Metalaxyl degradation

Businelli, M., Patumi, M., and Marncchini, C. Identification and determination of some metalaxyl degradation prodncts in lettuce and sunflower, J. Agric. Food Chem., 32(3) 644-647,1984. 

Buser H-R, MD Muller, ME Balmer (2002) Environmental behavionr of the chiral acetamide pesticide metalaxyl enantioselective degradation and chiral stability in soil. Environ Sci Technol 36 221-226. 

CASRN 57837-19-1 molecular formula C15H21NO4 FW 279.30 Soil. Little information is available on the degradation of metalaxyl in soil however, Sharom and Edgington (1986) reported metalaxyl acid as a possible metabolite. Repeated applications of metalaxyl decrease its persistence. Following an initial application, the average half-life was 28 d. After repeated applications, the half-life decreased to 14 d (Bailey and Coffey, 1985). 

Owen, W.J. and Donzel, B. Oxidative degradation of chlortoluron, propiconazole, and metalaxyl in suspension cultures of various crop plants, Pestic. Biochem. Physiol, 26 75-89, 1986. 

Metalaxyl Study of chiral separations to study microbial enantioselective degradation of metalaxyl in soil [535]... 

Monkiedje, A., Spiteller, M., Bester, K. (2003) Degradation of racemic and enantiopure metalaxyl in tropical and temperate soils. Environ. Sci. Technol. 37, 707-712. 

Laboratory studies on the degradation of metalaxyl, a transparent pesticide, indicate that photosensitization may be operative and the whole process seems to be favored in the presence of water. In general, photopersistence of soil adsorbates is greater in dry soils and at higher clay content [78]. 

Metalaxyl was lost more rapidly in soil at 23°C than the -counterpart (Fig. 9.20). The acid produced by hydrolysis of the ester, was the primary metabolite detected with the chiral configuration being retained. By using the racemic mixture, first-order rate constants for the R- and 5-enantiomers were found to be 0.060 and 0.015 day respectively. The degradation of the acid derivatives was also shown to be stereoselective, however, the 5-enantiomer was lost more rapidly than the 7 -form (0.030 vs. 0.014 day ). Starting with a racemic mixture the enantiomer ratio (ER = [5]/[R]) can be expressed as a function of the degradation rate constants of each enantiomer ... 

Figure 9.20 Degradation of rac-, (R)- and (5)-, metalaxyl in soil, (a) Degradation of mc-metalaxyl showing faster loss of the (ff)-enantiomer. (b) Degradation of (ff)-metalaxyl. (c) Degradation of (5)-metalaxyl showing a pronounced lag phase, (d) Plot of In ER (ER = [5]/[R]) with time giving a rate difference of 0.038 day and a hnear relation showing that the enantioselectivity was maintained until t > 60 day. [Reproduced with permission from H. Buser, M. D. Muller, T. Poiger, and M. E. Balmer, Environ. Set Technol. 36, 221 (2002). Copyright 2002, American Chemical Society.]...

Figure 2 Visual identification of analyte degradation in the injector and/or in the D column in the contour plot (right side) and in nonconverted chromatograms (left side) [1]. Peak identification (1) chlorothalonil, (2) vinclozolin, (3) metalaxyl, (4) penconazole, (5) procymidone, (6) myclobutanil, (7A, 7B) propiconazole diastereomers, (8) tebuconazole, (9B) iprodione, and (9A) iprodione degradation product.

Fig. 1 Electropherograms of metalaxyl enantitxneis in a series of slurry samples revealing the change in aiantioselective degradation pattern with incubation time. The first peak is /f-(+)-metalaxyl. Migration times vary with time due to changes in the CE column EOF. Source From Application of capillary electrophoresis to study the enantioselective transformation of five chiral pesticides in aerobic soil slurries, in J. Agric. Food Chem. ...

Soil thin-layer chromatography is very useful in the investigation of the translocation and degradation of pesticides in soil. These layers combined with silica layers allow study of the movement of the pesticides and their breakdown products as well. Photochemical oxidation of aiyldialkylthiourea herbicides on the soil surface can be investigated when these plates are exposed to sunlight (143). The sorption coefficients and the mobility of C-metalaxyl was investigated on three Brazilian soil... 

---