Abstract: A chromatograph detection system for differentiating pure components of a chromatogram for accurate measurement or collection of such components. The light beam passing through a single detector flow cell is split and absorbance is detected at two differing wavelengths. Undesirable overlapping components are eliminated by scaling the chromatogram at one wavelength to equal the chromatogram at the other wavelength, and then subtracting the chromatograms. Purity of component substances is determined by continuously dividing the chromatogram signals to determine the absorbance ratio and its characteristics over time.