Rapid screening of plasma volume expanders in urine using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry

The use of plasma volume expanders, especially those based on chemically modified polysaccharides such as hydroxyethyl starch, has found its way from the medical field to the athletic community in the everlasting drive for performance enhancement. As such, plasma volume expanders have been placed on the list of banned substances by the International Olympic Committee, and in turn require accurate and sensitive analytical tools for their detection in complex biological matrices. Here we present a relatively straightforward method for the detection of polysaccharidebased plasma volume expanders (PVE) in urine, based on the carefully controlled partial acid hydrolysis of urine (20 muL) in a total volume of 500 muL 4 M trifluoroacetic acid. Following the incubation (30 min at 100degreesC) an aliquot of the hydrolysate is dried, re-suspended in the analytical matrix (e.g. 2,5-dihydroxybenzoic acid) and examined by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). The obtained mass spectrometric profile reveals a high number of characteristic peaks in the mass range between 500 and 3000 Da, a region that in urine samples devoid of PVE appears relatively clean, and thus allows the unambiguous identification of the presence of such PVE. This approach is fast (the mass profile can be obtained within 90min), highly sensitive (the effective sample amount on the MALDI target is equivalent to 100nL urine), needs little sample handling (four steps), requires no derivatisation and is devoid of interference from other biomolecules. The approach has been worked-out for hydroxy ethyl starch but can be applied to other polymer-derived plasma expanders such as dextran and probably the newly developed acetyl starch. Copyright (C) 2004 John Wiley Sons, Ltd.