The aim of this project is to elucidate the structure of two novel biomarker for Pompe disease that were found in previous metabolomics studies that were performed here at the EMC. In an initial screening these markers seemed to be specific for classic infantile Pompe patients. The markers were found in plasma and urine. In order to develop a quantitative assay, isotope labelled standards will have to be synthesized, hence the need for structural elucidation. The intention for these biomarkers is to be used for the Dutch national neonatal screening which is performed in dried blood spots by the RIVM. But with emerging therapies for Pompe disease there is a need for biomarkers for clinical screening as the current marker Glc₄ does not correlate well with patient status.