VOLTAMMETRIC PROBE OF MILK SAMPLES BY USING A PLATINUM MICROELECTRODE

Milk is a complex heterogeneous fluid containing many components in several states of dispersion. When used as a bulk solvent for studying electrochemical processes of some of the electroactive species present, it displayed mainly aqueous solution properties. With microelectrodes (25 μm in diameter) some typical constituents can be detected and the reproducibility of the processes studied was found to be satisfactory, with relative standard deviations (r.s.d.s.) lower than 2%, whereas measurements with conventional-sized platinum electrode (3 mm in diameter) gave r.s.d.s, of about 10%. Moreover, because of enhanced mass transport associated with the smallest electrodes, it was possible to diagnose the formation of precipitates of calcium phosphates on the electrode surface, as a consequence of a CEC electrode process at -0.920 V vs. SCE, involving protons released by H2PO-4, HPO2-4 formed in the electrode reaction and Ca2+. The reduction of acidic groups from casein, the oxidation of ascorbate and oxygen effects were also studied. © 1990.