Determination of homocysteine thiolactone in urine by field amplified sample injection and sweeping MEKC method with UV detection

Homocysteine thiolactone (Hcy-thiolactone), an intramolecular thioester, easily acylates free-amino groups in proteins, which impairs or alters the protein's biological function. Here, we describe new capillary electrophoresis assay for the determination of Hcy-thiolactone in human urine based on a field amplified sample injection and sweeping MEKC with UV detection. The two steps procedure relies on sample liquid-liquid extraction followed by CE separation and UV detection at 240 nm. The Hcy-thiolactone standard added to the urine before the extraction step shows that the response of the detector is linear within the range studied, from 0.1 to 1 μmol L−1 urine. The intra- and interday precision and recovery were 3.2-14.4% (average 5.1% and 9.3%) and 92.5-112.6% (average 99.8% and 99.1%), respectively. The lower limit of quantification was 0.09 nmol Hcy-thiolactone in 1 mL of urine. The proposed method was applied for the analysis of 15 urine samples donated by apparently healthy volunteers. The average concentration of the analyte was 0.170 ± 0.029 μmol L−1.