A RATIO FORMING POINT SCANNING PHOTODENSITOMETER

Abstract

This thesis describes some aspects of the design and construction of a point scanning dual wavelength ratio forming photodensitometer for the analysis of thin media chromatograms. By utilizing dual wavelength ratio forming techniques, the effects of spatial variations in light transmission of the chromatographic support medium are greatly reduced, thus greatly increasing the sensitivity of chromatographic analysis by optical transmission methods. In addition, point scanning, as opposed to conventional fixed slit scanning, overcomes the limitations imposed by the non-linearity of the optical transfer function of the medium upon the geometry of the chromatographic zone at higher concentrations of separated chromogen. Preliminary results here indicated roughly a 25 fold increase in sensitivity of this double light beam system over conventional single light beam systems. It is expected that further refinements to the system will increase the sensitivity to higher limits.