A Rapid Method for Calculation of the Total Amount of Absorbing Substance in Microextracts

The amount of a light-absorbing substance in tissue components can be determined in situ or after extraction by photographic or photoelectric measurement of the absorption. In the case of an extract, spheres (1) or lens-shaped droplets (2) can be used as microcuvettes. With spheres, a determination of the total absorption is straightforward since the volume of the absorbance per unit length can be determined directly. In the second case, it has so far been necessary to integrate the absorption determined for about 40 points (2). We propose to approximate the densitometer curve (Fig. 2) of the lens-shaped drops of RNA extract (Fig. 1) as a parabola which would permit the use of a simple equation based on three measurements for determining absorption in this paraboloid-shaped "cuvette" model.