Quantitation of ethyl glucuronide in serum & urine by gas chromatography - mass spectrometry

BACKGROUND & OBJECTIVES Alcohol misuse has now become a serious public health problem and early intervention is important in minimizing the harm. Biochemical markers of recent and high levels of alcohol consumption can play an important role in providing feedback regarding the health consequences of alcohol misuse. Existing markers are not sensitive to recent consumption and in detecting early relapse. Ethyl glucuronide (EtG), a phase-II metabolite of ethanol is a promising marker of recent alcohol use and can be detected in body fluids. In this study an analytical technique for quantitation of EtG in body fluids using solid-phase extraction (SPE) and gas chromatography (GC) with mass spectrometric detection (MS) was developed and validated. METHODS De-proteinization of serum and urine samples was done with perchloric acid and hydrochloric acid, respectively. Serum samples were passed through phospholipids removal cartridges for further clean up. EtG was isolated using amino propyl solid phase extraction columns. Chromatographic separation was achieved by gas chromatography with mass spectrometry. RESULTS Limit of detection and limit of quantitation were 50 and 150 ng/ml for urine and 80 and 210 ng/ml for serum, respectively. Signal to noise ratio was 3:1, mean absolute recovery was 80-85 per cent. Significant correlation was obtained between breath alcohol and serum EtG levels (r=0.853) and urine EtG and time since last abuse (r = -0.903) in clinical samples. INTERPRETATION & CONCLUSIONS In the absence of other standardized techniques to quantitate EtG in biological samples, this gc - ms method was found to have high throughput and was sensitive and specific.