Short drop time, second harmonic alternating current polarography. Minimization of adsorption and amalgam effects

The use of short controlled drop times down to 50 ms in phase-selective second harmonic a.c. polarography is discussed. From the analytical point of view, apart from the smaller current per unit concentration, advantages are gained in many areas over the use of gravity controlled natural drop times. For example, some systems suffering from severe inhibition due to adsorption give close to the normal response at short drop times. The cadmium-tribenzylamine system is used to illustrate this aspect. The theory applicable to short drop times appears to be substantially the same as for the conventional method, except that for electrode processes forming amalgams, asymmetry arising from spherical diffusion terms is minimized. Use of a.c. cyclic voltammetry confirms that short drop time scale a.c. techniques do minimize amalgam formation effects, but other unexplained phenomena still remain.