Methodology for elemental analysis of a mineral fertilizer, some of its raw materials and limestone using microwave-induced plasma optical emission spectrometry (MIP OES)

Abstract

The elemental analysis of complex matrices such as superphosphate-fertilizers and agricultural inputs by means of microwave-induced plasma optical emission has been evaluated in the present study. A commercial single superphosphate-fertilizer and three certified reference materials – CRMs (multi-nutrient, phosphate rock and dolomitic limestone) were analysed. Samples were submitted for three different analyte extraction or decomposition procedures; microwave assisted digestion (MAD), extraction by heating on a metallic plate and ultrasound assisted extraction (US). Analyte recovery tests were carried out to evaluate dilutions of the obtained sample solutions to reduce or avoid matrix effects. Better results were obtained for samples submitted for MAD and the concentration values found agreed with those certified or known for the CRMs. Inductively coupled plasma optical emission spectrometry (ICP OES) was employed as an independent technique for analyte determination in the superphosphate-fertilizer submitted for MAD. The concentrations found by both techniques were in agreement with each other for most of the investigated elements. As such, MIP OES has demonstrated good performance for the determination of 19 elements.