A POLAROGRAPHIC STUDY OF CARMINIC ACID

在醋酸盐缓冲溶液中,可获得胭脂红酸的单扫可逆吸附波。在pH4.3时,E_p=一0.65V(vs.S.C.E.),电极反应是由醌型还原为氢醌型。胭脂红酸在汞电极上的吸附符合Frumkin等温武。测得吸附系数β=7.0×10~6,作用因素v=-0.92,吸附速率常数k_(ads)=9.7×10~(-8)cms~(-1)。In 0.2 mol L-1 acetate buffer solution, at pH 4.2-4.5, carminic acid exhibits a reversible adsorptive wave in single sweep polarogram. The electrode reaction is (H2L-)(ads) + 2H(+) + 2e reversible arrow (H2L/(-))(ads) H2L-, and H2L'(-) are the anthraquinone and alpha ihydroanthraquinone ions of carminic acid respectively. On the surface of mercury electrode, the adsorption of carminic acid obeys Frumkin adsorption isotherm, The adsorption coefficient (beta = 7.0 x 10(6)), the interaction factor (upsilon = -0.92), the amount of saturated adsorption (Gamma(a) = 1.39 x 10(-10) mol cm(-2)) and the adsorptive rate constant (k(ads) = 9.7 x 10(-8)cm s(-1)) have been determined.SCI(E)106549-553