Automated serum chloride analysis using the Apple computer

Abstract

Chloride analysis employing a coulometric technique is a well-established method. However, the equipment needed is specialized and somewhat expensive. The purpose of this paper is to report the development of the hardware and software to perform this analysis using an Apple computer to control the coulometric titration, as well as to automate it and to print out the results. The Apple computer is used to control the flow of current in a circuit, which includes silver and platinum electrodes where the following reactions take place: Ag → Ag+ + le- (at silver node) 2H2O + 2e- → 2OH- + H2 (at platinum cathode). The generated silver ions then react with the chloride ion in the sample to form AgCl. Ag+ + Cl- → AgCl(s). When all of the chloride ion has been titrated, the concentration of silver ions in solution increases rapidly, which causes an increase in the current between two silver microelectrodes. This current is converted to a voltage and amplified by a simple circuit. This voltage is read by the analogue-to-digital converter. The computer stops the titration and calculates the chloride ion content of the sample. Thus, the computer controls the apparatus, records the data, and reacts to the data to terminate the analysis and prints out the results and messages to the analyst. Analysis of standards and reference sera indicate the method is rapid, accurate and precise. Application of this apparatus as a teaching aid for electronics to chemistry and medical students is also described.