[Behavior of Ethephon residues on tomatoes. Part I. Green house tomatoes].
The preparation Flordimex, which contains Ethephon (2-chloroethanephosphonic acid) as the active ingredient, is used for accelerating the ripening of tomatoes. During the years 1974--1977, tomato samples from 89 experiments were tested for Ethephon residues. The determination was performed gas chromatographically using alkali flame ionization detector as 2-chloroethanephosphonic acid dimethyl ester; the detection limit of the method was 0.01 mg/kg. The observed results must be evaluated on the basis of the permissible value (1 mg/kg) stipulated for vegetables by the Ministry of Health of the GDR. 1--2 days after the use of concentrations of 0.1%, 0.2%, 0.3% and 0.4%, respectively, the following mean residue values were found: 0.31, 0.50, 0.39 and 0.91 mg/kg, respectively, which decreased but slowly. This leads to the conclusion that formulation concentrations of more than 0.3% and applications of more than 6 1/ha should not be allowed by the Ministry. In case of repeated uses, 3-week intervals are imperative. Under the above-mentioned conditions of use, the mean residue values determined 4--5 days after application approximated 0.6 mg/kg. This period is to be regarded as a tentative waiting-period that must be respected after the treatment of glasshouse tomatoes with Flordimex.