The analysis of gold by inductively coupled plasma atomic emission spectrometry (ICP-AES) in aqueous solution in the presence of up to 50% w/v of ionic liquid is reported. The ionic liquids investigated contain the 1-butyl-3-methyl-imidazolium (bmIm) cation with the anions Cl⁻, BF₄⁻, HSO₄⁻, or N(CN)₂⁻. A facile route to the HSO4⁻ salt is also described. The presence of ionic liquids alter the nebulization efficiency and sample transport properties, and the AES signal intensity and apparent concentration of gold in solution is usually suppressed as a result, principally, of increased viscosity of solutions containing an ionic liquid. However, the counterplay between a lower surface tension and a higher viscosity is illustrated by the results for the [bmIm][BF₄] ionic liquid. The presence of this liquid at low concentrations causes an enhanced apparent concentration of gold whereas at higher concentrations the apparent concentration is diminished as the viscosity of the solution increases. Comparative data with simple sodium salts is also reported. Use of the standard addition method to compensate for matrix effects in the presence of ionic liquids is effective.
Australian Journal of Chemistry Vol. 57, Issue 2, p. 151-155