Quantitation of Fat Soluble Vitamins in Different Walnut Genotypes and Commercial Cultivars; a Comprehensive and Robust LC-MS/MS Method Validation

Walnut, being both nutritious and delicious, has been regarded as a health food due to its preventive and therapeutic effects. In the present study, a robust LC-MS/MS analytical method was developed to simultaneously quantify five fat soluble vitamins ( D 2 , D 3 , K 2 , E, K 1 ) in eleven walnut genotypes and two commercial cultivars. Linearity, accuracy, inter- and intra-day precision, detection limit (LOD), quantification limit (LOQ) and uncertainty (U at confidence level of 95% (k = 2)) were the validation parameters of the developed LC-MS/MS method. The established linearity ranges for the studied vitamins were between 50 and 1200 mg L −1 for v itamins D 2 , D 3 , K 1 , between 100-2400 mgL −1 for vitamin E and between 200-4800 mg L −1 for vitamin K 2 . The coefficients of determination for the vitamins D 2 , D 3 , K 2 , E, K 1 were between 0.9990 , 0.9991, 0.9995, 0.9997, 0.9991, respectively. Vitamins D 3 , K 2 and K 1 were not present in the analysed walnut samples. On the other hand, vitamins E and D 2 were in high quantities in all studied walnut samples. D 2 and E were the most abundant fat soluble vitamins in MDE32 (29.1 mg g -1 dry plant) and MDE5 (15.2 mg g -1 dry plant) genotypes. Despite the fact that the walnut was selected as real life sample, the validated LC-MS/MS method is enforceable to a broad range of food species.