IN-VITRO DETECTION OF FOLPET AND ITS DEGRADATION OF PHTHALIMIDE IN AQUEOUS-SOLUTIONS AND IN YEAST SUSPENSIONS

Folpet, N-(trichloromethylthio)-phthalimide, hydrolyzes in aqueous sol utions to phthalimide, carbon dioxide, hydrochloric acid, and sulfur. Using a slightly modified HPLC method, the decrease in folpet concentr ation and the simultaneous increase in phthalimide were investigated i n different aqueous solutions. If the solution contained Saccharomyces cerevisiae cells, folpet was adsorbed by the yeast cells because of i ts lipophilic character. When the folpet concentration in the presence of yeast cells was high, only folpet was isolated after an incubation time of two hours, and at low folpet concentration only phthalimide w as isolated. We thus conclude that yeast cells influence the decomposi tion of folpet. The transition from folpet to phthalimide detection to ok place at 6.7 x 10(-8) mg folpet/yeast cell. In this range the yield of phthalimide was 27% of the original folpet amount. At folpet conce ntrations higher than 6.7 x 10(-8) mg folpet/yeast cell 70% to 80% of original amount was present as folpet, at lower concentrations 75% to 90% was present as phthalimide. These observations were made in soluti ons containing intact yeast cells, and the substance phthalimide was s table under these conditions for months. However, if the yeast suspens ion was heated to 70 degrees C for two hours, neither folpet nor phtha limide was detected. It would, therefore, appear that destroyed yeast cells also affect the decomposition of folpet and phthalimide. We conc lude from these results that folpet and phthalimide in aqueous solutio n can be analyzed quantitatively and qualitatively as long as no micro organisms such as yeasts are present.