THE ADAPTATION OF THE BECKMAN SPECTROPHOTOMETER TO MEASUREMENTS ON MINUTE QUANTITIES OF BIOLOGICAL MATERIALS

Abstract

The smallest volume that has been used with commercial photocolorimeters is about 1 ml. The sensitivity and optical system of the Beckman spectrophotometer (model D or DU) are such that it can be readily adapted to volumes of the order of 50 c.mm. (0.05 ml.) without sacrificing length of the light path through the colored solution. With volumes of this order of magnitude the size of sample required is so small that it has been easily possible to devise methods for determining a number of substances of nutritional significance on a single sample of finger blood (e.g. vitamin A, carotene, ascorbic acid). Since it seems likely that calorimetry or spectrophotometry on this scale may prove useful on other occasions, particularly with biological material, when the size of sample is limited, the means of adaptation is described, together with some data illustrative of the precision which can be expected.