T3 column(100 mm×2.1 mm,1.8μm)and a gradient elution method consisting of mobile phase solution A(0.1%formic acid in water)and B(acetonitrile)at a flow rate of 0.4 mL/min.The detection was performed using a triple quadrupole tandem mass spectrometer in the multiple reaction monitoring mode and using an electrospray ionization source in the positive ionization mode.Results:High efficiency was achieved with an analysis time of 4 min/sample.The calibration curve linear in the concentration range of 1250 ng/ml(R^(2)≥0.9900)and the lower limit of quantification is 1 ng/ml.The intraday and interday precision(relative standard deviation)values were lower than 9.4.Accuracy(relative error)was within 10.3%at all three quality control levels.Conclusions:This method was successfully applied in pharmacokinetics of tetrandrine,fangchinoline,and cyclanoline in rats after oral administration of Stephaniae Tetrandrae Radix extracts.The maximum plasma concentration(C_(max))of tetrandrine,fangchinoline,and cyclanoline was 124.71±16.08,84.56±3.28,and 57.61±6.26 ng/mL,respectively.The time to reach C_(max)was 10.39±3.04 for tetrandrine,10.17±3.04 for fangchinoline,and 6.40±3.16 for cyclanoline.The pharmacokinetic results might help further guide the clinical application of Stephaniae Tetrandrae Radix.

Simultaneous determination of five anti-epilepsy drugs in human plasma using liquid chromatography-mass spectrometry

A new liquid chromatography-mass spectrometry method for the determination of carbamazepine,clonazepam,alprazolam,estazolam and phenytoin in human plasma has been developed by using diazepam as an internal standard.Chromatographic separation was performed on a Zorbax SB-C18 column(30 mm × 2.1 mm,3.5 ?m) with a mobile phase consisting of methanol and aqueous 25 mM ammonium acetate using gradient elution.A diethyl ether extraction method was used for the extraction of five anti-epilepsy drugs.The final extract was injected for analysis by LC-MS/MS.The method was validated within the concentration range of 50-5000 ng mL-1 for five anti-epilepsy drugs.The precision of the assay(RSD%) was less than 10% at all concentration levels within the tested range.The method recoveries for all samples were more than 90%.The results indicate that the method is specific,sensitive and accurate,and suitable to study the pharmacokinetics,to adjust the dosage for individual administration,and to monitor the drug-concentration and drug abuse of the five anti-epilepsy drugs.

Quantitative analysis of trace levels of β-ionone in water by liquid-liquidphase extraction-gas chromatography-mass spectrometry(LLE-GC-MS)

A simple and rapid technique based on liquid-liquid extraction coupled to gas chromatography-mass spectrometric detection(LLE-GC-MS) was developed for analysis of taste and odour compound β-ionone in water. Instrument parameters including programmed oven temperature, injection temperature and ion source temperature were evaluated and optimized. Effects of extraction time, ionic strength and p H on the detection efficiency were investigated and optimum conditions were 8 min of extraction time, without Na Cl addition at p H=9. Good linearity(R2=0.9997) was obtained when the linear range was 10-500 μg/L. The recoveries of β-ionone in ultrapure water and tap water samples were 88%-95% and 110%-114%, respectively. The relative standard deviations(RSD) were less than 10%. The method detection limit(MDL) and rejection quality level(RQL) were achieved at1.98 μg/L and 6.53 μg/L, respectively. LLE-GC-MS was demonstrated to be a rapid and convenient method for the determination ofβ-ionone in water samples.

Mechanism of Cinnamomum camphora essential oil for analgesia based on gas chromatography-mass spectrometry integrated network pharmacology

This study aims to explore the analgesic ingredients and mechanism of Cinnamomum camphora essential oil(CCEO).The constituents in CCEO were characterized qualitatively by gas chromatography-mass spectrometry.Targets related to active ingredients were collected by PubChem and Swiss Target Prediction.Targets related to pain were screened by TTD and OMIM database,and compound-target network was established by Cytoscape software.Gene ontology(GO)function and Kyoto encyclopedia of genes and genomes(KEGG)pathway enrichment analysis of targets were carried out by DAVID database.Protein-protein interaction(PPI)network was established and analyzed by STRING database.Molecular docking method was used to verify the interaction between main components and relevant core targets.A total of 13 compounds were identified in CCEO,and 58 related targets were predicted.GO function enrichment analysis revealed that the selected targets were mainly involved in biological processes such as chemical synaptic transmission and molecular function such as neurotransmitter receptor activity;24 signal pathways were screened by KEGG pathway enrichment analysis,including neuroactive ligand-receptor interaction,retrograde endocannabinoid signaling and calcium signaling pathway.Docking results showed that the main constituents had certain affinities with the key targets.The active ingredients in CCEO regulated multiple signaling pathways to ameliorate pain through AR,ACHE,ESR1,GABRG2,PTGS2 and PPARγ.

Chemical profiling of bioactive compounds in the methanolic extract of wild leaf and callus of Vitex negundo using gas chromatographymass spectrometry

BACKGROUND The investigation of plant-based therapeutic agents in medicinal plants has revealed their presence in the extracts and provides the vision to formulate novel techniques for drug therapy.Vitex negundo(V.negundo),a perennial herb belonging to the Varbanaceae family,is extensively used in conventional medication.AIM To determine the existence of therapeutic components in leaf and callus extracts from wild V.negundo plants using gas chromatography-mass spectrometry(GCMS).METHODS In this study,we conducted GC-MS on wild plant leaf extracts and correlated the presence of constituents with those in callus extracts.Various growth regulators such as 6-benzylaminopurine(BAP),2,4-dichlorophenoxyacetic acid(2,4-D),α-naphthylacetic acid(NAA),and di-phenylurea(DPU)were added to plant leaves and in-vitro callus and grown on MS medium.RESULTS The results clearly indicated that the addition of BAP(2.0 mg/L),2,4-D(0.2 mg/mL),DPU(2.0 mg/L)and 2,4-D(0.2 mg/mL)in MS medium resulted in rapid callus development.The plant profile of Vitex extracts by GC-MS analysis showed that 24,10,and 14 bioactive constituents were detected in the methanolic extract of leaf,green callus and the methanolic extract of white loose callus,respectively.CONCLUSION Octadecadienoic acid,hexadecanoic acid and methyl ester were the major constituents in the leaf and callus methanolic extract.Octadecadienoic acid was the most common constituent in all samples.The maximum concentration of octadecadienoic acid in leaves,green callus and white loose callus was 21.93%,47.79%and 40.38%,respectively.These findings demonstrate that the concentration of octadecadienoic acid doubles in-vitro compared to in-vivo.In addition to octadecadienoic acid;butyric acid,benzene,1-methoxy-4-(1-propenyl),dospan,tridecanedialdehyde,methylcyclohexenylbutanol,chlorpyrifos,n-secondary terpene diester,anflunine and other important active compounds were also detected.All these components were only available in callus formed in-vitro.This study showed that the callus contained additional botanical characteristics compared with wild plants.Due to the presence of numerous bioactive compounds,the medical use of Vitex for various diseases has been accepted and the plant is considered an important source of therapeutics for research and development.

Determination of penehyclidine hydrochloride in beagle dog plasma by liquid chromatography-electrospray ionization mass spectrometry and the pharmacokinetic study

To develop a fast and sensitive liquid chromatography-mass spectrometry method for the determination of penehyclidine hydrochloride （PH） in beagle dog plasma. PH and diphenhydramine hydrochloride （internal standard, IS） were extracted with a solvent mixture of petroleum ether-ethyl ether （7：3）. Chromatographic separation was achieved on a reversed-phase Eclipse XDB-C18 column （4.6 mm × 150 mm, 5 um） using the eluent of methanol-water （5 mmol/L ammonium acetate） （90：10, v/v, pH 5.8） as mobile phase. The electrospray ionization source was set at the positive multiple reaction monitoring （MRM） mode. This method involved the use of the [M＋H]^＋ ions of PH and diphenhydramine hydrochloride at m/z 316.4- 128.2 and m/z 256.4-167.2. The calibration curve was linear in the range of 1-1000 ng/mL with a correlation coefficient of 0.9988. The lower limit of quantification was 0.05 ng/mL. The precision, accuracy and recovery of the method were acceptable. Following intravenous injection admires＇ tration at doses of 0.5, 1 and 5 mg/kg PH, the main pharmacokinetic parameters were as the followings, t1/2a 0.33 h, t1/2β 2.44 1% tmax 0.058 1% AUC and Cmax exhibited a linear increase along with the increase of dose. The two-compartment model fit the three dose groups. This method was sensitive, accurate and fast for the determination of concentration of PH in beagle dog plasma. It could be used in pharmacokinetic studies of PH.

Untargeted and targeted mass spectrometry reveal the effects of theanine on the central and peripheral metabolomics of chronic unpredictable mild stress-induced depression in juvenile rats

L-theanine has been shown to have a therapeutic effect on depression.However,whether L-theanine has an excellent preventive effect on depression in children and adolescents and what its mechanism is have not been well explained.Given the complexity of the pathogenesis of depression,this study investigated the preventive effect and mechanism of L-theanine on depression in juvenile rats by combining serum and hippocampal metabolomic strategies.Behavioral tests,hippocampal tissue sections,and serum and hippocampal biochemical indexes were studied,and the results confirmed the preventive effect of Ltheanine.Untargeted reversed-phase liquid chromatography-quadrupole-time-of-flight mass spectrometry and targeted hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry were developed to analyze the metabolism changes in the serum and hippocampus to screen for potential biomarkers related to L-theanine treatment.The results suggested that 28 abnormal metabolites in the serum and hippocampus that were considered as potential biomarkers returned to nearnormal levels after L-theanine administration.These biomarkers were involved in various metabolic pathways,mainly including amino acid metabolism and lipid metabolism.The levels of amino acids and neurotransmitters in the phenylalanine,tryptophan,and glutamic acid pathways were significantly reduced after L-theanine administration compared with chronic unpredictable mild stress-induced rats.In summary,L-theanine had a significant preventive effect on depression and achieved its preventive results on depression by regulating various aspects of the body,such as amino acids,lipids,and inflammation.This research systematically analyzed the mechanism of L-theanine in preventing depression and laid the foundation for applying L-theanine to prevent depression in children and adolescents.

Application of Mass Spectrometry (MS)-coupled Techniques in Pesticide Residue Detection

Pesticide residue detection is an important work to ensure the quality safety of agricultural products.In the process of agricultural production,in order to prevent and control agricultural diseases and pests,a certain amount of pesticides need to be used.However,if pesticides are used excessively,there will be certain pesticide residues in crops and related products.Therefore,it is necessary to do a good job in pesticide residue detection.The gas chromatography-mass spectrometry(GC-MS)and liquid chromatography-mass spectrometry(LC-MS)detection methods have good results and can effectively detect pesticide residues in related products.This paper reviewed and analyzed the application of GC-MS and LC-MS in pesticide residue detection,and proposed optimization measures based on practical experience,hoping to provide reference for relevant scholars.

Simultaneous Determination of 8 Pesticide Residues in Green Tea Based on Gas Chromatography-mass Spectrometry

To improve pesticide residues detection efficiency in tea, simultaneous de- termination of eight pesticide residues in green tea was developed based on gas chromatography-mass spectrometry （GC-MS）. The results showed that, - detected by the GC-MS under following conditions： acetonitrile as extraction and elution solvent, activated carbon and PSA tandem column as the stationary phase, elution volume of 12 ml the relationship between peak area and concentration of each residue （ametryn in the range of 0-100 pg/L, napropamide in the range of 0-10 000 gg/L, other pesticides in the range of 0-1 000 tJg/L） were linearly related, and their corre- lation coefficients were all greater than 0.999. The recovery rate the pesticides added to tea sample at legal concentration limits ranged from 73.6% to 116.8%, and the relative standard deviation from 1.47% to 15.58%. The new method we de- veloped is sensitive, specific and anti-interference, and thus provides test basis for the development of pesticide matrix reference materials in tea.

Simultaneous Determination of Hexoestrol, Diethylstilbestrol, Estrone and 17-Beta-estradiol in Feed by Gas Chromatography-mass Spectrometry

A method was developed for the simultaneous determination of four kinds of estrogens （hexoestrol, diethylstilbestrol, estrone, and 17-beta-estradiol） in feed by gas chromatography-mass spectrometry （GC-MS）. After the sample was extracted by ethyl ether and cleaned-up on HLB phase extraction column, four kinds of estrogens were derived and quantified in gas chromatographymass spectrometry. The results showed that the linear detectable ranged from 2.5 ng· mL-1 to 250 ng· mL-1for hexoestrol and from 5 ng· mL-1 to 500 ng· mL-1 for three other estrogens with the correlation coefficients （R2） were no less than 0.990. The recoveries were in the range of 76.34%-96.33% and the relative standard deviation was no more than 22.7%. The limits of quantitation （LOQ） for all analytics were between 10 ug· kg^-1 and 20 ug· kg^-1. The method was accurate and sensitive and could meet the actual requirements for the analyses of feed samples.