液相色谱-稳定同位素比值质谱测定燕窝中唾液酸的碳稳定同位素比值

该文建立了适合液相色谱-稳定同位素比值质谱(liquid chromatography-stable isotope ratio mass spectrometry, LC-IRMS)测定干燕窝中唾液酸δ¹³C值的方法。样品前处理方法加标回收率为75.2%～100.6%,前处理方法可显著降低蛋白质等大分子对色谱柱的影响且不会干扰碳稳定同位素的准确分析；研究并优化了LC-IRMS对唾液酸δ¹³C值测定的影响，优化后的色谱条件：采用Hyper REZ XP Carbohydrate H+(300 mm×7.7 mm, 8μm)柱，柱温30℃,在0.250 mL/min流速下用90%B(H₂O)+10%D(pH 2的H₂SO₄)洗脱。方法稳定性、重复性均良好，可准确测定样品δ¹³C值。对6个干燕窝样品和4个市售唾液酸进行测定，其唾液酸δ¹³C值分别为(-29.55±0.39)‰和(-15.18±2.45)‰,2种不同来源唾液酸碳稳定同位素特...     

乙醇C、O、H稳定同位素在白酒掺伪鉴别中的潜在差异分析

采用气相色谱-稳定同位素比质谱(GC-IRMS)建立了白酒、食用酒精和工业酒精中乙醇C、H、O稳定同位素比值的测定方法,并优化了稀释倍数、进样体积和分流比等前处理。通过检测分析28种白酒、7种工业酒精和5种食用酒精的乙醇δ¹³C、δ¹⁸O和δ²H值发现：工业酒精与白酒之间乙醇δ¹³C和δ¹⁸O值差异较大,食用酒精与白酒之间乙醇δ¹³C值差异较小但乙醇δ¹⁸O值差异较大,三者的乙醇δ²H值差异较小;在鉴别白酒是否掺假工业酒精或食用酒精时,鉴别能力：氧稳定同位素>碳稳定同位素>氢稳定同位素。     

稳定碳同位素判别浓香型白酒的品牌

为了辨别浓香型白酒(strong-flavor Baijiu,SFB)的品牌,利用稳定同位素质谱仪(stable isotope ratio mass spectrometry,IRMS)测定了来自13个品牌共计301个浓香型白酒样品的乙醇、风味物质(异戊醇、己酸乙酯、乳酸乙酯、己酸)稳定碳同位素比值(stable carbon isotope ratios,δ¹³C)。结果发现,不同品牌浓香型白酒拥有不同稳定碳同位素特征,单独利用乙醇δ¹³C对浓香型白酒品牌进行判别时,总正确判别率较低,只有44.5%,结合4种风味物质δ¹³C后,总正确判别率提升到82.7%,说明浓香型白酒中多种物质δ¹³C相联合的方法能有效的辨别浓香型白酒的品牌。     

酿造食醋中碳、氧同位素比值的测定及应用研究

以酿造食醋为研究对象,建立元素分析/连续流-稳定同位素比质谱法（EA/GasBench Ⅱ-IRMS）测定食醋总碳、水中氧同位素比值（δ13C和δ18O）的方法。通过优化稀释倍数与进样体积,得到δ13C值测定最佳条件为食醋稀释2倍,进样体积1.0 μL;通过优化平衡时间和样品体积,得到δ18O值测定时平衡时间为24 h,样品体积为500 μL。结果表明,在最佳条件下,食品样品碳同位素比测定值标准偏差（SD）值均＜0.30‰,氧的同位素比测定值的SD值均＜0.10‰,表明该测定方法的稳定性较好。山西食醋总碳δ13C值分布在-23.26‰～-20.80‰,水中氧的δ18O值在-5.66‰～-4.49‰;镇江食醋总碳δ13C值在-25.93‰～-20.70‰,水中氧的δ18O值在-8.35‰～-5.61‰;结合碳氧同位素比值分析,可以将山西老陈醋、镇江香醋和镇江陈醋区分开（P＜0.01）。     

同位素内标法-高效液相色谱-串联质谱法测定海产品中的甲醛含量

目的 建立海产品中甲醛的同位素内标-高效液相色谱-串联质谱分析方法。方法 样品经水超声处理，10%三氯乙酸(V/V)溶液沉淀蛋白，正己烷除脂肪净化后，下清液通过2,4-二硝基苯肼衍生，衍生产物经电喷雾离子源(electrospray ionization, ESI-)电离，多反应监测(multiple reaction monitoring, MRM)模式检测和内标法定量。结果 甲醛衍生物的检测线性范围为1.0~50.0 ng/mL，相关系数为0.9996，方法检出限为0.3 μg/kg。平均加标回收率在71.4%~94.0%之间，相对标准偏差<15.0%。结论 该方法前处理简单、快速、有效、准确灵敏、适合于海产品中甲醛的定性、定量检测。     

基于稳定同位素比值的不同产地枸杞特征分析及判别

原产地差异导致枸杞价格悬殊,为促进国内枸杞市场健康有序发展,该文应用元素分析仪-稳定性同位素质谱（elemental analyzer-stable isotope mass spectrometry, EA-IRMS）测定了来自青海、宁夏和新疆3个地区共97份枸杞样品δ¹³C、δ¹⁵N、δ²H、δ¹⁸O和δ³⁴S 5种稳定同位素组成,结合箱线图、单因素方差分析以及主成分分析（principal component analysis, PCA）对不同产地枸杞中稳定同位素比值分布规律和相关性进行了讨论,应用线性判别分析（linear discriminant analysis, LDA）和支持向量机（support vector machine, SVM）2种算法建立不同产地枸杞判别模型。结果显示,枸杞样品中δ¹³C、δ¹⁵N、δ²H和δ¹⁸O 4种稳定同位素对产地判别贡献率较大,δ^...     

食品中甲醛的稳定碳同位素特征分析及其在甲醛源解析中的应用

采用衍生化—气相色谱—燃烧—同位素比质谱法（Gas Chromatography-Combustion-Isotope Ratio mass Sprectrometry，GC/C/IRMS）对水产品、蔬菜制品、果蔬的甲醛含量和δ ¹³C值进行了测试。结果表明，鱿鱼样品中甲醛含量为0.341~24.185 mg/kg，δ ¹³ C值为-48.167‰~-24.514‰，龙头鱼中甲醛含量为54.555~121.416 mg/kg，δ ¹³C值为-45.430‰~-27.468‰；蔬菜制品中仅干香菇中检出了甲醛，其含量高达212.741 mg/kg，δ ¹³C值为-41.293‰~-20.293‰；果蔬中甲醛含量较低。水产品的δ ¹³C值随贮藏时间的增加逐渐偏负，香菇的δ ¹³C 值随贮藏时间的增加逐渐偏正。龙头鱼中外源性加标模拟试验结果表明，利用同位素定量分析模型计算得到的贡献率与理论值偏差低于15%。     

元素分析-同位素质谱法鉴定麦卢卡蜂蜜中碳-4植物糖掺假

目的建立元素分析-同位素质谱法(elementanalyzerstableisotopeproportionalmassspectrometry,EA-IRMS)鉴定麦卢卡蜂蜜中碳-4植物糖掺假的新方法。方法样品经前处理后,利用元素分析-同位素质谱仪测定蜂蜜的碳同位素比值δ~(13)C_H、蜂蜜中总蛋白质的碳同位素比值δ~(13)C_P、蜂蜜中花粉的碳同位素比值δ~(13)C_F。用麦卢卡蜂蜜中δ~(13)C值更为稳定的δ~(13)C_F值为标准,δ~(13)C_H值与其进行比较,参照GB/T 18932.1-2002《蜂蜜中碳-4植物糖含量测定方法稳定碳同位素比率法》计算方式,来建立新的计算麦卢卡蜂蜜中碳-4植物糖含量X(%)的计算方式。结果对纯正麦卢卡蜂蜜提出:0X(%)7,δ~(13)C_Fδ~(13)C_Pδ~(13)C_H。新方法利用测定麦卢卡蜂蜜中δ~(13)C值更为稳定的δ~(13)C_F值,代替了原有的比较不稳定的δ~(13)C_P为标准,解决了原方法对于麦卢卡蜂蜜中碳-4植物糖检测的假阳性问题。结论本方法显示出较好的准确度,大大提高了掺假检测的能力。     

2,4-二硝基苯肼比色法测定食品中甲醛的改进

通过改进2,4-二硝基苯肼比色法测定食品中甲醛的不足,对显色条件进行了优化,并评价了方法的性能指标,对市售腐竹、米粉、毛肚三种食品中的甲醛含量进行了测定分析。建立一种将甲醛衍生成甲醛-2,4-二硝基苯腙,甲醛-2,4-二硝基苯腙与强碱作用生成酒红色的醌类物质,进行吸光度值的测定的方法。试验方法:甲醛溶液与2.8 m L 2,4-二硝基苯肼乙醇饱和溶液在酸性条件下于50℃水浴衍生30 min,冷却室温,先后加入无水乙醇、KOH-乙醇溶液,稳定10 min在432 nm波长下测得吸光度值。结果表明:甲醛标准曲线的线性方程为Y=0.6788X+0.0102,相关糸数R 2=0.999,线性范围为1~12μg/m L;平均回收率为102.8%(RSD=3.99%);最低检出限为0.0025μg/m L。结论:改进的方法灵敏、准确、精密度高,能够满足食品中甲醛分析准确度的要求。     

液相色谱串联质谱法测定白菜中的甲醛含量

文中使用2,4-二硝基苯肼衍生法使白菜中甲醛生成甲醛-2,4-二硝基苯腙,再使用乙腈提取富集甲醛-2,4-二硝基苯腙(衍生物),后经液相色谱串联质谱对其浓度进行检测。结果显示,该法中甲醛的检出限为3.06μg/kg,当白菜中甲醛添加含量在1~18 mg/kg时,甲醛线性良好(r2=0.994)。对白菜中3种浓度(0.5、1、5 mg/kg)甲醛添加进行6次平行回收实验,结果表明,3种浓度平行添加回收率在102%~105%,相对标准偏差为3%~8%,回收稳定,精密度良好。     

低纬高原气候带分布差异对不同烤烟品种δ13C值的影响

选具有近4个纬度差异,地处2个不同气候带的玉溪市通海县和昭通市鲁甸县2个生态烟区,研究了K326、红花大金元和KRK26烤烟品种在旺长和成熟期的稳定碳同位素（＆13C）分布值对气候环境的响应。结果表明,3个品种烟叶δ13C值的范围为．26．56‰～24．36‰,旺长期烟叶δ13C值表现为通海大于鲁甸,成熟期除KRK26外,巧δ13C值表现为鲁甸大于通海。对比旺长期和成熟期,两地各品种的δ13C值都表现为成熟期大于旺长期,即随着烟叶成熟度增加,分布在2个气候带烤烟的水分利用效率都在逐渐提高。品种间比较表明,无论是旺长期还是成熟期,通海都表现为KRK26的δ13C值最大,鲁甸则表现为红花大金元的巧δ13C值最大。而3个品种下部叶和中部叶δ13C的平均值都表现为通海大于鲁甸,且均与旺长期表现出一致的规律,支持温度较高,日照时数较长,降水量较少,δ13C值越大的结论。     

Carbon Stable Isotope Analysis for Glucose in Sake: Simple Freeze-Dried Sake Can Substitute for Glucose Following HPLC Isolation

Carbon stable isotope analysis of ethanol is an established method for determining the authenticity of alcoholic beverages, but there is no accepted method for measurements of glucose carbon stable isotopic composition (δ ¹³C). This study aims to establish two methods to determine accurately the δ ¹³C value of glucose isolated from sake by high-performance liquid chromatography (HPLC) after three clean-up steps using ion exchange chromatography and in simple freeze-dried sake (total nonvolatile matter) and to examine two methods that yield different δ ¹³C values. In the glucose isolation procedure, the δ ¹³C values of glucose were not significantly affected by the glucose concentration, solvent (water or aqueous acetonitrile), drying method (freeze-dry or nitrogen-spraying), the clean-up step using ion exchange chromatography (weakly acidic cation-exchange, strongly acidic cation-exchange, and weakly basic anion-exchange resins), or HPLC isolation. Glucose nitrogen spray-dried after isolation by ion exchange chromatography and HPLC showed a carbon isotope discrimination value of <0.1 ‰. The glucose δ ¹³C values ranged from ?26.8 to ?25.5 ‰ in authentic sake and from ?27.0 to ?11.0 ‰ in commercial sake samples. This HPLC isolation approach may provide a first step toward visualizing the brewing process via isotopic carbon flow during fermentation. Additionally, there was no significant difference between the δ ¹³C values of glucose and total nonvolatile matter from sake. The δ ¹³C measurement of simple freeze-dried sake can substitute for glucose δ ¹³C measurement using HPLC isolation, thus aiding high-throughput detection of carbon derived from C₄ plants in sake.     

Use of isotope analysis to characterize meat fromIberian-breed swine

We describe a method based on isotope analysis (δ¹³C) for characterization and differentiation of Iberian pork meat as a function of the diet of the animal. Using adipose tissue, it is possible to classify unknown samples in group of animals designated “acorn-fed”, “recebo=mixed-fed” and “feed raised” according the δ¹³C value obtained, from the calibration straight line of y=−22.12–0.35x, with a correlation coefficient r=0.982 and s=0.1‰; where y=δ¹³C and x=arrobas of acorn and range forage received by the animals during the fattening period. Stress should be placed on the economic and industrial importance of Iberian-breed swine because the market prices of Iberian swine products depends on the classification of the animals according to the type of feeding regimen which they are subjected to.     

Isotope Ratio Mass Spectrometry Coupled to Element Analyzer and Liquid Chromatography to Identify Commercial Honeys of Various Botanical Types

The aim of the present work was to investigate whether honeys of various botanical characteristics could be discriminated and identified on the basis of the isotopic data. For this purpose, 45 commercial honey samples of various botanical types were analyzed using isotope ratio mass spectrometry (IRMS) coupled to element analyzer (EA) and liquid chromatography (LC). δ ¹³C values of honey; corresponding extracted protein and individual sugars (sucrose, glucose, and fructose) of honey; reducing sugar; and sucrose contents were determined and utilized to demonstrate the authenticity of commercial honeys of different botanical types. Results indicated that a very strong correlation (δ ¹³C_protein = 0.862δ ¹³C_honey + 0.800, R ² = 0.944) was observed between δ ¹³C honey values and δ ¹³C protein values of real honey samples. δ ¹³C_honey and δ ¹³C_protein should range from ?27.2 to ?23.5 and ?26.9 to ?23.6‰ for pure honeys of various botanical types investigated in this study. The use of isotopic compositions and some systematic differences as authenticity criterion permits the honey samples of various botanical types to be reliably detected.     

基于稳定碳同位素示踪技术的商品植物油掺杂鉴别研究

本文旨在运用所建立的纯植物油的脂肪酸组成及其稳定碳同位素比值判别标志对广州市售商品植物油是否掺杂进行判识。先在广州某大型超市购得18种商品植物油(包括3种茶籽油、5种花生油、2种葵花油、2种玉米油和6种橄榄油);然后采用气相色谱-质谱联用仪(GC-MS)、气相色谱-同位素比值质谱仪(GC-IRMS)和元素分析-同位素比值质谱仪(EA-IRMS)对这18种商品油的脂肪酸组成和全油及其脂肪酸的稳定碳同位素比值进行测定;最后将本次检测所获得的数据与作者之前建立的判别标志进行对比分析。对比结果表明,本批商品植物油的品质总体较好,但其中50%的植物油商品存在掺杂。因此,将植物油脂肪酸组成数据与其稳定碳同位素比值数据相结合,可灵敏地确定待检植物油是否存在掺杂。     

烤烟烟叶稳定同位素与化学成分关系研究

通过相关和典型相关分析研究了烤烟烟叶中稳定同位素与化学成分的相互关系.结果表明,碳稳定同位素丰度在烟叶中变异较小,而氮稳定同位素丰度则存在广泛的变异;碳稳定同位素与氮稳定同位素间存在显著正相关关系,与总氮含量呈极显著正相关关系,与碳氮比和总钾含量存在极显著负相关关系,与钾氯比存在显著负相关关系.典型相关分析表明,随着烟叶中碳稳定同位素丰度的提高,烟叶中钾含量和钾氯比存在下降的变化趋势.说明烟叶中稳定碳同位素与常规化学成分间存在一定的相关关系,对烟叶中不同化学成分含量有一定的影响.     

δ13C values and phytanic acid diastereomer ratios: combined evaluation of two markers suggested for authentication of organic milk and dairy products

Authentication of organic milk by suitable markers is currently attracting more and more interests in food control. In this study, we aimed to compare the efficiency of the markers stable carbon isotope ratio (δ¹³C value) with the SRR/RRR phytanic acid diastereomer ratio (SRR/RRR) of milk fat for distinguishing different feeding systems. For stable carbon isotope ratio analysis by elemental analysis–isotope ratio mass spectrometry (EA-IRMS), we first developed a simple sample preparation method based on milk fat extracts allowed to evaporate the solvent in tin capsules for liquid samples. The δ¹³C values and reproducibility measured with this alternative sample pre-treatment method excellently matched those obtained with the current standard method. Applied to milk samples, the results of the EA-IRMS analysis were linked to the SRR/RRR, and both markers allowed to distinguish milk from cows fed with hay (δ¹³C value > ?28.0 ‰, SRR/RRR <1.5) from feed used in conventional milk production which contained maize silage (C₄-plants) (p < 0.001). Milk fat of organic retail cheese samples was also highly depleted in ¹³C (δ¹³C value ?30.0 ‰ ± 1.1), and the SRR/RRR was low (<1.5). However, seven cheese samples showed inconsistent δ¹³C values and SRR/RRR, most likely due to the feeding of grass silage. Both parameters (δ¹³C values and SRR/RRR), together with the phytanic acid content of milk fat, also allowed distinguishing between the feeding of high amounts of pasture, hay, and/or grass silage.     

基于氮稳定同位素比例质谱和液相色谱-高分辨质谱的有机番茄鉴别

为了解决有机食品鉴别需要多种参数指标进行综合判定,制样过程繁琐,判别正确率偏低的问题,本研究提出一种基于稳定同位素比例质谱和液相色谱-高分辨质谱分析技术,结合偏最小二乘法判别分析（partial least squares-discriminant analysis,PLS-DA）的有机番茄鉴别方法。将采集的94 个番茄样品（有机番茄50 个,普通番茄44 个）匀浆破碎、冷冻干燥后,分析并采集氮同位素比值（δ15N）和液相色谱-高分辨质谱数据,应用PLS-DA方法提取数据信息,建立有机番茄判别模型,筛选并确证出其中判别的标志因子,包括氮同位素比值以及有机酸、黄酮类等13 个特征化合物。所建立的模型对有机番茄的判别正确率为93.4%,基本可以满足有机番茄判别的需要。该研究为有机西红柿的快速判定提供了一种新的技术手段。