Determining Ascorbic A c i d in Large Numbers Plant Samples
OF
E. H. LUCAS, Michigan Agricultural
Experiment Station, Ea* Lansing, Mich.
A procedure for the determination 01 ascorbic acid in plant material is described which has been iovnd useful in plant breeding and other plant research. It allows the ,&id determination of ascorbic acid in a large number of sampler of plant material with a rstidsctory degree of accuracy.
I 'THE N
course of plant breeding experiments the author d e sired t o know the ascorbic acid content of many plants at different stages of development. Available methods for the determination of this substance in plants were too timeconsuming to assure a reliable comparison of values from different sources inasmuch as changes might ocour in the tissue while awaiting analysis. Hence i t seemed imperative to devise a method which would permit the assay of many samples in the shortest poasihle time. This paper describes a procedure which has enabled the author and three student assistants to make 500 w a y s for ascorbic acid per day and to compare the results thus obtained with those of published methods. It was obvious from early experiments that a more effective and rapid meam of disintegrating plant tissue than hand grinding was necessary in order to gain speed in the aseay as a whole. Hence a mechanical device (Figure 1) which makes possible the Simultaneous disintegration of ten samples within 2 t o 6 minutes, depending upon the texture of the tissue, was designed for the purpose and constructed in the machine shop of Michigan State College.
adequate for the author's purpose. Morell made use of the socalled Waring Blendor for the maceration of plant samplcs. The efficiency of this Blendor was compared with that of the grinding machine described, The Blendor permits the use of much larger samples, and therefore reduces the error, but this advantage is lost if very small samples have to be disintegrated. Furthermore, the Blendor is ineffective for macerating certain types of plant material, such as seeds and fibrous tissue. These difficulties could not be overcome by the use of smaller Blendor cups as described by Davis (5)and Benne (1). ASSAY
The Waring Blendor was used in most eases, but where i t did not work well with a particular tissue the grinding machine was used.
A new method of handling very large samples, especially if a number of leafy plants should be examined together, has, been successfully tested. A small portion of B sample is placed xu the container with the liquid necessary for the extraction, and the mehinV i q q r m t r d long cnuiisli to ohtnin a homugcneouv mixturr. The m x t r is stopped, mother part of thc sample is ndded, and tlie D ~ O W is JU continued ~~ w t i l the entire r;amule has bcen disinteGted. I n such a manner. voluminous samdles weighing over 160 p a m i van be srinlyzd, but the C X I M C ~ S
