Extraction of methylmalonic acid from serum using ISOLUTE SAX prior to LC-MS/MS analysis

Methylmalonic acid (MMA) in serum is measured to help diagnose a number of disorders, primarily vitamin B12 deficiency. This application note describes a simple, effective protocol for the extraction of MMA from serum using ISOLUTE SAX strong anion exchange solid phase extraction plates, demonstrating high, reproducible analyte recoveries with low protein and phospholipid content in the extracts. The well known isobaric interference, succinic acid, is chromatographically separated to allow accurate quantitation of the MMA.

ISOLUTE SAX is a silica-based strong anion exchange sorbent used to extract acidic analytes, such as MMA, from aqueous samples. Very clean extracts are possible due to the purely anion exchange retention mechanism available using this silica based sorbent. This minimizes the co-extraction of endogenous interferences through hydrophobic (or non-polar) retention.