Combination with Gas Flotation Preconcentration Based on Ternary Association Complexes and Flame Atomic Absorption Spectrometry Detection for Trace Heavy Metals in Complicated Water Samples

A ternary association complex [MI_n+1]^-[MB]⁺, which were formed by metals (Mⁿ⁺), iodine anion (I^-) and basic dye methylene blue (C₁₆H₁₈ClN₃S-3H₂O, MB), was applied in the preconcentration of trace heavy methylene blue (Ag, Cu, Cd, Pb) in complicated water samples, such as high salty solution, by gas flotation. The ternary association complexes was floated and absorbed into 5 mL of toluene, and the toluene phase was directly determined by the flame atomic absorption spectrometry (FAAS). Several parameters, including flotation pH, volume of KI and methylene blue solution, and selection of organic solvent were studied. Under the optimum conditions, the enrichment factor for 200 ng/mL interest elements almost equal to the ratio of the aqueous solution volume to organic solvent volume. The detection limits for Cu, Pb, Cd and Ag were 0.9, 0.8, 0.5 and 0.4 ng/mL, respectively. The interference of coexist elements to the determination were also studied. The developed method was applied in the determination of trace Cu, Pb, Cd and Ag in artificial seawater, the average recoveries of interested metals were about 89.1%-92.9%.