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1.
The stability of lycopene in an olive oil/tomato emulsion during thermal processing (80-140 °C) was studied. Initially, the degradation of total lycopene (all-E plus Z-forms) occurred quickly at temperatures above 100 °C. However, a nonzero plateau value, depending on the processing temperature, was attained after longer treatment times. Besides degradation, the isomerization of total-Z-lycopene as well as the individual isomerization of all-E-, 5-Z-, 9-Z-, and 13-Z-lycopene was studied in detail. After prolonged heating, the isomer conversion reached a temperature-dependent equilibrium state. The degradation of total lycopene and the isomerization could be described by a fractional conversion model. The temperature dependency of the corresponding reaction rate constants was quantified by the Arrhenius equation. The activation energy of degradation was estimated to be 28 kJ/mol, and the activation energy of overall (all-E and total-Z) isomerization was estimated to be 52 kJ/mol.  相似文献   

2.
Degradation parameters of purified anthocyanins from purple-fleshed potato (cv. Purple Majesty) heated at high temperatures (100-150 °C) were determined. Purified anthocyanins, prepared by removing salts, sugars, and colorless nonanthocyanin phenolics from the crude extract, were monitored and quantified using HPLC and spectrophotometry for heat-induced degradation products. Separation of colorless phenolics from the anthocyanins was confirmed using HPLC at two wavelengths, 280 and 520 nm. The degradation kinetics of purified anthocyanins followed a first-order reaction with reaction rate constants (k values) of 0.0262-0.2855 min(-1), an activation energy of 72.89 kJ/mol, thermal death times (D values) of 8.06-8789 min, and a z value of 47.84 °C over the temperature range of 100-150 °C. The enthalpy and entropy of activation were 59.97 kJ/mol and -116.46 J/mol·K, respectively. The antioxidant capacity in the purified anthocyanins, measured by DPPH and ABTS assays, was increased after the thermal treatment, indicating antioxidant activities of degradation products in the samples.  相似文献   

3.
The reaction between the triplet excited state of riboflavin and amino acids, peptides, and bovine whey proteins was investigated in aqueous solution in the pH range from 4 to 9 at 24 degrees C using nanosecond laser flash photolysis. Only tyrosine and tryptophan (and their peptides) were found to compete with oxygen in quenching the triplet state of riboflavin in aqueous solution, with second-order rate constants close to the diffusion limit, 1.75 x 10(9) and 1.40 x 10(9) L mol(-1) s(-1) for tyrosine and tryptophan, respectively, with beta-lactoglobulin and bovine serum albumin having comparable rate constants of 3.62 x 10(8) and 2.25 x 10(8) L mol(-1) s(-1), respectively. Tyrosine, tryptophan, and their peptides react with the photoexcited triplet state of riboflavin by electron transfer from the tyrosine and tryptophan moieties followed by a fast protonation of the resulting riboflavin anion rather than by direct H-atom abstraction, which could be monitored by time-resolved transient absorption spectroscopy as a decay of triplet riboflavin followed by a rise in riboflavin anion radical absorption. For cysteine- and thiol-containing peptides, second-order rate constants depend strongly on pH, for cysteine corresponding to pKaRSH = 8.35. H-atom abstraction seems to operate at low pH, which with rising pH gradually is replaced by electron transfer from the thiol anion. From the pH dependence of the second-order rate constant, the respective values for the H-atom abstraction (k = 1.64 x 10(6) L mol(-1) s(-1)) and for the electron transfer (k = 1.20 x 10(9) L mol(-1) s(-1)) were determined.  相似文献   

4.
The oxidation of linolenic acid (LNA) and soy lecithin was studied by differential scanning calorimetry (DSC) with linear programmed heating rates (non-isothermal mode). The interpretation of the shape of DSC curves is discussed, and it has been concluded that temperatures of the extrapolated start of heat release are the most reliable data for the rapid estimation of the oxidative stability of lipid materials. The Ozawa-Flynn-Wall method was used to calculate the kinetic parameters of the process: for LNA autoxidation the activation energy, Ea, and pre-exponential factor, Z, are 66 +/- 4 kJ/mol and 1.5 x 10(7) s(-1), respectively, and the autoxidation of lecithin is described by Ea = 98 +/- 6 kJ/mol and Z = 9.1 x 10(10) s(-1). Values of Ea and Z can be applied for calculation of the overall first-order rate constant of autoxidation at various temperatures, k(T). For the two studied lipids the comparison of k(T) values shows the inversion of their oxidative stabilities; that is, below 167 degrees C lecithin is more stable than LNA, k(T)lecithin < k(T)LNA, and above that temperature (termed the isokinetic temperature) k(T)lecithin > k(T)LNA. The calculated inversion of oxidative stabilities can be an explanation of similar observations for other pairs of lipids if the results of accelerated tests measured at temperatures above 100 degrees C are compared with the results obtained at temperatures below 100 degrees C.  相似文献   

5.
Activated sodium peroxydisulfate has the potential to in situ destruct many organic contaminants because of the generation of the stronger oxidant sulfate radical. From photochemical activation of peroxydisulfate in flash-photolysis experiments, the bimolecular rate constants for the reaction of sulfate radical with glyphosate (1.6 × 10(8) M(-1) s(-1)) and paraquat (1.2 × 10(9) M(-1) s(-1)) at 25 °C were obtained. Thermal activation of peroxydisulfate was shown to degrade the herbicides clomazone, paraquat, and glyphosate. Although the herbicide degradation was observed to take place in less than 1 h, the mineralization of the organic carbon required longer reaction times, because of the formation of stable organic intermediates. For similar initial total organic carbon (TOC) values, TOC profiles were similar for experiments with different substrates (the herbicides, humic acids, and a mixture of glyphosate and humic acids), which indicates that the mineralization of all of the samples is limited by the production of SO(4)(?)?(-) radicals. A linear correlation between the initial amount of SO(4)(?)?(-) needed per mole of C and the average oxidation state was found.  相似文献   

6.
In this work the oxidative degradation of resveratrol catalyzed by lipoxygenase-1 (LOX-1) has been studied. The process has been characterized by spectroscopic and polarographic measurements. The oxidation of resveratrol was dependent on the concentration of resveratrol and the enzyme. When resveratrol was incubated in the presence of lipoxygenase at pH 9.0, the reaction displayed a k(M) value of 18.6 x 10(-)(6) M and a catalytic efficiency (k(cat)/k(M)) of 4.3 x 10(4) s(-)(1) M(-)(1). These values are close to those shown by the enzyme when linoleic acid is used as the substrate. The effect of lipoxygenase inhibitors on the lipoxygenase-catalyzed resveratrol oxidation was also evaluated. The rate of resveratrol oxidation was markedly decreased by the presence of NDGA in the incubation mixture. From HPLC measurements, it can be deduced that resveratrol is oxidatively decomposed to a complex mixture of products similar to those obtained when the molecule is oxidized by hydrogen peroxide.  相似文献   

7.
Kinetics of chlorophyll degradation and color loss in heated broccoli juice   总被引：2，自引：0，他引：2  
Degradation of chlorophyll in broccoli juice occurred at temperatures exceeding 60 degrees C. Chemical analysis revealed that degradation of chlorophyll a and b to pheophytin a and b, respectively, followed first-order kinetics and that chlorophyll a was more heat sensitive than chlorophyll b. Temperature dependencies of chlorophyll a and b degradation rate constants could be described by Arrhenius equations with activation energies (E(a)) of 71.04 +/- 4.89 and 67.11 +/- 6.82 kJ/mol, respectively. Objective greenness measurements, using the -a value as the physical property, together with a fractional conversion kinetic analysis, indicated that green color degradation followed a two-step process. Kinetic parameters for the first degradation step were in accordance with the kinetic parameters for pheophytinization of the total chlorophyll content, as determined by chemical analysis (E(a) approximately 69 kJ/mol). The second degradation step, that is, the subsequent decomposition of pheophytins, was characterized by an activation energy of 105.49 +/- 4.74 kJ/mol.  相似文献   

8.
The free radical scavenging capacity (RSC) of antioxidants from sesame cake extract was studied using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)()) on a kinetic model. Pure lignans and lignan glycosides isolated from methanolic extract by preparative HPLC were used in the study. To understand the kinetic behavior better and to determine the RSC of sesame antioxidants, the second-order rate constant (k(2)) was calculated for the quenching reaction with [DPPH(*)] radical. The k(2) values of the sesame antioxidants were compared with those of butylated hydroxytoluene and alpha-tocopherol. The k(2) values for sesamol, sesamol dimer, sesamin, sesamolin, sesaminol triglucoside, and sesaminol diglucoside were 4.00 x 10(-)(5), 0.50 x 10(-)(5), 0.36 x 10(-)(5), 0.13 x 10(-)(5), 0.33 x 10(-)(5), and 0.08 x 10(-)(5) microM(-)(1) s(-)(1), respectively.  相似文献   

9.
A combined high-pressure carbon dioxide (HP-CO 2) and thermal degradation reaction of betanin and isobetanin in aqueous solution was investigated and can be described by a first-order decay. At 45 degrees C, the degradation rate constant ( k) for each pigment component significantly increased (the half-life ( t 1/2) decreased, p < 0.05) with elevated pressure. Furthermore, HP-CO 2 treatment led to lower k values (higher t 1/2 values) than thermal treatment. However, k and t 1/2 values approached those of thermal treatment when the pressure was >30 MPa combined with temperatures exceeding 55 degrees C. Moreover, betanin was more stable than isobetanin under HP-CO 2. E a values ranged from 94.01 kJ/mol for betanin and 97.16 kJ/mol for isobetanin at atmospheric pressure to 170.83 and 142.69 kJ/mol at 50 MPa, respectively. A higher pressure and temperature as well as longer exposure time resulted in higher values of L*, b*, C*, and h degrees . HP-CO 2 induced more degradation products from betanin and isobetanin than thermal treatment with an identical temperature and exposure time.  相似文献   

10.
Tocopherols (alpha, beta, gamma, and delta) and Trolox were found to deactivate triplet-excited riboflavin in homogeneous aqueous solution (7:3 v/v tert-butanol/water) with second-order reaction rates close to diffusion control [k2 between 4.8 x 10(8) (delta-tocopherol) and 6.2 x 10(8) L mol(-1) s(-1) (Trolox) at 24.0 +/- 0.2 degrees C] as determined by laser flash photolysis transient absorption spectroscopy. In aqueous buffer (pH 6.4) the rate constant for Trolox was 2.6 x 10(9) L mol(-1) s1 and comparable to the rate constant found for ascorbate (2.0 x 10(9) L mol(-1) s(-1)). The deactivation rate constant was found to be inferior in heterogeneous systems as shown for alpha-tocopherol and Trolox in aqueous Tween-20 emulsion (approximately by a factor of 4 compared to 7:3 v/v tert-butanol/water). Neither beta-carotene (7:3 v/v tert-butanol/water and Tween-20 emulsion), lycopene (7:3 v/v tert-butanol/water), nor crocin (aqueous buffer at pH 6.4, 7:3 v/v tert-butanol/water, and Tween-20 emulsion) showed any quenching on the triplet excited state of riboflavin. Therefore, all carotenoids seem to reduce the formation of triplet-excited riboflavin through an inner-filter effect. Activation parameters were based on the temperature dependence of the triplet-excited deactivation between 15 and 35 degrees C, and the isokinetic behavior, which was found to include purine derivatives previously studied, confirms a common deactivation mechanism with a bimolecular diffusion-controlled encounter with electron (or hydrogen atom) transfer as rate-determining step. DeltaH for deactivation by ascorbic acid, Trolox, and homologue tocopherols (ranging from 18 kJ mol(-1) for Trolox in Tween-20 emulsion to 184 kJ mol(-1) for ascorbic acid in aqueous buffer at pH 6.4) showed a linear dependence on DeltaS (ranging from -19 J mol(-1) K(-1) for Trolox in aqueous buffer at pH 6.4 to +550 J mol(-1) K(-1) for ascorbic acid in aqueous buffer pH 6.4). Among photooxidation products from the chemical quenching, lumicrome, alpha-tocopherol quinones and epoxyquinones, and alpha-tocopherol dimers were identified by ESI-QqTOF-MS.  相似文献   

11.
Using 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) as substrate, it has been shown that the increased peroxidase activity for decreasing pH of myoglobin activated by hydrogen peroxide is due to a protonization of ferrylmyoglobin, MbFe(IV)=O, facilitating electron transfer from the substrate and corresponding to pK(a) approximately 5.2 at 25.0 degrees C and ionic strength 0.16, rather than due to specific acid catalysis. On the basis of stopped flow absorption spectroscopy with detection of the radical cation ABTS(.+), the second-order rate constant and activation parameters for the reaction between MbFe(IV)=O and ABTS were found to have the values k = 698 +/- 32 M(-1) s(-1), DeltaH# = 66 +/- 4 kJ mol(-1), and DeltaS# = 30 +/- 15 J mol(-1) K(-1) at 25.0 degrees C and physiological pH (7.4) and ionic strength (= 0.16 M NaCl). At a lower pH (5.8) corresponding to the conditions in meat, values were found as follows: k = 3.5 +/- 0.3 x 10(4) M(-1) s(-1), DeltaH# = 31 +/- 6 kJ mol(-1), and DeltaS# = -53 +/- 19 J mol(-1) K(-1), indicative of a shift from outersphere electron transfer to an innersphere mechanism. For steady state assay conditions, this shift is paralleled by a shift from saturation kinetics at pH 7.4 to first-order kinetics for H2O2 as substrate at pH 5.8. In contrast, the activation reaction between myoglobin and hydrogen peroxide was found at 25.0 degrees C to be slow and independent of pH with values of 171 +/- 7 and 196 +/- 19 M(-1) s(-1) found at physiological and meat pH, respectively, as determined by sequential stopped flow spectroscopy, from which a lower limit of k = 6 x 10(5) M(-1) s(-1) for the reaction between perferrylmyoglobin, .MbFe(IV)=O, and ABTS could be estimated. As compared to the traditional peroxidase assay, a better characterization of pseudoperoxidase activity of heme pigments and their denatured or proteolyzed forms is thus becoming possible, and specific kinetic effects on activation, substrate oxidation, or shift in rate determining steps may be detected.  相似文献   

12.
The browning of glucose-fructose-glycine mixtures involves parallel glucose-glycine and fructose-glycine reactions, which share a common intermediate, the immediate precursor of melanoidins in the kinetic model. At pH 5.5, 55 degrees C glucose is converted into this intermediate in a two step process where k(1) = (7.8 +/- 1.1) x 10(-)(4) mol L(-)(1) h(-)(1) and k(2) = (1.84 +/- 0.31) x 10(-)(3) h(-)(1) according to established kinetics, whereas fructose is converted into this intermediate in a single step where k(4) = 5.32 x 10(-)(5)()()mol L(-)(1) h(-)(1). The intermediate is converted to melanoidins in a single rate limiting process where k(mix) = 0.0177 h(-)(1) and the molar extinction coefficient (based on the concentration of sugar converted) of the melanoidins so formed is 1073 +/- 4 mol(-)(1) L cm(-)(1). Whereas the value of k(mix) is the same when the individual sugars undergo browning, the value of the molar extinction coefficient is similar to that for melanoidins from the glucose-glycine reaction (955 +/- 45 mol(-)(1) L cm(-)(1)) but it is approximately double the value for melanoidins from the fructose-glycine reaction (478 +/- 18 mol(-)(1) L cm(-)(1)). This is the reason that the effects of glucose and fructose on the rate of browning are synergistic.  相似文献   

13.
Tea catechins may undergo complex reactions such as oxidation, polymerization, and epimerization during thermal processing. The thermal stability of tea catechins in an aqueous system, including degradation and epimerization reactions, was investigated using a microwave reactor. Reactions were controlled at high temperatures ranging from 100 to 165 degrees C with various durations up to 120 min. Three sources of tea catechins containing different levels of (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), and their epimers were studied. Kinetic models for the degradation/epimerization of tea catechins were developed and validated by the reactions at 145 degrees C. It was shown that the epimerization and degradation of tea catechins followed first-order reactions and the rate constants of reaction kinetics followed the Arrhenius equation. Values of the activation energy (E(a)) for the epimerization of EGCG from epi- to nonepi-structures, the epimerization of GCG from nonepi- to epi-structures, and the total degradation of EGCG and its epimer GCG were 117.6, 84.2, and 42.8 kJ/mol, respectively. For ECG and CG, the E(a) values were 119.3, 96.2, and 41.6 kJ/mol, respectively. The mathematical models may provide a useful prediction for the loss of tea catechins during any thermal processing.  相似文献   

14.
Kinetics of reduction of iron(IV) in ferrylmyoglobin by chlorogenate in neutral or moderately acidic aqueous solutions (0.16 M NaCl) to yield metmyoglobin was studied using stopped flow absorption spectroscopy. The reaction occurs by direct bimolecular electron transfer with (2.7 +/- 0.3) x 10(3) M(-)(1).s(-)(1) at 25.0 degrees C (DeltaH( )(#) = 59 +/- 6 kJ.mol(-)(1), DeltaS(#) = 15 +/- 22 J. mol(-)(1).K(-)(1)) for protonated ferrylmyoglobin (pK(a) = 4.95) and with 216 +/- 50 M(-)(1).s(-)(1) (DeltaH( )(#) = 73 +/- 8 kJ. mol(-)(1), DeltaS( )(#) = 41 +/- 30 J.mol(-)(1).K(-)(1)) for nonprotonated ferrylmyoglobin in parallel with reduction of a chlorogenate/ferrylmyoglobin complex by a second chlorogenate molecule with (8.6 +/- 1.1) x 10(2) M(-)(1).s(-)(1) (DeltaH( )(#) = 74 +/- 8 kJ.mol(-)(1), DeltaS( )(#) = 59 +/- 28 J.mol(-)(1).K(-)(1)) for protonated ferrylmyoglobin and with 61 +/- 9 M(-)(1).s(-)(1) (DeltaH( )(#) = 82 +/- 12 kJ.mol(-)(1), DeltaS( )(#) = 63 +/- 41 J. mol(-)(1).K(-)(1)) for nonprotonated ferrylmyoglobin. Previously published data on ascorbate reduction of ferrylmyoglobin are reevaluated according to a similar mechanism. For both protonated and nonprotonated ferrylmyoglobin the binding constant of chlorogenate is approximately 300 M(-)(1), and the modulation of ferrylmyoglobin as an oxidant by chlorogenate (or ascorbate) leads to a novel antioxidant interaction for reduction of ferrylmyoglobin by ascorbate in mixtures with chlorogenate.  相似文献   

15.
In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and alpha-acids/iso-alpha-acids complexation), this investigation on alpha-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 degrees C). Rate constants and activation energies for the formation of individual iso-alpha-acids were determined. It was found that iso-alpha-acid formation follows first-order kinetics and Arrhenius behavior. Differences in activation energies for the formation of trans- and cis-isomers were noticed, the activation energy for the formation of trans-iso-alpha-acids being approximately 9 kJmol (-1) lower.  相似文献   

16.
A PVC membrane electrode of the coated wire type was prepared which is selective for thioredazine. It showed a Nernstian response over a thioredazine concentration range 6.3 x 10(-6) to 2.5 x 10(-3) M, at 25 degrees C, and was selective, precise, and usable within the pH range 2.1-7.0. The standard electrode potentials, E degrees, were determined at different temperatures and used to calculate the isothermal temperature coefficient of the electrode. The photoreaction occurring in thioredazine solution exposed to daylight did not affect the electrode performance. This reaction was investigated kinetically to determine its rate constant and half-life at different temperatures.  相似文献   

17.
The relative rate constants for the reaction of ozone were determined for several substituted anilines in aqueous solutions at pH 6.5 and 1.5. At pH 6.5, with the exception of m- and p-nitroaniline, the rate constants obey Hammett's equation: log(k(X)/k(H)) = rho sigma. The departure of m- and p-nitroaniline may be explained by direct conjugation of the reaction center. The commonly used sigma(p)(-) value of 1.27, which extends the range of applicability of the Hammett equation, was insufficient to account for the conjugation effects on ozonation of p-nitroaniline; rho = -1.48 (R = 0.973). Use of amine group atomic charge determinations significantly improved correlations: (k(X)/k(H)) = 48.7 delta - 18.2 (R = 0.996). A linear plot of Hammett constants versus relative rate data at pH 1.5 showed poor correlation: rho = 0.72 (R = 0.572). Poor correlation was similarly observed for amine group atomic charge determinations, suggesting varied reaction mechanisms.  相似文献   

18.
Treatment of olive oil mill wastewater by Fenton's reagent   总被引：5，自引：0，他引：5  
Wastewater from olive oil mills has been treated by means of the Fe(II)/H(2)O(2) system (Fenton's reagent). Typical operating variables such as reagent concentration (C(H(2)O(2)) = 1.0--0.2 M; C(Fe(II)) = 0.01--0.1 M) and temperature (T = 293--323 K) exerted a positive influence on the chemical oxygen demand and total carbon removal. The optimum working pH was found to be in the range 2.5--3.0. The exothermic nature of the process involved a significant increase of the temperature of the reaction media. The process was well simulated by a semiempirical reaction mechanism based on the classic Fenton chemistry. From the model, the reaction between ferric iron and hydrogen peroxide [k = 1.8 x 10(15) exp((-12,577 +/- 1248)/T)] was suggested to be the controlling step of the system. Also, the simultaneous inefficient decomposition of hydrogen peroxide [k = 6.3 x 10(12) exp((-11,987 +/- 2414)/T)] into water and oxygen was believed to play an important role in the process. On the basis of stoichiometric calculations for hydrogen peroxide consumption, an estimation of the process economy has been completed.  相似文献   

19.
Vanillin was found to be efficient as a deactivator of ferrylmyoglobin with a second-order rate constant of k(2) = 57 ± 1 L mol(-1) s(-1) for reduction to metmyoglobin with ΔH(?) = 58.3 ± 0.3 kJ mol(-1) and ΔS(?) = -14 ± 1 J mol(-1) K(-1) in aqueous pH 7.4 solution at 25 °C. Binding to β-lactoglobulin (βLG) was found to affect the reactivity of vanillin at 25 °C only slightly to k(2) = 48 ± 2 L mol(-1) s(-1) (ΔH(?) = 68.4 ± 0.4 kJ mol(-1) and ΔS(?) = 17 ± 1 J mol(-1) K(-1)) for deactivation of ferrylmyoglobin. Binding of vanillin to βLG was found to have a binding stoichiometry vanillin/βLG > 10 with K(A) = 6 × 10(2) L mol(-1) and an apparent total ΔH° of approximately -38 kJ mol(-1) and ΔS° = -55.4 ± 4 J mol(-1) K(-1) at 25 °C and ΔC(p, obs) = -1.02 kJ mol(-1) K(-1) indicative of increasing ordering in the complex, as determined by isothermal titration microcalorimetry. From tryptophan fluorescence quenching for βLG by vanillin, approximately one vanillin was found to bind to each βLG far stronger with K(A) = 5 × 10(4) L mol(-1) and a ΔH° = -10.2 kJ mol(-1) and ΔS° = 55 J mol(-1) K(-1) at 25 °C. The kinetic entropy/enthalpy compensation effect seen for vanillin reactivity by binding to βLG is concluded to relate to the weakly bound vanillin oriented through hydrogen bonds on the βLG surface with the phenolic group pointing toward the solvent, in effect making both ΔH(?) and ΔS(?) more positive. The more strongly bound vanillin capable of tryptophan quenching in the βLG calyx seems less or nonreactive.  相似文献   

20.
The kinetics of the reactions of chlorpyrifos-methyl, an organophosphorus insecticide, with hydrogen sulfide (H(2)S) and bisulfide (HS(-)) were determined in well-defined aqueous solutions. The resulting pseudo-first-order rate constant for chlorpyrifos-methyl with bisulfide yielded a second-order rate constant of (2.1 +/- 0.3) x 10(-3) M(-1) s(-1). The second-order rate constant for chlorpyrifos-methyl with hydrogen sulfide is significantly slower than the second-order rate constant with bisulfide. The contribution of H(2)S to the observed degradation rate constant of chlorpyrifos-methyl at concentrations of up to 4 mM H(2)S is not significant. The second-order rate constant of chlorpyrifos-methyl with H(2)S was too low to be measured in this study. The results indicate that HS(-) present at environmentally relevant concentrations may represent an important sink for phosphorothionate triesters in a coastal marine environment, while H(2)S reacts too slowly to be environmentally relevant (pH 6-9). Trichloropyridinol, the major product of hydrolysis of chlorpyrifos-methyl, is only a minor product of the reaction of chlorpyrifos-methyl with bisulfide; however, trichloropyridinol was found to be stable under the experimental conditions.  相似文献   

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