Evaluation of derivative normal pulse polarography for use in metal speciation studies

A simple inexpensive microcomputer-orientated approach for obtaining pseudo-derivative polarograms is demonstrated. The method, called derivative normal pulse polarography (d.n.p.p.), produces better signal-to-noise ratios, and therefore lower detection limits, than differential pulse polarography (d.p.p.). The foremost advantage of d.n.p.p. is its relative freedom from influences of homogeneous chemical kinetics which makes it an excellent method for metal speciation studies. Response curve shapes for Pb(II) between 2 × 10^-4 and 8 × 10^-4 M exhibit excellent agreement with theory. Titration of EDTA with 0.01 M Cu(II) and 0.01 M Cd(II) using d.n.p.p. for detection exhibited recoveries of 98.0 and 99.5%, respectively.