Electrochemical response of new carbon electrodes bulk modified with cobalt phthalocyanine to some thiols in the presence of heptane or human urine Original Research Article

The method for preparation of solid working electrodes from carbon powder proposed earlier has been simplified and the conditions of bulk modification of the new electrodes with Co(II) phthalocyanine (CoPC) has been investigated using thiol oxidation as an example. The dependence of operational potential and of the analytical signal on the concentration of the modifier CoPC has been studied. The maximum sensitivity is at 12–15% (w/w) CoPC. The second-order rate constants K1o and electron transfer constants Kel value for some thiols have been evaluated. It was shown that K1o value are large (∼104 l mol−1 s−1), i.e. CPrEM shows a high catalytic effect and the Kel value is relatively low (∼10−4 cm s−1). The sensitivity for mercaptoethanol determination in a petroleum fraction (heptane) diluted 1:200 in the range 0.25–3.25 μM is 6.37 nA μM−1. That for cysteine in human urine diluted 1:100 in the range 1–12 μM is 8.89 nA μM−1. The detection limit for mercaptoethanol in the diluted petroleum is 0.8×10−7 M and that of cysteine in diluted human urine is 2×10−7 M.