Determination of the cardiac drug amiodarone and its N-desethyl metabolite in sludge samples

Abstract

For the first time, a procedure for the simultaneous determination of the iodinated drug amiodarone and its major metabolite, N-desethylamiodarone, in sludge from urban sewage treatment plants (STPs) is proposed. Matrix solid-phase dispersion (MSPD) followed by on-line cationic exchange clean-up, in mod- ular configuration, was used as sample preparation technique. Liquid chromatography with tandem mass spectrometry (LC–MS/MS), based on a hybrid quadrupole time-of-flight (QTOF) system, was employed for the selective determination of target compounds. The optimized procedure provided exhaustive recov- eries with little effect of the sample matrix in the efficiency of electrospray ionization (ESI). The overall recoveries of the method ranged between 95 and 111%, for samples spiked at different concentration levels. The achieved limits of quantification (LOQs) remained below 10 ng g−1 for both compounds, and the linear response range extended up to 2500 ng g−1. Amiodarone and N-desethylamiodarone were ubiquitous in sludge samples, from different STPs located in the Northwest of Spain, with maximum concentrations above 300 ng g−1 referred to the freeze-dried matrix. They were also present in stabilized sludge (mixed with lime and thermally dehydrated), which is mostly disposed in agriculture fields as fertilizer. Furthermore, mono-iodinated analogues of amiodarone and N-desethylamiodarone were also tentatively identified in some samples from their accurate MS and MS/MS spectra