Vitamin K (phylloquinone and menaquinones) in foods - Cost-effective quantification by LC-ESI-MS/MS.

Further research on vitamin K is necessary as growing evidence of vitamin K's importance in human health beyond blood coagulation and bone health is emerging. We present a cost-effective LC-ESI-MS/MS method for quantification of phylloquinone (PK), and menaquinones (MK) 4-10 in food using deuterium labelled (d7) compounds (d7-PK, d7-MK-4, d7-MK-7 and d7-MK-9) as internal standards. The validation of the method included assessment of matrix effect, limit of quantification (LOQ), precision, and trueness. The LC-ESI-MS/MS method runtime is 9 min. The method was compared to a validated LC-FLD method (CEN 14148), for quantification of vitamin K in broccoli, cheese, natto, liver, and microalgae. LOQs of the LC-ESI-MS/MS method were ≤4 µg/100 g food. The intra- and inter-assay precision was <15% for PK, MK-4, MK-7 and MK-9; <20% for MK-5, MK-8, and MK-10, and ≤25% for MK-6. No significant differences between the quantified content by the LC-ESI-MS/MS and LC-FLD methods were observed.