红景天中红景天甙和酪醇的毛细管电泳法分析

利用毛细管电泳法分离测定两种红景天中红景天甙和酪醇的含量,所用毛细管规格为48.5 cm×50 μm, 二极管阵列紫外检测器 (DAD)检测波长221 nm, 最佳分离条件:电压21 kV, 分离温度25 ℃,背景电解质为含有30 mmol/L 十二烷基硫酸钠(SDS), 2.5+97.5(V/V)乙腈的14 mmol/L硼酸溶液,pH 10.7.红景天甙与酪醇分别在60.0～7.5 μg/mL 和 27.5～3.5 μg/mL质量浓度范围内与电泳峰面积呈现良好线性关系,检测下限分别为3.0和1.5 μg/mL .对标准品进行6次测定, 迁移时间的RSD为0.25%和0.39%, 峰面积的RSD为5.26%和3.52%.

Comparative study on CO2 emissions from different types of alpine meadows during grass exuberance period

Potentilla fruticosa scrub, Kobresia humilis meadow and Kobresia tibetica meadow are widely distributed on the Qinghai-Tibet Plateau. During the grass exuberance period from 3 July to 4September, based on close chamber-GC method, a study on CO2 emissions from different treatments was conducted in these meadows at Haibei research station, CAS. Results indicated that mean CO2emission rates from various treatments were 672.09+152.37 mgm-2h-1 for FC (grass treatment); 425.41+191.99 mgrn-2h-1 for FJ (grass exclusion treatment); 280.36+174.83 mgrn-2h-1 for FL (grass and roots exclusion treatment); 838.95+237.02 mgm-2h-1 for GG (scrub+grass treatment); 528.48+205.67 mgm-2h-1for GC (grass treatment); 268.97 ±99.72 mgm-2h-1 for GL (grass and roots exclusion treatment); and 659.20±94.83 mgm-2h-1 for LC (grass treatment), respectively (FC, FJ, FL, GG, GC, GL, LC were the Chinese abbreviation for various treatments). Furthermore, Kobresia humilis meadow, Potentilla fruticosa scrub meadow and Kobresia tibetica meadow differed greatly in average CO2 emission rate of soil-plant system, in the order of GG＞FC＞LC＞GC. Moreover, in Kobresia humilis meadow,heterotrophic and autotrophic respiration accounted for 42% and 58% of the total respiration of soil-plant system respectively, whereas, in Potentilla fruticosa scrub meadow, heterotrophic and autotrophic respiration accounted for 32% and 68% of total system respiration from G-G; 49% and 51%from GC. In addition, root respiration from Kobresia humilis meadow approximated 145 mgCO2m-2h-1,contributed 34% to soil respiration. During the experiment period, Kobresia humilis meadow and Potentilla fruticosa scrub meadow had a net carbon fixation of 111.11 grn-2 and 243.89 grn-2,respectively. Results also showed that soil temperature was the main factor which influenced CO2 emission from alpine meadow ecosystem, significant correlations were found between soil temperature at 5 cm depth and CO2 emission from GG, GC, FC and FJ treatments. In addition, soil moisture may be the inhibitory factor of CO2 emission from Kobresia tibetica meadow, and more detailed analyses should be done in further research.

反相高效液相色谱法测定大鼠肝组织中DNA的碱基含量

利用反相高效液相色谱法，采用Supelcosil LC-18色谱柱（250 mm * 4.6 mm i.d.，5μm ），以甲醇-0.05 mol/L KH_2PO_4缓冲液（体积比为20：80）为流动相，流速0.8 mL/min，在254 nm波长处检测，对生活在高原（海拔2.3 km）的习服大鼠肝组织中脱氧核糖核酸（DNA）的碱基含量进行了检测，发现各碱基在DNA中所占的比例是相对稳定的：腺嘌呤（A）28.8%、鸟嘌呤（G）23.3%、胞嘧啶（C）17.4%、胸腺嘧啶（T）25.3%，并利用内标法对DNA甲基化水平进行了测定。

Detection of carbohydrates using new labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone by capillary zone electrophoresis with absorbance (UV)

A novel labeling reagent 1-(2-naphthyl)-3-methyl-5-pyrazolone (NMP) coupled with capillary electrophoresis (CE) with DAD detection for the determination of carbohydrates has been developed. The chromophore in the 1-phenyl-3-methyl-5-pyrazolone (PMP) reagent is replaced by naphthyl functional group, which results in a reagent with very high molar absorptivity (epsilon(251nm) = 5.58 x 10(4) L mol(-1) cm(-1)). This pen-nits NMP-labeled carbohydrates to be detected with UV absorbance in standard 50-mu m-i.d. fused silica capillaries by zone electrophoresis. in this mode, nanomolar concentrations of detection limits are obtained. The method for the derivatization. of carbohydrates with NMP is simplified. The derivatization reaction is rapid and mild in the presence of ammonia catalyst without further transfer steps. Nine monosaccharide derivatives such as mannose, galacturonic acid, glucuronic acid, rhamnose, glucose, galactose, xylose, arabinose and fucose can successfully be detected in CE mode. Good reproducibility can be obtained with relative standard deviation (R.S.D.) values of the migration times and peak area, respectively, from 0.44 to 0.48 and from 3.2 to 4.8. Furthermore, the developed method has been successfully applied to the analysis of carbohydrates in the hydrolyzed rape bee pollen samples. (C) 2008 Published by Elsevier B.V.

Identification of phenolics and nucleoside derivatives in Gastrodia elata by HPLC-UV-MS

An HPLC-UV-MS method for simultaneous identification of predominant phenolics and minor nucleoside derivatives in Gastrodia elata was developed, which was based on their UV and MS characteristics summarized through a series of homemade reference standard experiments. Phenolics showed characteristic UV lambda(max) at 267 nm, [M + NH4](+) base peak in positive mode and [M - H](-) base peak in negative mode while nucleosides exhibited UV lambda(max) at 255 nm, [M + H](+), [M - H + 2H(2)O](-) or [M - H + CH3COOH](-). Phenolics conjugates mainly underwent the consecutive loss of gastrodin residue (- 268 U) and the combined loss of H2O and CO2 from the citric acid unit under negative MS/MS conditions whereas nucleosides simply lost the ribose (- 132 U) under positive MS/MS conditions. According to these characteristics, a special pattern under MS/MS conditions and reported compound data for G. elata in the literature, not only 15 phenolics were identified but also 6 nucleoside derivatives were identified. Among these compounds, seven phenolics and three nucleoside derivatives have not been reported yet from G. elata.

Determination of amines using 2-(11H-benzo[a]carbazol-11-yl) ethyl chloroformate (BCEC-Cl) as labeling reagent by HPLC with fluorescence detection and identification with APCI/MS

A pre-column derivatization method for the sensitive determination of amines using a labeling reagent 2-(11H-benzo[a]-carbazol-11-yl) ethyl chloroformate (BCEC-Cl) followed by high-performance, liquid chromatography with fluorescence detection has been developed. Identification of derivatives was carried out by LC/APCI/MS in positive-ion mode. The chromophore of 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC-Cl) reagent was replaced by 2-(11H-benzo[a]-carbazol-11-yl) ethyl functional group, which resulted in a sensitive fluorescence derivatizing reagent BCEC-Cl. BCEC-Cl could easily and quickly label amines. Derivatives were stable enough to be efficiently analyzed by HPLC and showed an intense protonated molecular ion corresponding m/z [M+ H](+) under APCI/MS in positive-ion mode. The collision-induced dissociation of the protonated molecular ion formed characteristic fragment ions at m/z 261.8 and m/z 243.8 corresponding to the cleavages of CH2O-CO and CH2-OCO bonds. Studies on derivatization demonstrated excellent derivative yields over the pH 9.0-10.0. Maximal yields close to 100% were observed with three- to four-fold molar reagent excess. In addition, the detection responses for BCEC-derivatives were compared to those obtained using 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC-Cl) and 9-fluorenyl methylchloroformate, (FMOC-Cl) as labeling reagents. The ratios I-BCEC/I-BCEOC = 1.94-2.17 and I-BCEC/I-FMOC = 1.04-2.19 for fluorescent (FL) responses (here, I was relative fluorescence intensity). Separation of the derivatized amines had been optimized on reversed-phase Eclipse XDB-C-8 column. Detection limits calculated from 0.50 pmol injection, at a signal-to-noise ratio of 3, were 1.77-14.4 fmol. The relative standard deviations for within-day determination (n = 11) were 1.84-2.89% for the tested amines. The mean intra- and inter-assay precision for all amines levels were < 3.64% and 2.52%, respectively. The mean recoveries ranged from 96.6% to 107.1% with their standard deviations in the range of 0.8-2.7. Excellent linear responses were observed with coefficients of > 0.9996. (C) 2006 Elsevier B.V. All rights reserved.

Mass spectrometric identification of multihydroxy phenolic compounds in Tibetan herbal medicines

A highly selective and accurate method based on derivatization with dansyl chloride coupled with liquid chromatography-mass spectrometry has been developed for identification of natural pharmacologically active phenolic compounds in extracts of Lomatogonium rotatum plants (Tibetan herbal medicine) obtained by solid-phase extraction. The number of hydroxyl groups on the dansylated phenols was estimated by LC-MS-MS analysis in positive-ion mode. Dansyl derivatization of the compounds introduced basic secondary nitrogen into the phenolic core structures and this was readily ionized when acidic HPLC mobile phases were used. MS fragmentation of the derivatives generated intense protonated molecular ions of m/z [MH](+) (phenol aglycones were transformed into the corresponding free phenols by cleavage of an aglycone bond). Collision-induced dissociation of the protonated molecule generated characteristic product ions of m/z 234 and 171 corresponding to the protonated 5-(dimethylamino)naphthalene sulfoxide and 5 -(dimethylamino) naphthalene moieties, respectively. Selected reaction monitoring based on the m/z [MH](+) to 234 and 171 transitions was highly specific for these phenolic compounds. Characteristic ions with m/z values of [MH - 234](+), [MH 2 x 234](+), and [MH - 3 x 234](+) were of great importance for estimation of the presence of multihydroxyl groups on the phenolic backbone.

Fingerprinting quality control of Qianghuo by high-performance liquid chromatography-photodiode array detection

A novel, simple and accurate fingerprint method was developed using high-performance liquid chromatography-photodiode array detection (HPLC-DAD) for the quality control of Qianghuo, a Tibetan folk and Chinese herbal medicine used as a diaphoretic, an antifebrile and an anodyne. For the first time, the feasibility and advantages of employing chromatographic fingerprint were investigated and demonstrated for the evaluation of Qianghuo by systematically comparing chromatograms of aqueous extracts with the professional analytical software recommended by State Food and Drug Administration (SFDA). Our results revealed that the chromatographic fingerprint combing similarity evaluation could efficiently identify and distinguish raw herbs of Qianghno from different sources and different species. The effects on Notopterygium forbesii Boiss (Apiaceae) chromatographic fingerprints resulted from collecting locations, harvesting time were also examined. (c) 2006 Elsevier lrelanc Ltd. All rights reserved.

Effects of forage composition and growing season on methane emission from sheep in the Inner Mongolia steppe of China

Understanding the effects of dietary composition on methane (CH4) production of sheep can help us to understand grassland degradation resulting in an increase of CH4 emission from ruminant livestock and its resulting significance affecting CH4 source/sink in the grazing ecosystem. The objective of this study was to investigate the effect of forage composition in the diet of sheep in July and August on CH4 production by sheep in the Inner Mongolia steppe. The four diet treatments were: (1) Leymus chinensis and Cleistogenes squarrosa (LC), (2) Leymus chinensis, Cleistogenes squarrosa and concentrate supplementation (LCC), (3) Artemisia frigida and Cleistogenes squarrosa (AC), and (4) Artemisia frigida, Cleistogenes squarrosa and concentrate supplementation (ACC). CH4 production was significantly lower in July than in August (31.4 and 36.2 g per sheep-unit per day, respectively). The daily average CH4 production per unit of digestive dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) increased by 10.9, 11.2 and 42.1% for the AC diet compared with the LC diet, respectively. Although concentrate supplementation in both the AC and LC diets increased total CH4 production per sheep per day, it improved sheep productivity and decreased CH4 production by 14.8, 12.5 and 14.8% per unit of DM, OM and NDF digested by the sheep, respectively. Our results suggested that in degraded grassland CH4 emission from sheep was increased and concentrate supplementation increased diet use efficiency. Sheep-grazing ecosystem seems to be a source of CH4 when the stocking rate is over 0.5 sheep-units ha(-1) during the growing season in the Inner Mongolia steppe.

Enhancement of atmospheric pressure chemical ionization for the determination of free and glycine-conjugated bile acids in human serum

A highly sensitive and accurate method based on the precolumn derivatization of bile acids (BA) with a high ionization efficiency labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl-benzenesulfonate (BDEBS) coupled with LC/MS has been developed. After derivatization, BA molecules introduced a weak basic nitrogen atom into the molecular core structure that was readily ionized in commonly used acidic HPLC mobile phases. Derivatives were sufficiently stable to be efficiently analyzed by atmospheric pressure chemical ionization (APCI)-MS/MS in positive-ion mode. The MS/MS spectra of BA derivatives showed an intense protonated molecular ion at m/z [M + H](+). The collision-induced dissociation of the molecular ion produced fragment ions at [MH - H2O](+), [MH - 2H(2)O](+), [MH - 3H(2)O](+). The characteristic fragment ions were at m/z 320.8, 262.8, and 243.7 corresponding to a cleavage of N - CO, O - CO, and C - OCC, respectively, and bonds of derivatized molecules. The selected reaction monitoring, based on the m/z [M + H]+ -> [MH - H2O](+), [MH - H2O](+), [MH - 2H(2)O](+), [MH-3H(2)O](+), 320.8, 262.8, and 243.7 transitions, was highly specific for the BA derivatives. The LODs for APCI in a positive-ion mode, at an S/N of 5, were 44.36-153.6 fmol. The validation results showed high accuracy in the range of 93-107% and the mean interday precision for all standards was < 15% at broad linear dynamic ranges (0.0244-25nmol/mL). Good linear responses were observed with coefficients of > 0.9935 in APCI/MS detection. Therefore, the facile BDEBS derivatization coupled with mass spectrometric analysis allowed the development of a highly sensitive and specific method for the quantitation of trace levels of the free and glycine-conjugated BA from human serum samples.

Comparative analysis of allantoin quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in Nitraria tangutorum Bobr. Seed by HPLC-APCI-MS and CE

This paper describes the simultaneous determination of allantoin, quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCCA) in Nitraria tangutorum Bobr seed by HPLC-APCI-MS and CE (capillary electrophoresis) methods. The final optimized chromatographic conditions were investigated in a reversed-phase Eclipse XDB-C8 column (150 x 4.6 mm, 5 mu m). A seventeen-minute gradient elution, (A: aqueous acetonitrile 20% (v/v); B: aqueous acetonitrile 60% (v/v); C: pure acetonitrile 100%) at a flow rate of 1.0 mL/min was selected for the separation of three natural products with diode array detection (DAD) at 220 nm. A CE experiment was carried out in a fused silica capillary with 32 mmol/L boric acid (pH 10), 32 mmol/L SDS and acetonitrile (10.0%, v/v). The applied potential and temperature was, respectively, set at 19 kV and 25 degrees C. After development, the validation was performed in parallel for HPLC and CE, with the same standards and sample to avoid differences due to the manipulation. The validation parameters of both techniques were adequate for the intended purpose.

2-(2-Phenyl-1H-phenanthro-[9,10-d]imidazole-1-yl)-acetic acid (PPIA) and its application for determination of amines by high performance liquid chromatography with fluorescence detection and identification with mass spectroscopy/atmospheric pressure chemical ionization

A simple, sensitive, and mild method for the determination of amino compounds based on a condensation reaction with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC-HCI) as the dehydrant with fluorescence detection has been developed. Amines were derivatized to their acidamides with labeling reagent 2-(2-phenyl-1H-phenanthro-[9,10-d]imidazole-1-yl)-acetic acid (PPIA). Studies on derivatization conditions indicated that the coupling reaction proceeded rapidly and smoothly in the presence of a base catalyst in acetonitrile to give the corresponding sensitively fluorescent derivatives with an excitation maximum at lambda(ex) 260nm and an emission maximum at lambda(em) 380nm. The labeled derivatives exhibited high stability and were enough to be efficiently analyzed by high-performance liquid chromatography. Identification of derivatives was carried out by online post-column mass spectrometry (LC/APCI-MS/MS) and showed an intense protonated molecular ion corresponding m/z [MH](+) under APCI in positive-ion mode. At the same time, the fluorescence properties of derivatives in various solvents or at different temperature were investigated. The method, in conjunction with a gradient elution, offered a baseline resolution of the common amine derivatives on a reversed-phase Eclipse XDB-C-8 column. LC separation for the derivatized amines showed good reproducibility with acetonitrile-water as mobile phase. Detection limits calculated from 0.78 pmol injection, at a signal-to-noise ratio of 3, were 3.1-18.2 fmol. The mean intra- and inter-assay precision for all amine levels were < 3.85% and 2.11%, respectively. Excellent linear responses were observed with coefficients of > 0.9996. The established method for the determination of aliphatic amines from real wastewater and biological samples was satisfactory. (c) 2006 Elsevier B.V. All rights reserved.

Determination of five pharmacologically active compounds extracted from Rhodiola for natural product drug discovery with HPLC-APCI-MS

A rapid and sensitive liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) assay for the determination of five pharmacologically active compounds (PAC) extracted from the traditional Chinese medicine, Rhodiola , namely salidroside, tyrosol, rhodionin, gallic acid, and ethyl gallate has been developed. In this method, PAC could be baseline separated and detected with DAD at 275 nm. The validation of the method, including sensitivity, linearity, repeatability, and recovery, was examined. The linear calibration curves were acquired with correlation coefficient >0.999 and the limits of detection LOD (at a signal-to-noise ratio=3:1) were between 0.058 and 1.500 mu mol/L. It was found, that the amounts of PAC varied with different species of Rhodiola . The established method is rapid and reproducible for the separation of five natural pharmacologically active compounds from extracts of Rhodiola with satisfactory results.

Development of a sensitive fluorescent derivatization reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) and its application for determination of amino acids from seeds and bryophyte plants using high-performance liquid chromatography with fluorescence detection and identification with electrospray ionization mass spectrometry

A pre-column derivatization method for the sensitive determination of amino acids and peptides using the tagging reagent 1,2-benzo-3,4dihydrocarbazole-9-ethyl chloroformate (BCEOC) followed by high-performance liquid chromatography with fluorescence detection has been developed. Identification of derivatives was carried out by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS/MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent was replaced by 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing reagent BCEOC. BCEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. The derivatives showed an intense protonated molecular ion corresponding m/z (M + H)(+) under electrospray ionization (ESI) positive-ion mode with an exception being Tyr detected at negative mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 246.2 corresponding to the cleavage of C-O bond of BCEOC molecule. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0-10.0. Maximal yields close to 100% are observed with a 3-4-fold molar reagent excess. Derivatives exhibit strong fluorescence and extracted detzvatization solution with n-hexane/ethyl acetate (10:1, v/v) allows for the direct injection with no significant interference from the major fluorescent reagent degradation by-products, such as 1,2-benzo-3,4-dihydrocarbazole-9-ethanol (BDC-OH) (a major by-product), mono- 1,2-benzo-3,4-dihydrocarbazole-9-ethyl carbonate (BCEOC-OH) and bis-(1,2-benzo-3,4-dihydrocarbazole-9-ethyl) carbonate (BCEOC)(2). In addition, the detection responses for BCEOC derivatives are compared to those obtained with previously synthesized 2-(9-carbazole)-ethyl chloroformate (CEOC) in our laboratory. The ratios AC(BCEOC)/AC(CEOC) = 2.05-6.51 for fluorescence responses are observed (here, AC is relative fluorescence response). Separation of the derivatized peptides and amino acids had been optimized on Hypersil BDS C-18 column. Detection limits were calculated from 1.0 pmol injection at a signal-to-noise ratio of 3, and were 6.3 (Lys)-177.6 (His) fmol. The mean interday accuracy ranged from 92 to 106% for fluorescence detection with mean %CV < 7.5. The mean interday precision for all standards was < 10% of the expected concentration. Excellent linear responses were observed with coefficients of > 0.9999. Good compositional data could be obtained from the analysis of derivatized protein hydrolysates containing as little as 50.5 ng of sample. Therefore, the facile BCEOC derivatization coupled with mass spectrometry allowed the development of a highly sensitive and specific method for the quantitative analysis of trace levels of amino acids and peptides from biological and natural environmental samples. (c) 2005 Elsevier B.V. All rights reserved.

大气中甲酸和乙酸的碳同位素分析方法及其应用研究

生物有机酸是大气对流层中重要的微量挥发性有机碳组分，它广泛存在于对流层大气中，对气候、环境、生态系统以及人类健康产生了重要影响。探索有机酸碳同位素（δ13C值）的分析测试方法，能够为大气有机酸生物地球化学循环研究开辟一片新的天地，从而使该领域研究向前推进一步。本研究初步建立了以甲酸、乙酸为代表的大气中低分子有机酸的碳同位素测试分析方法，为研究“已知有机酸来源中，不同来源对大气有机酸含量的贡献大小问题”、“人类污染对大气中有机酸的贡献比例问题”以及“是否存在尚未认知的有机酸来源问题”等奠定了方法学基础。 研究工作围绕如下五个方面内容而展开：首先是回顾和总结大气中低分子有机酸的研究沿革，详细摘录了国内外不同站点不同形式的大气样品中有机酸含量水平及其分布情况；其次是回顾和总结了大气中低分子有机酸的含量分析方法，并从中获取适宜于气相色谱/燃烧炉/同位素比值质谱（GC/C/IRMS）接口的样品富集、分离技术；第三是对水溶液中低分子有机酸的固相微萃取研究；第四是对实际大气样品中微量甲酸、乙酸的固相微萃取研究及其碳同位素分析结果的初步分析；第五是对其它天然产物或人为活动排放源所释放的甲酸、乙酸碳同位素进行研究。研究内容的重点是：应用目前对水溶液中痕量有机酸而言最恰当的针阱捕集固相微萃取技术建立有机酸分子碳同位素组成分析方法。在方法建立过程中主要获得了如下成果： 1. 建立了以甲酸、乙酸为代表的液态挥发性有机化合物标准样品的碳同位素组成分析测试方法。 法兰静密封技术与石英管的连接技术可以有效地获得较高真空度的石英管，这使得向低CO2污染的石英管内无损耗地注入挥发性有机物的标准样品成为可能。进一步使用炬枪密闭-石英管燃烧法制备挥发性有机化合物标准同位素样品，可有效避免制备过程中因挥发所导致的同位素分馏和环境CO2对测定值的影响。以市售高纯度的甲酸、乙酸为标准同位素样品，重复制备它们的同位素分析样各5次，并在Finnigan MAT-252气体同位素比值质谱仪上测定其δ13C值。结果显示此法具有极高的重现性，所测δ13C值相对标准偏差仅为0．07％（甲酸，n=5）、0．04％（乙酸，n=5）。与之对比，另一套同位素测定系统GC/C/IRMS对同一标准物质的同位素测定结果并无显著差别，但在精度上却明显不及前者。由于避免了样品制备过程中可能因挥发而导致的同位素分馏以及可能因环境中CO2造成污染等问题，使得该方法可推广应用于其它挥发性有机化合物标准的δ13C标定，为准确测定实际样品中对应挥发性有机化合物δ13C值的准确测定提供基础条件，也为同类物质标准的碳同位素测定提供了准确、廉价、方便的分析手段。 2. 确立了甲酸、乙酸在线分离的气相色谱条件以及同位素分析所需的同位素比值质谱条件。 为了能对非衍生化处理的甲酸、乙酸进行有效分离，我们选取了低吸附性、高样品容量，可直接分析未衍生化游离酸的Stabilwax-DA色谱柱作为分离甲酸、乙酸的分析柱。气相色谱分离过程中He载气均处于恒流模式，进样口施行不分流进样，并进样口温度设置为200℃，采用两阶段程序升温，在此条件下乙酸、甲酸的出峰时间先后相隔了0.79分钟，且多次测定甲、乙酸出峰时间的相对标准偏差不大于0.05分钟，据此可认为甲、乙酸获得了良好的分离。 气相色谱分离出的甲酸、乙酸通过串联接口与燃烧炉 (串联接口与燃烧炉都是加热装置，温度分别设置成350 C和 850C)相接，随后有机物在燃烧炉中被高温焚烧转变为CO2和H2O，再经Nafion半透膜祛除H2O，从而获取纯化干燥的CO2以适宜于同位素比值质谱分析。 3. 确立了水相中甲酸、乙酸的微萃取条件，设计制作了与萃取工作配套固相微萃取装置。 NeedlEx针阱捕集的固相微萃取技术可解决水溶液中低分子有机酸的分离萃取问题，并能与气相色谱接口的兼容，还有集采样、富集、保存、分析为一体的优点。因此探索利用脂肪酸型NeedlEx完成对水溶液相中有机酸的萃取是本文研究的关键所在。为了提高分析效率，降低环境污染，我们设计了一整套吹扫-捕集的动态固相微萃取装置，并对甲酸、乙酸的水溶液实施了萃取研究。 由于实验装置是在吹扫捕集原理的基础上建立起来的，因此随着吹扫捕集气体体积的增加有机酸在萃取针上的对富集量也呈现出一定增长趋势，尤其是在最初的几次循环中，有机酸在萃取针中的总量得到迅速的增加，在萃取气体体积达到400mL后，萃取针中的有机酸含量增加趋于缓慢。为了获得更多物质量的有机酸，实验中我们分别尝试了1000和2000mL的气体吹扫体积，分别对有机酸在色谱上的响应值以及同位素分析结果的统计显示这两种萃取体积并无显著差异，为兼顾工作量我们拟定1000mL吹扫气体体积作为实验条。 由于离子态的有机酸具极强的亲水性，因而很难挥发至顶空或吹扫气体中，只有自由的分子态有机酸方可被萃取针中疏水的固定相所富集。为使的解离反应方向朝着有利于分子态有机酸形成方向发展，我们评估了不同酸化条件对萃取效果的影响。实验中我们普遍采用了500μL 4mol/L的磷酸溶液对样品进行了酸化，结果表明，酸化对提高待测物质的分析量十分有利，以10μg/mL的甲酸、乙酸标准溶液为例，酸化后甲酸萃取率提高了30.12%，乙酸的萃取效率也提高了14.46%。酸化、不酸化处理以及不同浓度有机酸溶液所测定的甲、乙酸碳同位素值在总体上不具备显著性的差异。但是，由于有机酸碳同位素测定精度与待测物物质量具有一定正相关关系，因此酸化后样品中有机酸同位素的分析精度要优于未经酸化样品的同位素的分析精度。 温度的增加可以适量地提高部分有机酸的萃取效率，但温度增加导致水汽进入萃取针，中从阻碍了有机酸的有效萃取，因此本文建议在25℃室温的下进行萃取。此外，在传统的固相微萃取过程，搅动样品溶液常常是作为缩短萃取时间，提高的萃取效率的重要措施。原则上搅拌速度越快越好，但为了不使溅起水花影响到萃取针头，因而选择2000r/min搅拌速度比较适宜。 基于上述实验条件，本文考察了浓度为10~300μg/mL的甲酸、乙酸标准溶液的色谱响应值及其同位素分析结果。结果显示对不低于浓度为10μg/mL标准溶液，其中甲酸、乙酸的δ13C值都可被检测出。只不过浓度过低则响应值信号弱，不能准确计算出各质荷比信号峰面积是低浓度条件下同位素测不准的主要原因。要想使得甲、乙酸同位素测定值的相对标准偏差控制在1以内，则对应有机酸浓度则需达到85μg/mL以上。 4. 克服了实际水相样品中有机酸浓度低，不能直接对其实施NeedlEx萃取的难题，初步实现了对降水中甲酸、乙酸的碳同位素分析。 除了某些有机酸含量水平较高的降雨可以直接运用动态针阱捕集固相微萃取与GC/C/IRMS联用技术直接进行甲酸、乙酸碳同位素的分析外，普通含量水平的有机酸碳同位素测定尚具有一定的难度。研究中我们使用了阴离子交换型固相萃取小柱LC-SAX(规格：500mg/3mL；交换容量：0.2meq/g)对1L浓度为50~2000μg/L甲酸、乙酸标准混合溶液进行了萃取，并对所属浓度条件下δ13C测定值与理论值之间的差异性进行了T检验统计分析，结果表明绝大多数情况（200μg/L乙酸同位素测定值除外）下甲、乙酸的相伴概率分别伴概率大于了显著性水平0.05，表现出有机酸碳同位素测定的均值与离线法测定的甲酸同位素理论值无显著差异。 然而，降水中普遍具有有机酸含量低，其它阴离子含量高，组分复杂特点，严重影响阴离子交换型萃取小柱对有机酸的萃取。为此我们先用离子色谱对降水中阴离子组成及其含量进行分析，了解降水中主要的阴离子构成及其含量，再根据所测定结果再安排对应交换容量萃取小柱实施萃取，而后再进行针阱捕集的萃取及其碳同位素分析。 5. 对以甲酸、乙酸为代表的大气中低分子有机酸碳同位素分析结果的初步研究。 以贵阳为代表的西南城市地区大气中有机酸浓度较高，这为使用本方法研究该地区有机酸的碳同位素分析创造了有利条件。经离子色谱测定，2008年8月下旬至2008年10月中旬贵阳地区6次降水中甲、乙酸浓度范围分别为5.75~22.43μmol/L和5.43~13.09μmol/L。与之对应，六次降水中甲酸δ13C值的范围为-25.72‰至-29.08‰之间，乙酸δ13C值的最大值则为-26.23‰，最小值则为-30.40‰。6次降水中甲酸、乙酸的δ13C值将它们的来源指向了直接或间接的陆源特征。结合离子色谱对降水中甲酸、乙酸浓度分析，利用亨利系数判定法可知，六次降水中间接来源是大气中低分子有机酸的主要来源，通过δ13C值的初步判断，可以看出这些二次来源应该主要由生物质燃烧，C3植物以及人类活动向大气释放的不饱和有机物经二次氧化而形成。 以往甲酸、乙酸同源的依据皆以降水中甲、乙酸浓度具有显著线性相关做为判断指标，本研究中6次降中的甲酸、乙酸浓度亦然呈现出良好的相关性（R2=0.87）而降水中甲、乙酸具有相似的δ13C值，这充分说明降水中甲、乙酸的同源特征。 针阱捕集萃取方式还适宜于对大气中自由有机酸的直接富集。利用这一特性，我们分别对贵阳市市郊森林公园、城市居民区以及交通要塞等三个不同地方大气中的自由有机酸进行了同位素分析，结果发现贵阳市大气中乙酸δ13C值介于-31.03‰至-26.37‰之间，乙酸δ13C值的总体均值等于-28.74‰，与之对应，甲酸的δ13C值范围为-29.42‰至-22.97‰，均值为-27.12‰。贵阳市大气中自由甲酸、乙酸的同位素值与降水中的甲、乙酸同位素值具有类似的变化范围，这表明大气气相中自由有机酸与降水中的甲、乙酸具有大致相同的来源构成。 我们还利用此法对汽车尾气以及蚁酸蚁所释放的甲酸、乙酸δ13C值进行了分析，其中汽车尾气中所含甲酸δ13C值等于-23.25±1.25‰，乙酸δ13C值为-24.55±0.85‰，而蚁酸蚁所释放的甲酸δ13C值则为-22.43±0.43‰。由于汽车尾气以及乙酸蚁释放有机酸的δ13C值要低于大气样品对应有机酸的δ13C值，据此认为汽车尾气和蚁酸蚁不是大气有机酸的主要来源。 6. 有机酸碳同位素分析技术在检验食品参假行为时的扩展应用研究。 由于C3和C4循环会导致植物及其产品的δ13C值不同，因此碳同位素技术在食品控制方面发挥了特别作用，能够解决一些常规分析解决不了的问题。经分析发现，食醋中醋酸的δ13C值与其原材料密切相关，如以麦麸、大米为原材料所生食醋醋酸δ13C值在-27‰左右。而以高粱、大麦、黄豆为生产原料的食醋醋酸δ13C值在-19‰左右，明显高于了以大米、麦麸等为原料所生产的食醋醋酸δ13C值。此外，单纯以大米发酵生产的食醋醋酸δ13C值为-29‰左右。食醋中醋酸δ13C值与生产工艺、原材料高度相关的特征为质检部门更好的识别食醋参假行为提供了良好的解决办法。