Jiuxin Chen | PubMed Health

PubMed2005

Development of a controlled release formulation based on a starch matrix system.

Controlled release formulation (CRF) of the insecticide acetamiprid was made using tapioca starch, urea and sodium borate. The data show the recovery of this CRF process is > 95.43%, there is no obvious difference with increase of sodium borate added, however, with the increase of urea in the mixture, the formulation has a decrease recovery. In stability test, the decomposition rate of acetamiprid CRF was less one tenth than that of the acetamiprid emulsifiable concentrate (EC) under UV radiation. The release kinetics of acetamiprid from granules with variation content of urea, sodium borate and granule sizes were evaluated in water under laboratory condition. The release data were fitted to the generalized model Mt/Mz = kt(n), where Mt/Mz is the percentage of insecticide released at time t, k and n are constants, and n is constant that indicates the mechanism of release. The results indicated that the release of acetamiprid was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, T50, was also calculated for the comparison of formulations. The results showed that the formulation with the increasing urea in formulation had the higher value of T50, which means a slower release of the active ingredient, while that the formulation with the increasing sodium borate in formulation had the lower value of T50, which means a faster release of the active ingredient. It was also found that as the size of this formulation decreased, the release of the active ingredient was faster.

Borates↗

PubMed2005

HPLC/UV analysis of chlorfenapyr residues in cabbage and soil to study the dynamics of different formulations.

The chlorfenapyr analysis method of residue, its degradation and final residue in soil and cabbage were studied. Residues of chlorfenapyr were extracted from soil and cabbage with acetone/water, purified by liquid/liquid partition and chromatographic column, concentrated to a small volume, and then determined by HPLC equipped with UV detector. The mean accuracy of analytical method were 93.3% and 90.6% in soil and cabbage, respectively; the precision (repeatability) in cabbage ranging from 1.7% to 11.8%, in soil ranging from 2.8% to 11.2%; the precision (reproducibility) in cabbage ranged from 2.2% to 12.1%, in soil it ranged from 2.4% to 11.5%. The minimum detectable amount of chlorfenapyr was 0.65 ng, the minimum detectable concentration was 0.0162 mg kg-1. The degradation of chlorfenapyr formulations in soil and cabbage was determined. The results showed that chlorfenapyr nanoformulation and suspension concentration degradation in soil coincided with C=0.2538 e-0.1612t, C=0.537 e-0.1754t, respectively; the half-lives were about 4.3 d and 3.9 d, respectively. Two kinds of chlorfenapyr formulation degradation in cabbage coincided with C=4.0431 e-0.3103t, C=6.9611 e-0.2686t respectively; the half-lives were about 2.2 d and 2.6, d, respectively. When chlorfenapyr formulations were applied according to the double recommended dose, the final residues in cabbage were much lower than the USA EPA's maximum residue limit of 1 mg kg-1 in vegetables. The degradation rate of chlorfenapyr nanoformulation was faster than that of suspension concentration, and the former residue was also less in soil. Therefore, a harvest interval should be more than 5 d, and a dosage of 900 mL/hm2 was suggested for chlorfenapyr suspension concentration, which could be considered as safe to human beings and animals. Chlorfenapyr nanoformulation was safer than suspension concentration, its harvest interval and dosage can attain a high level.

Brassica↗