Quantitation of Vitamin K in Milk Products by Pre-column Reduction HPLC–Fluorescence

Vitamin K is a dietary component that, as a cofactor, has critically important physiological roles in the body. As it is present in milk at very low levels, it is fortified at higher levels in paediatric milk-based formulae. Currently, the predominant analytical strategy for both food database surveys and routine compliance testing is high-performance liquid chromatography with post-column zinc reduction and fluorescence detection. This study presents a single-laboratory validation of a pre-column reduction modification that provides enhanced sensitivity (> 2×) and increased analytical throughput. Accuracy was confirmed by analysis of a certified reference infant formula and milk proficiency samples, and by comparison against the reference method for a wide range of dairy products containing vitamin K 1 at both natural and supplemented levels. The method offers several performance advantages and is suitable for routine product compliance release testing.