  Quantification of sulfated polysaccharides in urine samples is relevant to
pharmacokinetic studies in drug development projects and to the non-invasive
diagnosis and therapy monitoring of mucopolysaccharidoses. The Heparin Red Kit
is a particularly simple and user friendly fluorescence assay for the
quantification of sulfated polysaccharides and has recently emerged as a novel
tool for the monitoring of their blood levels during pharmacokinetic studies in
clinical trials. The standard protocol for the blood plasma matrix is, however,
not suited for urine samples due to matrix interference. The present study
identifies inorganic sulfate as the interfering component in urine. The sulfate
level of urine is typically 1-2 orders of magnitude higher compared with the
blood plasma level. Addition of either hydrochloric acid or magnesium chloride
counteracts sulfate interference but still enables sensitive detection of
sulfated polysaccharides such as heparin, heparan sulfate and dermatan sulfate
at low microgramm per milliliter levels. This study extends the application
range of the Heparin Red Kit by a simple modification of the assay protocol to
the direct quantification of various sulfated polysaccharides in human urine.
