Determination of trans vitamin K1 in infant and medical nutritional products using AOAC Method 999.15 with modified preparation and extraction procedures and C30 bonded phase chromatography: single-laboratory validation.

Modifications were made to AOAC Official Method 999.15 to extend its applicability to specialty infant formulas containing hydrolyzed proteins and free amino acids, and to medical and adult nutritional products. Minor changes to the sample preparation procedure and chromatographic separation improved vitamin K1 recoveries and reduced chromatographic interferences in these types of matrixes. Currently AOAC Method 999.15 is applicable only to the determination of total vitamin K1 (phylloquione) in infant formula and milk (fluid, ready-to-feed, and powdered) containing > 1 microg vitamin K1/100 g solids. AOAC Method 999.15 recoveries of vitamin K1 were improved by altering sample sizes, extraction solvents and amounts, and the reagent addition order and amount of water or aqueous solutions added. The chromatographic separation of vitamin K1 in medical nutritional products containing canola and marine oils was improved, and trans vitamin K1 was separated from the biologically inactive cis isomer in all products with a C30 3 microm column and a 100% methanol mobile phase. With these modifications to the extraction procedure and chromatographic separation, AOAC Method 999.15 demonstrated acceptable precision and accuracy for the quantitation of trans vitamin K1 in specialty infant formulas containing hydrolyzed proteins and free amino acids, and medical and adult nutritional products. A single-laboratory validation of these minor modifications was completed. Fourteen different product matrixes were analyzed during validation. The intermediate precision averaged 4.15% RSD (range 2.52-5.81% RSD), and recovery data averaged 100.1% (range 92.2-109%).