A Rapid Sensitive Method for Determination of Low Concentrations of 2, 4-Dichlorophenoxyacetic Acid in Aqueous Solution

Abstract

Germinating seeds of the common cucumber (Cucumis sativus) were found to be very sensitive to low concs. of 2,4-dichlorophenoxyacetic acid. Utilizing this fact the authors devised a bio-assay method for this acid. The procedure involves placing 25 seeds (var. Early Fortune) on a filter paper in a 6-in. Petri dish and adding 15 ml. of an aqueous soln. of the 2,4-D under test. After the dishes are covered they are stored in the dark at 28[degree]C for 96 hrs., after which period the lengths of the primary roots and shoots are measured in mm. These are expressed in terms of % of a control in which no acid was present, and compared with a standard curve. Initial surface sterilization of the seeds, selection of pregerminated seeds of certain root lengths, and special equipment are not necessary. The method is sensitive to 0.005 ppm. and is applicable up to 5 ppm.