Selective sequential dissolution for the determination of inorganic indium compounds in the particulate matter of emissions and workplace air

A speciation method was developed for the determination of inorganic indium compounds in the particulate matter of emissions and workplace, based on selective sequential extractions. In(III) soluble salts such as sulphate and chloride, In and In(III) insoluble compounds such as oxide, sulphide and indium arsenide were separated and determined. These are the main inorganic indium compounds that are expected to be present in the atmospheric particulate of the industrial production of indium and in the manufacture of indium compounds. The procedure has been tested on spiked Coal Fly ash SRM 1633a and Urban Particulate NIST SRM 1648, whose consensus value for the total indium content were reported. The indium recovery was in the range 93 % - 105%. Indium was determined by Optical and Mass Spectrometry Inductively Coupled Plasma, depending on its concentration in the samples.