Quantitative gas chromatographic headspace determination of choline in adult and infant formula products

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.