Novaes Fábio Junior Moreira, Kulsing Chadin, Bizzo Humberto Ribeiro, de Aquino Neto Francisco Radler, Rezende Claudia Moraes, Marriott Philip John
Aroma Analysis Laboratory, Chemistry Institute, Federal University of Rio de Janeiro, 21941-909, Rio de Janeiro, RJ, Brazil; Laboratory of Capillary Column Preparation and Chromatography, Chemistry Institute, Federal University of Rio de Janeiro, 21941-598, Rio de Janeiro, RJ, Brazil; Australian Centre for Research on Separation Science, School of Chemistry, Monash University,Wellington Road, Clayton, Victoria, 3800, Australia.
Australian Centre for Research on Separation Science, School of Chemistry, Monash University,Wellington Road, Clayton, Victoria, 3800, Australia.
J Chromatogr A. 2018 Feb 9;1536:75-81. doi: 10.1016/j.chroma.2017.08.069. Epub 2017 Aug 30.
Comprehensive two-dimensional gas chromatography (GC×GC) approaches with cryogenic modulation were developed for the qualitative analysis of selected low volatility compounds in raw coffee bean extracts, without derivatisation. The approaches employed short first (D) and second (D) dimension columns, specifically a D 65% phenyl methyl siloxane column (11m) and a D 5% phenyl methyl siloxane column (1m), which allowed elution of high molar mass compounds (e.g.>600Da). Solutes included hydrocarbons, fatty acids, diterpenes, tocopherols, sterols, diterpene esters, and di- and triacylglycerides. An oven temperature program up to 370°C was employed. The effects of experimental conditions were investigated, revealing that the GC×GC results strongly depended on the cryogenic trap T, and oven T program. An appropriate condition was selected and further applied for group type analysis of low volatility compounds in green Arabica coffee beans. Retention indices were compiled for 1D GC analysis and were similar for the composite column data in GC×GC. The elution of some compounds was confirmed by use of authentic standards. The approach allowed direct analysis of coffee extract in ethyl acetate solution, with improved analyte peak capacity (approximately 200 compounds were detected) without prior fractionation or pre-treatment of the sample. This avoided potential hydrolysis of high molar mass conjugate esters as well as degradation of thermally labile compounds such as the derivatives of the diterpenes cafestol and kahweol.
开发了具有低温调制功能的全二维气相色谱（GC×GC）方法，用于生咖啡豆提取物中选定低挥发性化合物的定性分析，无需衍生化。该方法采用短的第一（D）维和第二（D）维色谱柱，具体为一根D 65%苯基甲基硅氧烷柱（11米）和一根D 5%苯基甲基硅氧烷柱（1米），这使得高摩尔质量化合物（如>600Da）得以洗脱。溶质包括烃类、脂肪酸、二萜类、生育酚、甾醇、二萜酯以及甘油二酯和甘油三酯。采用了最高温度达370°C的柱温程序。研究了实验条件的影响，结果表明GC×GC结果强烈依赖于低温捕集阱温度（T）和柱温程序（T）。选择了合适的条件并进一步应用于绿咖啡豆中低挥发性化合物的族类型分析。编制了一维气相色谱分析的保留指数，且与全二维气相色谱中复合柱数据的保留指数相似。通过使用标准品确认了一些化合物的洗脱情况。该方法允许直接分析乙酸乙酯溶液中的咖啡提取物，提高了分析物的峰容量（检测到约200种化合物），无需对样品进行预先分馏或预处理。这避免了高摩尔质量共轭酯的潜在水解以及热不稳定化合物（如二萜类化合物咖啡醇和卡韦醇的衍生物）的降解。
