Identification of Chinese green tea (Camellia sinensis) marker metabolites using GC/MS and UPLC-QTOF/MS

Food Science and Biotechnology - Tea is one of the most widely consumed aromatic beverages in the world because of its taste and flavor, as well as due to many potential health beneficial...     

Investigation of spectrophotometrically determined substances in Yucca extract by GC/MS, TLC and on-column injection GC

Spectrophotometrically determined substances in Yucca extract, listed as "Yucca foam extract" in the "List of Existing Food Additives in Japan", were investigated by GC/MS, TLC and GC. A TLC method using an anisaldehyde color developing reagent similar to that employed in spectrophotometry was established for selective detection of sapogenins in Yucca extract. Several steroidal sapogenins were found by GC/MS in the fractions corresponding to spots on the TLC plate, and these were assumed to have contributed to the color development in spectrophotometry. Sarsasapogenin and smilagenin were the dominant sapogenins. An on-column injection GC method to determine these sapogenins in Yucca extract was also developed. The sum of these two sapogenins in Yucca extract was 0.9%. The total amount of sapogenin estimated by GC was approximately 2%, which was similar to that measured by spectrophotometry.     

GC/MS联用法测定煎炸油中挥发性组分

研究了采用固相微萃取与气质联用法分析了煎炸油样品中的挥发性成分,在萃取温度为70℃、平衡时间为30 min、解析时间为4 min的条件下,对煎炸油和未煎炸植物油的挥发性组分进行分析。结果表明:植物油在煎炸3 h时就含有大量的反式烯醛、烷烃类挥发性成分;在煎炸15 h后产生了小分子的脂肪酸,其中最典型物质为占总挥发性成分的20%以上的反,反-2,4-葵二烯醛,其在新鲜植物油中不含或含量极少,而在煎炸初期,其生成量就高出原料的50多倍,随着煎炸时间的延长,有所降低最终趋于平缓,但仍远远高于原料,因此可以通过反,反-2,4-葵二烯醛的含量来鉴别煎炸油。     

两种不同酯化方法分析荞麦中脂肪酸成分

采用索氏提取法对荞麦油进行了提取,分别采用两种方法进行甲酯化处理,以气相色谱-质谱联用仪进行了分析,对脂肪酸组成和含量进行了比较。结果表明:两种酯化方法分别鉴定出8种脂肪酸,占荞麦油总量的98.64%和99.97%;方法1鉴定出的主要脂肪酸为:棕榈酸占脂肪酸总量的15.92%,亚油酸占脂肪酸总量的30.37%,油酸占脂肪酸总量的35.32%;方法2鉴定出的棕榈酸占脂肪酸总量的35.66%,亚油酸占脂肪酸总量的11.75%,油酸占脂肪酸总量的33.26%。     

Multiresidue method for pesticides and veterinary drugs in bovine milk using GC/MS and LC/MS/MS

A simple, sensitive and selective method with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed to detect 342 pesticides and veterinary drugs contaminating bovine milk at the maximum residue limits (MRLs) defined in the "positive list system". Sample preparation was performed by extracting the analytes with acetonitrile, followed by salting-out with sodium chloride. For some pesticides, the extract was further cleaned up by n-hexane partitioning and PSA cartridge column chromatography. GC/MS-EI or -NCI was used to determine pesticide residues, while LC/MS/MS-ESI was applicable to the determination of pesticide and veterinary drug residues. The variation of the recoveries of these drugs at MRL was relatively wide; however the relative standard deviations of the recovery of each drug were within 28%, suggesting that the present method is good enough for use as a screening test for contaminants at the MRLs. These results show that this method is useful for multiresidue analysis of numerous pesticides and veterinary drugs in bovine milk.     

Determination of bisphenol A in foods using GC/MS

An analytical method using GC/MS was developed for bisphenol A (BPA) in foods and BPA was determined in canned foods and fresh foods such as vegetables, fruit and meat. BPA was extracted with acetone from the samples and the extract was concentrated at under 40 degrees C in vacuo to afford an aqueous solution, which was washed with hexane after alkalization and extracted with 50% diethyl ether-hexane after acidification. Extracts were cleaned up on a PSA and/or a C18 cartridge column, and BPA was derivatized with heptafluorobutyric anhydride and determined by GC/MS (SIM). This method was applicable to the detection and determination of BPA residues in food samples at the level of 1 ng/g. Among canned foods, BPA was found in 6 corned beef, 1 chicken, 9 sweet corn and 3 bean samples at the levels of 17-602 ng/g, 212 ng/g, 2.3-75 ng/g and 3.5-26 ng/g, respectively. BPA was also detected in 1 retort soup and 1 retort pack product at the levels of 11 ng/g and 86 ng/g, respectively. As for dairy products, BPA was not detected in butter and milk. Among fresh foods, BPA was detected in 2 fish and 3 liver samples at the levels of trace (tr)-6.2 ng/g and tr-2.2 ng/g, respectively. In vegetables, fruits and chocolates, a trace level of BPA was detected in only 1 chocolate. Traces of BPA were also detected in 3 samples of 6 boxed lunches.     

The analysis of fluvalinate in beeswax using GC/MS

A method for quantitation of the synthetic pyrethroid fluvalinate in beeswax has been developed. The method uses the internal standard permethrin added in the first acetonitrile extraction step. Subsequent cleanup involves partitioning into ether and use of a florisil column. The final gas chromatography was performed on a capillary column with selected ion monitoring detection using a mass spectrometer. The presence of fluvalinate was confirmed by the retention times of two identical peaks which had a 75:25 area ratio of the peaks at m/z of 250:252 (ion contains chlorine). Fluvalinate recovery of 108 and 97% were obtained at the 0.52 and 1.04 ppm spike level (respectively) using peak area calculations. The detection limit was determined to be 0.05 ppm.     

Quantitative determination of perfluorochemicals and fluorotelomer alcohols in plants from biosolid-amended fields using LC/MS/MS and GC/MS

Analytical methods for determining perfluorochemicals (PFCs) and fluorotelomer alcohols (FTOHs) in plants using liquid chromatography/tandem mass spectrometry (LC/MS/MS) and gas chromatography/mass spectrometry (GC/MS) were developed, and applied to quantify a suite of analytes in plants from biosolid-amended fields. Dichloromethane-methanol and ethylacetate were chosen as extracting solutions for PFCs and FTOHs, respectively. Nine perfluorocarboxylic acids (PFCAs), three perfluorosulfonic acids (PFSAs), and ten FTOHs were monitored. Most PFCAs and perfluorooctanesulfonate (PFOS) were quantifiable in plants grown in contaminated soils, whereas PFCs went undetected in plants from two background fields. Perfluorooctanoic acid (PFOA) was a major homologue (～10-200 ng/g dry wt), followed by perfluorodecanoic acid (～3-170 ng/g). [PFOS] in plants (1-20 ng/g) generally was less than or equal to most [PFCAs]. The site-specific grass/soil accumulation factor (GSAF = [PFC](Grass)/[PFC](Soil)) was calculated to assess transfer potentials from soils. Perfluorohexanoic acid had the highest GSAF (= 3.8), but the GSAF decreased considerably with increasing PFCA chain length. Log-transformed GSAF was significantly correlated with the PFCA carbon-length (p < 0.05). Of the measured alcohols, 8:2nFTOH was the dominant species (≤1.5 ng/g), but generally was present at ≥10× lower concentrations than PFOA.     

气相色谱-质谱联用法鉴别调味品中动物性和植物性蛋白水解液

建立了精确测定水解蛋白类调味品中胆固醇、豆固醇、谷固醇和菜油固醇等甾族化合物的气-质联用法,方法最低检测限(3 S/N)为0.20 μg/mL,用标准加入法进行回收试验,测得回收率在82.1%92.8%之间.确定以胆固醇为特征指标,建立起判别水解蛋白类调味品中是否存在动物性蛋白质成分方法.经对大量实际样品和模拟样品的检测,证实本方法行之有效,可应用于进出口水解蛋白类调味品的检验.     

微波萃取-GC/MS/MS测定抗菌织物的三氯生含量

以二氯甲烷为萃取溶剂,采用微波辅助萃取技术萃取抗菌织物中的抗菌剂三氯生;萃取液经衍生化处理后进行气相色谱/串联质谱(GC/MS/MS)分析,从而建立了一种测定抗菌织物中三氯生的气相色谱/串联质谱方法.该方法灵敏度高,检出限为0.3 ng/mL( S/N= 10),平均回收率为99.1％～101.2％,精密度为3.0％ ～7.1％.     

GC与GC/MS定量分析香料的比较

分别采用气相色谱法(GC)、气相色谱/质谱总离子流法[GC/MS(TIC)]、气相色谱/质谱选择离子法[GC/MS(SIM)]3种仪器测定方式和2种定量方法———峰面积归一化法和内标标准曲线法对13种香料标样进行了定量分析比较。比较的内容包括:测试方法的重复性、内标标准曲线以及应用内标标准曲线的定量结果。结果表明:①对于内标标准曲线法,GC和GC/MS(SIM)分析的13种香料的CV均不大于1%,多数香料的内标法标准曲线的r>0.999,显示出很好的线性关系和重复性,适宜进行准确的定量分析;②GC/MS(TIC)分析的重复性以及所得内标法标准曲线的线性关系一般;③3种仪器测试方式的峰面积归一化法定量结果与实际情况偏差较大,尤其是2种GC/MS方式。     

Identification of the key odorants in barley malt (caramalt) using GC/MS techniques and odour dilution analyses

Application of the aroma extract dilution analysis (AEDA) on a distillate prepared from ground caramalt kernels followed by identification experiments revealed 3-methylbutanal (malty), 1-octen-3-one (mushroom-like), methional (cooked potato), (E,E)-2,4-decadienal (fatty, waxy), vanillin (vanilla-like), 2- and 3-methylbutanoic acid (sweaty) and 4-hydroxy-2,5-dimethyl-3-(2H)-furanone (caramel-like) as the most odor-active compounds. Using static headspace/olfactometry, the very volatile odorants dimethyl sulfide (cooked vegetable-like) and 2-methylpropanal (malty) were identified as additional odorants contributing to the overall rye-bread crust-like odour of the caramalt.     

Aroma characterisation of Pu-erh tea using headspace-solid phase microextraction combined with GC/MS and GC–olfactometry

Volatile compounds from Pu-erh tea were extracted using a headspace-solid phase microextraction (HS-SPME), and analysed with a gas chromatography–mass spectrometry (GC–MS) and a gas chromatography olfactometry (GC–O). Results showed that a total of 66 major volatile compounds were identified by GC–MS analysis; among them, methoxy-phenolic compounds (33.58%), alcohols (23.01%) and hydrocarbons (11.62%) were the major chemical classes. It was found that 1,2,3-trimethoxybenzene (17.16%) was the most abundant aroma components, followed by α-terpineol (5.68%), 1,2-dimethoxybenzene (4.64%) and linalool oxide II (4.29%) in order. Twenty-nine odour active compounds were perceived by GC–O analysis. Further investigation showed that 1,2-dimethoxybenzene, 1,2,3-trimethoxybenzene, 1,2,3-trimethoxy-5-methylbenzene, 4-ethyl-1,2-dimethoxy-benzene, β-ionone, β-linalool, linalool oxides, decanal, etc. were responsible for the special flavour in Pu-erh tea. It seems that the methoxy-phenolic compounds and alcohols play a vital role in the special flavour of Pu-erh tea.     

Congener-specific analysis of Pcbs in food samples by using GC/MS

A GC/MS method for congener-specific analysis of polychlorinated biphenyls (PCBs) in food samples was evaluated. There was good agreement between total concentration of PCBs in fish samples (n = 16) measured by using the GC/MS method and the conventional GC-ECD method. The total diet study samples (fishery food, meat, egg, milk, and their products) collected from Osaka in 1982-2001 were analyzed by using the GC/MS method to estimate the temporal trend of daily intake of PCBs from food. The estimated daily intake of total PCBs (sum of tri- to heptaCBs) was in the range of 0.7-4.4 microg/person/day, far below the Japanese provisional acceptable daily intake (250 microg/50 kg-person/day). The dominant congener was 2,2',4,4',5,5'-hexachlorobiphenyl (#153), which accounted for 9-15% of total PCB. The ratio of lower chlorinated congeners decreased from the 1980's to post-2000. The results indicate that the PCB congener profile in foods has gradually changed.     

Research Watch: GC/MS analysis

Measurements.     

卷烟烟气中稠环芳烃的分析研究

本项研究建立了一种测定卷烟烟气中稠环芳烃的分析方法--气质联用法。优化了方法的前处理过程、仪器分析条件,对分析方法的重复性、回收率、检测限进行了研究。确定了环己烷萃取卷烟烟气总粒相物中的稠环芳烃,萃取液经硅胶固相萃取柱净化,用气相色谱-质谱联用仪定量检测苯并[a]芘、苯并[a]蒽和Chrysene 3种稠环芳烃含量的分析方法。该检测方法设计合理,稳定性和重复性好、准确性和精确性高,具有较好的可操作性和推广性。本项目应用该方法对国内外较有代表性的81种卷烟样品中苯并[a]芘、苯并[a]蒽和Chrysene进行了系统的分析测定,研究了国内外混合型与烤烟型卷烟中苯并[a]芘等稠环芳烃含量分布的规律,讨论了卷烟烟气中苯并[a]芘、苯并[a]蒽和Chrysene之间的含量关系及其与总粒相物、焦油的关系。      

GC/MS、GC×GC/TOFMS分析烟草半挥发性中性成分比较

为比较气相色谱质谱(GC/MS)与全二维气相色谱/飞行时间质谱(GC×GC/TOFMS)在定性定量方面的差别,考察了色谱柱系统、操作条件(调制周期、柱头压力和初始温度等)对两维分离的影响,建立了烟草半挥发性中性化学成分分析的GC×GC/TOFMS方法,并采用这2种方法分析了云烟85的C3F烟叶的半挥发性中性成分。结果显示①GC/MS法共分离出400多个峰,鉴定出73种成分,而GC×GC/TOFMS法分离出近万个峰,共鉴定出569种成分;②在一维GC中峰形很好的β-大马酮的色谱峰,在GC×GC中经调制后被分离成6种成分1-氧化乙烯基癸烷、1-甲基-4-(2-甲基环氧乙烷基)-7-氧-二环[4,1,0]庚烷、二联苯、β-大马酮、10-乙酰甲基-3-蒈烯和正十四烷。因此,GC×GC/TOFMS分离能力更强,定性定量结果更可靠,更适合复杂体系的分离分析。