Solid phase extraction procedure for urinary organic acid analysis by gas chromatography mass spectrometry

We have developed a solid phase extraction procedure for the detection of organic acids by GC-MS using a strong anion exchange column (Sep-Pak Vac RC, Accell Plus QMA cartridge). Extraction efficiencies of 25 organic acids were established by analyzing standards in water based solutions. High extraction efficiencies (90 to 100%) were found for many of the compounds studied. We estimated the limit of detection for 48 organic acids and glycine conjugates. They were below 5 nmole with the exception of malonic and oxalic acids and mevalonic acid lactone. This method provides the advantage of higher recoveries for a wide range of compounds of interest and therefore can be a potential alternative to liquid-liquid extraction for organic acid screening. It is especially sensitive for the detection of some polar compounds, such as 3-OH-glutaric and N-acetylaspartic acids.