Measuring total antimony in geothermal waters by flame atomic absorption spectrometry

A flame atomic absorption procedure utilizing an electrodeless discharge lamp is described for determining total solute antimony in silica-rich geothermal waters. Following NaNO₂ oxidation of Sb⁺³, SbCl₅ is extracted from 6 N HCl solution by using MIBK (methyl isobutyl ketone) ; silica in the organic layer is removed by centrifugation. The analytical detection limit for antimony is about 6 micrograms per liter in the original sample; the coefficient of variation is 4 percent at the 250 μg/L Sb level. Comparable total antimony levels were found in sample splits which had been either filtered and acidified (to pH less than 1.5) with HNO₃ or left untreated at the time of sample collection.