Prevention of adsorption of .ALPHA.,.BETA.,.GAMMA.,.DELTA.-tetrakis(1-methylpyridinium-4-yl) porphine and its cadmium(II) chelate on a glassware surface.

Abstract

Complexation of cadmium(II) with α, β, γ, δ-tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) was examined in a micellar solution of sodium dodecylbenzenesulfonate (SDS). Although complexation in the absence of SDS quantitatively occurs within 5 min in the pH range 9 to 11.5, TMPyP and its cadmium(II) chelate in a basic solution give rise to adsorption on glassware surface, thus resulting in large errors in the determination of cadmium(II). The adsorption of TMPyP and its chelate was prevented by addition of SDS after complete complexation. When SDS was added before complexation, 40 h were required for full color development. The concentration of SDS should be higher than the critical micelle concentration (1 × 10-3 mol dm-3). SDS was also effective in preventing adsorption of other TMPyP chelates, such as lead(II), zinc(II) and copper(II), on the surface of glassware.