Vitamin D levels in fish and shellfish determined by liquid chromatography with ultraviolet detection and mass spectrometry

Vitamin D3 (cholecalciferol) levels were determined in finfish and shellfish using UV detection at 265 nm (combined with auxiliary full scan UV detection) and selected ion monitoring (SIM) mass spectrometry (MS), using vitamin D2 (ergocalciferol) as an internal standard. Analysis of standard reference material (SRM) NIST 1849 (Infant/Adult Nutritional Formula) was included to validate the method. Three-point calibration curves were employed, allowing values to be determined over a range of species, from those having little or no detectable vitamin D3 (e.g., pollock, shrimp) to those with high levels (e.g., salmon with up to 33.23 μg/100 g). The limit of detection (LOD) and limit of quantitation (LOQ) calculated from the uncertainty and intercept of the calibration curves were 1.22 μg/100 g and 5.30 μg/100 g, respectively, based on all analyses (n = 27 sequences). Use of response factors (RF) allowed quantitation at lower levels of vitamin D3, with an LOQ of <0.20 μg/100 g. The values obtained using the validated methodology agreed well with literature and tabulated database results for most species. However, much lower average vitamin D3 concentrations were found for oysters (0.05 μg/100 g, raw) and clams (0.18 μg/100 g, cooked) compared to other reports for these products.