Analysis of cocaethylene, benzoylecgonine and cocaine in human urine by high-performance thin-layer chromatography with ultraviolet detection: a comparison with high-performance liquid chromatography

Cocaine and ethanol are frequently used at the same time, resulting in the formation of cocaethylene by transesterification. We studied the capability of high-performance thin-layer chromatography (HPTLC) to simultaneously detect cocaethylene, cocaine and benzoylecgonine in 16 urine specimens of drug addicts, previously tested as positive for benzoylecgonine at immunoenzymatic screening. Accuracy and precision, as well as detection and quantitation limits of the method, were evaluated by comparison with high-performance liquid chromatography (HPLC). HPTLC limit of quantitation was 1.0 μg/ml for the three compounds, whereas HPLC limits were 0.2 μg/ml for benzoylecgonine and cocaine, and 0.1 μg/ml for cocaethylene. The relative standard deviation (RSD) ranged from 1.03 to 12.60% and from 1.56 to 16.6% for intra- and inter-day HPTLC analysis, respectively. In the case of the HPLC method, the RSD for the intra-day precision ranged from 0.79 to 5.05%, whereas it ranged from 1.19 to 10.64% for the inter-day precision. In comparison with HPLC, HPTLC is less expensive and faster, requiring 2–3 h to analyze 10–12 samples on a single plate. In conclusion, HPTLC is suitable for determinations of the three analytes only for samples with high concentrations.