Construction and Evaluation of a Solid State Photometer as an Alternative to Conventional Spectrophotometers

Abstract

A Solid State Photometer has been constructed using light emitting diodes (LEDS) as light source and a photodiodes as photodetector. Rate constants as functions of reactant concentration, hydrogen ion concentration and ionic strength were obtained using the kinetic set and compared with those obtained from a Unicam SP 1750 uv-visible Spectrophetometer. Statistical parameters applied to the results obtained with the two system showed that there was no significant difference between the two methods at 0.05 confident level. The solid state photometer can be interfaced to a computer (Datadise Pro for windows) to automatically record the rate of change of absorbance or transmittance. This arrangement provides the user with digitized version of the experimental signal which can be processed in a multitude of increasingly complex way in order to extract as much chemical information as possible. Apart from the fact that the LEDs are cheap, compact and commercially available, equipment constructed from this system have small size, light weight, low power consumption and negligible warm up time. The solid state photometer is a rugged, reliable, low-cost alternative to commercially available spectrophotometers. Its use is therefore recommended as a compliment or an alternative to the expensive spectrophotometer.