Malathion physical

Results of volatilization and leaching estimations are reported for six pesticides that span a wide range of the physical/chemical properties that affect fate at the soil/air interface. The pesticides are Mirex, toxaphene, methoxychlor, lindane, malathion, and dibromochloropropane (DBCP). These particular pesticides were chosen for discussion here because they illustrate the methods for assessing the fate of organics at the... 

Chemical/Physical. Hydrolyzes in water forming cis-diethyl fumarate, tra/ s-diethyl fumarate (Suffet et ah, 1967), thiomalic acid, and dimethyl thiophosphate (Mulla et al., 1981). The reported hydrolysis half-lives at pH 7.4 and temperatures of 20 and 37.5 °C were 10.5 and 1.3 d, respectively (Freed et al, 1977). In a preliminary study, Librando and Lane (1997) concluded that the hydrolysis of malathion is very sensitive to pH. At pH 8.5, <5% of the malathion remains after 2 d, whereas at pH 5.7, >90% remains after 20 d. 

A column performance test is used to ensure the proper condition of columns and the stability of retention parameters. Because CWC-related chemicals greatly differ both chemically and physically from each other, the test chemicals have been selected so that their physical, chemical, and retention properties are different, and so that they elute evenly over the whole chromatogram. The use of the following chemicals in a column performance test is recommended trimethylphosphate, 2,6-dimethylphenol, 5-chloro-2-methylaniline, tri-n-butylphosphate, dibenzothiophene, malathion, and methyl stearate. The concentration of test chemicals depends on the sensitivity of detectors. The... 

PHYSICAL PROPERTIES clear yellow to deep brown liquid a solid below 37 F garlic-like odor slightly soluble in water miscible with most organic solvents including alcohols, ketones, ethers, esters, aromatic and alkylated aromatic hydrocarbons, and vegetable oils solubility is limited in certain alkane hydrocarbons petroleum ether is soluble to about 35% in malathion MP (3.0 C, 37.4 F) BP (156-157 C, 313-315"F at 0.7 mmHg) DN (1.23 g/mL liquid at 25 C) LSG (1.21 at 20 C) VD (11.4) REL DN vapor/air mixture (1.00 at 20 C) VP (4 x 10 mmHg at 20 C). 

Controlled-release solid formulations of selected volatile organophosphorus pesticides (malathion, DDVP, sumithion, chlorpyriphos, and sulprofos) were studied by Szente [33]. These solid formulations exhibited negligible vapor pressure and preserved their entrapped pesticide content even at elevated temperature. Malathion and chlorpyriphos formulations showed increased physical stability, and resulted in an effective masking of the unpleasant smell while the complex formulations existed as dry solid. Sulfluramid is an expensive insecticide that is lost by volatilization, but complexation to j8-CyD reduced the loss [21]. 

B. Matrix Incorporation. Matrix incorporation is probably the most common method for the preparation of physically bonded pesticides. Five methods illustrate the wide variety available for the preparation of incorporated aldicarb and dif lubenzuron (Dimilin Both are carbamate insecticides. Selected methods were used for the matrix adsorption of the following organic insecticides Abate, Dursban, malathion, and naled ... 

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