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.

Determination of sterols in tobacco leaves by gas chromatography-tandem mass spectrometry

The purpose of the study was to establish an analytical method to simultaneously determine multiple sterols in tobacco leaves rapidly and accurately.In this gas chromatography-triple quadruple tandem mass spectrometry(GC-MS/MS)based method,various conditions for sterols extraction were assessed and the instrumental operation parameters were optimized with 5α-cholane as an internal standard.Using this method,eight plant sterols,namely lanosterol,campesterol,chenodeoxycholic acid,cholesterol,β-sitosterol,stigmasterol,dihydrotachysterol and ergosterol,were separated in less than 30 min.The linear correlation coefficients were over 0.998 9,the low detection limits were in the range of 0.010 3-0.141 4 μg/g.The recoveries were from 87.30% to 115.60%,with low standard deviations.In conclusion,this method demonstrates good repeatability,accuracy,and high sensitivity,and is best suited for rapid analysis of multiple sterols in tobacco leaves.

The Detection of THCA Using 2-Dimensional Gas Chromatography-Tandem Mass Spectrometry in Human Fingernail Clippings: Method Validation and Comparison with Head Hair

Marijuana use as well as abuse is a significant public health and public safety concern in the United States and using hair to identify marijuana users and abusers has been gaining acceptance in a number of venues including workplace, court ordered, and substance abuse treatment monitoring. After the presentation of a fully validated 2-dimensional gas chromatography-tandem mass spectrometry method for the detection of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCA), the chief metabolite of the main psychoactive compound in marijuana, Δ9-tetrahydrocannabinol (THC), we evaluated the usefulness of fingernail clippings as an alternative specimen type to hair by the analysis of a set of 60 matched pairs of head hair and fingernail clippings. The limit of detection was 10 fg/mg, the limit of quantitation was 20 fg/mg, and the assay was linear from 20 fg/mg to 500 fg/mg. The intra- and inter-assay imprecision and bias studies at 4 different concentrations (50, 100, 500, and 1000 fg/mg) were acceptable where all % Target observations were within 16% of their expected concentrations and all %CV calculations were less than 13.5%. THCA was detectable in more fingernail specimens (53.3%) than hair specimens (46.7%) and the mean concentrations in nails were on average 4.9 times higher than in hair (1813 fg/mg and 364 fg/mg, respectively). The THCA concentrations in hair and nail were strongly associated (r = 0.974, P < 0.01, n = 60) and the association was significant. The study demonstrated that fingernail clippings are a suitable alternative specimen type to hair to monitor for marijuana use and abuse.

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.

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.

Pyrolysis-Gas Chromatography/Mass Spectrometry for Microstructure and Pyrolysis Pathway of Polyester-Polyether Multiblock Copolymer

The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/MS). PGC was applied to study the F t curve of the multiblock copolymer and PGC/MS was used to separate and identify the pyrolyzates. DTA experiment was used to study the decomposition temperature. The results show that the beginning point of elastomer’s decomposition was about 300?℃ and the decomposition temperature of most of the sample was 550?℃. Many pyrolyzates were produced because of the breaking of weak bonds in the sample. The possible microstructure was verified and the pyrolysis pathway of the copolymer was investigated.

Metabolomics of gastric cancer metastasis detected by gas chromatography and mass spectrometry

AIM:To elucidate the underlying mechanisms of metastasis and to identify the metabolomic markers of gastric cancer metastasis.METHODS:Gastric tumors from metastatic and nonmetastatic groups were used in this study.Metabolites and different metabolic patterns were analyzed by gas chromatography,mass spectrometry and principal components analysis (PCA),respectively.Differentiation performance was validated by the area under the curve (AUC) of receiver operating characteristic curves.RESULTS:Twenty-nine metabolites were differentially expressed in animal models of human gastric cancer.Of the 29 metabolites,20 were up-regulated and 9 were down-regulated in metastasis group compared to non-metastasis group.PCA models from the metabolite profiles could differentiate the metastatic from the nonmetastatic specimens with an AUC value of 1.0.These metabolites were mainly involved in several metabolic pathways,including glycolysis (lactic acid,alaline),serine metabolism (serine,phosphoserine),proline metabolism (proline),glutamic acid metabolism,tricarboxylic acid cycle (succinate,malic acid),nucleotide metabolism (pyrimidine),fatty acid metabolism (docosanoic acid,and octadecanoic acid),and methylation(glycine).The serine and proline metabolisms were highlighted during the progression of metastasis.CONCLUSION:Proline and serine metabolisms play an important role in metastasis.The metabolic profiling of tumor tissue can provide new biomarkers for the treatment of gastric cancer metastasis.

Detection of 36 antibiotics in coastal waters using high performance liquid chromatography-tandem mass spectrometry

Among pharmaceuticals and personal care products released into the aquatic environment, antibiotics are of particular concern, because of their ubiquity and health effects. Although scientists have recently paid more attention to the threat of antibiotics to coastal ecosystems, researchers have often focused on relatively few antibiotics, because of the absence of suitable analytical methods. We have therefore developed a method for the rapid detection of 36 antibiotic residues in coastal waters, including tetracyclines （TCs）, sulfanilamides （SAs）, and quinolones （QLs）. The method consists of solid-phase extraction （SPE） and liquid chromatography-tandem mass spectrometry （LC-MS/MS） analysis, using electrospray ionization （ESI） in positive mode. The SPE was performed with Oasis HLB and Oasis MCX cartridges. Chromatographic separation on a Cr8 column was achieved using a binary eluent containing methanol and water with 0.1% formic acid. Typical recoveries of the analytes ranged from 67.4% to 109.3% at a fortification level of 100 ng/L. The precision of the method, calculated as relative standard deviation （RSD）, was below 14.6% for all the compounds. The limits of detection （LODs） varied from 0.45 pg to 7.97 pg. The method was applied to detemaine the target analytes in coastal waters of the Yellow Sea in Liaoning, China. Among the tested antibiotics, 31 were found in coastal ＇waters, with their concentrations between the LOD and 212.5 ng/L. These data indicate that this method is valid for analysis of antibiotics in coastal waters. The study first reports such a large number of antibiotics along the Yellow Sea coast of Liaoning, and should facilitate future comprehensive evaluation of antibiotics in coastal ecosystems

Determination of urine catecholamines and metanephrines by reversed-phase liquid chromatography-tandem mass spectrometry

The measurement of urine catecholamine and metanephrine concentrations is important for biochemical screening and diagnosis of pheochromocytoma.The goal of this work was to develop a simple liquid chromatography-tandem mass spectrometry(LC-MS/MS)method for determining catecholamines and metanephrines in urine to replace an existing liquid chromatographic method using electrochemical detection.Urine samples were prepared using Oasis weak-cation-exchange cartridges.The eluate was analyzed on an Agilent ZORBAX Eclipse Plus Phenyl-Hexyl column in 3 min.Adrenaline,noradrenaline,dopamine,metanephrine,normetanephrine,and their deuterated internal standards were monitored in positive electrospray ionization mode by multiple reaction monitoring(MRM).No evidence of ion suppression was observed.The assay was linear up to 5μmol/L for adrenaline,5μmol/L for noradrenaline,6.1μmol/L for dopamine,5.6μmol/L for metanephrine,and 34.6μmol/L for normetanephrine,with lower limits of quantification of 5,5,12,6 and 7nmol/L,respectively.The intra-day and inter-day precisions for all analytes ranged from 0.59%to 4.64%and1.98%to 4.80%,respectively.External quality assurance samples were assayed and showed excellent agreement with the target values.This simple method provides an improved assay for determining urine catecholamines and metanephrines.

Gas chromatography/mass spectrometry based metabolomic study in a murine model of irritable bowel syndrome

AIM To study the role of microbial metabolites in the modulation of biochemical and physiological processes in irritable bowel syndrome(IBS).METHODS In the current study, using a metabolomic approach, we analyzed the key metabolites differentially excreted in the feces of control mice and mice with IBS, with or without Clostridium butyricum(C. butyricum) treatment. C57 BL/6 mice were divided into control, IBS, and IBS + C. butyricum groups. In the IBS and IBS + C. butyricum groups, the mice were subjected to water avoidance stress(WAS) for 1 h/d for ten days. Gas chromatography/mass spectrometry(GC-MS) together with multivariate analysis was employed to compare the fecal samples between groups. RESULTS WAS exposure established an appropriate model of IBS in mice, with symptoms of visceral hyperalgesia and diarrhea. The differences in the metabolite profiles between the control group and IBS group significantly changed with the progression of IBS(days 0, 5, 10, and 17). A total of 14 differentially excreted metabolites were identified between the control and IBS groups, and phenylethylamine was a major metabolite induced by stress. In addition, phenylalanine metabolism was found to be the most relevant metabolic pathway. Between the IBS group and IBS + C. butyricum group, 10 differentially excreted metabolites were identified. Among these, pantothenate and coenzyme A(Co A) biosynthesis metabolites, as well as steroid hormone biosynthesis metabolites were identified as significantly relevant metabolic pathways.CONCLUSION The metabolic profile of IBS mice is significantly altered compared to control mice. Supplementation with C. butyricum to IBS mice may provide a considerable benefit by modulating host metabolism.

Determination of constituents of essential oil from Angelica sinensis by gas chromatographymass spectrometry

Gas chromatographymass spectrometry (GC-MS) coupled with chemometric resolution upon two- dimensional data was employed to analyze the constituents of essential oils of Angelica sinensis. Constituents in essential oils of Angelica sinensis root were identified by GC-MS with the help of subwindow factor analysis (SFA) method resolving two-dimensional original data into mass spectra and chromatograms. 76 of 97 separated constituents in essential oil of Angelica sinensis root were identified and quantified, and they account for about 91.36% of the total content. The results show that ligustilide, butylene phthalide, 2-methoxy-4-vinylphenol, carvacrol, allo-ocimene,2,6,6-trimethylbicyclo-[3,1,1]hept-2-ene are the main constituents in essential oil of Angelica sinensis root.

Simultaneous determination of 15 pesticide residues in Chinese cabbage and cucumber by liquid chromatography-tandem mass spectrometry utilizing online turbulent flow chromatography

In this experiment,a liquid chromatography tandem mass spectrometry method was built to determine 15 pesticide residues in Chinese cabbage and cucumber samples based on online turbulent flow chromatography purification.After modified quick,easy,cheap,effective,rugged,and safe(QuEChERS)extraction,extracts were directly injected to the TLX(TurboFlow Liquid Xcalibur)system and brought to TurboFlow™columns for on-line purification and then transferred to analytical column for further separation and analysis.TurboFlow™columns types,transfer flow rate,and transfer time were optimized.Limits of detection and limits of quantification of the method obtained for 15 pesticide residues were ranged between 0.2–1.0μg/kg and 0.5–2.0μg/kg in Chinese cabbage and cucumber samples.Recoveries of pesticide residues were in range of 75.3%–103.7%.Matrix effects for 15 pesticides were in range of 5.6%–106.6%.The developed method has been successfully used for the determination of 15 pesticide residues in real samples.

Simultaneous Determination of Bisphenols and Alkylphenols in Water by Solid Phase Extraction and Ultra Performance Liquid Chromatography-tandem Mass Spectrometry

To establish an analytical method for determination of four bisphenols （BPA, BPB, BPF, and BPS） and two alkylphenols （4-n-OP, 4-n-NP） in water by ultra performance liquid chromatography- tandem mass spectrometry （UPLC/MS/MS）. The water samples were extracted and condensed with solid-phase extraction （SPE） using C18 cartridges and eluted by acetonitrile. Separation was carried out with Acquity BEH C8 column and detection were performed by UPLC/MS/MS. Quantification was calculated by using the internal standard BPA-d16 and 4-n-NP-d8. The linear correlation coefficients of these compounds in the range of 1.0-100.0μg/L were all over 0.999. The minimum detectable concentrations were 0.75-1.0 ng/L, and the recoveries ranged from 87.0% to 106.9%.

Determination of Steroid Hormone Residues in Fish Tissues Using Gel Permeation Chromatography and Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

A highly sensitive method was developed for the simultaneous determination of 8 steroid hormones in high-fat fish tissues using ultra high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The 8 steroid hormones were extracted from the tissues with diethyl ether.Differing from other common purification methods,the extract solutions were cleaned by gel permeation chromatography(GPC) using ethyl acetate-cyclohexane solution(1:1,v/v) as the mobile phase.The separation of target compounds was carried out by a BEH C18 column and a gradient elution consisting of acetonitrile and 0.2% aqueous formic acid(v/v).The compounds were detected under the multiple reaction monitoring(MRM) mode and quantified with external standard method.This method was validated with respect to linearity,specificity,accuracy and precision.A linearity with correlation coefficient larger than 0.995 was achieved in the range of 0.5 to 50 ng m L^(-1).The average recoveries at the spiked levels of 1.0,5.0,and 10.0 μg kg^(–1) varied between 81.7% and 90.8%,with the relative standard deviations(n=5) ranged from 3.50% to 10.0%.The limit of quantification(LOQ) for 8 steroid hormones ranged from 0.2 to 1.5 μg kg^(-1).It was concluded that this method can be successfully applied for the determination of 8 steroid hormones in complicated matrices including high-fat fish tissues.

Determination of Sulfadimidine in Royal Jelly by C_(18)-functionalized Magnetic Silica Nanoparticles Solid Phase Extraction-High Performance Liquid Chromatography-Tandem Mass Spectrometry

[Objective] This study aimed to develop a method of C_18-functionalized magnetic silica nanoparticles solid phase extraction-high performance liquid chro- matography-tandem mass spectrometry for the determination of sulfadimidine in royal jelly. [Method] The royal jelly samples were pretreated by MCX SPE column and C_18-functionalized magnetic silica nanoparticles, and the purified samples were de- tected by HPLC-MS/MS. [Result] The detection method showed a good linear rela- tionship in the range of 5-80 ugkg （r=0.993 1）. The recovery ranges were between 93%- 104% with the relative standard deviations （RSD） below 11.3%. [Conclusion] Combined with automation equipment, the method is simple, fast, time-saving, and easy to real- ize the automation of sulfadimidine in the royal jelly samples before determination.

Development of a Liquid Chromatography-tandem Mass Spectrometry Method for Determination of Butoconazole Nitrate in Human Plasma and Its Application to a Pharmacokinetic Study

Summary： A liquid chromatography-tandem mass spectrometry （LC-MS/MS） method was developed and validated for the determination of butoconazole in human plasma. Human plasma samples of 0.2 μL were pretreated by a single step protein precipitation procedure and analyzed using a high performance liquid chromatography （HPLC） electrospray tandem mass spectrometer system. The compounds were eluted isocratically on an Inertsil ODS-SP column （100 min×2.1 mm, 3 μm）, ionized using a positive ion atmospheric pressure electrospray ionization source and analyzed using multiple reaction monitoring （MRM） mode. The ion transitions monitored were m/z 412.8→q65.1 for butoconazole and m/z 453.4→230.3 for the internal standard. The chromatographic run time was 3.5 min per injection, with retention time of 2.47 rain and 2.15 min for butoconazole and repaglinide, respectively. The method was validated to be linear over the range of 20 to 8000 pg/mL （r〉0.999） by using a weighted （1/x2） quadratic regression. The mean recovery rate was more than 86.7%, and the intra- and inter-day precision of the quality control samples （QCs） was less than 8.3% and the accuracy ranged from 96.0% to 110.2%, which indicated that the quantitative method was reliable and accurate. The method is simple, rapid, and has been applied successfully to a pharmacokinetics study of butoconazole nitrate suppositories in healthy Chinese females.

Extraction of essential oil from shaddock peel and analysis of its components by gas chromatography-mass spectrometry

Essential oil, with more than thirty kinds of compounds separated and identified by gas chromatography-mass spectrometry, was extracted from Shatian shaddock peel and Sweet shaddock peel by squeeze-steam distillation and direct steam distillation method. Among their composition, the main components are terpene compounds, which account for 93.926% (mass fraction, the same below) and 85.843% of essential oils extracted from Shatian shaddock peel and Sweet shaddock peel, respectively. Although nootkatone is the major contributor of shaddock characteristic scent, and its contents are 1.069% and 1.749% of essential oils from Sweet shaddock peel and Shatian shaddock peel, respectively. The results show that squeeze-steam distillation gives higher yield and good quality of essential oil and the compositions of essential oils from two kinds of shaddock peels are different, but the main contributors of the shaddock scent are the same.

Headspace Solid-Phase Micro-Extraction Gas Chromatography/Mass Spectrometry(HS-SPME-GC/MS)-Based Untargeted Metabolomics Analysis for Comparing the Volatile Components from 12 Panax Herbal Medicines

Quality control of ginseng currently is mainly based on ginsenoside analysis,but rarely focuses on the volatile organic components.In the current work,an untargeted metabolomics approach,by headspace solid-phase micro-extraction gas chromatography/mass spectrometry(HS-SPME-GC/MS),was elaborated and further employed to holistically compare the compositional difference of the volatile components simultaneously from 12 Panax herbal medicines,which included P.ginseng(PG),P.quinquefolius(PQ),P.notoginseng(PN),red ginseng(PGR),P.ginseng leaf(PGL),P.quinquefolius leaf(PQL),P.notoginseng leaf(PNL),P.ginseng flower(PGF),P.quinquefolius flower(PQF),P.notoginseng flower(PNF),P.japonicus(PJ),and P.japonicus var.major(PJvm).Chromatographic separation was performed on an HP-5MS elastic quartz capillary column using helium as the carrier gas,enabling good resolution within 1 h.We were able to characterize totally 259 volatile compounds,including 82 terpenes(T),46 alcohols(Alc),29 ketones(K),25 aldehydes(Ald),21 esters(E),and the others.By analyzing 90 batches of ginseng samples based on the untargeted metabolomics workflows,236 differential ions were unveiled,and accordingly 36 differential volatile components were discovered.It is the first report that simultaneously compares the compositional difference of volatile components among 12 Panax herbal medicines,and useful information is provided for the quality control of ginseng aside from the well-known ginsenosides.

Determination of 8 Diuretics and Probenecid in Human Urine by Gas Chromatography-Mass Spectrometry: Confirmation Procedure

A fast and sensitive method for determination of 8 diuretics (acetazolamide, bendroflumethiazide, bumetanide, chlorthalidone, furosemide, hydrochlorothiazide, metolazone, triamterene) and masking agent (probenecid) in human urine using gas-chromatography with mass spectrometric detection is described. The extraction of the substances as function of the nature of organic solvent, mixing time and pH of aqueous phase was studied. The tandem mass spectrometry was used to increase selectivity of diuretics determination due to elimination of background interferences. Fragmentation reactions were studied for each compound and their collision energies were optimized to obtain the best selectivity. The results of method’s validation demonstrate its suitability in routine analysis for confirmation purposes.

Analyzing crude oils from the Junggar Basin(NW China) using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry(GC×GC-TOFMS)

As a new technology of analyzing crude oils, comprehensive two-dimensional gas chromatography cou- pled with time-of-flight mass spectrometry （GCxGC- TOFMS） has received much research attention. Here we present a case study in the Junggar Basin of NW China. Results show that the hydrocarbons, including saturates and aromatics, were all well-separated without large co- elution, which cannot be realized by conventional one-dimensional GC-MS. The GC×GC technique is especially effective for analyzing aromatics and low-to-middle- molecular-weight hydrocarbons, such as diamondoids. The geochemical characteristics of crude oils in the study area were investigated through geochemical parameters extracted by GC×GC-TOFMS, improving upon the understanding obtained by GC-MS. Thus, the work here represents a new successful application of GC×GC- TOFMS, showing its broad usefulness in petroleum geochemistry.