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 proteinʹs 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.