The long term objective of this study is the development of microspectrophotometric apparatus with sensitivities orders of magnitude greater than heretofore possible. The research project will investigate techniques for fabricating unique capillary cells to be used as microanalytical cuvettes. Experiments will be conducted to confirm light absorption linearity as a function of fluid analyte concentration for fluid sample volumes of as little as I microliter or less. Performance will be compared with the same measurements on a conventional spectrophotometer at I milliliter volumes for the same concentration ranges. The behavior of the capillary cells will be studied in the visible and ultra violet wavelength ranges. Spectrophotometric instruments with greatly enhanced sensitivity and very low fluid sample volume requirements will find ready acceptance in the research instrument market.