Determination of urea using high-performance liquid chromatography with fluorescence detection after automated derivatisation with xanthydrol

A high-performance liquid chromatography (HPLC) method for the determination of urea that incorporates automated derivatisation with xanthydrol (9H-xanthen-9-ol) is described. Unlike the classic xanthydrol approach for the determination of urea, which involves the precipitation of dixanthylurea (N,N′-di-9H-xanthen-9-ylurea), the derivatisation procedure employed in this method produces N-9H-xanthen-9-ylurea, which remains in solution and can be quantified using fluorescence detection (λex = 213 nm; λem = 308 nm) after chromatographic separation from interferences. The limit of detection for urea was 5 × 10−8 M (0.003 mg L−1). This method was applied to the determination of urea in human and animal urine and in wine.