牛组织中稳定性同位素碳、氮随饲料变化的研究

研究了饲料组成不同时,牛不同组织中δ13C和δ15N值的变化规律.将9头12～14月龄的青年牛随机分为3组,分别饲喂C4植物含量为100%、50%、0%的饲料,132 d后屠宰.利用同位素比率质谱仪测定了牛尾毛、脱脂牛肉、粗脂肪、各种饲料的δ13C和δ15N值.结果表明,饲喂同种饲料的牛个体间碳、氮同位素组成随着时间的延长差异减小;牛尾毛、脱脂肌肉、粗脂肪中的δ13C值呈极显著相关性(P＜0.01),并均与C4植物含量呈极显著的相关性(P＜0.01);牛组织中的δ15N值并未随饲料呈现规律性变化.用牛组织中的δ13C值可以预测饲料中C4植物所占的比例,牛尾毛、脱脂肌肉、粗脂肪均可作为牛肉溯源的材料.     

鸡肉中稳定同位素组成与饲料和饮水关系的研究

通过稳定同位素质谱技术分析了鸡肉中的稳定同位素1δ3C和2δH值、饲料中的1δ3C值,及饮水中的1δ8O值,研究鸡肉中稳定同位素组成与肉鸡的饲料和饮水的关系,从而为动物产品的溯源技术奠定基础。分别从不同地区采集鸡肉、饲料及饮水样品,测定其1δ3C、2δH及1δ8O值。结果表明:鸡肉和饲料中的1δ3C值呈极显著的正相关(相关系数达0.782,P<0.01),鸡肉中的2δH值和饮水中的1δ8O值呈高度正相关(相关系数达0.816,P<0.01)。说明可以根据鸡肉中的1δ3C、2δH值推断肉鸡的饲料和产地。     

稳定同位素碳、氮、硫、氢在鸡肉产地溯源中的应用研究

利用同位素比值质谱仪测定了来自北京、山东、湖南、广东4省9个不同地区鸡肉粗蛋白中的δ^13C、δ^15N、δ^34S、δ^2H值和相应各地饮水中的δ^180值。多元方差分析结果表明,δ^13C、δ^15N、δ^34S、δ^2H 4种稳定同位素在不同地区的鸡肉中均有显著差异（p〈0．05）;4参数同时对鸡肉产地的正确判别率达到了100％;各地饮水中的δ^18O值和鸡肉中的δ^2H值呈现显著正相关性（p〈0．01）。碳、氮同位素受饲料、气候等因素的影响,硫同位素依赖于地理位置和产地表面的地质特点。     

基于稳定同位素的5种蔬菜产地真实性判别

为保护蔬菜产地真实性,以上海市场5种常见蔬菜(生菜、茼蒿、辣椒、番茄和黄瓜)为研究对象,应用单因素方差分析上海和其他产地蔬菜的δ~(13)C、δ~(15)N、δ~2H和δ~(18)O值差异,并通过主成分分析(PCA)和偏最小二乘判别分析(PLS-DA)建立上海地产蔬菜真实性判别模型。结果表明,上海地产5种蔬菜总的δ~(15)N、δ~2H和δ~(18)O值与其他产地蔬菜差异显著(P<0.05),包括番茄的δ~(15)N和δ~(18)O值、辣椒的δ~2H值、茼蒿的δ~(15)N值,说明上海本地产蔬菜所施用肥料类型和灌溉水来源与其他产地不同;PCA很难将上海地产蔬菜与其他产地蔬菜识别,PLS-DA最优模型可以很好地判别上海地产生菜(准确率100.00%)、茼蒿(准确率91.67%)和番茄(准确率85.71%)的真实性,辣椒和黄瓜的产地真实性判别模型仍需进一步优化,PLS-DA模型的重要变量为δ~(15)N、δ~2H和δ~(18)O值,进一步说明了蔬菜所施用肥料类型和灌溉水来源的差异是实现上海地产蔬菜真实性判别的重要因素。研究结果为蔬菜产地真实性判别提供参考方法。     

牛奶中碳、氮、氢和氧稳定同位素比的测定及其在产地溯源分析中的应用

应用元素分析-同位素质谱仪(EA-IRMS)和多用途气体制备-连续流稳定同位素质谱仪(GasBench-IRMS)分别测定了来自国内外7个不同国家(澳大利亚、新西兰、西班牙、德国、奥地利、意大利和中国)的83件牛奶样品中碳、氮、氢、氧的稳定同位素比值(δ13 C、δ15 N、δ2 H和δ18 O)。对所测得的数据用SPSS 20.0软件分别进行了方差分析、聚类分析以及牛奶产地的判别分析。从所得结果可见,上述4项稳定同位素比值中的每一项都可获得相关牛奶样品产地来源的若干信息,但还不足以作为相关牛奶样品的溯源地判别的充分依据。而将测试结果进行组合后,对δ13 C、δ15 N和δ2 H三项指标组合交叉检验整体判别正确率达到84.3%,据此采用3项组合指标对牛奶产地进行判别分析,并在此项组合指标的基础上建立了产自7个国家的牛奶的判别模型。对自来这7个不同国家的牛奶盲样进行判别时,可将所测得样品中上述3项稳定同位素的δ值代入所建立的模型中,并比较各模型所得的Y值的大小,其中Y值最大的,即归属于此模型所代表的国家。     

气相色谱同位素比质谱测定不同产地鱼油中5种不饱和脂肪酸碳同位素比值

以IAEA-600咖啡因(δ13C-27.771‰)作为溯源标准,建立了气相色谱同位素质谱技术测定鱼油中功能因子亚油酸(LIA)、亚麻酸(LNA)、花生四烯酸(ARA)、二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)等5种不饱和脂肪酸碳稳定同位素比值δ13C的分析方法。鱼样品先经HCl水解,乙醚液液萃取脂肪,提取的脂肪在2 mol/L KOH-甲醇溶液中反应生成脂肪酸甲酯,采用强极性毛细管气相色谱柱(Sil-88 100 m×0.25 mm×0.2μm)分离,稳定同位素比质谱测定。方法经日内、日间和人员比对验证,表明测定结果稳定,标准偏差小于0.82%。收集了不同产地的241个淡水鱼和深海鱼,对于提取的天然鱼油进行5种不饱和脂肪酸同位素比值分析,测得天然鱼油中5种不饱和脂肪酸同位素比值(δ13C)在-32.87‰~27.07‰之间,经计算,鱼油中不饱和脂肪酸δ13C值与硬脂酸δ13C值之比在-5.79~1.88之间,同时测得了相同的产地、品种鱼油中不饱和脂肪酸δ13C的分布范围,构建了天然鱼油的同位素指纹特征数据库,用于鉴定鱼油真伪。将不同浓度玉米油添加至天然金枪鱼油中进行测定,证明δ13C值的变化与掺入C4植物油量呈良好的线性关系,方法可根据δ13C值的变化鉴别掺假的鱼油。     

气相色谱-燃烧-同位素比率质谱法测定葡萄酒中5种挥发性组分的碳同位素比值及其在产地溯源中的应用

建立了一种利用气相色谱-燃烧-同位素质谱(Gas chromatography-combustion-Isotope ratio mass spectrometers,GC-C-IRMS)测定葡萄酒中5种挥发性组分(即乙醇、丙三醇、乙酸、乳酸乙酯、2-甲基-丁醇)碳稳定同位素比值新方法。优化了GC-C-IRMS测定条件,进样量小于0.5μL,样品分析时间小于14 min。对以上5种挥发性成分标准品的测定精密度为0.08‰~0.25‰,葡萄酒样品的测定精密度为0.09‰~0.36‰,与元素分析-同位素比率质谱仪(Element analyzer-isotope ratio mass spectrometers,EA-IRMS)比较,其测定偏差低于0.5‰。利用该技术分析了产自法国、澳大利亚、美国和中国共54支葡萄酒中5种挥发性组分的碳稳定同位素值并进行产地溯源分析,判别分析(Discriminant analysis,DA)结果表明,仅利用以上5种挥发性组分的碳同位素比值就能有效区分以上4个产地的葡萄酒,说明葡萄酒挥发性成分稳定碳同位素可应用于葡萄酒的产地溯源。     

GC–IRMS测定白色块状天然气水合物气体中的碳氢同位素

研究了GC–IRMS联用技术测定烃类气体碳氢稳定同位素的方法。利用气相色谱仪将烃类气体各组分分开,通过高温燃烧/裂解转化为CO2和H2,然后导入MAT–253稳定同位素质谱仪进行测试。用该方法测试的标准甲烷气体碳、氢同位素值和其标定值一致,测定结果的相对标准偏差分别为0.222‰和0.950‰。用该法测定了广东沿海珠江口盆地东部海域首次钻获的高纯度天然气水合物样品所释放的烃类气体碳氢稳定同位素值,其中δ13C为–69.78‰(VPDB),δD为–184.4‰(VSMOW)。GC–IRMS法精确度高,可用范围广,适用于海洋天然气水合物样品所释放烃类气体碳氢同位素的测定。     

数据融合策略在食品产地溯源中的应用进展

产地溯源技术可有效识别食品来源,在保护消费者权益和维护产品声誉方面具有重要作用。产地溯源常用的检测手段包括光谱、质谱、色谱和传感器技术等,但是对于化学组成较复杂的食品,单一的分析技术通常无法获得足够的化学信息,而数据融合策略可以通过对不同检测技术获取的数据进行处理及联合,获取更多的有用信息,提高在产地溯源过程中的鉴别效果。目前,数据融合策略已经广泛应用于食品产地溯源领域。本文介绍了包括光谱、质谱、色谱和传感器技术等产地溯源检测技术,总结了基于这些技术的数据融合策略在食品产地溯源中的应用现状,并对数据融合策略在食品产地溯源方面的发展前景进行了展望,以期为食品产地溯源的研究及发展提供参考。     

单体烃氢同位素测试系统高温热转化装置的研制

研制了单体烃氢同位素在线测试系统(GC-TC-IRMS)中的高温热转化装置(TC).该装置主要由高温电热元件、高温裂解管、温控系统等部分组成.实验表明,高温热转化装置控温精度良好(±3 ℃);在1250～1500 ℃之间选择13个温度点,并选用最稳定的烃类化合物CH4,在每个温度点进行反复实验对比(n≥6),甲烷氢同位素值(δDCH4)随反应温度增高逐渐变轻;通过对标准多元气态烃类化合物、标准液态烃类化合物及原油样品测试结果的对比分析,表明所研制的TC具有很好的稳定性与可靠性,δDn-alkane的测试精度优于±2.5‰, 完全达到研究需求.     

Multi-element (H,C,N,S) stable isotope characteristics of lamb meat from different European regions

Multi-element (H,C,N,S) stable isotope ratio analysis was tested for its suitability as a means for geographical provenance assignment of lamb meat from several European regions. The defatted dry matter (crude protein fraction) from lamb meat was found to be a suitable probe for "light" element stable isotope ratio analysis. Significant differences were observed between the multi-element isotope ratios of lamb samples from different regions. The mean hydrogen isotopic ratios of the defatted dry matter from lamb were found to be significantly correlated with the mean hydrogen isotopic ratios of precipitation and groundwater in the production regions. Carbon and nitrogen isotopic ratios were influenced by feeding practices and climate. Sulfur isotopic ratios were influenced by geographical location and surface geology of the production region. The results permitted differentiation of lamb meat, from most production regions, by inspection. However, more sophisticated evaluation of the data using multivariate methods, such as linear discriminant analysis, achieved 78% correct classification.     

Stable isotope variation as a tool to trace the authenticity of beef

Organic beef coming principally from Germany was analysed for the hydrogen, carbon, oxygen, nitrogen and sulfur stable isotopic composition to test the possibility of tracing back the geographical origin. Since there is a well-known pattern of D/H and ¹⁸O/¹⁶O in meteoric water and in ground water, there is an existing link to tissue water in the beef. By including the stable isotope ratios of the other elements of life further information is available: soils show different isotope ratios of ¹⁵N/¹⁴N and ³⁴S/³²S depending on the geological composition, cultivation and atmospheric sulfur deposition. As organic farming is mainly obliged to use only their produced fodder, that ratio is reflected in the beef as well.Different organic beef samples from various German farms have been collected and analysed over nearly two years. To check the differentiation of foreign beef, samples from Argentina and Chile were also included in the study. The analyses of meat samples indicate that it is possible to trace back the region (e.g. Argentina and Germany) by using isotopes of oxygen and hydrogen. A local geographical differentiation can be done by using the stable isotopes of nitrogen and sulfur, as was demonstrated for three farms in Colonia Bay. An optimal differentiation also depends on the quality of further information (e.g. the season, kind of cattle breeding or the declaration of the local geographical origin). Certainly authenticity of beef is not only linked with the geographical origin but can also reflect the differentiation of organic and conventional farming. The fodder of organic cattle farming consists mainly of C₃ plants and the use of C₄ plants is more usual in conventional cattle farming. A ¹³C/¹²C ratio above –20 appears as a limit for organic farming. Increased values have to be controlled based on their authenticity.     

Hydrogen isotope type-curves of very hot crude oils

Several crude oil accumulations in the Pannonian Basin are trapped in uncommonly hot (>170°C) reservoirs. Their maturities range from mature to very mature on the basis of cracking parameters of their biological marker homologous series (ratio of products to reactants). A stable carbon isotopic study of these oils, poor in biological markers commonly used for correlation purposes, did not provide a reliable oil-to-oil correlation. As an alternative tool, the hydrogen isotope compositions of oil fractions separated on the basis of different polarities were measured, and hydrogen isotope type-curves were generated for a set of mature to very mature crude oil samples. This method of presenting hydrogen isotope composition of fractions as type-curves is novel. Nineteen samples (17 crude oils from SE-Hungary, 1 oil condensate and 1 artificial oil) were chosen for the present study. The aim was to examine the applicability of hydrogen isotope type-curves in oil-to-oil correlation and to test the simultaneous application of carbon and hydrogen isotope type-curves in the field of petroleum geochemistry. We have shown that, although the conventionally used co-variation plots proved to be inadequate for the correlation of these hot and mature oils, the simultaneous use of carbon and the newly introduced hydrogen isotope type-curves allows us to group and distinguish oils of different origins.     

常见炸药的稳定同位素比值分析方法研究进展

炸药的深度比对与溯源对于爆炸案事件的侦破具有重大意义,以不同地域来源的原料或不同生产工艺生产的炸药,其组成元素的稳定同位素比值具有差异,因而稳定同位素比值可作为炸药深度比对与溯源的重要指标。稳定同位素比值质谱法(IRMS)作为一种高精度的稳定同位素比值测量手段,已逐渐发展成熟,与元素分析仪、气相色谱仪、液相色谱仪等仪器联用,在食品安全、环境保护、法庭科学等领域应用广泛。IRMS在炸药比对与溯源上亦发挥了重要作用,自1975年IRMS被应用于区分不同国家生产的三硝基甲苯(TNT)以来,IRMS已成功用于多种炸药的分析。但目前尚未见有文献系统地总结常见炸药的稳定同位素比值分析研究进展。该文介绍了稳定同位素比值分析的相关原理、仪器组成及特点,分别总结了硝酸铵、黑火药、TNT、太恩、黑索金等常见炸药的稳定同位素比值分析方法,汇总了文献报道的不同国家生产的硝酸铵、黑火药、TNT等炸药的稳定同位素比值。文章就不同炸药的稳定同位素比值差异、炸药生产、存储过程中相关因素对同位素比值的影响,爆炸前后稳定同位素比值的变化情况等内容进行了分析。本文还指出了目前炸药的稳定同位素比值分析研究中存在的问题,对可能的解决办法进行了讨论,对未来的发展方向提出了建议。     

The use of stable carbon isotope analysis to detect the abuse of testosterone in cattle.

The use of stable carbon isotope analysis to detect the administration of anabolic steroids to cattle was investigated. Samples were extracted by solid-phase extraction on C18 cartridges. Stable isotope ratios (13C:12C) were measured by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) of the underivatised extracts. A programmed temperature vaporiser (PTV) injector was installed in the GC-IRMS system, which conferred a number of advantages. First, it allowed large volumes of sample to be injected whilst the injector liner was cool. The solvent was subsequently vented to the atmosphere prior to transfer of the sample to the GC column. Thus a significantly greater amount of sample could be presented for analysis, thereby increasing the sensitivity. Second, by this means virtually all the solvent could be removed prior to analysis. This eliminates solvent peak tailing, which can be a major problem in GC-IRMS. Finally, the PTV allowed the use of higher initial GC oven temperatures, which in turn facilitated the analysis of underivatised steroids by reducing the GC run time and improving the chromatographic peak shape. The carbon isotope composition of 5 beta-androstane-3 alpha,17 alpha-diol, the major metabolite of testosterone found in bovine bile, was measured in bile samples from untreated cattle and from cattle injected intramuscularly with testosterone or a mixture of testosterone esters. There was considerable inter-animal variation in the values obtained and there was no significant difference between samples from treated and untreated animals. However, when the isotopic composition of the metabolite was normalised with respect to that of an endogenous reference compound (cholesterol) in the same sample, the difference between treated and untreated animals become statistically significant.     

Investigation of the feeding effect on the 13C/12C isotope ratio of the hormones in bovine urine using gas chromatography/combustion isotope ratio mass spectrometry

The effect of the feeding on the 13C/12C isotope ratio of four endogenous steroid hormones testosterone (T), epi-testosterone (epi-T), dehydroepiandrosterone (DHEA) and etiocholanolone (ETIO) in bovine urine was investigated. An analytical method to determine the accurate isotope ratio was developed including an extensive clean up followed by enrichment of the analytes in two steps of HPLC fractionation. Feeding experiments with four young animals were performed using C3 and C4 plants (grass, maize silage, hay, etc.) over a time period of about 280 days. One cattle was used as a control animal with no change of its diet over the full period. The detection of the 13C/12C isotope ratio of the acetylated extracts was performed by gas chromatography/combustion isotope ratio mass spectrometry. After the first change of the feeding from C4 to C3 plants significant changes of the delta 13C % values were observed from the -19 to -23% level to the -24 to -32% level for etiocholanolone and epi-testosterone in urine of three animals, whereas the DHEA values remained under the level of the two metabolites. Testosterone could not be detected with GC-C-IRMS due to its low concentration in young animals. After the second change of the diet from C3 to C4 plants (after 222 days), the measured delta 13C % values have been stabilised at the original level. The results show that in case of the feeding with only C3 plants the endogenous delta values of -32% can be reached. In this case the contribution of exogenous material with a delta value of -32% could not be detected independently of the concentration. If the diet contains C4 plants the difference or the ratio of the delta 13C % values becomes the determinant in the discriminatory power. For validation of the method a human and a cattle were treated with testosterone and the delta 13C % values were measured in incurred human and cattle urine.     

Evaluation of measurement uncertainty in EA–IRMS: for determination of δ 13C value and C-4 plant sugar content in adulterated honey

In this study, the method for determining the stable carbon isotope ratio value was validated. Measurement uncertainty of stable carbon isotope ratio value of whole honey and its extracted protein derived from repeatability, reference gas, reference standards and calibration curve was calculated by applying the “bottom-up” approach according to Eurachem/CITAC guide. The expanded uncertainties for all results ranged from 0.14 to 0.19 ‰, with most of them between 0.15 and 0.16 ‰ (the coverage factor k = 2, the level of confidence p is approximately 95 %). The percentage contribution of each source to the relative combined uncertainty was calculated. The data indicated that calibration curves have more contribution to the relative combined uncertainty than repeatability and reference standards. On the other hand, the measurement uncertainty of C-4 sugar content in honey was estimated. Based on these results, 58 honey samples, such as acacia, chaste, Northeast China black bee, flowers and jujube honey, have been gathered to determine the C-4 plant sugar content adulteration in honey by elemental analyzer with an isotope ratio mass spectrometer. It can be found that all honey samples were not adulterated by C-4 plant sugar.     

δ13C, δ15N and δ2H isotope ratio mass spectrometry of ephedrine and pseudoephedrine: application to methylamphetamine profiling

Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (δ¹³C), nitrogen (δ¹⁵N) and hydrogen (δ²H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the δ¹³C, δ¹⁵N and δ²H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC‐IRMS) in high‐purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi‐synthetic, or fully synthetic origin. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd.     

Compound-specific stable isotope analysis of organic contaminants in natural environments: a critical review of the state of the art,prospects, and future challenges

Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L^–1 range, and the development of methods for CSIA of other elements are reviewed. Furthermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.Abbreviations BTEX benzene, toluene, ethylbenzene, xylenes - MTBE methyl tert-butyl ether - PAHs polycyclic aromatic hydrocarbons - VOCs volatile compounds - PCBs polychlorinated biphenyls - CSIA compound-specific (stable) isotope (ratio) analysis - GC-IRMS, GC/IRMS or GCIRMS gas chromatography-isotope ratio mass spectrometry - GC-C-IRMS, GC/C/IRMS or GCC-IRMS gas chromatography-combustion-isotope ratio mass spectrometry - irmGC/MS isotope ratio monitoring gas chromatograph-mass spectrometry - GC/P/IRMS gas chromatography-pyrolysis-isotope ratio mass spectrometry (used for D/H) - KIE kinetic isotope effect - PSIA position-specific isotope analysis (for intramolecular isotope distribution) - SNIF-NMR site-specific natural isotopic fractionation by nuclear magnetic resonance spectroscopy     

Calling all archaeologists: guidelines for terminology,methodology, data handling,and reporting when undertaking and reviewing stable isotope applications in archaeology

Stable isotope analysis has been utilized in archaeology since the 1970s, yet standardized protocols for terminology, sampling, pretreatment evaluation, calibration, quality assurance and control, data presentation, and graphical or statistical treatment still remain lacking in archaeological applications. Here, we present recommendations and requirements for each of these in the archaeological context of: bulk stable carbon and nitrogen isotope analysis of organics; bulk stable carbon and oxygen isotope analysis of carbonates; single compound stable carbon and nitrogen isotope analysis on amino acids in collagen and keratin; and single compound stable carbon and hydrogen isotope analysis on fatty acids. The protocols are based on recommendations from the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) as well as an expanding geochemical and archaeological science experimental literature. We hope that this will provide a useful future reference for authors and reviewers engaging with the growing number of stable isotope applications and datasets in archaeology.