Analysis of ethoxyquin and its oxidation products in swine tissues by gas chromatography-tandem mass spectrometry for evaluating the feed-toanimal tissue transfer of ethoxyquin and its metabolites

Background:Ethoxyquin(EQ)is a common antioxidant which is widely used in animal feed.But the supplement of EQ in animal feed may lead to the residues of EQ and its major oxidation products:ethoxyquin quinone imine(EQI)and ethoxyquin dimer(EQDM)in animal tissue.Thus,it would pose potential health hazards to consumers.However,the method for the simultaneous determination of EQ,EQI and EQDM in animal tissues is currently not available,and the accumulation extend of these chemicals in animal tissues after EQ administration remains to be evaluated.Results:A gas chromatography-tandem mass spectrometry method was successfully developed for the simultaneous determination of EQ,EQI and EQDM in swine tissues.The quantitative limits of EQ,EQI and EQDM can achieve to 0.5,5.0 and 5.0μg/kg in swine tissues,respectively.The spiked-recovery ratios of the three analytes(5–2000μg/kg)were in the range of 64.7%–100.7%with relative standard deviations below 11.6%.Moreover,the utilization of this method for the analysis of actual swine tissue samples revealed that the application of commercial EQ additive in swine diet would produce the residues of all the three chemicals(EQ,EQI and EQDM)in fat,kidney,liver and muscle.Conclusions:The assay accuracy and precision of this GC-MS/MS method can meet the requirement of quantitative analysis.Meanwhile,the safety of EQ as a feed additive should be seriously considered with regard to food safety concerns since the oxidation product of EQ may have potential carcinogenicity.

Sensitive and Rapid Quantification of Felodipine by High-performance Liquid Chromatography-tandem Mass Spectrometry(HPLC-MS/MS) and Its Pharmacokinetics in Healthy Chinese Volunteers

To investigate the pharmacokinetics of felodipine in the plasma of healthy Chinese volunteers, 30 healthy volunteers received a single oral dose of 5 mg of extended release felodipine tablets. The felodipine was extracted from the matrix with a liquid-liquid extract procedure and analyzed by high-performance liquid chromatography-tandem mass spectrometry in the multiple reaction monitoring（MRM） mode using an electrospray ion source with positive ion detection. The method was validated over a felodipine concentration range of 0. 05-10.00 ng/mL in human plasma. Its main pharmacokinetic parameters values were： ρmax = （ 1.67 ± 0. 84 ） ng/mL, occurring at （ 3.93 3± 2. 49 ） h; the plasma elimination half-life： （23. 08 3± 9. 48） h and the area under the plasma concentration versus time curve： （29. 94 ± 14. 39） ng · h/mL. The validation results demonstrated that this method showed a satisfactory precision and accuracy across the calibration range. The procedure involved minimal drug administration, sample preparation, and a 2. 5-min chromatographic run time. It was well suited to clinical studies of the drug involving large numbers of samples.

Liquid chromatography-tandem mass spectrometry method for the estimation of adefovir in human plasma:Application to a pharmacokinetic study

An analytical method based on solid phase extraction was developed and validated for analysis of adefovir in human plasma. Adefovir-d4 was used as an internal standard and Synergi MAX RP80A （150rnmx4.6mm. 41am） column provided the desired chromatographic separation of compounds followed by detection with mass spectrometry. The method used simple isocratic chromato- graphic condition and mass spectrometric detection in the positive ionization mode. The calibration cuives were linear over the range of 0.50-42.47 ng/mL with the lower limit of quantitation validated at 0.50 ng/mL. Matrix effect was assessed by post-column infusion experiment to monitor phospholipids and post- extraction addition experiment was performed. The degree of matrix effect for adefovir was determined as 7.5% and ion-enhancement in five different lots of human plasma was 7.1% and had no impact on study samples analysis with 4.5 rain run time. The intra- and inter-day precision values were within 7.7% and 7.8%, respectively, for adefovir at the lower limit of quantification level. Validated bioanalytical method was successfully applied to clinical sample analysis.

Liquid chromatography–tandem mass spectrometry method for simultaneous determination of valproic acid and its ene-metabolites in epilepsy patient plasma

A simple and high throughput method was developed and validated for simultaneous determination of valproic acid and its two toxicant ene-metabolites, 2-enevalproic acid and 4-enevalproic acid in epilepsy patient plasma using liquid chromatography-tandem mass spectrometry. Probenecid was used as in- ternal standard and solid-phase extraction was selected for sample preparation. A chromatographic separation was performed on an Agilent Poroshell SB-C18 column （50 mm × 4.6 mm i.d., 2.7μm） by an optimized gradient elution at a flow rate of 0.9 mL/min. The total run time was 7 rain. Electrospray ionization was used in negative ion mode by multiple reaction monitoring of the precursor-to-product ion transitions at m/z 143.0→143.0 for valproic acid, m/z 140.9 →140.9 for 2-enevalproic acid and 4-enevalproic acid for their poor fragments, and m/z 283.9→239,9 for probenecid. The results showed good linearity ofvalproic acid, 2-enevalproic acid and 4-enevalproic acid in their respective linear ranges. The correlation coefficients were more than 0.998, The intra- and inter-day precision of the assay was less than 11.0% and the accuracy ranged from 2% to 12%. This analytical method was successfully applied to assay plasma concentrations of valproic acid and its two ene-metabolites in epilepsy patient plasma and used for therapeutic drug monitoring.

固相萃取-气相色谱-串联质谱法测定生活饮用水中18种邻苯二甲酸酯

建立生活饮用水中18种邻苯二甲酸酯类化合物(phthalic acid esters,PAEs)残留量的气相色谱-串联质谱(gas chromatography-tandem mass,GC-MS/MS)检测方法。生活饮用水样品经亲水亲酯平衡柱(hydrophilicl pophilibalance,HLB)玻璃小柱富集,二氯甲烷洗脱,采用GC-MS/MS多反应监测模式分析,外标法定量。结果表明,采用优化后条件,18种PAEs在0.02 mg/kg^1.00 mg/kg的定量范围内,线性关系良好,相关系数均在0.998以上。按照建立的方法,分别进行添加浓度为0.02、0.1、0.2 mg/kg的加标回收率试验,18种PAEs的平均回收率范围为71.3%~113%,相对标准偏差小于6.8%。4种色谱纯有机溶剂二氯甲烷、甲醇、正己烷、乙腈浓缩10倍后均检出邻苯二甲酸二异丁酯(diisobutyl phthalate,DIBP)、邻苯二甲酸二丁酯(dibutyl phthalate,DBP)和邻苯二甲酸二(2-乙基己)酯(bis(2-ethylhexyl)phthalate,DEHP)3种PAEs,含量范围为0.006 95 mg/kg^0.323 mg/kg,同时进行多次过程空白试验可排除试剂带入的干扰。本方法富集倍数高、快速、准确,可用于生活饮用水中18种PAEs的实际检测分析。

Exploration of Nonlinear Modeling Techniques to Predict the Retention Time of Organic Pollutants in Natural Water and Wastewater

Water pollution affects plants and organisms living in these bodies of water; and, in almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities. Genetic algorithm and kernel partial least square （GA-KPLS） and Levenberg- Marquardt artificial neural network （L-M ANN） techniques were used to investigate the correlation between retention time （tR） and descriptors for 150 organic contaminants in natural water and wastewater, which are obtained by gas chromatography coupled to high-resolution time-of-flight mass spectrometry （GC-TOF MS）. The L-M ANN model gave a significantly better performance than the GA-KPLS model. This indicates that L-M ANN can be used as an alternative modeling toot for quantitative structure-retention relationship （QSRR） studies.

Analysis of 19-nortestosterone residue in animal tissues by ion-trap gas chromatography-tandem mass spectrometry

A rapid sample treatment procedure for the gas chromatography-tandem mass spectrometry （GC-MS） determination of 19-nortestosterone （19-NT） in animal tissues has been developed. In our optimized procedures, enzymatic hydrolysis with β-glucuronidase from Escherichia coliwas performed in an acetate buffer （pH 5.2, 0.2 mol/L） Next, the homogenate was mixed with methanol and heated at 60℃ for 15 min, then placed in an ice-bath at -18℃ for 2 h. After liquid-liquid extraction with n-hexane, the analytes were subjected to a normal-phase solid phase ex- traction （SPE） C18 cartridge for clean-up. The dded organic extracts were derivatized with heptafluorobutydc anhydride （HFBA）, and then the products were injected into GC-MS. Using electron impact mass spectrometry （El-MS） with positive chemical ionization （PCI）, four diagnostic ions （mlz 666, 453, 318, and 306） were determined. A standard calibration curve over the concentration range of 1-20 ng/g was reached, with Y=467084X-68354 （R^2=0.9997） for 19-NT, and the detection limit was 0.3 ng. When applied to spiked samples collected from bovine and ovine, the recoveries ranged from 63% to 101% with relative standard deviation （RSD） between 2.7% and 8.9%. The procedure is a highly efficient, sensitive, and more economical method which offers considerable potential to resolve cases of suspected nandrolone doping in husbandry animals.

Atmospheric pressure gas chromatography-tandem mass spectrometry analysis of fourteen emerging polycyclic aromatic sulfur heterocycles in PM_(2.5)

Research on pollution characteristics and toxicities of emerging polycyclic aromatic sulfur heterocycles(PASHs) in PM_(2.5) has not been reported due to the lack of analytical method with the needed performance.In the present study,a novel method for the determination of 14 PASHs in PM_(2.5) was developed using atmospheric pressure gas chro matography-tandem mass spectrometry(APGC-MS/MS).Atmospheric pressure chemical ionization was operated with multiple reaction monitoring in positive ionization mode.High sensitivity(method detection limit <1.673 pg/m^(3)),acceptable re coveries(67.6%-120.8%) and precisions(RSD of 2.2%-15.4%) were obtained.The method was successfully applied for analyzing PASHs in 10 PM_(2.5) samples collected from Taiyuan,a typical industrial city in China,in 2016,The total concentrations were from 929 pg/m^(3) to 14,593 pg/m^(3).The determined levels indicated that further investigations on environmental fate and toxicities of PM_(2.5)-bound PASHs may be needed.

Reliable screening of pesticide residues in maternal and umbilical cord sera by gas chromatography-quadrupole time of flight mass spectrometry

The widespread use of pesticides induces heavy adverse effects on human health,especially for the pregnant women and the newborns.In this study,a screening method has been developed for the determination of multi-pesticides in maternal and umbilical cord sera.All pesticides in sera were collected using solid phase extraction(SPE),and analyzed by gas chromatography-quadrupole time of flight mass spectrometry(GC-QTOF MS).To set up the quality criteria,a database of 50 pesticides was created and the accurate masses of 3 up to 5 representative ions with their intensity ratios were included for each pesticide.In addition,a novel"identification points"(IPs)system relying on the accurate MS1 and MS2 spectra was used to interpret the data for each suspected pesticide.The methodology was then applied to a pair of maternal and umbilical cord sera.A total of six pesticide residues were screened out successfully.In conclusion,GC-QTOF MS combined with an accurate mass database seemed to be one of the most efficient tools for systematic pesticide analysis.

Trace analysis of off-flavor/odor compounds in water using liquid-liquid microextraction coupled with gas chromatography--positive chemical ionization-tandem mass spectrometry

A rapid, inexpensive and laboratory friendly method was developed for analysis of off-flavor/odor compounds in fresh and salt water using gas chromatography with chemical ionization-tandem mass spectrometry. Off-flavor/odor compounds, included geosmin, 2- methylisobomeol （MIB）, 2-isobutyl-3-methyoxypyrazine （IBMP）, and 2-isopropyl-3-methoxypyrazine （IPMP）. Using this method, a single sample can be extracted within minutes using only 1 mL of organic solvent. The ion transitions for IPMP, IBMP, MIB, and geosmin were 153 〉 121, 167 〉 125, 152 〉 95, and 165 〉 109, respectively. The linearity of this method for analyzing MIB ranged from 4 to 200ng·L^-1, and from 0.8 to 200ng·L^-1 for the other analytes. Method recoveries ranged from 97% to 111% and percent relative standard deviations ranged from 3% to 9%, indicating that the method is accurate, precise, and reliable.

A Preliminary Gas Chromatography‑Mass Spectrometry‑Based Metabolomics Study of Rats Ingested Diazepam or Clonazepam

Drug-facilitated sexual assault(DFSA)is a sexual act in which the victim is unable to give or rescind consent due to alcohol or drug intoxication,which involved the abuse of benzodiazepines around the world.Conventional techniques used for the analysis of benzodiazepines have the limitation of short detection time window due to the rapid metabolism of these drugs in body.This study aimed to investigate the characteristic changes of metabolites in the blood of rats after ingesting diazepam/clonazepam through a gas chromatography-mass spectrometry-based metabolomics method,allowing the indirect reveal of the rats ingested diazepam/clonazepam.First,we found that diazepam and clonazepam in the blood of rats could not be detected by liquid chromatography-tandem mass spectrometry after 48 h of ingestion.Then,orthogonal partial least squares discrimination analysis regression models were,respectively,constructed to determine whether the rats ingested diazepam/clonazepam after 48 h.The results showed that 5 metabolites were found to be associated with diazepam exposure,and 7 metabolites were found to be associated with clonazepam exposure,which may be characterization for the evaluation of digestion of diazepam and clonazepam in rat.

Seed metabolomic study reveals significant metabolite variations and correlations among different soybean cultivars

Soybean[Glycine max（L.） Merr.]is one of the world＇s major crops,and soybean seeds are a rich and important resource for proteins and oils.While ＂omics＂ studies,such as genomics,transcriptomics,and proteomics,have been widely applied in soybean molecular research,fewer metabolomic studies have been conducted for largescale detection of low molecular weight metabolites,especially in soybean seeds.In this study,we investigated the seed metabolomes of 29 common soybean cultivars through combined gas chromatography-mass spectrometry and ultra-performance liquid chromatography-tandem mass spectrometry.One hundred sixty-nine named metabolites were identified and subsequently used to construct a metabolic network of mature soybean seed.Among the 169 detected metabolites,104 were found to be significantly variable in their levels across tested cultivars.Metabolite markers that could be used to distinguish genetically related soybean cultivars were also identified,and metabolitemetabolite correlation analysis revealed some significant associations within the same or among different metabolite groups.Findings from this work may potentially provide the basis for further studies on both soybean seed metabolism and metabolic engineering to improve soybean seed quality and yield.

Low temperature purification method for the determination of abamectin and ivermectin in edible oils by liquid chromatographytandem mass spectrometry

In this study, a method based on low temperature purification （LTP） coupled with liquid chromatography-tandem mass spectrometry （LC-MS/MS） was developed for the determination of abamectin （ABA） and ivermectin （IVR） in edible oils. ABA and IVR were extracted using conventional liquid-liquid extraction followed by purification via precipitation of interfering fatty components at low temperature without an additional cleanup step. LTP is simple, easy to use, labour-saving and cost effective, and requires reduced amounts of organic solvent. The linear ranges of ABA and IVR were 5- 1000 t^g/L using matrix-matched standards. Limits of detection （LOD） and limits of quantification （LOQ） were in the range of 0.1-0.4 i^g/kg and 0.3-1.3 p^g/kg, respectively. The LOQs were below the strictest maximum residue limits established by Codex Alimentarius Commission. Recoveries at three spiked levels of 10, 20 and 100 i^g/kg in peanut oil, corn oil, olive oil, soybean oil and lard ranged from 71.1% to 119.3% with relative standard deviations of 3.2%-10.3%, which were in agreement with those obtained by the solid phase extraction method. The proposed method was utilized in the analysis of 10 edible oil samples from local market and neither ABA nor IVR was detected. As far as we know, this is the first time that LTP is applied to the determination of avermectins in edible oils.

A new analytical method for quantifying of sterane and hopane biomarkers

An analytical method for quantifying biomarker compounds of the sterane and the hopane existing in saturated hydrocarbons has been established by using comprehensive two-dimensional gas chromatography-flame ionization detector(GC×GC-FID) with optimized operating parameters. The new method achieves the quantification by using a GC×GC-FID system which is able to completely separate steranes from hopanes. The data obtained by the new method are of good repeatability and reliability. Compared with the original data, the relative standard deviations(RSDs) of 12 reference compounds are less than 5%. The RSDs of the quantitative results of the biomarkers based on seven separate analyses are also less than 5%. Compared with the traditional method of gas chromatography-mass spectrometry(GC-MS), the new method has a number of advantages, such as common internal standards(ISs), high resolution, no co-eluting peak, and no interference caused by diagnostic ion peaks. The new method provides petroleum geologists with an effective and scientific means in future researches.

Multiresidue pesticide analysis in tomato using GC-MS/MS using modified QuEChERS method with titanium-coated graphite with CNT-ABS nanocomposite as dispersive solid-phase extraction materials

The presence of pesticide residues in food and vegetables is a growing concern for consumers.To monitor these residues reliably,a selective and sensitive multiresidue system has been developed and validated in tomato by gas chromatography–tandem mass spectrometry(GC-MS/MS).Titanium-coated graphite with carbon nanotube(CNT)in acrylonitrile–butadiene–styrene(ABS)used as reversed-dispersive solid-phase extraction materials with modified QuEChERS(Quick,Easy,Cheap,Effective,Rugged,and Safe)method.Titanium-coated graphite with CNT-ABS is synthesized,characterized by X-ray diffraction and scanning electron microscopy.The clean-up performance of titanium-coated graphite with CNT-ABS was demonstrated to be better to primary secondary amine and graphitized carbon black cartridges.The processing of two multiple reaction monitoring transformations for each analyte is done using GC-MS/MS in electron impact mode.Satisfactory purification and recovery effects(74%–100%)of 35 pesticides were achieved in tomato matrices when using 5 mg of titanium-coated graphite ABS-CNT nanocomposite.It was observed that quinolphos and deltamethrin are present above the maximum residue limit.The technique proved to be reliable and sensitive in tomato samples for the routine testing of 35 pesticides.