Semiquantitative determination of residues of amphetamine in sewage sludge samples

A procedure based on HPLC and mass spectrometric detection has been developed for screening of residues of the illicit drug amphetamine in sewage sludge. Sample pretreatment consisted in extraction by 50 mM formic acid and methanol (80:20 v/v), followed by adjustment of the pH to 10 and preconcentration by SPE at poly(divinylbenzene)-N-vinylpyrrolidone. HPLC separation of the extract was done on a C18 RP with a mixture of 50 mM formic acid and methanol (SO: 20 v/v) as mobile phase. The mass spectrometer was operated in the MS2 and MS3 mode using the transition from m/z 136 to 119 and from m/z 119 to 91. Due to the complex matrix, ionization suppression effects as well as shifts in the sensitivity of the detector within a series of runs could not be fully excluded. Therefore, quantitation was done by standard addition together with external standards, so that semiquantitative results could be obtained down to concentrations of 2 mu g/kg sewage sludge. Samples taken from various municipal sewage treatment plants indicate that amphetamine residues are ubiquitous in urban areas.