Abstract: Powdered multi-vitamin tablets equivalent to ~200 iu of vitamin D2 or D3 were spiked with 5 µg of vitamin D2 or D3 as appropriate (internal standard), dispersed in 10 mL of aqueous 50% methanol (1:1) and extracted three times with 15 mL of hexane. The organic phase was evaporated to dryness under vacuum and redissolved in 1 mL of aqueous 90% methanol. Portions (20 µL) were analyzed on a column (15 cm x 4 mm i.d.) of TSK-gel ODS 80 (5 µm) with aqueous 90% methanol as mobile phase (1 ml/min) and atmospheric pressure (AP) CIMS in the selected ion monitoring mode (details given). The calibration graphs for vitamins D2 and D3, 1α-hydroxy-vitamin D3, 25-hydroxy-vitamin D3 and 1,25-dihydroxy-vitamin D3 were linear from 150-30 000 ng/ml and the detection limits were ~0.5 ng; the RSD were 1.9-5.7%. The results agreed with those obtained by HPLC with UV detection (details given). Flow injection AP CIMS with a flow rate of 2 ml/min and reduced amounts of sample also gave satisfactory results.

Abstract: A prototype automated system involving continuous-flow analysis and high performance liquid chromatography (CFA/ HPLC) has been developed for the analysis of fat-soluble vitamins in individual pharmaceutical tablets. The novel features are the front-end coupling of CFA to HPLC, injection of hexane solutions on reversed phase columns, separation/quantitation of vitamins A, D2 and E within single chromatographic runs for a wide variety of tablets, and a dynamic range sufficient to accommodate the 1000-fold higher levels of vitamins A and E over D2 in the same tablets. The analysis rate is 10 samples per hour, the precision better than 6% for all three vitamins, and the recovery is 70-90% of that obtained by the standard AOAC method. Although the system is a prototype, it already greatly outperforms current manual analyzes which are time consuming, tedious, and demanding in terms of the level of skill and experience of the experimenter. Included in this work are some retention comparisons of commercial columns.