Rizwanul Haque

Binding of DDT to Lecithin

An interaction between DDT and lecithin is indicated by the reciprocal effects of each compound on the proton magnetic resonance spectrum of the other. The phosphoryl choline moiety of the lecithin and the benzylic proton of the DDT seem to be involved. The most pronounced response in the proton magnetic resonance spectrum of the lecithin produced by increasing concentration s of DDT was a change in the chemical shift of the resonance peak due to the protons of the choline methyl groups. Increasing concentrations of lecithin produced changes in the chemical shift of the resonance peaks of the benzylic proton and adjacent ring protons of the DDT. Equilibrium constant of 0.597 �0.015 molal-1 was obtained for this interaction.

Studies on the adsorption of selected polychlorinated biphenyl isomers on several surfaces

The adsorption-desorption characteristics of three selected PCB isomers on a soil and some of its constituents have been determined. The extent of adsorption for all surfaces follows the sequence hexachloro greater than tetrachloro greater dichloro for the isomers chosen. For an individual isomer, the adsorption rates increase in the following sequence: Del Monte, sand, illite clay, Woodburn soil, and humic acid. These results are discussed relative to environmental transport of the chemicals.

Kinetic and equilibrium study of the adsorption of 2,4-dichlorophenoxy acetic acid on some surfaces

Abstract A detailed equilibrium and kinetic study of the adsorption of 2,4-dichlorophenoxy acetic acid (2,4-D) on some mineral surfaces such as clays, silica gel, sand, alumina, and humic acid has been made. The equilibrium data have been explained with the Freundlich type isotherm, and a fit of the kinetic data with a theory proposed by Fava and Eyring was tried. The heat of adsorption as a function of surface coverage has been calculated. The heat of adsorption changes exponentially with the amount of 2,4-D sorbed. In most cases the heat changes are small, but the heat changes for silica gel and sand are larger compared to other surfaces. This has been discussed in the light of weak hydrogen bonding between 2,4-D and the surface material. Humic acid and illite adsorb more 2,4-D than other surfaces. The rate constant varies from 10−3 to 10−5 sec−1 depending on the surface. The activation energy in most of the cases is almost negligible. The rate data indicate a physical type adsorption.

Physical chemical properties of several organophosphates: Some implication in environmental and biological behavior

Abstract The organophosphates are a class of chemicals noted for high biological activity. Their potential for transport and persistence in the environment, based on physical chemical properties, has not been thoroughly studied. Certain physical chemical properties of several organophosphates were measured and compared to organochlorine compounds whose transport and persistence are better known. Of interest was the potential for toxicity to human and other nontarget organisms. Certain organophosphates were found to have surprisingly high partition coefficients. This suggested the possibility of uptake by organisms, as well as indicating a propensity for storage and hence, a longer persistence. Rates of hydrolysis are some indication of the likelihood of persistence.

Binding of bis(p-chlorophenyl) acetic acid with bovine serum albumin

Abstract The binding of bis( p -chlorophenyl) acetic acid with bovine serum albumin has been monitored by observing the changes in the relaxation times of bis( p -chlorophenyl) acetic acid proton magnetic resonance peaks. The addition of bovine serum albumin to an aqueous solution of bis( p -chlorophenyl) acetic acid increased linewidths in a manner suggesting rapid, reversible binding. Line broadening was found to be greater for the ring protons than for the benzylic proton, indicating that the ring presents the stronger binding site. The equilibrium constant has been approximated. The binding results are discussed in terms of environmental and toxicological considerations.

Binding of organophosphate insecticides to lecithin: A proton magnetic resonance study

Abstract The interaction of four vinyl-type organophosphate insecticides with a phospholipid lecithin has been studied by proton magnetic resonance technique. The vinyl proton of organophosphate showed a low field chemical shift change when lecithin was added to a CCl 4 solution of the former. When organophosphate insecticide was added to a dilute solution of lecithin the choline protons peak also showed small chemical shift changes. These chemical shift changes suggest that the most probable binding site in the interaction involves a hydrogen bond formation between the vinyl proton and oxygen atom of phosphatidyl group of lecithin. Chemical shift data has been used to calculate the equilibrium constant of the interaction.

Studies on the vapor behavior of selected polychlorinated biphenyls.

The vapor loss of several PCB isomers from stainless steel planchets surfaces has been studied. Experiments were carried out under two different conditions. In one case, the vapor loss was observed from 2 molecular layers of PCB, while in the other series, the loss from approximately 200 molecular layers was observed. In both cases the loss of PCB from the surface was substantial, although the controlling mechanism of vapor loss was different. In the first case, the transport was approximated by a simple first order rate law, whereas in the latter case, it was a diffusion controlled process. In general, the vapor loss decreased with increasing number of chlorine atoms present in the isomer. The 4,4(1)-dichlorobiphenyl showed a deviation as compared to others indicating that such factors as the electronic distribution, position of chlorine atom on the biphenyl ring and symmentry of the molecule are also important in discussing the vapor transport.