Electrolytic Chromatography and Coulometric Detection with the Column Electrode

A very rapid electrolytic analysis termed 'electrolytic chromatography', using a column electrode with glassy carbon grains, has been developed. The column electrode has been used not only for coulometric detection, but also for separation of metals, elimination of interfering elements, unification of oxidation state, and concentration of an element. Some analytical applications of electrolytic chromatography are introduced especially with radioactive nuclides. Down to 1.0 i.tl of a l02 M or 1000 ml of a l0_8 M solution can be analysed with satisfactory accuracy. INTRODUCTION There have been proposed many separation methods based on a heterogeneous phase formation, such as adsorption, ion-exchange, solvent extraction, etc. Recently advances have been made in the use of most of these methods, to transfer them from batchwise procedures into chromatographic procedures. In the present paper, the author reports on a new method of multi-stage separation using electrolytic deposition and dissolution. The new 'electrolytic chromatography'1 utilizes the principle of controlled potential electrolysis and it produces a separated and localized deposition of metals followed by stepwise dissolution. For the detection and determination of metal ions in the eluate, d.c. and a.c. amperometric, spectrophotometric, radiometric and coulometric methods were employed as necessary. The d.c. amperometric method seemed practical and versatile for use with most metals but lacked sensitivity. The a.c. amperometric method proved more sensitive than the d.c. amperometric method if the potential was selected exactly and maintained at the peak of the wave. The spectrophotometric method was also satisfactory for the detection of metal ions such as bismuth, copper and lead by using xylenol orange as the universal colour developer and by the proper selection of the wavelength. The use of radioactivity was extremely effective in the detection of trace amounts if the active isotope was available. The method of coulometric detection was the most successful in the sense that it is relatively sensitive and also versatile to most of the metals examined. The total set-up is shown in Figure 1. As seen from the figure, the carrier solution which contains the supporting electrolyte and is deaerated if