2.3.4- Trichloro-4-pyridinol

M.A. Gonzalez-Martinez, R. Puchades, A. Maquieira, JJ. Manclus and A. Montoya, Automated immu-nosensing system for 3,5,6-trichloro-2-pyridinol application to surface water samples. Anal. Chim. Acta 392,113-123 (1999). 

The degradation half-life time (Tb 1/2) of chlorpyrifos is 7.1 days in seawater (Schimmel et al. 1983), and 53 days in distilled water (Freed et al. 1979). Degradation is usually through hydrolysis to produce 3,5,6-trichloro-2-pyridinol and phosphorthioic acid (Brust 1966 Smith 1966, 1968 Marshall and Roberts 1978). Temperature, pH, radiation, and metal cations all significantly affect chlorpyrifos Tb 1/2 in water half-life is decreased with increasing water pH, temperature, sunlight, and metal cation concentrations (Brust 1966 Mortland and Raman 1967 Smith 1968 Schaefer and Dupras 1969, 1970 Meikle and Youngson 1970 Menconi and Paul 1994). 

Smith, G.N. 1968. Ultraviolet light decomposition studies with Dursban and 3,5,6-trichloro-2-pyridinol. Jour. Econ. Entomol. 61 793-799. 

Surface Water In an estuary, the half-life of chlorpyrifos was 24 d (Schimmel et al., 1983). Photolytic. 3,5,6-Trichloro-2-pyridinol formed by the photolysis of chlorpyrifos in water. Continued photolysis yielded chloride ions, carbon dioxide, ammonia, and possibly poly-hydroxychloropyridines. The following photolytic half-lives in water at north 40° latitude were reported 31 d during midsummer at a depth of 10 cm 345 d during midwinter at a depth of 10 ... 

Chemical/Physical. Hydrolysis products include 3,5,6-trichloro-2-pyridinol, 0-ethyl O-hydrogen-0-(3,5,6-trichloro-2-pyridyl)phosphorthioate, and 0,0-dihydrogen-0-(3,5,6-trichloro-2-pyridyOphosphorothioate. Reported half-lives in buffered distilled water at 25 °C at pH values of 8.1, 6.9, and 4.7 are 22.8, 35.3, and 62.7 d, respectively (Meikle and Youngson, 1978). 

The hydrolysis half-life in three different natural waters was approximately 48 d at 25 °C (Macalady and Wolfe, 1985). At 25 °C, the hydrolysis half-lives were 120 d at pH 6.1 and 53 d at pH 7.4. At pH 7.4 and 37.5 °C, the hydrolysis half-life was 13 d (Freed et al, 1979). At 25 °C and a pH range of 1-7, the hydrolysis half-life was about 78 d (Macalady and Wolfe, 1983). However, the alkaline hydrolysis rate of chlorpyrifos in the sediment-sorbed phase were found to be considerably slower (Macalady and Wolfe, 1985). In the pH range of 9-13, 3,5,6-trichloro-2-pyridinol and 0,0-diethyl phosphorothioic acid formed as major hydrolysis products (Macalady and Wolfe, 1983). The hydrolysis half-lives of chlorpyrifos in a sterile 1% ethanoFwater solution at 25 °C and pH values of 4.5, 5.0, 6.0, 7.0, and 8.0 were 11, 11, 7.0, 4.2, and 2.7 wk, respectively (Chapman and Cole, 1982). 

Chlorpyrifos is stable to hydrolysis in the pH range of 5-6 (Mortland and Raman, 1967). However, in the presence of a Cu(lf) salt (i.e., cupric chloride) or when present as the exchangeable Cu(II) cation in montmorillonite clays, chlorpyrifos is completely hydrolyzed via first-order kinetics in <24 h at 20 °C. It was suggested that chlorpyrifos decomposition in the presence of Cu(II) was a result of coordination of molecules to the copper atom with subsequent cleavage of the side chain containing the phosphorus atom forming 3,5,6-trichloro-2-pyridinol and 0,0-ethyl-0-phosphorothioate (Mortland and Raman, 1967). 

CASRN 55335-06-3 molecular formula C7H4CI3NO3 FW 256.47 Soil. In soil, triclopyr degraded to 3,5,6-trichloro-2-pyridinol and 2-methoxy-3,5,6-trichloropyridine (Norris et al, 1987). The major route of dissipation from soil is likely due to microbial degradation (Newton et al, 1990). 

Plant. Fewer and Owen (1989) found 3,5,6-trichloro-2-pyridinol as the major metabolite in plants. Cultured soybean cells metabolized triclopyr to dimethyl triclopyr-aspartate and dimethyl triclopyrglutamate which can be rehydrolyzed to form the parent compound. 

Qilorpyrifos reacted with fi ee chlorine to form chlorpyrifos oxon, which is more toxic than the parent compound. Both compounds further hydrolyze to a more stable product, 3,5,6-trichloro-2-pyridinol [110]. 

Human subjects who ingested chlorpyrifos once daily for 4 weeks showed depression of plasma cholinesterase but were symptomless at a dose of 0.1 mg/kg. When four repeated doses were applied to the skin of human volunteers for 12 hours each, doses of 25 mg/kg depressed plasma cholinesterase but caused no symptoms. Chlorpyrifos and its principal metabolite, 3,5,6-trichloro-2-pyridinol, are rapidly eliminated, predominantly in the urine. ... 

The chlorpyrifos example described in Appendix B illustrates another caveat related to biomarkers that are urinary metabolites. A metabolite can sometimes appear in urine not only as a result of parent-chemical uptake and metabolism but also as a result of uptake of the metabolite from environmental media (Tu et al. 2005 Wilson et al. 2003). Thus, the biomarker for chlorpyrifos, 3,5,6-trichloro-2-pyridinol (TCP), occurs in a wide variety of environmental media, and the concentration in foods surpasses that of the parent chemical (Morgan et al. 2005). If the intake of the metabolite from environmental sources is substantial in comparison with that of the parent chemical, as in the case of chlorpyrifos and TCP, the extrapolation of urinary biomarker concentration to parent-chemical exposure dose is uncertain. 

Morgan, M.K., L.S. Sheldon, C.W. Croghan, P.A. Jones, G.L. Robertson, J.C. Chuang, N.K. Wilson, and C.W. Lyu. 2005. Exposures of preschool children to chlorpyrifos and its degradation product 3,5,6-trichloro-2-pyridinol in their everyday environments. J. Expo. Anal. Environ. Epidemiol. 15(4) 297-309. 

Dickson, W. (1956) The vapour pressure of l l p p -dichlorodiphenyl trichloroethane (D.D.T.). Trans. Farad. Soc. 52, 31-35. Dierberg, F.E., Pfeuffer, RJ. (1983) Fate of ethion in canals draining a Florida citrus grove. J. Agric. Food Chem. 31, 704—709. Dilling, W.L., Lickly, L.C., Lickly, T.D., Murphy, P.G., McKellar, R.L. (1984) Organic photochemistry. 19. Quantum yields for 0,0-diethyl 0-(3,5,6-trichloro-2-pyridinal) phosphorothioate and 3,5,6-trichloro-2-pyridinol in dilute aqueous solutions and their environmental transformation rates. Environ. Sci. Technol. 18, 540-543. 

McKellar, R.L., Dishburger, H.J., Rice, J.R., Craig, L F., Pennington, J.J. (1976) Residues of chlorpyrifos, its oxygen analogue, and 3,5,6-trichloro-2-pyridinol in milk and cream from cows fed chlorpyrifos. J. Agric. Food Chem. 24, 283-286. 

A United States study examined the aggregate exposures of preschool children to chlorpyrifos and its degradation product, 3,5,6-trichloro-2-pyridinol (TCP) (Morgan et al., 2005). Samples that were collected included duplicate diet, indoor and outdoor air, urine, solid and liquid food, indoor floor dust, play area soil, transferable residues, and surface wipes (hand, food preparation, and hard floor). Generally, levels of chlorpyrifos were higher than levels of TCP in all media, except for solid food samples. For these samples, the median TCP concentrations were 12 and 29 times higher than the chlorpyrifos concentrations at homes and day-care centres,... 

J.V. Sancho, O.J. Pozo, F. Hernandez, Direct determination of chlorpyrifos and its main metabolite 3,5,6-trichloro-2-pyridinol in human serum and urine by coupled-column LC-ESI-MS-MS, Rapid Commun. Mass Spectrom., 14 (2000) 1485. 

Coupled-column LC-MS for the determination of chlorpyrifos and its main metabolite 3,5,6-trichloro-2-pyridinol in human serum and urine [28]. 

Determination of Chlorpyrifos and Its Metabolite 3,5,6-Trichloro-2-Pyridinol in Bananas and Tap Water... 

Sample preparation Water was extracted with hexane for chlorpyrifos (a) and benzene for 3,5,6-trichloro-2-pyridinol (TCP) (b) banana samples were prepared using standard Food and Drug Administration procedures based on extraction, solvent partitioning, and silica gel or alumina column chromatography. 

In addition to the above-described alkyl phosphates, a few less common metabolites can be mentioned, e.g. 3,5,6-trichloro-2-pyridinol (TCP). TCP is a major product of esterase cleavage of the OPi chlorpyrifos and chlopyrifos-methyl." ° Urinary TCP, like other... 

Aprea C, Betta A, Catenacci G, Lotti A, Magnaghi S, Barisano A, et al. Reference values of urinary 3,5,6-trichloro-2-pyridinol in the Italian population - vahdation of analytical method and pre-hminary results (multicentric study). J AOAC Int 1999 82 305-12. 

Chlorovrifos. Prior applications of 3,5,6-trichloro-2-pyridinol, the hydrolysis product of chlorpyrifos, increased the persistence of chlorpyrifos (Table III). At the end of a 3-week incubation, there was about 5 to 10% increase in chlorpyrifos recovered in pyridinol-pretreated soils as compared with control soils. Increased persistence of a parent compound in soil pretreated with its degradation product is new to the literature. 

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