Simultaneous Determination of Vitamin A and β-Carotene in Dietary Supplements by Liquid Chromatography

Abstract Several liquid chromatography (LC) methods for analysis of vitamin A in oods and feeds have been previously reported but only a few have been applied in non-food matrixes. A validated LC method is needed for determination of vitamin A and β-carotene in the various matrixes presented by dietary supplements. The performance of a reversedphase method with methanol–isopropanol gradient elution was evaluated with standard retinyl derivatives and β-carotene. The reversed-phase method is capable of separating retinol from other derivatives such as retinyl acetate, retinyl palmitate, and β-carotene. Two types of extraction were used to extract the analytes from the dietary supplements: a hexane–methylene chloride extraction for soft-gel capsules containing β-carotene, and a direct solvent extraction for dietary supplements in tablet form. The direct solvent extraction consisted of treatment with ethanol and methylene chloride following addition of hot water (55°C). Results with the reversed-phase method for vitamin A and β-carotene in the products examined ( n = 8) indicated excellent method performance. The main form of vitamin A or β-carotene in dietary supplements was the all trans isomer. The reversed- phase method avoids saponification and is rapid, accurate, precise, and suitable for simultaneous determination of retinyl derivatives and β-carotene in dietary supplements.

Download Full-text

Method for the Determination of β-Carotene in Supplements and Raw Materials by Reversed-Phase Liquid Chromatography: Single Laboratory Validation

Journal of AOAC International ◽

10.1093/jaoac/87.5.1070 ◽

2004 ◽

Vol 87 (5) ◽

pp. 1070-1082 ◽

Cited By ~ 25

Author(s):

Joseph Schierle ◽

Bernd Pietsch ◽

Alan Ceresa ◽

Christian Fizet ◽

Edward H Waysek

Keyword(s):

Liquid Chromatography ◽

Dietary Supplements ◽

Raw Materials ◽

Collaborative Study ◽

Reversed Phase ◽

Raw Material ◽

Relative Standard ◽

Single Laboratory ◽

Β Carotene

Abstract A single laboratory validation (SLV) study was conducted for a liquid chromatography (LC) method for the determination of total and all-trans-β-carotene in a variety of dietary supplements, including multivitamin tablets, softgels, capsules, and beadlet raw materials. Extraction variants were developed for the different types of supplements tested based upon the supplement type and level of β-carotene. Water dispersible formulations such as powders, emulsions, tablets, and capsules were enzymatically digested with protease and extracted with dichloromethane–ethanol. Oily suspensions were directly dissolved in dichloromethane–ethanol. After appropriate dilution or concentration, the extracts were chromatographed by using either a reversed-phase C18 column or, in products containing high amounts of α-carotene, a reversed-phase C30 column. The LC systems provided linear responses in the range of 0.1–50 μg β-carotene/mL. The main geometrical isomers of β-carotene (all-trans, 9-cis, 13-cis, and 15-cis) were well separated from each other and from other carotenoids such as α-carotene, cryptoxanthin, lutein, lycopene, and zeaxanthin. Duplicate determinations of total β-carotene performed by 2 technicians in 8 different test materials on 5 different days resulted in relative standard deviations of 1.2–4.4%. Recoveries determined for supplements and beadlet raw material spiked with β-carotene levels of 10 μg to 100 mg/test portion and 0.2–40%, respectively, ranged from 97.5 to 102.1%. On the basis of the accuracy, precision, and recovery results from the SLV study, the method is suggested for a collaborative study on the determination of total and all-trans-β-carotene in dietary supplements.

Download Full-text