Determination of mercury ions on a diphenylcarbazone bulk modified graphite electrode

A bulk modified electrode prepared by pressing a mixture of carbon powder and diphenylcarbazone at 15.2 MPa was used for the determination of mercury in aqueous solutions. Mercury(II) ions are concentrated by complexation with the modifier in acidic (HNO₃) solution. After exchange of the medium for 1 M HCl and 1 M CaCl₂, mercury is reduced at ?0.8 V vs. SCE. The signal is generated by anodic stripping in the differential-pulse mode. The calibration graph is linear in the range 5×10^?8?5× 10^?6 M with a relative standard deviation of 7%. After enrichment for 10 min the detection limit is 5×10^?8 M. Silver, chromate and strong complexing agents interfere. The use of the electrode to determine the labile fraction in mercury speciation is discussed.