Gallium trace on-line preconcentration/separation and determination using a polyurethane foam mini-column and flame atomic absorption spectrometry. Application in aluminum alloys, natural waters and urine

A sensitive and selective flow injection time-based method for on-line preconcentration/separation and determination of gallium by flame atomic absorption spectrometry at trace levels was developed. The on-line formed gallium chloride complex is sorbed onto a polyether-type polyurethane foam mini-column, followed by on-line quantitative elution with isobutyl methyl ketone and direct introduction into the flame pneumatic nebulizer of the atomic absorption spectrometer. All chemical and flow variables of the system as well as the possible interferences were studied. The manner of strong HCl solutions propulsion was investigated and established using a combination of two displacement bottles. For 90 s preconcentration time, a sample frequency of 28 h⁻¹, an enhancement factor of 40, a detection limit of 6 μg l⁻¹ and a precision expressed as relative standard deviation (s_r) of 3.3% (at 1.00 mg l⁻¹) were achieved. The calibration curve is linear over the concentration range 0.02-3.00 mg l⁻¹. The accuracy of the developed method was sufficient and evaluated by the analysis of a silicon-aluminum alloy standard reference material. Finally, it was successfully applied to gallium determination in commercial aluminum alloys, natural waters and urine.