Capillary electrophoretic determination of oxalate in amniotic fluid

A capillary electrophoretic (CE) assay for oxalate has been applied to the quantitative determination of free oxalate in amniotic fluid. Indirect abso rbance detection of oxalate is accomplished with a chromate-based backgroun d electrolyte modified with ethylenediaminetetraacetic acid (EDTA). Detecti on interference due to the presence of high levels (approximate to 4 mg/ml) of inorganic chloride is eliminated through a direct sample clean-up proce dure based on cation (Ag+-form) resins. Separation interference from amniot ic fluid proteins is prevented through the use of a simple aqueous-based di lution procedure. This method for the determination of oxalate in amniotic fluid provides precision of approximate to 5% relative standard deviation ( RSD). Within-day precisions for the oxalate response and migration time are better than 3% RSD and 1% RSD, respectively. Between-day precisions for th e oxalate response and migration time are better than 6% RSD and 3% RSD, re spectively. The analytical recovery of oxalate (1000 ng/ml) spiked into amn iotic fluid was better than 96%. The limit of detection (LOD) for the metho d is approximate to 100 ng/ml oxalate. This method also shows promising res ults for the determination of oxalate in human blood plasma samples. (C) 20 00 Elsevier Science B.V. All rights reserved.