Design and Development of an Energy-Dispersive X-ray Spectrometer:

Abstract

Contribution of scientific research to local and international journals from Africa and indeed Kenya is weak in comparison to other regions. One of the main problems is the non-availability of reliable and affordable analytical instrumentation. Energy-Dispersive X-ray Fluorescence (EDXRF) analysis is a special analytical technique for trace elements in that it is economical and easy to use. Its analytical capacity has the advantage of having multi-elemental characteristics and satisfactory speed. Convectional EDXRF analysis is used in identifying toxic trace elements in the general environment, trace elements in airborne particles for source apportionment, investigation of micronutrients in different ecosystems and agriculture practices among other areas of scientific investigations. A new EDXRF Spectrometer has been built and installed at the Institute of Nuclear Science and Technology, College of Architecture and Engineering, University of Nairobi. It is a new research tool that has improved local analytical detection limits of heavy metals in environmental and air pollution samples. A Siemens type D x-ray tube-stand was modified to facilitate x-ray irradiation of a Mo-secondary target. The target is a glued disk that was cut from a 1 mm thick Mo plate of 99.99 % purity. The fluoresced secondary x-rays propagate through three Ag collimators giving a near monochromatic Mo characteristic x-rays for sample excitation. The disk holder was designed to be easily removable, from the Al-measuring head, thus allowing the flexibility of carrying out experiments using different secondary targets. Air samples on Teflon filters and water samples on Cellulose filters were analyzed. The results were better than those obtained in previous spectrometer setups. The detection limits of trace elements improved by a factor of 10. The spectrometer is an extra facility for direct analysis of trace elements in air and other environmental samples.