THERMAL-ANALYSIS OF CONTROLLED-RELEASE FORMULATIONS BASED ON ENTRAPMENT OF A LARVICIDE IN CROSS-LINKED CARBOXYMETHYLCELLULOSE

Thermal analysis of controlled-release formulations of fenthion, prepa red by its entrapment in cross-linked carboxymethylcellulose and carbo xymethylcellulose-gelatin matrices was carried out by thermogravimetri c analysis and under accelerated storage conditions. Thermograms of sa mples of sodium carboxymethylcellulose, cross-linked polymer samples, and the formulations were studied. The thermogravimetric analysis show ed improved heat resistance and retention of fenthion or its decomposi tion products in the formulated samples. The decomposition maximum of technical-grade fenthion was 260 degrees C and the corresponding weigh t loss was about 90%, whereas fenthion or its decomposition products a ppear to be retained up to temperatures ranging from 400 to 500 degree s C in the formulations. The half-life of fenthion in the mechanical m ixture with the carrier polymer was found to range from 19.92 to 29.98 days, whereas in the formulated samples, it was found to range betwee n 41.54 and 113.35 days. (C) 1994 John Wiley and Sons, Inc.