Biomedical subjects
Publications and source records attributed to F A Gunther.
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The degradation of ring-labeled 14C-phenthoate in a moist sandy loam and silty clay loam soil was studied. Phenthoate degradation was attributed to the action of extracellular heat-labile soil enzymes which converted to its carbon ester hydrolysis product, phenthoate acid. Thus, rate of phenthoate degradation was greatly retarded in autoclaved soil, but was equally rapid in nonsterile soil under both aerobic and anaerobic conditions. Degradation was also rapid even at a soil treatment of 100 ppm. Phenthoate acid was extensively degraded to 14CO2 by soil organisms under aerobic conditions, but due to unfavorable factors, degraded only by slow first-order kinetics under anaerobic conditions and at the 100 ppm fortification level under aerobic conditions. Phenthoate and phenthoate acid were confirmed as the principal soil components by isolation and identification by IR and NMR data.
Acetyl-Clx (x = 0,1,2 or 3) and nitroso derivatives of carbaryl, 1-naphthol. 5-hydroxycarbaryl, and 1,5-naphthalenediol were synthesized. Compounds were characterized by infrared, mass, and nuclear magnetic resonance spectroscopy. N-chloroacetylation (Cl = 0,1,2, or 3) of carbaryl was readily accomplished through the pyridine-catalyzed reaction of carbaryl with the appropriate acid chlorides. Trichloroacetylation was also possible through the pyridine-catalyzed reaction with the anhydride. N-nitrosation could also be done readily. N-nitroso- and N-trichloroacetyl carbaryl underwent decomposition to carbaryl on exposure to atmosphere moisture and could be maintained in the pure state only with difficulty. The other derivatives were stable under normal storage conditions.
Gas chromatographic (GLC) detection of aryl N-methylcarbamates as the N-acetyl-Clx or N-nitroso derivatives of the intact molecule was explored using carbaryl as the model compound. These derivatives were designed for use with the microcoulometric detector for chlorine and the solution conductivity detector for nitrogen but response to the electron capture detector was also studied. GLC characteristics of the derivatives were evaluated in terms of thermal stability and detector response. N-Trichloracetyl and N-nitroso carbaryl underwent extensive decomposition in the GLC system. Although the N-monochloroacetyl derivatives were also subject to thermal decomposition, they gave sufficient linearity and sensitivity with the microcoulometric detector for analysis at the residue level. N-Acetyl carbaryl was thermally stable and the response of electrolytic conductivity and the electron capture detectors were adequate for residue analysis.
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Parathion sorbed to dust can persist as dislodgable residues on citrus leaves. Semi-logarithmic plots of parathion dislodgable residue data were initially linear for the 6 soils studied and then a distinct change to lower rates occurred with 5 of the soils. As initial rates and the residue level at the rate change are dependent on the soil, foliar dust is implicated as a causative factor in the non-uniformity of residue dissipation rates. Soils can influence the conversion of parathion to paraoxon. Paraoxon levels differed greatly with the type of soil and were highest with Pike's Peak clay. Thus, its use in a parathion formulation could produce relatively high levels of paraoxon dislodgable residues. It is significant that, second to Pike's Peak clay, the highest total dislodgable residue level was found with Visalia silt loam which was collected from a grove where a worker poisoning episode had occurred in 1974.
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The extent and selectivity of transfer of the components of the polychlorinated biphenyl (PCB) Aroclor 1254 from a sandy loam soil into carrots under field conditions were studied. Five of the gas chromatographic peaks of this PCB, designated 1, 4, 5, 8, and 10 with increasing retention time, were quantitated. After 23 months the concentration of peak 10 in soil remained unchanged, but peak 1 decreased by 34 +/- 3%. Lesser chlorinated peak 1 was translocated from soil into carrots five to eight times more than highly chlorinated peak 10. The residues (in ppm) of peaks 1 and 10 in carrot root were 30 to 50% and 3 to 4%, respectively, of that of the soil: The degree of translocation for PCBs was of the same order of magnitude as for the persistent organochlorine insecticides. Carrot foliage contained 1 to 6% as much of the PCB residues (in ppm) as the soil. Since peak 1 was present in about 2.5 times greater amount than peak 10 in foliage, whereas it was present in about five to nine times greater amount in roots, direct foliar contamination by soil dust is suggested.
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