Microwave digestion technique for the extraction of minerals from environmental marine sediments for analysis by inductively coupled plasma atomic emission spectrometry and atomic absorption spectrometry

Abstract

A microwave digestion sample preparation technique for the determination of environmentally significant elements in marine sediments is discussed. Samples were digested with nitric and hydrochloric acids in unvented PFA vessels for periods of up to 20 min. The digestion time compared favourably with the 3 h required for a conventional hot-plate procedure. Recoveries of metals (using inductively coupled plasma atomic emission spectrometry and graphite furnace atomic absorption spectrometry) from an in-house reference sediment and National Research Council of Canada reference materials MESS-1 and BCSS-1 were comparable or superior to those attained by the conventional procedure (89–140%). Significant improvements in precision at the 95 and 99% confidence levels and a reduction in analytical blank levels were noted. Elements with the poorest precision by the conventional method showed the greatest improvement. Diluting the concentrated acids for digestion increased recoveries by 20–30%. The PFA vessels have been found to be resilient to repeated (>100) digestions of a wide variety of samples if properly annealed before use.