Pesticides, chlorinated Dieldrin

A chromatographic analysis for the chlorinated pesticide Dieldrin gives a peak with a retention time of 8.68 min and a baseline width of 0.29 min. How many theoretical plates are involved in this separation Given that the column used in this analysis is 2.0 meters long, what is the height of a theoretical plate ... 

Polychlorinated Pesticides. A once substantial but now diminished use for DCPD is in the preparation of chlorinated derivatives for further use or synthesis into pesticide compounds (see Insectcontrol technology). Soil permanence and solubiUty of the products in human fatty tissues have considerably restricted the use of these compounds. The more prominent chlorinated pesticides were aldrin, dieldrin, chlordane, and heptachlor, all of which use hexachorocyclopentadiene as a starting material. Aldrin and dieldrin are no longer used in the U.S. Chlordane and heptachlor are stiU produced, but only for export use. 

Picer and Picer [357] investigated the recovery from fO litre samples of seawater of 0.1-1.0 xg/l chlorinated pesticides (DDT, DDE, TDE, and Dieldrin), and 1-2 xg/l PCB (Aroclor 1254). The recovery of Mirex during these steps varied between 80% and 90%. Losses of the investigated chlorinated hydrocarbons during these steps were 10-30% for about 10 ng pesticides. 

GC is coupled with many detectors for the analysis of pesticides in wastewater. At the present time the most popular is GC-MS, which will be discussed in more detail later in this section. The flame ionization detector (FID) is another nonselective detector that identifies compounds containing carbon but does not give specific information on chemical structure (but is often used for quantification because of the linear response and sensitivity). Other detectors are specific and only detect certain species or groups of pesticides. They include electron capture,nitrogen-phosphorus, thermionic specific, and flame photometric detectors. The electron capture detector (ECD) is very sensitive to chlorinated organic pesticides, such as the organochlorine compounds (OCs, DDT, dieldrin, etc.). It has a long history of use in many environmental methods,... 

Terrence Collins is the Thomas Lord Professor of Chemistry at Carnegie Mellon University who contends that the dangers of chlorine chemistry are not adequately addressed by either academe or industry, and alternatives to chlorine and chlorine processors must be pursued. He notes, Many serious pollution episodes are attributable to chlorine products and processes. This information also belongs in chemistry courses to help avoid related mistakes. Examples include dioxin-contaminated 2,4,5-T, extensively used as a peacetime herbicide and as a component of the Vietnam War s agent orange chlorofluorocarbons (CFCs) polychlorinated biphenyls (PCBs the pesticides aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, lindane, mirex, and toxaphene pentachlorophe-... 

Estimated half-lives for chlorinated hydrocarbon pesticides vary widely [16, 22] Aldrin, 1-9 Dieldrin, 3-7 Chlordane, 1-8 Heptachlor, 1-4 and DDT, 3-10 years. Half-lives for PCBs range from one year to 16 years [23]. Other types of pesticides, e.g. organophosphates, triazines, carbamates and ureas, are generally less persistent [16, 24],... 

Very little recent information on concentrations of endrin in water could be found in the available literature. Unlike DDT, chlordane, aldrin/dieldrin, and a variety of other chlorinated pesticides, endrin was never used extensively in urban areas. This is reflected in the results from EPA s Nationwide Urban Runoff Program, which showed no detections in 86 high-flow water samples from 51 urbanized watersheds from 19 cities (Cole et al. 1984). Analysis of EPA STORET monitoring information from ambient surface water showed a significant percentage of detections for endrin (32% of 8,789 samples), but most were near the detection limits, with a national median concentration of 0.001 ppb (Staples et al. 1985). A similar analysis of STORET data for endrin aldehyde showed that this compound was not found in 770 samples of ambient surface water. More recently, endrin was not detected (detection limit 49 ng/L [0.045 ppb]) in surface water from the Yakima River Basin, Washington (Foster et al. 1993). However, in... 

The inclusion of a third-order term did not yield a significantly better fit (p > 0.6). There are no indications that PAHs and nonpolar chlorinated hydrocarbons have a different Ks - Ko dependence. By contrast, the moderately polar pesticides such as hexachlorocyclohexanes (HCHs), dieldrin, chlorpyrifos, heptachlor, and trifluralin (open and closed diamonds in Figure 3.3) have Ks values that are 0.6 log units lower than PAHs and PCBs with similar Ko values (p < 0.001). 

Dieldrin—which belongs to the 12 POPs banned by the Stockholm convention and is in the same class of other pesticides named drins, such as aldrin and endrin—possesses six aliphatic chlorine atoms on a polycyclic skeleton. The multiphasic dechlorination, in the presence of A336, isooctane, aqueous KOH, Pd/C, and hydrogen, proceeded with a different selectivity and degree of dechlorination, depending on the choice of catalyst system, and base concentration. It always required the base and was favored by the presence of A336. It produced a mixture of products derived from the subsequent removal of chlorines, up to a small percentage of monochlorinated derivative. ... 

That some chemicals persist for long periods has been recognized for many years. Most of the pesticidal chemicals that came into wide use in the 1930s and 1940s were chlorinated organic compounds such as DDT, dieldrin, chlordane, kepone, toxaphene, and several others. 

The acute and/or chronic nature of the toxicity of a chemical should be part of any decision-making process about its use or subsequent release. The focus cannot be solely on reduction of acute hazards, which tends to be easily achievable. The majority of cases in which chemicals have been released into the environment, only to cause serious ecological impacts over large spatial scales, were usually identified after many years, and at chronic low-dose exposures, with low acute toxicity to nontarget organisms. The classic examples of DDT and other chlorinated pesticides such as dieldrin and toxaphene, along with PCBs, exemplify the flaws in an approach that focuses on acute hazards, with more recent examples being the perfluorinated... 

Several widely used pesticides are highly chlorinated polycyclic compounds derived from hexachloropentadiene. They include Aldrin, Dieldrin, and Chlordane. Use of these substances is to be curtailed greatly because of undesirable environmental effects. 

When reviewing this list of pesticides, it can be seen that there are many different classes of pesticides (i.e., the chemical characteristic of that pesticide that makes it toxic). In other words, different chemicals are toxic because of their different chemistry. The industrial chemicals are basically petroleum compounds that may or may not contain chlorine. The combination of all these different compounds ultimately influences the toxic diversity of the chemical mixtures we all consume. It is also important is to note that some pesticides have been banned from use in the United States (e.g., dieldrin is listed as being banned). All of these banned pesticides were no longer in use in the United States by the late 1970s and early 1980s. 

The presence of a pesticide determined on one column must be confirmed on an alternate column. Also, certain pesticides coeluting on one column can be separated by using another column. For example, 4,4 -DDD and Endosulfan-II coeluting on SP-2250/SP-2401 can be effectively separated on the OV-1 packed column. Conversely, 4,4-DDE and Dieldrin coeluting on OV-1 are better separated on SP-2250/SP-2401 column. Mary chlorinated pesticides may coelute even on... 

The American Public Health Association [97,98] published an early gas chromatographic method for the solvent extraction and gas chromatographic determination of 11 chlorinated insecticides in water samples in amounts, down to 0.005mg L 1 p,p -DT)E, p,p -DDT, Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, Lindane, Isodrin and Methoxychlor. The insecticides Carbophenothion, Chlordane, Dioxathion, Diazinon, Ethion, Malathion, Parathion methyl, methyl Trithion, Parathion, Toxaphene and VC-13 may be determined when present at higher levels. Also, the chemicals chlordane, hexachlorobicycloheptadiene and hexachlorocyclopentadiene, which are pesticide manufacturing precursors, may be analysed by this method. 

Cyclodienes are an important group of chlorinated pesticides. The group hep-tachlor includes insecticides such as chlordane, aldrin, dieldrin, endosulfan, and heptachlor and its epoxide. These are used for the control of a variety of plant pests in agriculture and household environments. The entry of cyclodienes to the global market has created easy management for the control of crop pests. They appeared after World War II as tools to protect food crops and control diseases from pests. In fact, humans were protected from malaria, typhus, and loss of food crops by pesticides. 

Tissues such as fat, blood or liver can be examined for residues of the more stable chlorinated hydrocarbon pesticides. In most cases these tissues are available as a result of elective survery, autopsy or biopsy. Exposure to DDT results in some storage of the parent compound in body fat. A large portion, however, is metabolized and stored as DDE (jJ). Aldrin and hepta-chlor are similarly transformed and stored as dieldrin and hepta-chlor epoxide. Levels of the urinary metabolite DDA have been used to assess exposure or body burden of DDT (10, 11, 12). Hexachlorobenzene and the various isomers of hexachlorocyclo-hexane are stored in fat as the parent compound but a small... 

Chlorinated Pesticides. The major metabolic degradation pathways for toxaphene in all organisms are probably reductive dechlorination and reductive dehydrochlorination. In some cases, oxidative dechlorination has been observed to result in hydroxy derivatives, acids and ketones.76 Aldrin is transformed into dieldrin in biotic as well as abiotic transformation processes. 

Use of the techniques just described resulted in the identification and concentration values of the pesticides shown in Table III. The major pesticide components of the dust were DDT and chlordan, with DDE and Ronnel following closely. The remaining compounds, hepta-chlor epoxide, 2,4,5-T, and dieldrin, were present in relatively minor proportions. These seven pesticides accounted for a major portion of the organic chlorine content however, certain peaks are still unidentified. 

As an example of differences in soil residue persistence between the organophosphates and chlorinated hydrocarbon pesticides, parathion and malathion residues were present at the 0.1 p.p.m. level within 8 days of application whereas aldrin [according to Lichtenstein (23)] when applied at the same concentration, persisted 5 months longer as did aldrin and dieldrin at 40% of the applied dosage. Decker et al. (12) report that aldrin and dieldrin residues in soils never exceeded 13.2% of the total applied when tested one year after the last application. Other workers (24) have reported that on a loamy soil, under existing weather conditions, aldrin and dieldrin residues were present at a level of approximately 20% of the total applied insecticidal dosage over a 5-year period. 

Synthetic organic compounds are a vast group of man-made chemicals here we consider only a small subset including the polychlorinated biphenyls (PCBs) and various chlorinated organic pesticides (e.g., DDT, chlordane, and dieldrin), for which there are particular environmental... 

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