Determination of cadmium, copper, iron, manganese, lead and zinc in sewage sludges with prior acid digestion in a microwave oven and slurry introduction

Abstract

A method is proposed for the determination of six elements in sewage sludges by flame atomic absorption spectrometry. The recommended procedure consists of introducing 500 mg of sample, 5 ml of HNO₃ and two drops of 2-ethylhexan-1-ol into a 100-ml Pyrex reaction vessel, which is then hermetically sealed and introduced into a microwave oven; and the contents digested for 3 min at a power of 520 W. After digestion the residue is allowed to cool and is then diluted with distilled water. The resulting slurries of the digested samples in water are introduced directly into the flame using multi-elemental aqueous solutions as standards. The variables of the digestion procedure in the microwave oven, such as power, time, sample mass and acid volume, have been studied and the validity of the conditions for using aqueous standards in the analysis of slurries has been evaluated. The proposed method has been applied to the analysis of certified sewage sludge samples and the analytical parameters of the method have been evaluated.