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Fast-scan anodic stripping voltammetry (FSASV) was applied to sensitively detect Pb2+ on a mercury film electrode (MFE). The method was involved with a controlled preconcentration by accumulation of Pb2+ on the MFE followed by FSASV measurement. At the scan rate of 500 V/s, a linear relationship between the anodic stripping peak current and the logarithm of Pb2+ concentration in the solution was observed in the range from 0.1 µmol/L to 0.1 pmol/L with a detection limit of 0.1 pmol/L. The proposed method was successfully applied for the determination of Pb2+ in spiked water samples with satisfying recoveries in the range of 98.6 to 104.3%, and the corresponding relative standard deviation ranged from 3.7 to 5.5%. Therefore, FSASV is a sensitive, fast, cost-effective and simple method for the detection of Pb2+ at picomolar level and would be very promising in heavy metal determination.

In this work, a highly-sensitive polymeric membrane ion selective electrode for determination of tetracycline was constructed by using molecularly imprinted polymer (MIP) particles as quasi-ionophore. The water-compatible MIP particles targeting tetracycline were synthesized with tetracycline as a template molecule, methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, 2,2′-azobisisobutyronitrile as an initiator and lanthanum ion as a mediator. Benefited from the distinctive performance of the quasi-ionophore and the optimized composition of the membrane and the inner filling solution, the lower detection limit of the electrode was decreased to about 1 × 10−8 mol/l. It exhibited a good electrode slope 59.8 mV/decade near the theoretical Nernstian one, with a wide linear working range from 2.0 × 10−8 to 1.0 × 10−3 mol/l. Due to the specific recognition of tetracycline by the MIP particles, the selectivity coefficients for routine interferences were less than 10−4. The fabricated electrode should be used in pH 2–4, response time of which was less than 200 s when the concentration of tetracycline was higher than 1.0 × 10−6 mol/l and no more than 30 min at the concentration of 1.0 × 10−8 mol/l. Finally, the proposed highly-sensitive ion selective electrode has been successfully applied to the determination of tetracycline in aqueous samples.

Cytochrome c (cyt-c) entrapped in agarose hydrogel was electrostatically bound to the edge plane pyrolytic graphite electrode (EPPGE), and then stable agarose-cyt-c/EPPGE was prepared. Direct electrochemistry between cyt-c and the EPPGE was monitored by protein film voltammetry. The effects of ionic strength, pH and exterior substances on the direct electrochemistry, and electrocatalytic properties of cyt-c were also studied. Results show that the electrochemical behavior of heme Fe(III)/Fe(II) in cyt-c is quasireversible. Its electrochemical performance is the best when the concentration of supporting electrolyte phosphate buffer solution is 0.2 mol/l and pH is 7.0, and greatly inhibited by exterior metal ions. Catalytic reduction of oxygen could also be achieved at the agarose-cyt-c/EPPGE.