The determination of l-ascorbic, and dehydro-l-ascorbic plus diketo-l-gulonic acids in microgram quantities of tissue was described. The procedure used is an adaptation to the micro scale of macro methods based on spectrophotometric measurements of reactions involving 2,6-dichlorophenol indophenol and 2,4-dinitrophenylhydrazine, and it is well suited to serial analyses on large numbers of samples because of its relatively great simplicity and speed. The standard deviation in the ascorbic acid method is about 2% corresponding to about 3 mµg. of ascorbic acid for the equipment used. With pipettes and cuvettes of smaller capacity a reduction in the latter value by about one-third can be obtained without inconvenience.
