Degradation Dynamics And Residue Of Prochloraz In Freshness Preservation Of Guava

In this paper, the degradation dynamics and the final residues of prochloraz in the guava preservation were determined by gas chromatography mass spectrometry (GC-MS), and residue detection method of prochloraz was studied and optimized with it, while the safety of prochloraz used for guava preservation was briefly analyzed and evaluated. The results are as follows:1. Method of prochloraz residues determined by GC-MSThe extraction method of prochloraz residues in guava was studied by orthogonal test, the results showed that the rate of prochloraz extracted by acetonitrile was higher than acetone and methanol, and impurities and pigment in guava extracted by acetonitrile was lower,so in this study, acetonitrile was chosen to be the extraction solvent of prochloraz in guava, the amount was that 25g sample was added 50mL acetonitrile, homogenized time was 2min. Purification effect of amino column, LC-18 column, silicagel column, carbon and amino column, florisil column to extract liquid of prochloraz in guava was studied by adding standard prochloraz to guava, the results showed that purification effect of amino column, carbon and amino column, florisil column to extract liquid of prochloraz in guava were better, for amino column, under each 15mL 99:1,95:5 acetone+dichloromethane,99:1 acetonitrile+toluene,99: 1,99:5 acetonitrile+dichloromethane solvent, recoveries of prochloraz were 105.37%,95.50%,93.15%,90.83%,91.91%; For carbon and amino column, under each 25mL 99:1,95:5 acetone+dichloromethane,95:5 acetonitrile+toluene,99: 1,99:5,90:10 acetonitrile+dichloromethane solvent, recoveries of prochloraz were 96.71%,99.56%,97.70%,93.38%,92.56%,90.11%; For florisil column, under each 25mL 95:5 acetone+dichloromethane,99:1 acetonitrile+toluene,99 1 acetonitrile+dichloromethane solvent, recoveries of prochloraz were 91.87%, 95.21%,90.15%, all above are to meet guava purification needs, but consider the economic factors, we chose florisil, eluting solvent was 99:1 acetonitrile+toluene, the dosage was 25 mL.GC-MS test conditions of prochloraz:Column temperature 120℃(hold 1 min)→280℃(15℃/min, hold 10 min); not split injection; injector temperature 260℃; transmission line temperature 280℃; ion source temperature 250℃; carrier gas: Helium gas, purity≥99.999%, flow rate:1.0mL/min. Prochloraz SIM ion:180(Q, quantitative ion),266,308. Under these conditions, retention time of prochloraz 15.55min. 2. Residual dynamics of prochloraz of guava stored in room and low temperatureResidual dynamics of 45% prochloraz emulsion oil in water in guava preservation were studied according to spraying once, sampling time after time. The results show that:Degradation curve equations of prochloraz in guava stored in room temperature and soaked in 500 mg/kg,1000 mg/kg,1500 mg/kg liquor and stored in low temperature and soaked in 1000 mg/kg liquor were:C=2.1652e-0.0644t, C=3.7145e-0.0524t, C=6.2059e-0.0386t, c=4.1652e-0.0509t, and the correlation coefficient R were-0.9716,-0.9290,-0.9303,-0.9901, and the half lives were 10.8d,13.2d, 18.0d,13.6d. Residual degradation dynamics of them all accorded with C=Coe-kt, and all had high relativity, and in two storage conditions, degradations were very fast.3. Final residues of prochloraz of guava stored in room and low temperatureStored in room temperature for 10 days with in 500mg/kg, 1000mg/kg, 1500mg/kg liquor soaked 2 times and in low temperature with in 1000mg/kg liquor soaked 2 times, The prochloraz residues of guava were 2.5237 mg/kg,5.2858 mg/kg, 7.7981 mg/kg,5.4523mg/kg; For 15 days, the residues were 2.0630 mg/kg,4.4322 mg/kg,6.1910mg/kg,4,8651mg/kg; For 25 days, the residues were 1.1766mg/kg, 3.3932mg/kg,3.9967mg/kg,3.5155mg/kg. And stored in room temperature for 10 days with in 500mg/kg, 1000mg/kg,1500mg/kg liquor soaked 3 times and in low temperature with in 1000mg/kg liquor soaked 3 times, The prochloraz residues of guava were 3.4628mg/kg,7.3653 mg/kg,11.3487 mg/kg,7.4111 mg/kg; For 15 days, the residues were 3.0473mg/kg,5.7734mg/kg,8.4460mg/kg,6.0027mg/kg; For 25 days, the residues were 2.1046mg/kg,3.8374mg/kg,4.5103mg/kg,3.8792 mg/kg. Prochloraz residues in guava are as follows:residues soaked in high concentration liquor is higher than in low concentration, soaked 3 times higher than 2 times, stored in low temperature slightly higher than in room temperature.4. Safety evaluation of prochloraz in guava preservationDipping in normal recommended concentration of 900 times dilution (500mg/kg) for 1 time, interval of 7 days, the residue of 45% prochloraz emulsion oil in water in guava is 1.2793mg/kg and it is safe for customer, Dipping in concentration of 450 times dilution (1000mg/kg) for 1 time, interval of 15 days, the residues are 1.6198mg/kg and 1.9384mg/kg and it is also safe as food for customer.