Determination of vitamin D3 in liquid multivitamin preparation, using reverse phase, solid phase extraction liquid chromatography

A method is described for the determination of vitamin D3 in a liquid multivitamin preparation by liquid chromatography. Samples are purified on a disposable reverse phase extraction (SPE) column with a mobile phase of methanol-2-propanol (97 + 3) and are analyzed on a Zorbax ODS (5 micron) column with an acetonitrile-2-propanol-water (90 + 8 + 2) solvent system. Vitamin D3 is completely resolved from other interfering compounds within approximately 21 min and is detected with a UV detector at 254 nm. A mean of 98.5% of theory with a coefficient of variation of 3.8% was found for determination of vitamin D3 in a commercial preparation.