Sinusoidal a.c. polarography

The resultant peak current is greater than the dilfusion current recorded with a conventional d.c. polarograph by a factor of ten or even more. The method thus shows enhanced sensitivity and it can be used to make measurements with solutions having concentrations as low as 10 6 — 10 7M and with a resolution of the order of 0.05 V. 

can with advantage be replaced by an S.M.D.E. (Section 16.8), and it is possible to use platinum, graphite, or glassy carbon electrodes, in which case the procedure should be termed voltammetry rather than polarography. 

In this procedure, a constant sine wave a.c. potential of a few millivolts is superimposed upon the usual d.c. potential sweep. The applied d.c. potential is measured in the usual way and these results are coupled with measurements of the alternating current. 

If the values of the a.c. current are plotted against the potential applied by the potentiometer, a series of peaks are obtained as illustrated in Fig. 16.11(a) the normal d.c. polarogram of the same solution is also shown (b). 

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