Rapid, Phase-Sensitive, Three-Electrode Alternating Current Polarography

Previously, short controlled drop times have been employed with considerable advantage in ac polarography to permit faster scan rates of potential and short recording times. In this work, the possibility of using 3-electrode phase-sensitive detection with this so-called “rapid” ac polarographic technique has been investigated. Results show that theoretical relationships derived for natural drop time ac polarography can be extended to the rapid ac method. Thus, with 3-electrode phase-sensitive instrumentation, excellent discrimination against the charging current is still obtained at short controlled drop times. In fact, the degree of discrimination under rapid conditions was better than with natural drop time phase-sensitive ac polarography. This was particularly evident at high frequencies. With the rapid phase-sensitive ac technique, copper(II) and cadmium(II) could be detected down to the 5 × 10^-7M to 1 × 10^-6M level. The introduction of phase-sensitive readout to the rapid ac technique, therefore, provides a considerable improvement to results reported previously with non phase-sensitive instrumentation. Indeed, the technique appears to be highly attract.ve in many aspects, having the advantage of permitting fast scan rates, and thus short analysis times, while maintaining excellent discrimination against the charging curren., This is in contrast to other polarographic techniques where the use of short drop times necessarily results in a lowering of ability to discriminate against the charging current, and therefore a loss in sensitivity.