Rapid high-performance sample digestion of base metal ores using high-intensity infrared radiation with determination by nitrogen-based microwave plasma optical spectrometry

Infrared sample digestion technology has been rapidly developed in recent years and its application and digestion performance on a variety of ores of base metals was assessed in this study, using a 6-channel infrared digester. Digestion times of 10 min or less were achieved for all base metal ores investigated, including oxides, sulfides, and silicates of Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, W, and Zn. Performance criteria for all samples were excellent, reflected in z values of less than 2 in all cases. Various acid digestion methods were developed for the selected ore samples under high intensity infrared radiation and delivered virtually complete recoveries of all of the elements of interest. Chromite, the notoriously refractory chromium ore was digested within 10 min and gave 100% recovery of chromium. These digestions were accomplished without resorting to perchloric acid and, for most sample types, without hydrofluoric acid, significantly improving the workplace safety for analysts. Between-channel variation of the analyte recoveries from the 6-channel unit were generally below 2%, suggesting that the digestion methods developed with this platform provide reproducible results to meet various sample preparation demands. The high speed and analyte recovery of these digestions makes this methodology especially attractive for prospectors and developers who demand rapid and reliable results from exploration samples.