Azelaic and pimelic acids: Metabolic intermediates or artefacts?

Abstract
Azelaic and pimelic acids are excreted in elevated amounts in urine in disorders of mitochondrial β-oxidation and disorders of peroxisomal β-oxidation, for which they are of significant diagnostic value. We have detected the presence of azelaic, pimelic and even-chain-length dicarboxylic acids (adipic, suberic and sebacic acids) arising artefactually as a result of storage of small sample volumes in plastic containers. Storage of samples for organic acid analysis in glass containers is recommended.