A survey of extraction techniques for drugs of abuse in urine

Sixty nine participants in the United Kingdom national external quality ass essment scheme for drugs of abuse in urine reported details of their sample extraction technique by questionnaire. Laboratories were categorised by di fferences in technique and their analytical test results compared for sampl es containing D-amfetamine 0.4 (4) and 0.8 (3) mg/l, morphine 0.4 (4) and 0 .8 (4) mg/l, and benzoylecgonine 0.15/0.2 (2) and 0.45/0.5 (4) mg/l. Values in parentheses are numbers of samples, For amfetamine, there was no signif icant difference in the frequency of true positive results between liquid-l iquid or solid phase extraction and the Toxi-Lab A system at 0.8 mg/l. Toxi -Lab A gave significantly fewer positives when operating below its specifie d threshold at 0.4 mg/l. Paradoxically, laboratories using >5 mi urine volu me performed less well. Acidification of the extract before volume reductio n gave significantly more true positives. For extraction of morphine, solid phase systems significantly outperformed both liquid-liquid acid the Toxi- Lab A system at both 0.8 and 0.4 mg/l. No significant differences between e xtraction techniques were demonstrated for analysis of benzoylecgonine. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.