Evaluation of flow injection-solution cathode glow discharge-atomic emission spectrometry for the determination of major elements in brines

• SCGD could be used for the determination of alkaline and alkaline earth metals in brine samples.
• The interference of SO42− for Ca2+ and Mg2+ was eliminated in this paper.
• Supporting acid had difference effect between heavy metals and alkaline and alkaline earth metals.

A new method for the determination of major metal elements in high salinity brines was developed by solution cathode glow discharge (SCGD) with flow injection analysis (FIA). The matrix interferences of major cations and anions in brines have been evaluated. It was found that high concentration of Na+ and K+ could interfere each other, K+ at a concentration of 400 mg L−1 enhanced the signal intensity of Na+ more than 20%. The effect of the anions was observed and it was noted that the signal intensity of both Ca2+ and Mg2+ were suppressed significantly when the SO42− reached 100 mg L−1. It was demonstrated that some low molecular weight organic substances such as formic acid, glycerol and ascorbic acid could eliminate interference of SO42− even with volume percentages of 0.5%. Under the optimized condition, the proposed FIA-SCGD can determine K, Na, Ca and Mg with the limits of detection of 0.49 (K), 0.14 (Na), 11 (Ca) and 5.5 (Mg) ng mL−1. The proposed method has been successfully applied to the analysis of 5 salt lake samples and compared with those obtained with inductively coupled plasma atomic emission spectrometry (ICP-AES). The advantages of small size, low energy consumption, good stability and repeatability indicated that the SCGD is promising for the determination of major ions in brine samples.

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