Chromatography Forum

I have plenty of reverse phase LC applications for the analysis of vitamins but would like some guidance on a suitable extraction of Vitamin A and E and beta-carotene from vitamin tablets.

Thanks

Both are easily retained on a reversed-phase SPE device such as as an Oasis HLB cartridge. The separation from more polar vitamins can be performed by an appropriate selection of the washing conditions. Waht other analytes are in your sample?

Just a few other minerals. Would rather avoid SPE if possible and stick with a simple extraction and injection to HPLC.

The quicker and easier the better.

Thanks

Just a few other minerals. Would rather avoid SPE if possible and stick with a simple extraction and injection to HPLC.

The quicker and easier the better.

Thanks

Just a few other minerals. Would rather avoid SPE if possible and stick with a simple extraction and injection to HPLC.

The quicker and easier the better.

Thanks

Extract with ether, using low actinic glassware, filter/centrifuge, and analyse by HPLC. Quick, easy, and probably inaccurate.

The protocols for HPLC vitamin tablet assays take account of the forms of Vitamin A and E used to make the tablets. The alternative is to use wet chemical protocols, such as the IUPAC vitamin A assay in USP <571>.

HPLC methods usually are validated for the formulation ingredients, and it's not uncommon for some multivitamin formulations to generate low results unless great care is taken to exclude oxygen and light, and minimise extraction time and heat.

I'd suggest contacting either the manuafcturers of the tablets or the vitamin ( eg Roche ), and ask for guidance, as they may have standard protocols.

I have had pretty good results using the following: grind the tablet finely, and take about 150mg aliquot. Partition it between 1mL water and 5mL ethyl acetate. Shake well. Warm it to 60°C (no more than 10 min) and shake vigorously. Centrifuge, and inject 15 µL of the ethyl acetate phase. The reason for the heating is that the fat-soluble vitamins are carried in wax beads, and you need to melt them to get good extraction, but only long enough to melt the wax. Injecting ethyl acetate will reduce the efficiency of early eluting peaks like lutein and retinol acetate, but the alternative of evaporation and reconstitution loses too much of the sample. I published this method in American Laboratory News, Nov. 2005.

Making calibration standards is tricky. I used spectrophotometric assay and published absorbtion coefficients to assay the stock solution every time I diluted a working standard.

Thanks.