Square-wave polarography, development

He hoped that oscillopolarography, with controlled ac current, would bring discovery of new phenomena. Further development of analytical methods proved him wrong on this point, mostly because of complex conditions of electrolysis. On the other hand, he was very impressed by the achievements of square-wave polarography, the potential of which he fully appreciated. His enthusiasm was only dampened by the sometimes erratic performance of the expensive commercial square-wave polarograph (Figure 13), which in the fifties carried about 90 vacuum -tubes. The probability that one of them would not function properly was relatively high. 

The state of development and capability of square-wave polarography/voltammetry has been reviewed [8], [33]. 

Several other techniques related to polarography have been developed over the years, mainly to increase the sensitivity, but also to reduce the time of measurement and the amount of mercury used. The most common among them are differential-pulse (DP) and square-wave polarography (SW). These methods of employing the SDME for analytical applications have been widely treated in the literature and will not be discussed here. 

In connection with the square-wave technique, mention can be made of high-frequency polarography, also called radiofrequency polarography and developed by Barker53, in which a sinusoidal radio-frequency cu, (100kHz to 6.4 MHz) square-wave modulated at co2 (225 Hz) is superimposed on to the dc potential ramp as the wave form includes (apart from additional higher... 

We will consider five subtopics tast polarography and staircase voltammetry, normal pulse voltammetry, reverse pulse voltammetry, differential pulse voltammetry, and square wave voltammetry. Tast polarography, normal pulse voltammetry, and differential pulse voltammetry form a sequence of development rooted historically in polarography at the DME. To illustrate the motivating concepts, we will introduce each of these methods within the polarographic context, but in a general way, applicable to both the DME and SMDE. Then we will turn to the broader uses of pulse methods at other electrodes. Reverse pulse voltammetry and square wave voltammetry were later innovations and will be discussed principally outside the polarographic context. 

The first voltammetric method was polarography. Electrolysis at a dropping mercury electrode was first described by Heyrovsky in 1922, and the first po-larograph constructed by Heyrovsky and Shikita in 1925. Heyrovsky was awarded the Nobel Prize in 1959. Further developments of the method are linked with the names of Matheson and Nichols (oscillo-polarography), Heyrovsky (derivative polarography), and Barker (square wave and pulse polarography). 

Since its introduction, the technique has been associated with important applications in many branches of chemistry a principal example is in analytical chemistry, including that of organic substances. The method provides a simple technique for the detection and estimation of electroreducible ions and compounds present in solution at very small concentrations. The sensitivity of conventional polarography allows the measurement of concentrations of various ions to approximately 10 mol liter. Several procedures have been developed to extend the analytical range, notably the compensation method and the square wave polarographic technique introduced by Barker and Jenkins. " ... 

For the fast-scan technique in HPLC, in which the potential is varied rapidly across its full range, the method of square-wave voltammetry (- Analytical Voltammetry and Polarography) has provided the basis for the development of a rapid-scan square-wave voltammetric detector ... 

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