Determination of gallium in water samples by atomic emission spectrometry based on solution cathode glow discharge

A novel and rapid method was established for gallium determination by a home-made solution cathode glow discharger coupled with a portable fiber-optic spectrometer. Plasma was generated by the discharger and the emission line at 417 nm for gallium was observed with a portable fiber-optic spectrometer, whose spectral resolution was 1.1 nm based on the peak width of half height using a 10 mg/L gallium standard solution. The analytical conditions and instrumental parameters were optimized. The results showed acidity turned to be significantly influential for the emission intensity of the same sample. Therefore, acidity control of the testing solution was crucial. Under the optimized conditions, the limit of detection (LOD) for gallium was 0.47 mg/L calculated by 3SD(blank)/S. The stability was evaluated by the seven replicates of 10 mg/L gallium standard solution, and the relative standard deviation (RSD) was 2.1%. This method was applied to the analysis of gallium for river and waste water available in Beijing. The recoveries in the range of 92.0%-113.1% were acquired while the RSD values were below 7% (n = 5), which showed this method was feasible for gallium determination of real water samples. Moreover, only 1% HNO3 is demanded while the whole instrument is portable and works under ordinary atmospheric pressure so that the field test demand can be satisfied.