Riboflavin in a multivitamin

[Rick Jagielski]

I am working on an assay to determine water soluble vitamin concentrations in a multivitamin.

I currently am having problems with riboflavin. It seems like extraction in water is giving me erratic results and I suspect that it may be solubility issues.

Has anyone else attempted to quantify riboflavin, and if so what method of extraction would you suggest?

Thanks

Rick

[Mark Tracy]

Yes, I have done that. Riboflavin has poor solubility in water, and worse solubility in everything else! First you need to grind your vitamin pill very finely. Use mobile phase for an extraction solvent (I used pH 3.4 phosphate buffer). Then sonicate about 150 mg of powder in 100 mL of buffer for about 10 min. Filter. Inject up to 50 microliter. This extraction gets all the water-soluble vitamins except biotin and B12 in a concentration you can actually analyze by HPLC/UV

[Rick Jagielski]

Thanks, I will try this.

Do you have to use a huge volume for the standard preparation for riboflavin?

We typically do a dilution scheme so that our weigh outs are more than 25mg or so. When weighing out very small amounts <5mg it seems that we get a lot of error with standard preparation.

Thanks

Rick

[Mark Tracy]

Yes, my stock solution is only 0.10 mg/mL riboflavin. So you end up making more stock solution than you can possibly use up.