Saucerman J R, Winstead C E, Jones T M
J Assoc Off Anal Chem. 1984 Sep-Oct;67(5):982-5.
A gas chromatographic headspace method has been developed for the determination of choline in liquid and powder formula products. Choline undergoes the Hofmann elimination reaction during a 24 h, 120 degrees C alkaline digestion. Volatile trimethylamine (TMA) is produced and equilibrates between the liquid and vapor phase (headspace). A 50 microL headspace sample is chromatographed on a 28% Pennwalt 223-4% KOH column, with flame ionization detection. Choline is indirectly quantitated by comparing sample TMA peaks with peaks for a reference standard. Ethyl ether is used as an internal standard. Compared with previous methods, this procedure offers improved precision (7.7-9.6% relative standard deviation (RSD], accuracy, and specificity of both free and bound forms of choline. Estimated analysis rate using manual injection is 160 samples/week, requiring 35 work-hours. Automation of this procedure, using a commercially available headspace analyzer, resulted in a further improvement in precision (1.60-6.91% RSD) and a throughput of 400 samples/week.
已开发出一种气相色谱顶空分析法，用于测定液体和粉状配方产品中的胆碱。胆碱在120℃碱性消化24小时过程中发生霍夫曼消除反应。生成挥发性三甲胺（TMA），并在液相和气相（顶空）之间达到平衡。取50微升顶空样品，在28%的彭瓦尔特223 - 4%氢氧化钾柱上进行色谱分析，采用火焰离子化检测。通过将样品的TMA峰与参考标准品的峰进行比较，间接定量胆碱。使用乙醚作为内标。与以前的方法相比，该方法提高了精密度（相对标准偏差（RSD）为7.7 - 9.6%）、准确度以及胆碱游离形式和结合形式的特异性。使用手动进样时，估计分析速率为每周160个样品，需要35个工时。使用市售顶空分析仪对该方法进行自动化操作，进一步提高了精密度（RSD为1.60 - 6.91%），且每周通量达到400个样品。
