Abstract:The nitrogen and sulfur co-doped graphene quantum dots (NS-GQDs) with good water solubility and optical property were synthesized by hydrothermal method. Based on the electrochemical luminescence (ECL) quenching effect of Hg2+ on NS-GQDs, a method for the determination of Hg2+ was established based on NS-GQDs ECL quenching. The proposed method was applied for the determination of mercury in alunite. NS-GQDs were modified onto gold electrode and then used as ECL probe. Hg2+ standard solution was added into detection cell. Meanwhile, the phosphate buffer solution at pH 7.6 and 50 mmol/L K2S2O8 solution were also added. The solution was uniformly mixed for ECL detection. Under the selected experimental conditions, the ECL quenching value of NS-GQDs showed good linear relationship with Hg2+ concentration. The linear correlation coefficient was 0.999 7. The linear range was 0.1-220 μmol/L. The limit of detection was 0.03 μmol/L, and the limit of quantification was 0.05 μmol/L. The proposed method was applied to the determination of mercury in alunite ore sample. Moreover, the standard addition recovery tests were conducted. Meanwhile,atomic fluorescence spectrometry (AFS) was selected for check experiments. The relative standard deviations (RSD, n=6) of determination results were between 2.8% and 4.3%. The recoveries were between 96% and 106%. The t test method was used to compare the determination results of experimental method and AFS. The results showed that |ttest| was 0.33 at confidence interval of 95%, which was less than ttable of 2.776. It was indicated that there was no significant difference between the measurement results of two methods.
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