Agilent Technologies, Alameda Araguaia, 1142, CEP 06455-000 Barueri, SP, Brazil; Departamento de Química Fundamental - Instituto de Química - Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, CEP 05508-000 São Paulo, SP, Brazil.
Departamento de Química Fundamental - Instituto de Química - Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, CEP 05508-000 São Paulo, SP, Brazil.
Food Chem. 2018 Mar 15;243:305-310. doi: 10.1016/j.foodchem.2017.09.140. Epub 2017 Sep 28.
The detection of coffee adulteration with soybean and corn by capillary electrophoresis-tandem mass spectrometry was accomplished by evaluating the monosaccharides profile obtained after acid hydrolysis of the samples. The acid hydrolysis, using HSO as a catalyst, increases the ionic strength of the sample impairing the electrophoretic separation. Therefore, Ba(OH) was used to both neutralize the medium and reduce the content of sulfate by precipitation of BaSO. The best separation of nine determined monosaccharides (fucose, galactose, arabinose, glucose, rhamnose, xylose, mannose, fructose and ribose) plus inositol as internal standard was obtained in 500 mmol·L triethylamine, pH 12.3. The monosaccharides are separated as anionic species at this pH. The proposed method is simple, fast (<12.0 min), present linear calibration curves (r = 0.995), and relative standard deviation for replicate injections lower than 5%. The LOQ for all monosaccharides was lower than 0.01 mmol·L, which is in accordance with the tolerable limits for coffee. Principal component analysis (PCA) was used to evaluate interrelationships between the monosaccharide profile and the coffee adulteration with different proportions of soybean and corn. Fucose, galactose, arabinose, glucose, sucrose, rhamnose, xylose, mannose, fructose, and ribose were quantified in packed roast-and-ground commercial coffee samples, and differences between adulterated and unadulterated coffees could be detected.
采用毛细管电泳-串联质谱法，通过评估样品酸水解后得到的单糖图谱，实现了对咖啡掺大豆和玉米的检测。酸水解采用 HSO 作为催化剂，增加了样品的离子强度，从而影响了电泳分离。因此，使用 Ba(OH) 中和介质并通过沉淀 BaSO 来降低硫酸盐含量。在 500mmol·L 三乙胺（pH 12.3）中，可获得 9 种测定的单糖（岩藻糖、半乳糖、阿拉伯糖、葡萄糖、鼠李糖、木糖、甘露糖、果糖和核糖）加上肌醇内标物的最佳分离效果。在该 pH 值下，单糖以阴离子形式分离。该方法简单、快速（<12.0min），具有线性校准曲线（r=0.995），重复进样的相对标准偏差低于 5%。所有单糖的 LOQ 均低于 0.01mmol·L，符合咖啡的可接受限量。主成分分析（PCA）用于评估单糖图谱与咖啡中不同比例大豆和玉米掺假之间的相互关系。对包装烘焙和研磨的商业咖啡样品中的岩藻糖、半乳糖、阿拉伯糖、葡萄糖、蔗糖、鼠李糖、木糖、甘露糖、果糖和核糖进行定量分析，可检测到掺假和未掺假咖啡之间的差异。
