Determination of ethyl sulfate – a marker for recent ethanol consumption – in human urine by CE with indirect UV detection

Abstract

A CE method for the determination of the ethanol consumption marker ethyl sulfate (EtS) in human urine was developed. Analysis was performed in negative polarity mode with a background electrolyte composed of 15 mM maleic acid, 1 mM phthalic acid, and 0.05 mM cetyltrimethylammonium bromide (CTAB) at pH 2.5 and indirect UV detection at 220 nm (300 nm reference wavelength). This buffer system provided selective separation conditions for EtS and vinylsulfonic acid, employed as internal standard, from urine matrix components. Sample pretreatment of urine was minimized to a 1:5 dilution with water. The optimized CE method was validated in the range of 5-700 mg/L using seven lots of urine. Intra-and inter-day precision and accuracy values, determined at 5, 60, and 700 mg/L with each lot of urine, fulfilled the requirements according to common guidelines for bioanalytical method validation. The application to forensic urine samples collected at autopsies as well as a successful cross-validation with a LC-MS/MS-based method confirmed the overall validity and real-world suitability of the developed expeditious CE assay (sample throughput 130 per day).

Recent advances in the applications of CE to forensic sciences (2005–2007)

“…On the other hand, a recent paper from Lindner's group [45] reported a method for EtS analysis in urine. The background electrolyte was composed of 15 mM maleic acid, 1 mM phthalic acid and 0.05 mM CTAB.…”

Nonaqueous capillary electrophoresis for analysis of the ethanol consumption biomarker phosphatidylethanol

“…The timeliness of developing analytical methods for emerging ethanol consumption markers, e.g. ethyl glucuronide, ethyl phosphate and ethyl sulfate, is highlighted by recent studies [9][10][11].…”

Confirmation analysis of ethyl glucuronide and ethyl sulfate in human serum and urine by CZE‐ESI‐MSn after intake of alcoholic beverages

“…Furthermore, EtG in urine [20] and serum [19] can be monitored with an immunoassay. The CZE methods are based on the use of fused-silica capillaries whose inner walls were permanently coated with linear polyacrylamide [16][17][18][19] or dynamically coated with a polycation [14,15,19]. They were shown to be suitable to detect the two ethanol metabolites in urines of volunteers who ingested a known amount of alcohol and in urines of patients with an unknown history of alcohol consumption.…”

“…EtG and EtS are non-volatile, water soluble and stable. For their determination in biological samples, different analytical methods have been developed, including LC-MS/ MS with negative electrospray ionization (ESI) [8][9][10][11][12][13] and CZE with indirect UV detection [14][15][16][17][18][19]. EtG in serum and urine has also been determined by GC-MS [6].…”

“…With the CZE-MS setup, separation of EtS (pKaoÀ3.0 [14], mobility 4.86 Â 10 À8 m 2 /Vs [14], molecular mass 126.13 g/mol) and EtG (pKa 3.21 [16], mobility 2.35 Â 10 À8 m 2 /Vs [16], molecular mass 222.3 g/mol) was effected at 25 kV with a buffer composed of 20 mM ammonium acetate adjusted to pH 9.5 with ammonia. Sample injection occurred via application of 70 mbar constant pressure during 12 s and the sheath gas flow was interrupted during that time interval.…”