Study On The Residue Methods And Degradation Dynamical Rhythm Of Ethylene Dibromide Pesticide In Fruit And Canned Fruit

Ethylene Dibromide is a highly toxic pesticide and was prohibited in China. Far beyond the current technical conditions, the latest research reports on detection of Ethylene Dibromide residues in fruit was published in 1980s', and research on the canned fruit has not been reported by the mass media. It, therefore, is significantly important to carried out dibromoethane residues research for human health, and for to reduction of unnecessary agricultural loss.In this article, using chromatography technology, the author systematically studied the methods of determination Ethylene Dibromide pesticide residues in fruit including canned one. Then the study explored the degradation dynamical rhythm of chlorpyriphos in fruit. The results of the study are as follows:1. The method of operational conditions of pre-treatment with gas chromatography was introduced for determining Ethylene Dibromide pesticide residues in fruit and canned fruit. The effectiveness experimental conditions of extraction include:a mixture solvent of hexane/acetone (2:l,v/v), the fresh fruit and canned fruit's Sodium sulfate anhydrous concentration for 15% and 5%. GC conditions:HP-5 column; temperature programme:50℃(6 min)15℃/min 100℃(5min) 30℃/min 280℃(5 min); ingection port temperature:250℃; detector temperature:300℃; carrier gas:Nitrogen (purity>99.999%); flow rate:1.0 mL/min; injection mode:splitless; ingection volume:1μL. The recoveries obtained from fresh fruit and canned fruit samples(n=5) are in the ranges of 93.29%～106.75%, and 96.96%～105.55%, with the relative standard deviations(RSD) in the ranges of 1.58～8.34 and 2.27～7.72. The Method Detection Limit (MDL) was 0.5μg/kg. The satisfactory results are gained in the determination of fruit samples.2. A new method of gas chromatography-mass spectrometry whith use to determine Ethylene Dibromide pesticide in fruit and canned fruit was proposed. The MDL was 1μg/kg. GC-MS operation condition:Chromatographic column: fused silica capillary column, HP-530m×0.25μm(id)×0.25μm (film thickness) or equivalent; temperature programme:40℃(5 min) 15℃/min 100℃(1 min) 20℃/min 280℃(10min); Carrier gas:Nitrogen (purity>99.999%), flow rate:1.0 ml/min; ingection port temperature:250℃; GC-MS transfer temperature:280℃; ion source temperature:230℃; injection mode:splitless; ingection volume:1μL; ionization mode:EI; oniztion energy:70 ev; solvent delay:3min; detection mode:SIM. The average recoveries of fruit and canned fruit were 96.20%～106.59% and 94.94%～110.50%, with the RSD of 4.30～10.51 and 4.37～10.25. This method reached the international level.3. An effective and rapid analytical method for determination of EDB residues in fruit and canned fruit was developed. The headspace extraction conditions were optimized. It was found that the maximal extraction into the headspace was attained at 70℃for 55 min. The MDL was 2μg/kg. The average recoveries were 77.89%～94.86%, with the RSD of 4.07～10.66. The method has been proved to be simple, accurate and used for the fast determination of Ethylene Dibromide in fruit and canned fruit.4. Degradation of EDB residue in fruit was conducted. Samples were extracted by the distillation method, and determined by gas chromatography (GC-ECD). The result showed that initial Ethylene Dibromide residue on citrus and bananas were high. The dynamics of Ethylene Dibromide residue in citrus and bananas followed first order kinetics. The half life time (DT50) in fresh fruit was 0.64d and 0.81 d in the pericarp, and 0.84 d and 0.82 d in the pulp.5. The stability of Ethylene Dibromide standard solution was studied by GC-ECD. The results demonstrated that EDB standard solution(1～400μg/L) was stable while it was properly stored in refrigerator no less than 2.5 months. Thus the study provided theoretical details for period of validity of stable standard solution.