Moscerdam substrates are not only of high chemical purity, but more importantly are biochemically pure. Enzyme laboratory practice has shown that chemical purity does not always guarantee optimal performance of enzyme assays. Traces of impurity (< 1%) can severely jeopardise results. All Moscerdam substrates are tested with fibroblasts from patients with the corresponding lysosomal storage disease. This biochemical testing is the only way to ensure constant high-quality substrates.