3.1. Effect of HCl and NaBH4 concentrations
A study to evaluate the effect of the HCl concentration is shown in Fig. 2. The mercury signal intensity remains almost constant for the two gasoline solutions, except for a slight increase from 0.5 mol L− 1 to 1.5 mol L− 1. In view of this, the HCl concentration of 1.5 mol L− 1 was selected for further experiments.