Use of an Atomic Absorption Spectrophotometer for Colorimetric Analysis Michael A. Hildon Roan Consolidated Mines Research and Demlopment Depdrfment, P.O. Box I O , Kalulushi, Zambia MANYANALYTICAL LABORATORIES, particularly those engaged in metallurgical analysis, now rely almost exclusively on atomic absorption spectrophotometry for instrumental analysis. Some trace analysis, however, is still better carried out colorimetrically. There are a number of similarities between colorimetry and atomic absorption spectrophotometry in principle and in instrumentation; in both cases there is a source, an absorbing medium, a wavelength selector, and a detector. The source in a UV/visible spectrophotometer is a continuum, but in most inorganic analysis only the absorbance of a solution at a specific wavelength is measured. Thus a hollow cathode lamp, which produces a line spectrum, may equally well be used if there is a line at the required wavelength. A number of lamps, notably iron and vanadium, have extremely complex spectra, and, therefore, make convenient sources. The only modification necessary to convert an atomic absorption spectrophotometer to a colorimeter is the provision of a cell holder to hold an absorption cell in the position usually occupied by the flame. The limitation of this proposal is that absorbance us. wavelength scans cannot be made, but manual plots can be drawn by selecting wavelengths at suitable intervals and measuring the absorbance.
0.4C
0-3C
W
U
2
0.2c
0
K
SIm
