DETERMINATION OF NANOGRAM AMOUNTS OF COPPER(II) BY THE CATALYTIC-PHOTOMETRIC METHOD

The effect of several buffers was examined for the catalysis of copper(II) in the reaction of N,N-dimethyl-p-phenylenediamine with N,N-dimethylaniline to form Bindschedler's Green (lambda(max)=725 nm) in the presence of hydrogen peroxide. The buffer agents which were examined included imidazole, 2,4,6-trimethylpyridine(TMP), piperazine-N,N'-bis(2-ethanesulfonic) acid) (PIPES), N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), 3-(N-morpholino)-propanesulfonic acid (MOPS), and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Among them TMP was found to be the most favorable agent in this reaction system. The established catalytic method is given for the 0.05-1.0 ng cm-3 range of copper(II), and has an effective sensitivity index of 1.1 X 10(-3) ng cm-2.