Determination of vitamin K1 in medical foods by liquid chromatography with postcolumn reduction and fluorometric detection
Ware, G.M.; Chase, G.W.; Eitenmiller, R.R.; Long, A.R.; Ware, G.M.; Chase, G.W.; Eitenmiller, R.R.; Long, A.R.
Journal - Association of Official Analytical Chemists 83(4): 957-962
2000
ISSN/ISBN: 0004-5756 PMID: 10995121 Document Number: 516308
A liquid chromatographic (LC) method is described for the determination of vitamin K1 in medical foods. The sample is enzymatically digested with lipase and alpha -amylase and extracted with 1% sodium bicarbonate solution-isopropanol (1+1). After C18 solid-phase extraction, vitamin K1 is separated by nonaqueous reversed-phase LC, converted to the hydroquinone by postcolumn zinc reduction, and quantitated by fluorescence detection. The limit of detection is 8 pg (3 sigma ), and the limit of quantitation is 27 pg (10 sigma ) on column. Linear response ranged from 0.1 to 1.0 ng vitamin K1 (r=0.9999). The mean recovery (n=38) for all spiking levels was 101.6+or-2.85%. Analysis of Standard Reference Material 1846, Infant Formula, gave a mean value of 0.95+or-0.088 mg vitamin K/kg with a coefficient of variation of 9.26.