| The pesticide prochloraz, IUPAC name is N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl] imidazole-1-carboxamide, is currently used in a great part of the world withinagriculture and horticulture due to its fungicidal effects, and it is a fungicide belonging tothe class of imidazoles. Prochlorza has been shown to act via multiple mechanisms ofaction in vitro as it antagonizes the androgen and the estrogen receptor and inhibitsaromatase activity.Commonly, the degradation of prochloraz in environment is firstly a breaking of theimidazole ring with the formation of N-propyl-N-[2-(2,4,6-trichlorophenoxy) ethyl]ethylurea(BTS 44 595) and N-formyl-N-propyl-N-[2-(2,4,6-trichlorophenoxy) ethyl]ethylurea (BTS 44 596), which are then degraded to 2, 4, 6-trichlorophenol (2, 4, 6-TCP),present in environment in both the free and conjugated forms, together with trace of2, 4, 6-trichlorophenoxyacetic acid.In order to determine residues of prochloraz in mushroom and its soil, and toprovide scientific gist for estimating the security of prochloraz in environment andestablishing secure, reasonable using guide line of prochloraz in mushroom. In this paper,the main body of the study is as follows:1. The method of determination of prochloraz residues in mushroom by solid phaseextraction-high performance liquid chromatography (SPE-HPLC) had been established.In this method, acetonitrile and celite 545 were added into representative sample, and themixture was homogenized at ultra speed. After filtrated, the extract was purified by aliquid-liquid partitioning process with NaCl aqueous and dichloromethane firstly. Thedichloromethane phase evaporated to dryness, and residue was dissolved withacetonitrile. Then, the organic phase was purified by PSA and C18 SPE tubes secondly. Atlast, after filtrating with millipore filter, the organic phase was detected by HPLC. In thismethod, the limit of detection (LOD, S/N＞3) was 0.038mg/L, the mean fortifiedrecoveries of prochloraz ranged from 82.6% to 100.3%, with relative standard deviation(RSD, %) in the region of 1.8%-9.2%. Comparing to gas chromatography assay method,which used in a great part of the domain, SPE-HPLC method had simplicity,expeditiousness, economic and wide in linearity characteristic. 2. The second assay method of determination of prochloraz residues in mushroomand soil is the combination of liquid chromatography-electrospary ionization massspectrometry (LC-ESI/MS). In this method, samples were extracted from mushroom orsoil with acetonitrile, then the extracts was salted out with NaCl and MgSO4. The organicphase was concentrated with gas and cleaning-up with PSA. After centrifugated, theorganic phase was filtrated with millipore filter, and detected by LC-MS. In this method,the mean fortified recoveries of prochloraz ranged from 88.5% to 99.2%, with relativestandard deviation (RSD, %) in the region of 2.0%-7.7%. Without any concentration, theLOD (S/N＞10) was 2.86μg/L. Using the SPE-LC-ESI/MS assay method to determinethe residues of prochloraz in mushroom and soil, it had simplicity, expeditiousness, highsensitivity, and low detection limit characteristic.3. Using LC-ESI/MS assay method to determine the prochloraz residues inmushroom and its soil samples, which come from field testing. The results of dynamicresidue from 2004 to 2006 revealed that the degradation of prochloraz in mushroom wasrapid, and in soil was slow, the half life of them were 3.5days and 20.3days.The results of dynamic residue of prochloraz in mushroom accord with minusexponential equation:2005 C=12.6561e-0.1981t, r=-0.9898;2006 C=21.2882e-0.2205t, r=-0.9746.And the results of dynamic residue of prochloraz in soil accord with minusexponential equation:2005 C=17.0077e-0.0333t, r=-0.9618;2006 C=63.4902e-0.0341t, r=-0.9620.The results of final residues from 2004 to 2006 indicated that both in mushroom andsoil, the residues amount were higher when the applied amount of prochloraz in fieldtesting was larger or the applied times of prochloraz in field testing was more than thecomparative groups. And both in mushroom and soil, the residues amount was lowerwhen the interval to harvest was longer than the comparative groups.4. In this paper, 2, 4, 6-trichlorophenol, which is the final metabolites of prochloraz,was also detected with gas chromatography assay method, to probe into the degradedmechanism of prochloraz in mushroom and soil. The results shown that, after appliedprochloraz in testing field, the amount of 2, 4, 6-trichlorophenol in mushroom increased,and it got the maximum at the 3th day, then it turned into decreasing; and the residues of2, 4, 6-trichlorophenol in soil increased all the while, but its uptrend is more smooth thanthe uptrend in mushroom. |
