气相色谱法直接测定工业油酸中脂肪酸

建立了气相色谱直接测定工业油酸中未衍生化的6种常见脂肪酸含量的检测方法。样品用四氢呋喃(THF)溶解,通过氢火焰离子化检测器(FID)对目标化合物进行分析,外标法定量。在优化的气相色谱条件下,6种脂肪酸实现了有效分离,6种脂肪酸在5~5000 mg/L范围内定量曲线的相关系数(R2)均大于0.99991,表明线性关系良好,方法检出限(S/N≥3)为0.36~0.58 mg/L,相对标准偏差为3.4%~8.1%,加标回收率在84.7%~110.2%之间。选取4种工业油酸样品进行分析,实验结果表明,样品未经衍生化处理直接进样,本方法在10 min内能够对6种脂肪酸实现基线分离,为工业油酸的品质鉴定提供了一种快速有效的检测方法。     

气相色谱法测定中华绒螯蟹中脂肪酸组成与含量

中华绒螯蟹中脂肪酸组成与含量的测定对评估其营养价值与品质具有重要意义,但面对种类繁多的脂肪酸提取试剂和甲酯化试剂,测定结果参差不齐,很难对中华绒螯蟹中丰富的脂肪酸准确定量。研究通过比较4种常见的脂肪提取试剂、2种脂肪酸甲酯化试剂,确定以氯仿-甲醇(1∶1, v/v)为提取试剂,含2%硫酸的甲醇溶液为甲酯化试剂,建立了测定中华绒螯蟹肌肉中脂肪酸组成与含量的气相色谱分析方法。实验按照程序升温的条件,采用DM-2560毛细管色谱柱(100 m×0.25 mm×0.20 μm)分离37种脂肪酸,氢火焰离子化检测器(FID)检测,外标法定量。37种脂肪酸在0.5~100.0 μg/mL范围内线性关系良好,其相关系数(R²)为0.9981~0.9999,检出限(LOD)与定量限(LOQ)分别为0.01~0.02 mg/100 g和0.04~0.06 mg/100 g;以棕榈酸和硬脂酸进行加标回收验证,在1、2、10 mg/100 g 3个加标水平下的加标回收率为76.0%~97.5%,相对标准偏差(RSD, n=5)为3.31%~7.90%。该方法应用于中华绒螯蟹肌肉中脂肪酸组成与含量的测定,肌肉中共测得31种脂肪酸,碳链长度为12~24,脂肪酸总含量为281.03 mg/100 g,其中油酸、二十二碳六烯酸、二十碳五烯酸等为中华绒螯蟹肌肉中主要脂肪酸。该方法操作简便,试剂、样品用量少,且定性可靠,定量准确,能检测较多的脂肪酸种类,适用于中华绒螯蟹肌肉中脂肪酸组成与含量的快速检测。     

气相色谱法测定生物柴油中脂肪酸甲酯含量

生物柴油是利用动植物油脂等可再生资源通过酯交换技术制造的可以替代石化柴油的新型清洁安全燃料[1-3]它的主要成分是脂肪酸甲酯。由于不同油脂原料所生产的生物柴油的脂肪酸甲脂组成不同因而测定时所需的气相色谱条件与方法也不尽相同[4-6]。本文采用HP-innowax毛细管色谱柱,     

High‐throughput gas chromatography for volatile compounds analysis by fast temperature programming and adsorption chromatography

The synergy of combining fast temperature programming capability and adsorption chromatography using fused silica based porous layer open tubular columns to achieve high throughput chromatography for the separation of volatile compounds is presented. A gas chromatograph with built‐in fast temperature programming capability and having a fast cool down rate was used as a platform. When these performance features were combined with the high degree of selectivity and strong retention characteristic of porous layer open tubular column technology, volatile compounds such as light hydrocarbons of up to C₇, primary alcohols, and mercaptans can be well separated and analyzed in a matter of minutes. This analytical approach substantially improves sample throughput by at least a factor of ten times when compared to published methodologies. In addition, the use of porous layer open tubular columns advantageously eliminates the need for costly and time‐consuming cryogenic gas chromatography required for the separation of highly volatile compounds by partition chromatography with wall coated open tubular column technology. Relative standard deviations of retention time for model compounds such as alkanes from methane to hexane were found to be less than 0.3% (n = 10) and less than 0.5% for area counts for the compounds tested at two levels of concentration by manual injection, namely, 10 and 1000 ppm v/v (n = 10). Difficult separations were accomplished in one single analysis in less than 2 min such as the characterization of 17 components in cracked gas containing alkanes, alkenes, dienes, branched hydrocarbons, and cyclic hydrocarbons.     

Analysis of volatile fatty acids in biological specimens by capillary gas chromatography

A method was developed to analyze and quantitate volatile fatty acids such as acetic, propionic, butyric, iso-butyric, valeric, and iso-valeric acid from samples of biological origin. A capillary column system including an automatic on-column injection device as well as a precolumn of larger internal diameter than the analytical column was elaborated for this purpose. In order to obtain well resolved and correctly quantifiable chromatographic peaks it turned out to be essential to work under acidic/aqueous conditions. To achieve a better sample transfer into the chromatographic system an organic solvent had to be used together with the aqueous milieu, thus improving wetting properties of the liquid sample plug introduced into the column. Cold on-column injection was applied in order to avoid discrimination of the various acids due to sample splitting and the automatic technique was chosen in view of the large number of samples from biological extractions which had to be analyzed.     

气相色谱测定牦牛骨中脂肪酸的甲酯化方法比较

利用气相色谱（GC）技术,采用酸水解提取脂质,比较了6种甲酯化法（乙酰氯-甲醇法、H₂SO₄-甲醇法、HCl-甲醇法、KOH-甲醇法、KOH-甲醇+H₂SO₄-甲醇法和KOH-甲醇+HCl-甲醇法）对脂肪酸测定的影响,优选牦牛骨中脂肪酸测定的最佳方法。37种脂肪酸标准样品在0.28~250.00 mg/L范围内线性关系良好,相关系数均大于0.99（除C4：0外）。碱酯化法和酸碱结合法几乎无法测出牦牛骨中的脂肪酸,其测得的总脂肪酸含量小于0.20 g/100 g。乙酰氯-甲醇法测得的总脂肪酸含量（13.61 g/100 g）显著高于H₂SO₄-甲醇法（总脂肪酸含量为11.68 g/100 g）和HCl-甲醇法（总脂肪酸含量为3.18 g/100 g）测得的结果。乙酰氯-甲醇法和H₂SO₄-甲醇法的日内和日间精密度分别为0.27%~8.60%和0.34%~2.64%,两种方法中脂肪酸的回收率为83.06%~105.54%。结果表明,酸水解-乙酰氯-甲醇法是牦牛骨中脂肪酸测定的最佳方法。C18：1n9c、C16：0、C18：0和共轭亚油酸（CLA）是牦牛骨的主要脂肪酸,其总和达脂肪酸总量的85%以上,饱和脂肪酸与不饱和脂肪酸含量比值约为1：2。牦牛骨中脂肪酸的研究为骨资源脂质的有效利用提供了重要依据。     

快速气相色谱法测定食品中的常见防腐剂

摘要：建立了一种分离测定食品中6种常见防腐剂(山梨酸，苯甲酸，对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯)的简单、准确的快速气相色谱方法，采用长10m，内径100μm的HP-5熔融石英毛细管柱，在快速程序升温条件下，6种常见防腐剂的分析时间为1．3min。各组分平均回收率(n=3)为96．45％；检出限为1．2～10μg／mL；线性相关系数大于0．994。该方法已用于实际食品中防腐剂的检测。     

Fast esterification of fatty acids with alkyl chloroformates. Optimization and application in gas chromatography

Alkyl chloroformates with methyl, ethyl, and 2-chloroethyl substituents can instantaneously esterify fatty acids under proper reaction conditions. Apart from the formation of the corresponding alkyl esters, even the alkoxycarbonyl esters can be prepared. These derivatives are useful for the analysis of short-chain fatty acids. As alkoxycarbonyl ester, even acetic acid can already be separated from the solvent peak. The reaction conditions were examined, and the Influence of solvent polarity and reagent concentration on the conversion was studied. Quantitative conversion of acids to their easters was achieved in non-aqueous solutions, but even in the presence of water the yields were acceptable.     

Evaluation of fast gas chromatography and gas chromatography-mass spectrometry in the analysis of lipids

Fast and conventional gas chromatography (GC) techniques were applied to nine different lipidic matrices (butter, lard, tallow, and peanut, corn, sunflower, soya, olive, menhaden oils). Simultaneous methylic transesterification was performed on all samples prior to GC analysis. Several practical aspects concerning high speed analysis were investigated, such as the great increase in linear velocity, the use of fast temperature ramps, column sample capacity and detection systems. Analytical results showed certain losses in resolution, balanced by a consistent reduction in analysis time. The actual time savings were variable (60-70 min) as they were dependent on the complexity of the sample while the speed enhancement factor was equal to 10.5. Peak identification was achieved by means of different information sources, such as fast GC-mass spectrometry (MS), linear retention indices and comprehensive two-dimensional (2D) gas chromatography group patterns. The method developed was shown to be applicable in routine applications on complex natural samples.     

Characterization and purification of polyunsaturated fatty acids from microalgae by gas chromatography-mass spectrometry and countercurrent chromatography

Summary The present study was undertaken in order to characterize then to purify fatty acids from marine phytoplankton. From a crude mixture of fatty acid methyl esters it was possible to isolate by countercurrent chromatography a mixture of four polyunsaturated fatty acid methyl ester identified as being hexadecatrienoic acid methyl ester, octadecatetraenoic acid methyl ester, eicosapentaenoic acid methyl ester and docosahexaenoic acid methyl ester by gas chromatography coupled with mass spectrometry in electron impact and in positive-ion chemical ionization mode. The four polyunsaturated fatty acids are in different ratios in mixtures from the two microorganisms:Skeletonema costatum andIsochrysis galbana.     

Quantification of deformed peaks in capillary gas chromatography (CGC): application to simultaneous analysis of free fatty acids and less polar compounds in aqueous distillery effluent

The purpose of this study was to find a simple and rapid method allowing the simultaneous quantification of some alcoholic fermentation inhibitors present in aqueous distillery effluent in order to evaluate its recycling properties. A capillary gas chromatography (CGC) method was tested for the quantification of both short chain fatty acids (acetic to hexanoic) and neutral compounds (butane 2,3-diol, 2-furaldehyde, phenyl-2-ethane1-ol). A polyvalent column coated with ^®trifluoro-propyl-polysiloxane, allowing water injection, was tested and experiments were performed directly on untreated samples. During the development of the method, a deformation of acid peaks was observed; that could be explained by a secondary equilibrium, added to the chromatographic equilibrium. Although the acid peaks were deformed, calibration curves were produced and rigorously validated, proving that quantification is possible even when the best chromatographic conditions have not been achieved. Eventually, the method enabled the concentration of eight major fermentation inhibitors in distillery effluent to be measured.     

Validation of a Simple HPLC-Based Method for Lysine Quantification for Ruminant Nutrition

Robust and selective quantification methods are required to better analyze feed supplementation effectiveness with specific amino acids. In this work, a reversed-phase high-performance liquid chromatography method with fluorescence detection is proposed and validated for lysine quantification, one of the most limiting amino acids in ruminant nutrition and essential towards milk production. To assess and widen method applicability, different matrices were considered: namely Li₂CO₃ buffer (the chosen standard reaction buffer), phosphate buffer solution (to mimic media in cellular studies), and rumen inoculum. The method was validated for all three matrices and found to be selective, accurate (92% ± 2%), and precise at both the inter- and intra-day levels in concentrations up to 225 µM, with detection and quantification limits lower than 1.24 and 4.14 µM, respectively. Sample stability was evaluated when stored at room temperature, 4 °C, and −20 °C, showing consistency for up to 48 h regardless of the matrix. Finally, the developed method was applied in the quantification of lysine on real samples. The results presented indicate that the proposed method can be applied towards free lysine quantification in ruminant feeding studies and potentially be of great benefit to dairy cow nutrition supplementation and optimization.     

Analysis of isomeric tropane alkaloids from Schizanthus grahamii by very fast gas chromatography

This study presents a very fast GC analysis applied for the baseline separation of isomeric tropane alkaloids extracted from the stem-bark of Schizanthus grahamii (Solanaceae). The work provided a challenging application where isothermal analysis in conjunction with very short narrow bore columns (3 m x 100 microm ID and 1.5 m x 50 microm ID) was particularly suited for the speeding up. Experimental parameters were used in the optimisation steps, including selection of stationary phase, temperature, internal column diameter and optimal practicable gas velocity. Some considerations about sample injection in fast isothermal analysis are also briefly presented. Finally, the investigated approach allowed a very fast baseline separation of four positional and configurational isomers in less than 9 s.     

在线热辅助甲基化-气相色谱法分析棉籽仁中的脂肪酸组成

建立了分析棉籽仁中脂肪酸组成的在线热辅助甲基化-气相色谱法。将0.3 mg棉籽仁样品与2 μ L三甲基氢氧化硫（0.2 mol/L）加入裂解器,在350℃下进行甲基化反应,通过气相色谱仪进行分离分析,共检测到8种脂肪酸甲酯成分,分别为亚油酸（C18：2）、油酸（C18：1）、棕榈酸（C16：0）、硬脂酸（C18：0）、肉豆蔻酸（C14：0）、棕榈油酸（C16：1）、花生酸（C20：0）和二十二酸（C22：0）,不饱和脂肪酸的相对含量为66.30%~72.54%,其中亚油酸的相对含量为43.20%~53.61%,相对峰面积的相对标准偏差（RSD）小于10%（n=5）。通过分析5组棉籽仁样品与3种食用油中的脂肪酸组成,结果表明不同产地的棉籽仁中的脂肪酸组成差异不明显,且棉籽仁中的脂肪酸组成与玉米油最为接近,相似度为0.960~0.992。该方法简单、快速、准确,适合分析棉籽仁中的脂肪酸组成。     

Quantification of total cholesterol in human milk by gas chromatography

Human milk provides the key nutrients necessary for infant growth and development. The objective of this study was to develop and validate a method to analyze the cholesterol content in liquid human milk samples along lactation. Direct saponification of the sample using ethanolic potassium hydroxide solution under cold conditions was applied and unsaponifiable matter was separated by centrifugation. Cholesterol was converted into its trimethylsilyl ether and the derivative analyzed by gas chromatography coupled with a flame ionization detector. Cholesterol was quantified using epicoprostanol as internal standard. The method is suitable for the determination of cholesterol in only 0.3 g of human milk. It has been validated showing good repeatability (CV(r) < 15%) and intermediate reproducibility (CV(iR) < 15%). The method was used to analyze human milk obtained from five mothers collected at day 30(±3), 60 (±3) and 120 (±3) after delivery. The cholesterol content in human milk slightly decreased from 13.1 mg/100 g at 1 month to 11.3 mg/100 g 120 days after delivery. The method can also be used to determine desmosterol, an intermediate in cholesterol synthesis.     

Simultaneous determination of terpenes and cannabidiol in hemp (Cannabis sativa L.) by fast gas chromatography with flame ionization detection

Hemp (Cannabis sativa L.) has become widely used in several sectors due to the presence of various bioactive compounds such as terpenes and cannabidiol. In general, terpenes and cannabidiol content is determined separately, which is time consuming. Thus, a fast gas chromatography with flame ionization detection method was validated for simultaneous determination of both terpenes and cannabidiol in hemp. The method enabled a rapid detection of 29 different terpenes and cannabidiol within a total analysis time of 16 min, with satisfactory sensitivity (limit of detection = 0.03–0.27 µg/mL, limit of quantitation = 0.10–0.89 µg/mL). The inter‐ and intraday precision (RSD) was <7.82 and <3.59%, respectively. Recoveries at two spiked concentration levels (low, 3.15 µg/mL; high, 20.0 µg/mL) were determined on both apical leaves (78.55–101.52%) and inflorescences (77.52–107.10%). The reproducibility (RSD) was <5.94 and <5.51% in apical leaves and inflorescences, respectively. The proposed and validated method is highly sensitive, robust, fast, and accurate for determination of the main terpenes and cannabidiol in hemp and could be routinely used for quality control.     

Analysis of volatile fatty acids by gas chromatography separation of benzyl esters

Volatile fatty acids in aqueous media were esterfied in situ with phenyldiazomethane (PDM). Complete esterification was achieved in 3 h at 40°C under continuous stirring of an ether/water system. The process involved immediate transfer of benzyl esters into the organic phase. The separation of benzyl esters mixtures was carried out in glass capillary GC columns. The retention data and FID molar responses were determined for C1 to C6 acid benzyl esters, including 2-methylpropionic, 3-methylbutyric, 2-methylvaleric, and 2-ethylbutyric acid. An unusual relationship was observed between benzyl ester relative molar responses and carbon atom number.     

气相色谱法测定阳离子表面活性剂合成体系中脂肪烷基二甲基叔胺

选用HP-NINOWax毛细管色谱柱及氢火焰离子化检测器（FID），采用程序升温，建立了4种脂肪烷基二甲基叔胺的分析方法。结果表明，4种脂肪烷基二甲基叔胺质量浓度在0.005~1.0 g/L范围内，其峰面积与质量浓度有良好的线性关系，相关系数（R²）在0.9996以上。检出限（LODs，信噪比为3）在0.001~0.002 g/L之间，定量限（LOQs，信噪比为10）在0.003~0.005 g/L之间，回收率在90%~130%之间，相对标准偏差为1.3%~6.9%（n=6）。方法的线性范围宽、回收率高、选择性好，可用于叔胺的产品质量分析及生产过程控制分析。利用该方法对阳离子表面活性剂合成反应中十六烷基二甲基叔胺进行监测，结果很好地符合双分子亲核取代反应。该方法比滴定分析法更快速、精确，与液相色谱法相比，不需要进行柱前衍生或者使用色谱-质谱联用仪器。     

5种贝类脂肪含量及脂肪酸组成研究

 用氯仿 甲醇法测定了广州海鲜市场上棕带仙女蛤、波纹巴非蛤、文蛤、栉孔扇贝和园华扇贝等 5种贝类的脂肪含量 ,并用GC MS法测定了它们的脂肪酸组成。 5种贝类鉴定出的脂肪酸都在 99% (质量分数 )以上。它们的脂肪含量都大于 1% (质量分数 ) ,园华扇贝的脂肪含量最高。它们的ω 3多不饱和脂肪酸与ω 6多不饱和脂肪酸含量的比值基本上都大于 2。两种扇贝的廿碳五烯酸 (EPA)和廿二碳六烯酸 (DHA)含量都比较高。分析结果表明 ,园华扇贝不仅脂肪含量高 ,而且EPA与DHA的含量也比较高 ,是EPA和DHA理想的提取原料