Quantification of free and bound pantothenic acid in foods and blood plasma by a stable isotope dilution assay.

A stable isotope dilution assay for quantification of pantothenic acid in food and blood plasma uses a 4-fold labeled isotopomer of the vitamin as an internal standard. Pantothenic acid and its labeled analogue were detected as trimethylsilyl derivatives by gas chromatography-mass spectrometry, showing a minimized spectral overlap. In starch a detection limit of 44 microg/kg, an intrasample relative standard deviation of 6.7%, and recovery values ranging between 97.5 and 99.4% were determined. Total pantothenic acid content was determined in rice, milk powder, apple juice, and blood plasma after enzymatic hydrolysis of the vitamin's conjugates; free pantothenic acid was quantified prior to enzyme treatment. Almost all results were found to be in good agreement with literature data.