الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The present work was undertaken to evaluate the impurities in some generic pesticides that are recommended for use in Egypt. The percentages of impurities were assessed within different chemical groups of 11 generic pesticides, and so violation percentages were calculated for the impurities found in these generic pesticides based on allowed percentages specified by FAO and IUPAC. Some chemical and physical properties were also assessed for the generic pesticides (melting point, acidity & alkalinity) and compared to those specified by FAO.
Impurities in generic pesticides were identified and their percentages were calculated using GC-MS, and the active ingredient content was identified using FTIR and NMR.
The obtained results showed the following:
1- The generic sample of carbosulfan from China was assessed and identified carbofuran as an impurity within the sample. Carbofuran was found to be (3.8%)which is higher than the allowed percentage specified by the FAO and IUPAC.
2- Impurities were assessed for 2 samples of generic chlorpyrifos from 2 different sources (Denmark & China). In this respect, the three following impurities were identified in Denamrk sample:
(0,0-diethyl 0-6-chloro-2-pyridal phosphorothioate).
(0,0-diethyl 0-5,6-dichloro-2-pyridyl phosphorothioate).
(0-ethyl 0,0-bis (3,5,6-trichloropyridin-2-yl) phosphorothioate).
Percentages of the impurities were calculated to be (0.184%, 0.729% and 0.241%) respectively.The generic sample from China only identified one impurity which was
(0-ethyl 0,0-bis (3,5,6-trichloropyridin-2-yl) phosphorothioate),
with percentage of (0.390 %).
It is worth noting that although sulfotep is the main impurity listed in FAO specifications for chlorpyrifos, as well as another impurity 3,5,6- trichloropyridionl (listed in FAO and IUPAC), the generic samples did not contain sulfotep or 3,5,6-trichloropyridionl.
3- Impurities were assessed for 3 generic samples of chlorpyrifos methyl from 2 different sources ( one from Denmark & two from China). Three impurities were identified in the sample in the first generic sample from China as following (3,5,6-Trichloro-N-methyl-2-pyridone) , (2-(5-chloro-2-methoxyphenyl)pyrrolidine) and )O,O-dimethyl O-(3-chloro-2-pyridinyl)phosphorothioate). Their concentrations were calculated to be (0.457%), (0.221%) and (0.137%) respectively.
However, one impurity was found in the second generic sample from China which was: (2-hydroxy-3,5,6-trichloropyridine) and its concentration calculated to be 0.478%.
While no impurities was found in generic sample from Denmark
Though FAO and IUPAC specify the impurity 0,0,0’,0’-tetramethyl dithiopyrophosphate, it was not identified in any of the generic samples.
4- Difenoconazole generic sample (from China) was assessed but did not show any impurities at the conditions used for detecting impurities within this study. However, it was noticed that the ratio of cis-trans isomers in the compound was 3:1 which is different than that found in the original sample (ranging from 0.7-1.5).
5- The generic sample of Fenamiphos from China was assessed and identified (ethyl 2- (s-methyl-2,4-bis(methylthio)phenyl)propan-2-yl phosphoromidate) as an impurity within the sample. Percentage of the impurity was (0.225%). It is worth noting that the FAO and IUPAC did not also specify any impurities for Fenamiphos.
6- The impurities for generic flusilazole were assessed but none were detected under the testing conditions used in this study. It is worth noting that the FAO and IUPAC did not also specify any impurities for flusilazole.
7- Two Chinese samples of generic lambdacyhalothrin were assessed for impurities, and one impurity was found in both samples and identified as (3-phenoxybenzaldehyde). Its concentration in the first sample was calculated to be 6.107% and in the second was 6.780%. Though triethylamine is the impurity specified by FAO & IUPAC for lambdacyhalothrin, it was not identified in the generic samples.
8- The impurities for the generic sample of metalaxyl were assessed and 2 impurities were identified to be:
Methyl N-(2,6-dimethylphenyl)N-acetyl-DL alaninate
Methyl N-(2,6-dimethylphenyl)N-(2-chloro acetyl)DL alaninate
The percentages for these impurities were 2.22% and 2.07% respectively. Though FAO and IUPAC specify the 2,6-dimethylanline as an impurity for metalaxyl, it was not found in the generic sample.
9- The generic sample of Oxyfluorfen from China was assessed and one impurity was identified as α-(4-chlorophenyl)-4,6-dimethoxy-3-methylindole-7-methanol) within the tested sample. Percentage of the impurity was (1.23%).in this respect , It is worth to note that the FAO and IUPAC did not specify any impurities for Oxyfluorfen.
10- The impurities were assessed for a sample for the generic sample of prochloraz from China and three impurities were identified to be:
(urea,N-(4-chlorophenyl)-N,N-dimethyl), (Hexachloro benzene) and (1,2,3,8,9-Penta chloro dibenzo [1,4] dioxine)
The estimated concentration were calculated to be (0.294%, 0.218% and 0.542%) respectively.
11- The impurities were assessed for a sample for the generic sample of thiobencarb from China and two impurities were identified to be: (S-(2-chlorobenzyl)-N,N-diethyl thiol carbamat) and the concentration was calculated to be (0.326%)and (N-[4-(acetylamino)phenyl]-1-methyl-4-nitro-1H-pyrazole-3-carboxamide) , calculated to be (0.213%).
The melting point, acidity and alkalinity were assessed for all generic samples and compared to the standard values found in the FAO specifications. It was found that acidity and alkalinity values match those found in FAO specifications. As for the melting point, most calculated values for the generic samples are very close to the original ones found in FAO specifications, and the variance does not exceed 2-3°C.
Reviewing the fore mentioned result it could be concluded that there has been a growing interest lately in researching the impurities accompanying pesticides despite the fact that they are present in small concentrations within the active ingredient. but the obtained data have shown that some of these impurities can be highly toxic to mammals and the ecosystem. both FAO and IUPAC have specified and published these impurities for 131 active ingredients. These publications were based on studies conducted by basic producers or mother companies for such pesticides.
However, a large number of pesticides are registered in the EPA and EU and their impurities have not been specified by FAO or IUPAC, and there is not enough information regarding these impurities due to the secrecy of registration data and the suppression of such data by the basic producers.
The present work is a simplified study to assess impurities in some generic pesticides used in the Egyptian market. It identifies some of the impurities that have not been specified by FAO and IUPAC since basic producers are no longer the only source for such pesticides. And with the invasion of countries like China or India to the market, who have adapted different synthesis and manufacturing processes than those adapted by basic producers, it was expected to find several impurities that were not specified before existing any information regarding their toxicity or allowed percentages. In addition, impurities identification requires advanced analytical methods such as those required for pesticides containing chiral carbon which has diastereomers and can be difficult to isolate using traditional methods.
The studies regarding impurities are dependent upon the analysis of several batches of the pesticide during its manufacturing to be certain of the percentage of impurities in the technical material within these batches, which is known as 5 batch analysis studies.
Unfortunately, such resources and facilities were not available to us while conducting our study.
There may be substantial differences in the chemical composition of technical-grade products of the same active ingredient manufactured under different conditions, from different row materials, or by different routes of synthesis. Resulting differences in impurity content may significantly affect the toxicological properties of pesticide products. relevant impurities are those that may exhibit pronounced toxic effects compared to the active ingredient, affect phytotoxicity or physical properties of formulation.
The first safety assessment of an active ingredient by a regulatory body considers toxicological data developed on a representative both of technical products, with the assumption that the material produced commercially by the original or generic manufactures has an equal or higher content of active ingredient and contains the same fewer impurities at equal or lower concentrations as the fully characterized technical product used in the toxicological tests. Three steps are essential for ensuring the safety of commercial technical grade pesticide produced by the original manufacturers or by generic manufacturers. First, the identity and chemical structure of the impurities must be elucidated. This should include positive identification of major (≥1%) and all toxicologically or environmentally relevant impurities, and characterization of minor.