建立了固相萃取-高效液相色谱法测定可可粉及可可壳中2种脂肪酸色酰胺成分(二十二烷酸色酰胺和二十四烷酸色酰胺)的定量分析方法,根据2种物质在可可粉和可可壳中的含量差异进行可可粉中可可壳含量的测定。样品经过三氯甲烷涡旋振荡加超声提取,硅胶固相萃取柱净化,采用Venusil C₁₈色谱柱,乙腈+四氢呋喃+水为流动相,荧光检测器检测。在上述条件下,2种脂肪酸色酰胺在50～1 000 μg/L范围内线性关系良好(r>0.999 1),方法的检出限和定量限分别为0.03 mg/kg和0.1 mg/kg,加标回收率在92%～103%之间,相对标准偏差为2.1%～6.2%。利用可可粉中脂肪酸色酰胺含量与掺入的可可壳含量之间的线性关系,建立了计算可可粉中可可壳含量的简单定量分析模型,模拟样品和实际样品的验证结果表明,该模型的预测值与实际值有着较好的一致性,对可可粉中混入量5%及5%以上(质量分数)的可可壳可予以较好鉴定。

A new solid phase extraction coupled with high performance liquid chromatography method for quantitatively analyzing two fatty acid tryptamides (FATs), behenic acid tryptamide and lignocerinic acid tryptamide, was established. The cocoa shell content in cocoa powder was calculated according to the differences in FATs contents in the powder and shell. The samples were extracted by trichloromethane with vortex and ultrasonic extraction. The Venusil C₁₈ chromatographic column was used and eluted with acetonitrile/tetrahydrofuran/water,followed by using a fluorescence detector. The results showed that these two FATs showed good linear relationship (r>0.999 1) within their linear range(50-1 000 μg/L). The detection and quantification limits were 0.03 mg/kg and 0.1 mg/kg, respectively. The spike recovery rate was 92%-103% and the RSDs was 2.1%-6.2%. In addition, FATs levels and the cocoa shell contents in cocoa powder samples were processed to establish a simple analysis model. The prediction values had good corresponding relationship with true values. The results showed that cocoa powder adulterated with 5% or more (mass fraction) cocoa shell could be identified by this method.