A modification of the fluorescence method for micro inulin determinations

Abstract

The fluorescence method of Vurek and Pegram is one of the most commonly used techniques to measure tubular fluid insulin concentration in micropuncture studies. This method has the advantages of relative simplicity and low cost. However, the authors recently discovered an inherent, systematic error in this method when employed in the settling of prolonged experiments. A consistent decrease in blanks, background fluorescence of the dimedone phosphoric acid blacks, insulin standards and tubular fluid samples was discovered when transferring into reagent filled microcuvettes was carried out over several hours. The following report describes the manner in which the error was defined and outlines a technical modification which results in its correction.