Liquid chromatographic determination of S-adenosyl-L-methionine in dietary supplement tablets.

A simple and reliable liquid chromatographic method was developed for the determination of S-adenosyl-L-methionine (SAM) in dietary supplement tablets. SAM in products was extracted with a phosphate buffer and separated from the mixture on a reversed-phase C8 column by ion-pair chromatography. A gradient mobile phase containing phosphate buffer, sodium octanesulfonate as the ion-pair reagent, and acetonitrile at a flow rate of 1.2 mL/min was used in the analysis. The UV detection wavelength was set at 257 nm. The calibration curve was linear over a range of 75-375 microg/mL for the SAM active ion with R2 = 0.9999. Replicate tests indicated good reproducibility of the method with a relative standard deviation of 0.9% (n = 8). The multiple extractions and recoveries from fortified products showed the high accuracy of the analysis. The use of the acidic buffer for SAM extraction and elution and the use of a fresh standard for each calibration to counteract the instability of the SAM compound significantly improved the accuracy of the method.