果胶前驱体6-~(13)C标记示踪法研究果胶与木质素的连接方式

为了从碳水化合物的角度研究果胶-木素复合体之间的结构,本文采用13C同位素示踪标记法,通过对植物体中的果胶前驱物α-D-葡萄糖醛酸6位碳上进行13C同位素标记,得到植物体内合成的带13C6标记的果胶-木素复合体,并用果胶酶对果胶-木素复合体进行酶解,利用红外、高分辨率固体13C-NMR以及液体13C-NMR技术分析带13C标记的稻秆粉末、LCC以及酶解后LCC,发现果胶通过6位上的C原子与木质素苯丙烷结构以酯键的形式连接,且样品中木素结构单元之间主要以β-O-4、β-1、β-5和松柏醇结构的方式连接。     

吡罗昔康-d_3的合成

目的开发稳定同位素氘代标记吡罗昔康-d_3的合成方法。方法以邻苯甲酰磺酰亚胺为原料,氘代碘甲烷为氘代标记试剂,经过烷基化、重排、氘代甲基化与酯的氨解得到氘代标记的吡罗昔康-d_3。结果总收率为26.6%,化学纯度为99.2%,氘代丰度为99.3%,目标化合物结构经质谱、核磁共振等表征确定。结论该4步合成路线方法简单,原料易得、反应条件易于控制,产品可用于其在药代动力学方面的研究。     

食品接触材料中全氟烷基磺酸类化合物的HPLC-MS/MS测定

研究食品接触材料中全氟烷基磺酸类化合物的检测方法和该类化合物的残留水平。样品采用甲醇超声提取,液相色谱-质谱联用测定,以C18为分离柱,甲醇-5mmol/L乙酸铵溶液为梯度洗脱淋洗液,同位素内标法定量,内标物为13C标记的PFOS。该方法的检出限为0.5μg/kg,线性范围为0.5～10μg/kg,方法的平均回收率为91.1%～112.8%。结果证明,该方法准确、快速,可成功应用于16种食品接触材料实样的检测。     

气相色谱-燃烧-同位素质谱仪(GC-C-IRMS)测定游离氨基酸的δ13C值

氨基酸的δ13C值测定方法是开展13C标记代谢流分析研究的关键技术手段.建立了气相色谱-燃烧-同位素比率质谱仪测定发酵液中游离氨基酸的δ13C比值方法,结果表明,该方法稳定性好,氨基酸分离度佳,重复测定标准偏差小于0.5‰,完全满足在低丰度同位素标记代谢流分析精度要求,为今后采用大规模低丰度13C标记开展传统白酒和黄酒发酵过程的代谢机理的研究提供了有效的技术手段.     

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。     

低丰度~(13)C标记的酿酒酵母代谢通量分析探讨研究

通过对酿酒酵母发酵液进行低浓度的[1-13C]葡萄糖标记,并采用GC-C-IRMS测定发酵菌体中蛋白氨基酸的δ13C值,最终显示在0.5%~2%的标记浓度范围内,15种菌体蛋白氨基酸δ13C值与标记浓度呈现出很好的线性关系。证明了0.5%或者更低的浓度标记都可以用于13CMFA中,大大降低了碳同位素标记代谢流成本,为13CMFA应用于传统白酒和黄酒大生产发酵过程中的复杂代谢机理研究提供一种手段。     

猪肉、猪肝中 17 种全氟烷基化合物的HPLC-MS/MS 测定

目的建立猪肉、猪肝中17种全氟烷基化合物(perflurorinated alkylated substances,PFASs)的高效液相色谱-串联质谱(HPLC-MS/MS)检测方法。方法样品经酸化乙腈提取、混合吸附剂纯化后,应用HPLC-MS/MS技术检测,以Poroshell 120 EC-C18为色谱柱,甲醇-5 mmol/L乙酸铵水溶液梯度洗脱,多反应监测负离子模式扫描,同位素内标法定量,内标物为经13C或者18O标记的相应外标物。结果应用该方法检测猪肉样品中17种全氟烷基化合物的检出限(LOD,S/N=3)为0.009~0.047μg/kg,在猪肝样品中的检出限(LOD,S/N=3)为0.003~0.031μg/kg;在0.5μg/kg、1.0μg/kg、1.5μg/kg三个加标浓度下,该方法的平均加标回收率约为80%~110%,平均相对标准偏差(RSD)小于10%。结论该方法可有效应用于猪肉、猪肝中17种全氟烷基化合物的检测。     

2,3-吡嗪二甲酸二茴香酯的合成及其热裂解

为了开发新型吡嗪类烟用香料,以茴香醇和2,3-吡嗪二甲酸为原料,N,N′-二环己基碳二亚胺(DCC)为缩水剂,在4-二甲氨基吡啶(DMAP)的催化作用下,合成了化合物Ⅲ。通过IR,1H NMR,13C NMR和HRMS等波谱技术确证了产物结构,并进行了热裂解实验。结果表明:1化合物Ⅲ为目标产物2,3-吡嗪二甲酸二茴香酯。2合成化合物Ⅲ的最佳条件为:2,3-吡嗪二甲酸∶茴香醇=1∶2.1(摩尔比),2,3-吡嗪二甲酸和DMAP的用量均为1.5 mmol,常温下反应12 h,收率57%。3化合物Ⅲ的初次裂解温度为266.9Ⅲ,二次裂解温度为530.8Ⅲ;在400Ⅲ左右失重约70.62%,失重率在274.9Ⅲ时达到最大。4裂解温度对热裂解产物的种类和相对质量分数影响较大;各温度下的主要裂解产物有吡嗪、对甲基茴香醚、大茴香醚、大茴香醛和苯甲醛等香味成分。     

酚型木素模型物硫酸盐法蒸煮过程中LCC形成的研究

合成了带13C同位素标记的酚型木素模型物——愈创木基丙三醇-β-愈创木基醚-[α-13C],模拟了硫酸盐法蒸煮过程,将合成的木素模型物和典型的半纤维素组成部分——木糖进行蒸煮,然后利用酸析沉淀木素、乙酸乙酯抽提等方法将蒸煮后的产物分级,并利用13C-NMR(13C-核磁共振波谱)和二维HMQC(异核多量子相干谱)对分级后的各个部分进行分析,研究传统硫酸盐法蒸煮过程中LCC的形成情况。研究发现:酚型木素模型物的中间产物和木糖衍生物(糖醛酸等)形成了少量苯甲醚键型LCC结构,这些新形成的LCC结构主要存在于乙酸乙酯抽提物中。     

抗抑郁新药阿戈美拉汀杂质的合成

目的合成抗抑郁药物阿戈美拉汀的两个杂质。方法以(7-甲氧基-1-萘基)乙腈为起始原料,经氢化、乙酰化、柱层析得阿戈美拉汀二聚乙酰胺(杂质A)。以2-(7-甲氧基-1-萘基)乙基胺为起始原料,制备阿戈美拉汀二聚尿素(杂质B)。结果两个目标化合物经1H NMR、13C NMR、MS确证其结构。结论合成的两个杂质可作为阿戈美拉汀质量控制对照品,本工艺操作可行,原料易得。     

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.     

Hydrogen and carbon isotope fractionation during aerobic biodegradation of benzene

The main aim of the study was to evaluate hydrogen and carbon isotope fractionation during biodegradation of benzene as a possible tool to trace the process in contaminated environments. Aerobic biodegradation of benzene by two bacterial isolates, Acinetobacter sp. and Burkholderia sp., was accompanied by significant hydrogen and carbon isotope fractionation with hydrogen isotope enrichment factors of -12.8 +/- 0.7 per thousand and -11.2 +/- 1.8 per thousand, respectively, and average carbon isotope enrichment factors of -1.46 +/- 0.06 per thousand and -3.53 +/- 0.26 per thousand, respectively. Inorganic carbon produced by Acinetobacter sp. was depleted in 13C by 3.6-6.2 per thousand as compared to the initial delta13C of benzene, while the produced biomass was enriched in 13C by 3.8 per thousand. The secondary aim was to determine isotope ratios of benzenes from different manufacturers with regard to the use of isotopes for source differentiation. While two of the four analyzed benzenes had similar delta13C values, each of them had a distinct delta2H-delta13C pair and delta2H values spread over a range of 66.5 per thousand. Thus, combined analyses of hydrogen and carbon isotopes may be a more promising approach to trace sources and/or biodegradation of benzene than measuring carbon isotopes only.     

Stable carbon isotopes and the study of prehistoric human diet

Mass spectrometric analysis of the stable carbon isotope composition (13C/12C or delta 13C) of bone collagen from human remains recovered at archaeological sites provides a direct chemical method for investigating dietary patterns of prehistoric human populations. This methodology is based on the facts that (1) different food items within the human diet have distinct delta 13C values, and (2) the delta 13C value of human bone collagen is determined by the delta 13C value of the diet. Studies of the development of subsistence patterns based on corn agriculture, one of the most significant developments in North American prehistory, can benefit from the use of stable carbon isotope techniques because corn has a high delta 13C value relative to other components of the human diet. Measurements of delta 13C of bone collagen from prehistoric human skeletal remains from southeastern Missouri and northeastern Arkansas indicate that intensive corn agriculture began in this region around A.D. 1000, that the incorporation of corn into the human diet was a rapid phenomenon, and that 35 to 77% of the human diet from A.D. 1000 to A.D. 1600 consisted of corn. Results from an isochronous population in southeastern South Dakota (A.D. 1400) suggest that 78 to 90% of the diet of this group consisted of corn, with no difference between males and females. Coupled with more traditional archaeological methods, stable carbon isotope analysis of bone collagen can significantly enhance reconstruction of dietary patterns of prehistoric humans.     

Stable carbon isotope evidence for intrinsic bioremediation of tetrachloroethene and trichloroethene at area 6, Dover Air Force Base

Area 6 at Dover Air Force Base (Dover, DE) has been the location of an in-depth study by the RTDF (Remediation Technologies Development Forum Bioremediation of Chlorinated Solvents Action Team) to evaluate the effectiveness of natural attenuation of chlorinated ethene contamination in groundwater. Compound-specific stable carbon isotope measurements for dissolved PCE and TCE in wells distributed throughout the anaerobic portion of the plume confirm that stable carbon isotope values are isotopically enriched in 13C consistent with the effects of intrinsic biodegradation. During anaerobic microbial reductive dechlorination of chlorinated hydrocarbons, the light (12C) versus heavy isotope (13C) bonds are preferentially degraded, resulting in isotopic enrichment of the residual contaminant in 13C. To our knowledge, this study is the first to provide definitive evidence for reductive dechlorination of chlorinated hydrocarbons at a field site based on the delta13C values of the primary contaminants spilled at the site, PCE and TCE. For TCE, downgradient wells show delta13C values as enriched as -18.0/1000 as compared to delta13C values for TCE in the source zone of -25.0 to -26.0/1000. The most enriched delta13C value on the site was observed at well 236, which also contains the highest concentrations of cis-DCE, VC, and ethene, the daughter products of reductive dechlorination. Stable carbon isotope signatures are used to quantify the relative extent of biodegradation between zones of the contaminant plume. On the basis of this approach, it is estimated that TCE in downgradient well 236 is more than 40% biodegraded relative to TCE in the proposed source area.     

Efficient wastewater treatment by membranes through constructing tunable antifouling membrane surfaces

In the present study, a facile in situ approach for constructing tunable amphiphilic or hydrophilic antifouling membrane surfaces was demonstrated by exquisitely manipulating the microphase separation and surface segregation behavior of the tailor-made ternary amphiphilic block copolymers during the commonly utilized wet phase inversion membrane-formation process. Under dead-end filtration for oily wastewater treatment, the membrane with amphiphilic surface exhibited over 99.5% retention ratio of chemical oxygen demand (COD) without appreciable membrane fouling: the water permeation flux was slightly decreased during operation (total flux decline was 6.8%) and almost completely recovered to the initial value (flux recovery ratio was more than 99.0%) after simple hydraulic washing. While for the proteins-containing wastewater treatment, the membrane with hydrophilic surface exhibited about 52.6% COD retention ratio and superior antifouling performance: only 17.0% total flux decline and also more than 99.0% flux recovery ratio. Hopefully, the present approach can be developed as a competitive platform technology for the preparation of robust and versatile antifouling membrane, leading to the high process efficiency of wastewater treatments.     

液相色谱-质谱联用测定蛋粉中胆固醇含量

建立了液相色谱-大气压化学电离-同位素稀释质谱法测定蛋粉中的胆固醇含量的方法。本方法采用选择离子模式检测,用括弧法对蛋粉胆固醇进行定量计算。通过胆固醇一级标准物质保证测量过程的溯源性,通过采用添加胆固醇同位素标记物作为内标减少了样品前处理过程和液相色谱-质谱测定时物质响应所产生的误差,提高了测量结果的准确性。本方法具有较高的测量准确度和精密度,可作为复杂基体胆固醇测定的高准确度测定方法。     

Carbon isotope fractionation during diffusion and biodegradation of petroleum hydrocarbons in the unsaturated zone: field experiment at Vaerløse Airbase, Denmark, and modeling

A field experiment was conducted in Denmark in order to evaluate the fate of 13 volatile organic compounds (VOCs) that were buried as an artificial fuel source in the unsaturated zone. Compound-specific isotope analysis showed distinct phases in the 13C/12C ratio evolution in VOC vapors within 3 m from the source over 114 days. At day 3 and to a lesser extent at day 6, the compounds were depleted in 13C by up to -5.7% per hundred with increasing distance from the source compared to the initial source values. This trend can be explained by faster outward diffusion of the molecules with 12C only compared to molecules with a 13C. Then, the isotope profile leveled out, and several compounds started to become enriched in 13C by up to 9.5% per hundred with increasing distance from the source, due to preferential removal of the molecules with 12C only, through biodegradation. Finally, as the amount of a compound diminished in the source, a 13C enrichment was also observed close to the source. The magnitude of isotope fractionation tended to be larger the smaller the mass of the molecule was. This study demonstrates that, in the unsaturated zone, carbon isotope ratios of hydrocarbons are affected by gas-phase diffusion in addition to biodegradation, which was confirmed using a numerical model. Gas-phase diffusion led to shifts in delta(13)C >1% per hundred during the initial days after the spill, and again during the final stages of source volatilization after >75% of a compound had been removed. In between, diffusion has less of an effect, and thus isotope data can be used as an indicator for hydrocarbon biodegradation.     

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）。     

Preparation of [13C3]-melamine and [13C3]-cyanuric acid and their application to the analysis of melamine and cyanuric acid in meat and pet food using liquid chromatography-tandem mass spectrometry

For the determination of melamine and cyanuric acid the labelled internal standards [(13)C(3)]-melamine and [(13)C(3)]-cyanuric acid were synthesized using the common substrate [(13)C(3)]-cyanuric chloride by reaction with ammonia and acidified water, respectively. Standards with excellent isotopic and chemical purities were obtained in acceptable yields. These compounds were used to develop an isotope dilution liquid chromatography/mass spectrometry (LC/MS) method to determine melamine and cyanuric acid in catfish, pork, chicken, and pet food. The method involved extraction into aqueous methanol, liquid-liquid extraction and ion exchange solid phase clean-up, with normal phase high-performance liquid chromatography (HPLC) in the so-called hydrophilic interaction mode. The method had a limit of detection (LOD) of 10 microg kg(-1) for both melamine and cyanuric acid in the four foods with a percentage coefficient of variation (CV) of less than 10%. The recovery of the method at this level was in the range of 87-110% and 96-110% for melamine and cyanuric acid, respectively.     

Fractionation of stable isotope-labeled organic pollutants as a potential tracer of atmospheric transport processes

To test the potential for using stable isotope fractionation to examine the atmospheric transport of semivolatile organic compounds (SOCs), we conducted simplified distillation experiments in the laboratory and a tracer-release experiment using mixtures of stable isotope-labeled (D and 13C) and unlabeled SOCs. Perdeuterated phenanthrene and alpha-hexachlorocyclohexane were transported more slowly via air-water gas exchange in our laboratory experiments, resulting in significant isotope fractionation of perdeuterated/unlabeled compound mixtures. In contrast, isotope fractionation of 13C6-labeled SOCs was much lower. A field tracer-release study was then conducted by spiking a seawater retention pond with a mixture of D10-labeled, 13C2-labeled, and unlabeled phenanthrene and examining isotope fractionation of the mixture after air-water gas exchange. No preferential fractionation of D10-vs 13C2-labeled phenanthrene was observed in the pond water; however, greater fractionation of D10-vs 13C2-labeled phenanthrene was observed in air samples collected within a 1-100 m radius of the pond. Thus, stable isotope tracers may provide a means of examining the atmospheric transport and air-earth exchange rates of POPs in an environmental realistic setting.