N-methyl Carbamate Research Articles

Influence of different factors on the adsorption of carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl- N-methyl carbamate) on soils

The effects of exchangeable cations (H + and Na +), autoclaving, organic matter, cationic and anionic surfactants, and temperature on the adsorption of carbofuran on two different types of soils were studied. The adsorption isotherms for all effects/treatments were in close agreement with the Freundlich equation and yielded S-shaped isotherms. The amount of carbofuran adsorbed in all cases was higher in Jhansi red loam soil than in Pilibhit sandy loam soil and was related to organic matter content, clay content, CaCO 3 content, surface area, and cation-exchange capacity of the soils. The adsorption on soils from both sites follows the order H soil → Na soil → natural soil at 25°C → autoclaved soil → soil from which organic matter had been removed → cationic surfactant → anionic surfactant → natural soil at 50°C and was in accordance with Freundlich constant K values and distribution coefficient K d values. The adsorptive capacity of carbofuran for organic matter and clay content for both the Jhansi and the Pilibhit soils was also evaluated by calculating K om and K c values, and it was found that the carbofuran adsorption was better correlated with clay content than with organic matter content of soils. On the basis of adsorption isotherms, various thermodynamic parameters such as the thermodynamic equilibrium constant K 0, standard free energy ( ΔG°) changes, standard ethalpy ( ΔH°) changes, and standard entropy ( ΔS°) changes have been calculated in order to predict the nature of isotherms.

Ion formation of N-methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

The effects of three additives—ammonium acetate, ammonium formate, and nicotinic acid—to the liquid chromatographic (LC) eluent and of the vaporizer temperature on the ion formation of N-methyl carbamate pesticides in thermospray (TSP) mass spectrometry was investigated by using filament- or discharge-assisted ionization. Nineteen carbamates and 12 of their known environmental degradation products were used as model compounds. The additives cause a strong reduction in the abundance of the characteristic fragment ions [M + H − CH 3NCO] + and [M − CH 3NCO] − for some of the carbamates. The addition of nicotinic acid reduces the quasimolecular ion intensity and, in most cases, produces nicotinic acid adduct ions. The addition of ammonium acetate or ammonium formate increases the intensity of the quasimolecular ion and in most cases produces a base peak for the ammonium adduct ion. The combination of a suppression of fragmentation and an enhancement of quasimolecular ion formation produces an overall gain in sensitivity. As to more specific effects, the addition of the ammonium salts reduces the intensity of M −• with the chlorinated carbamate barban and suppresses the formation of “odd” adduct ions in the TSP mass spectra of most other carbamates. Monitoring the intensity of the fragment and the quasimolecular ion signal as a function of the probe stem temperature, and the related probe tip temperature, proved to be an easy method to study the thermal degradation of the carbamates. This monitoring procedure showed that methiocarb and its sulfone already suffer from thermal degradation at a stem temperature of 90 °C and that these compounds will therefore present problems in quantitation with LC/TSP mass spectrometry.

A Rapid Multiresidue Screen for Organophosphorus, Organochlorine, and N-Methyl Carbamate Insecticides in Plant and Animal Tissues

A multiresidue screen for the quantitative determination of 43 organophosphorus, 17 organochlorine, and 11 N-methyl carbamate insecticides in 10 g of plant or animal tissues is described. The insecticides are extracted with 5% ethanol in ethyl acetate (v/v). Samples with high lipid content are cleaned up by automated gel permeation chromatography with a 30% ethyl acetate in hexane (v/v) eluant and in-line silica gel minicolumns. Highly pigmented samples are cleaned up with class-specific solid-phase extraction columns. The concentrated extracts are analyzed by selective detection with gas chromatography or liquid chromatography. Recovery of 71 insecticides ranged from 77 to 113%. Analysis of fortified bovine liver (n = 5) resulted in an average recovery of 96 +/- 4% at the 0.5 to 0.05 micrograms/g level. Analysis of fortified alfalfa hay (n = 5) resulted in a mean recovery of 94 +/- 4% at the 0.06 to 0.5 micrograms/g level, and analysis of fortified fresh tomatoes (n = 5) resulted in an average recovery of 97 +/- 3% at the 0.06 to 0.5 micrograms/g level. Method detection limits ranged from 0.02 to 0.5 micrograms/g for the compounds studied with a nominal 10 g sample.

A Simple Approach for Removal of Carbaryl and Its Monitoring in Water Matrices

Abstract Carbaryl, 1-napthyl N-methyl carbamate, is an extremely, broad spectrum, contact action insecticide having wide acceptance because of its low mammalian toxicity and less persistent nature. Because Carbaryl is widely used in monsoon season, it finds its way into aquatic environment. The feasibility of Carbaryl removal by alum coagulation, was checked and found to be suitable for 98% removal of Carbaryl along with efficient turbidity removal in water matrices. The low level monitoring of Carbaryl was performed by spectroscopic technique.

Interlaboratory Study of a Thermospray-Liquid Chromatographic/Mass Spectrometric Method for Selected N-Methyl Carbamates, N-Methyl Carbamoyloximes, and Substituted Urea Pesticides

Abstract A thermospray-liquid chromatographic/mass spectrometric (TS-LC/MS) method was evaluated in an interlaboratory study for determining 3 N-methyl carbamates (bendiocarb, carbaryl, and carbofuran), 3 N-methyl carbamoyloximes (aldicarb, methomyl, and oxamyl), 2 substituted urea pesticides (diuron and linuron), and 1 ester of a substituted carbamic acid (carbendazim). The purpose of this study was to establish whether these 9 compounds can be reliably detected and quantitated with this method, and to establish the interlaboratory precision and accuracy of the method with currently available instrumentation. The study design was based on AOAC INTERNATIONAL’S blind replicate design with balanced replicates. The samples consisted of solutions of the 9 test compounds in methanol at 3 concentrations that were unknown to the participating laboratories and that covered the linear range of the method. Nine volunteer laboratories participated in the study. Linear regression equations are presented that calculate the accuracy of the method, i.e., the percent recovery of each of the 9 compounds at any concentration within the range of concentrations tested (5–90 (μg/mL for each compound, except carbendazim, for which the range was 1.25–22.5 μg/mL). The intra laboratory precisions of the TS-LC/MS method ranged from 6.5 to 33.1 % relative standard deviation, depending on the compound. The interlaboratory method precisions ranged from 29.8 to 98.2% relative standard deviation over the concentration range tested. Analysis of variance indicates that for all compounds tested, the variation from laboratory to laboratory is greater than that attributed to analytical error displayed within laboratories. There are many operational parameters that could contribute to interlaboratory variability; one of them, the thermospray tip temperature, can play a major role in adduct formation and ion fragmentation in the case of thermally labile carbamate pesticides and, therefore, needs to be monitored and controlled carefully. The correlation of mass spectral data with the thermospray tip temperature was attempted using principal component analysis.

Molecular dissection of cholinesterase domains responsible for carbamate toxicity

Carbamate compounds marked for their cholinesterase (ChE) inhibition are widely used as therapeutics and as insecticides. Groups of closely related carbamate molecules provide an important tool in the understanding of the domains responsible for binding these ligands to ChEs. Comparative inhibition profiles were derived for five N-methyl carbamates, mostly carbofuran derivatives, differing in length and branching of their hydrocarbonic chain towards human erythrocyte acetylcholinesterase (H.AChE), human serum butyrylcholinesterase (H.BChE) in its normal form or in a mutant form containing the point mutation Asp 70→Gly, and Drosophila nervous system ChE. Carbofuran was more toxic to all three ChEs than any of the other derivatives, with IC50 values which differed by more than 1000-fold. Drosophila ChE appeared to be most sensitive to all of the examined carbamates, and H. AChE was consistently more sensitive than H. BChE. Morever, inhibition efficiency for H. BChE decreased more effectively than it did for H. AChE with increased length and complexity of the side chain, indicating less flexible carbamate binding site in BChE as compared with AChE. The Asp 70→Gly mutation had no apparent effect on H. BChE inhibition by N-methyl carbamates, suggesting that the Asp 70 domain localized near the rim of the active site groove is not important in carbamate binding. Comparison of the carbamate IC50 values with published LD 50 values demonstrated correlation between the in vivo toxicity and inhibition of BChE by carbamates, suggesting a biological in addition to scavenging importance for BChE in mammals. Pinpointing different domains characteristic of carbamate binding in each member of the ChE family can thus shed light on the variable toxicity of these inhibitors to insects and mammals, predict the toxicity of yet untested inhibitor molecules and help in designing novel and improved ChE inhibitors.

Studies of the amplification of carbaryl toxicity by various oximes

The administration of 2-pyridine aldoxime methyl chloride (2-PAM Cl) is a standard part of the regimen for treatment of human overexposure to many organophosphorus pesticides and nerve agents. However, some literature references indicate that poisoning by carbaryl (1-naphthyl N-methyl carbamate), an insecticide in everyday use, is aggravated by the administration of 2-PAM Cl. This effect has been reported in the mouse, rat, dog and man. We have found that the inhibition of both eel acetylcholinesterase (eel AChE, EC 3.1.1.7) and human serum cholinesterase (human BuChE, EC 3.1.1.8) by carbaryl was enhanced by several oximes. Based on 95% confidence limits the rank order of potentiation with eel AChE was TMB-4 = Toxogonin > HS-6 = HI-6 > 2-PAM Cl. By the same criterion, the rank order of potentiation with human BuChE was TMB-4 > Toxogonin > HS-6 = 2-PAM Cl. Carbaryl-challenged mice also reflected a potentiation since TMB-4 exacerbated the toxicity more than 2-PAM Cl. Our hypothesis is that certain oximes act as allosteric effectors of cholinesterases in carbaryl poisoning, resulting in enhanced inhibition rates and potentiation of carbaryl toxicity.

An evaluation of atmospheric pressure ionization techniques for the analysis of N-methyl carbamate pesticides by liquid chromatography mass spectrometry

Atmospheric pressure ionization (API) techniques are evaluated for the mass spectral analysis of N-methyl carbomate pesticides. Atmospheric pressure chemical ionization (APCI) using a heated nebulizer interface provided both protonated molecules and abundant, characteristic fragment ions. With ion spray (ISP; pneumatically assisted electrospray ionization), which utilizes a milder “ion evaporation” process, primarily protonated molecules were obtained, although fragment ions similar to those observed in APCI could be induced by variation of the API orifice voltage. Product ion spectra of ISP-derived protonated molecules, generated by tandem mass spectrometry using collision-induced dissociation, are also presented. The APCI and ISP spectra of the carbamates are compared to those obtained with a thermospray interface and also to their electron ionization and methane CI spectra obtained with a particle beam interface. For all four interfaces, combined liquid chromatography mass spectrometry methods using conventional (4.6 mm i.d.) columns are described for the separation and detection of pesticide mixtures. These methods are applied to the confirmatory analysis of three representative carbamate pesticides, spiked at the 0.1-ppm level in green peppers. For those carbamates amenable to gas chromatography mass spectrometry, comparative results are presented.

Rectal bioavailability of delta-9-tetrahydrocannabinol from various esters

The bioavailability of delta-9-tetrahydrocannabinol ( Δ 9-THC) from suppository formulations containing several polar esters was studied. The esters tested were the hemisuccinate, N-formyl alaninate, N-methyl carbamate, and methoxy acetate. These esters were administered to monkeys in both lipophilic and hydrophilic suppository bases, namely, Witepsol Hl5 and polyethylene glycol, respectively. Each suppository contained a dose equivalent to 10 mg Δ 9-THC. Blood samples were analyzed for both Δ 9-THC and its carboxylic acid metabolite (ll-nor- Δ 9-THC-9-COOH) using gas chromatography/mass spectrometry. The data showed that, with the exception of the hemisuccinate, no Δ 9-THC or its metabolite was detected in the blood samples using the Witepsol Hl5. Using polyethylene glycol, low levels of Δ 9-THC and its metabolite were detected in blood for all esters tested. The levels, however, were lower than those observed with Δ 9-THC hemisuccinate using Witepsol Hl5. Subsequent studies in the conscious dog using the hemisuccinate in Witepsol Hl5 showed 67% bioavailability of Δ 9-THC with a linear response in the dose range equivalent to 5–20 mg of Δ 9-THC. No significant bioavailability differences were found when Δ 9-THC hemisuccinate ester was administered in various lipophilic bases (Hydrokote 25, Kaomel, Suppocire AIML, and Witepsol Hl5).

Field leaf-test kit for rapid determination of dislodgeable foliar residues of organophosphate and N-methyl carbamate insecticides

Field leaf-test kit for rapid determination of dislodgeable foliar residues of organophosphate and N-methyl carbamate insecticides

1-Naphthyl N-Methyl carbamate effect on intra- and extracellular concentrations of arachidonic acid metabolites, and on the chemiluminescence generation by mouse peritoneal macrophages

1-Naphthyl N-methyl carbamate (carbaryl®), potent carbamate insecticide with anticholinesterase activity, was tested for its ability to affect mouse peritoneal macrophages in particular arachidonic acid (AA) metabolism and oxidative burst. Carbaryl® inhibited in a dose-related manner the reactive oxygen intermediate dependent chemiluminescence (CL) induced by opsonized zymosan (OZ), 12- O-tetradecanoyl phorbol-13-acetate (TPA) and calcium ionophore (A23187); this carbamate did not affect CL-mediated by AA. The intracellular and extracellular concentrations of prostaglandins (PGs) and 5-hydroxyeicosatetraenoic (5-HETE) generated in macrophages stimulated with OZ has been investigated for various periods. Carbaryl effect displayed two successive phases on AA metabolism stimulation. In a first phase (up to 2 – 5 min), carbaryl did not alter the rapid AA metabolite synthesis (total amount of intra- and extracellular metabolites) but it increased intracellular concentration of PGE 2, PGA 2, PGF 2α and decreased 5-HETE intracellular concentration. In a second phase (after 2–15 min), carbaryl inhibited AA metabolite synthesis. The release of cyclooxygenase (CO) and lipoxygenase (LO) metabolites decreased, in particular PGF 2α and PGD 2 which in addition seemed to be submit to a cellular retention; the inhibition of other metabolite release appeared essentially related to the inhibition of their synthesis since the intracellular amount did not augment. The inhibition by carbaryl of the NADPH-oxidase dependent CL induced by OZ may be related to the alteration of the intra- and extracellular concentrations of AA metabolites.

The relationship between oxime-induced reactivation of carbamylated acetylcholinesterase and antidotal efficacy against carbamate intoxication

The efficacy of the oximes pyridinium-2-aldoxime methochloride (2-PAM) and 1-[[[(4-aminocarbonyl)pyridinio]methoxy]methyl]-2-[(hydroxyimino)methyl]pyridinium dichloride (HI-6), in combination with atropine (At), against lethality by either carbaryl (CA) or physostigmine (Phy) was investigated in rats. The protection by At, 8 mg/kg, iv, against CA intoxication was reduced by 2-PAM (22 mg/kg, iv) and HI-6 (50 mg/kg, iv) from a protective ratio (PR) of 6.6 to 3.5 and 2.3, respectively. However, in Phy-intoxicated rats, the administration, iv, of At alone, At + 2-PAM, or At + HI-6 at 1 min following Phy provided good protection and resulted in PRs of 7.2, 8.8, and 23.3, respectively. In experiments on decarbamylation of inhibited acetylcholinesterase (AChE), HI-6 and 2-PAM accelerated ( p < 0.05) the decarbamylation of Phy-inhibited AChE in vitro, and HI-6 decreased ( p < 0.05) the inhibition of whole blood AChE in Phy-intoxicated rats. These findings show that the protection was increased substantially by the use of either 2-PAM or HI-6 against Phy-induced lethality, whereas the use of oximes against carbaryl poisoning was contraindicated. Furthermore, even though CA and Phy are both N-methyl carbamates, the data indicate that there is no adverse interaction between 2-PAM or HI-6 and Phy.

Simplified Multiresidue Method for Liquid Chromatographic Determination of /V-Methyl Carbamate Insecticides in Fruits and Vegetables

A simplified method is described for determining 7 N-methyl carbamates (aldicarb, carbaryl, carbofuran, methiocarb, methomyl, oxamyl, and propoxur) and 3 related metabolites (aldicarb sulfoxide, aldicarb sulfone, and 3-hydroxy carbofuran) in fruits and vegetables. Residues are extracted from crops with methanol; coextractives are then separated by gel permeation chromatography (GPC) or GPC with on-line Nuchar-Celite cleanup for crops with high chlorophyll and/or carotene content (e.g., cabbage and broccoli). Carbamates are separated on a reverse-phase liquid chromatography column, using a methanol-water gradient mobile phase. Separation is followed by postcolumn hydrolysis to yield methylamine, and the formation of a fluorophore with o-phthalaldehyde and 2-mercaptoethanol prior to fluorescence detection. Recovery data were obtained by fortifying 5 different crops (apples, broccoli, cabbages, cauliflower, and potatoes) at 0.05 and 0.5 ppm. Recoveries averaged 93% at both fortification levels except for the very polar aldicarb sulfoxide for which recoveries averaged around 52% at both levels. The coefficient of variation of the method at both levels is less than 5% and the limit of detection, defined at 5 times baseline noise, varies between 5 and 10 ppb, depending on the compound.

13C N.M.R. Spectra of ortho-Substituted Phenyl N,N-Dimethyl-Carbamates and N-Methyl Carbamates

We measured 13C nuclear magnetic resonance spectra of O-substituted phenyl N,N- dimethyland N-methyl- carbamates and compared the results with those for the corresponding m- and p-substituted derivatives. The additivity relationship on the basis of the substituent chemical shift for monosubstituted benzenes ( scsphx ) did not hold well because of the ortho effect. However, the scs of C2(ipso), C3(ortho) and C5(para) was correlated excellently with scsphxX . Dual substituent parameter (DSP) analyses of the scs of C5 and the carbonyl carbon in the fixed side chain showed that correlation was very good for C5 but moderate for C=O. These observations suggested that the X substituent lay in almost the same plane as the aromatic ring, whereas the OCONMe2 group may have changed its conformation somewhat. In O-substituted derivatives, the carbon nucleus that is directly attached to the aromatic ring (γ to the oxygen; OCONMe2)had a pronounced upfield shift relative to the corresponding m- and p-substituents by 4-5 ppm . This phenomenon was explained by the γ-effect caused by the oxygen atom.

Methiocarb-Induced Aversion to Grapes by Gray-Backed White-Eyes

Gray-backed white-eyes (Zosterops lateralis) formed a conditioned aversion to grapes sprayed with methiocarb but not when a visual mimic, calcium phosphate, was substituted. The birds did not use a visual cue to distinguish between treated and untreated grapes, but probably used a taste cue. White-eyes that had previously eaten grapes formed a specific aversion while those that had not eaten grapes formed a nonspecific aversion. This suggests methiocarb can be successfully used as a border treatment for protection of crops from 1st-year birds. If invading birds are older and therefore at eating grapes, the entire crop would need to be treated. J. WILDL. MANAGE. 48(2):444-449 Damage to grapes by the gray-backed white-eye was a problem of economic proportions in Western Australia during the early development of the colony (Hallack 1891, Anonymous 1904, Milligan 1904). Despite the continuing loss of production and the lowering of wine quality caused by this bird, there has been little scientific effort devoted toward alleviating the problem. Apart from the limited use of a promising acoustic device that interferes with the birds' communication system (Knight and Robinson 1978a,b), methods of control have advanced little beyond shooting the birds and picking the crop early. Investigations were initiated in southwest Western Australia, near Margaret River (34?00'S, 115000'E), to ascertain the efficacy of the insecticide, molluscicide, and avian emetic, methiocarb [4-(methylthio)-3,5-xylyl N-methyl carbamate] in protecting ripening grapes from whiteeyes. Methiocarb repels birds from crops (Guarino 1972, Stone et al. 1974, Porter 1977, Henkes 1979, Ruelle and Bruggers 1979). It can also protect grapes from depredations by white-eyes (Bailey and Smith 1979, Menzies 1979). A recent study has shown, however, that methiocarb reduces crop depredations by birds because, in some instances, it reduces insect numbers; thus the birds find a crop with few insects an unacceptable area in which to forage (Woronecki et al. 1981). Some evidence is available which suggests that the reported crop protection provided by methiocarb has a more direct, physiological-psychological basis. Rogers (1974) demonstrated that methiocarb causes a response to feeding in redwinged blackbirds (Agelaius phoeniceus) similar to that caused by lithium chloride, an agent well known for forming conditioned aversions. Rogers (1978) also found that redwings form a specific conditioned aversion to two foods, a formulated product and finely ground rice, treated with methiocarb and that the cue used in the formation of the aversion is probably taste. Rooke (1983) demonstrated that whiteeyes develop a specific conditioned aversion to their food when it has methiocarb added if a visual cue is provided. In the absence of a visual cue, food consumption decreased due to a nonspecific aversion or to debilitation caused by methiocarb. Thus, methiocarb has the potential to directly deter white-eyes from eating grapes rather than merely reducing damage in a vineyard by making the area unaccept444 J. Wildl. Manage. 48(2):1984 This content downloaded from 157.55.39.177 on Tue, 15 Nov 2016 04:02:18 UTC All use subject to http://about.jstor.org/terms METHIOCARB-INDUCED AVERSION IN WHITE-EYES * Rooke 445 able for foraging because of methiocarb's insecticidal properties. The present study was conducted to determine whether white-eyes develop a conditioned aversion to grapes sprayed with methiocarb (experiment I). If the cue used by white-eyes in the formation of a specific aversion to treated grapes is visual, then it should be possible to use a visual mimic of methiocarb to form an aversion in birds that have previously eaten grapes treated with methiocarb. Such a mimic could be cheaper and nontoxic and, therefore, more compatible with the grape and wine industries. To test this possibility, a second experiment was conducted to determine whether calcium phosphate would act as a visual mimic of methiocarb in the formation of an aversion (experiment II). The two experiments were conducted using white-eyes whose previous experience with eating grapes was unknown. In a vineyard there would be two classes of birds: adults that had eaten grapes in previous seasons, and 1st-year birds that had not had the opportunity to eat grapes. Because it is well known that animals readily form aversions to novel food but not to familiar food (Revusky and Bedarf 1967, Wittlin and Brookshire 1968, Shettleworth 1972), it is likely that experienced grape-eaters would not as readily form an aversion to treated grapes as animals to which grapes were novel. To test this hypothesis, experiments were conducted to determine the difference in aversive behavior between these two classes of white-eyes (experiments III, IV).

Liquid Chromatographic Residue Analysis of Carbaryl Based on a Post-Column Catalytic Reactor Principle and Fluorigenic Labelling

Abstract A method is described for the residue analysis of carbaryl in polluted water samples. The technique is based on catalytic hydrolysis of the carbaryl on anion exchangers followed by fluorescence detection of the α-naphthol or the OPA derivative of the methyl amine. A low cost 200 mesh Amberlite strong anion exchanger can be used for this purpose when coupled to the OPA reaction detector. Combining this approach with on-line preconcentration and clean-up on an 3P-18 loaded precolumn can provide a powerful tool for automated residue analysis of carbaryl (and other N-methyl carbamates) in polluted water sources. Recoveries in the order of 100% are reported. The reproducibility of the technique is better than 2% rel. st. dev. Detection limits are 0.4–2 ng per injection for carbaryl depending on the system and linearity of response is more than two orders of magnitude with r = 0.9998. The selectivity and sensitivity of this method permits residue analysis at the sub ppb concentration level in heavily p...

Effects of Dilute and Concentrated Sprays of NAA and Carbaryl in Combination with Daminozide and Pesticides on Fruit Size and Return Bloom of ‘Starkrimson Delicious’ Apple1

Abstract Naphthaleneacetic acid (NAA) and 1-naphthyl N-methyl carbamate (carbaryl) applied separately in both dilute and concentrated sprays significantly increased fruit size; however, when butanedioic mono-2,2-dimethylhydrazide (daminozide) was added, fruit size remained about the same as on unsprayed check trees. Crop load was not significantly affected by any of these treatments. Dilute and concentrated sprays of carbaryl produced more return bloom than did NAA. The most effective treatments were combinations of NAA and carbaryl, either dilute or concentrated. Combining first-cover pesticides [azinphosmethyl (guthion) and cis-N-(trichloromethyl)thio)-4-cy-clonexane-l,2-dicarboximide (captan)] with NAA, and captan with carbaryl, produced satisfactory thinning.

Chain length dependency of fatty acid and carbamate binding to serum albumin

The binding interactions of bovine serum albumin (BSA) with the unbranched fatty acids (FA) pentanoate (five-carbon chain length: C5) up to nonanoate (C9), and the carbamates n-methyl carbamate (equivalent to C3) up to n-hexyl carbamate (equivalent to C8) were examined using an ultrafiltration technique. A single, high-affinity site was observed for each of the FA, with an increasing number of secondary sites with increasing chain length. From binding affinity and competition data, there appear to be distinct albumin sites for the short-chain (⩽C7) and the medium-chain (⩾C8) FA. Published data suggest that the medium-chain FA site is one of the major drug-binding sites on human serum albumin (HSA) or BSA, the indole/benzodiazepine site. Competition between the FA and warfarin for BSA or HSA binding was studied by ultrafiltration and fluorescence methods and suggests that the short-chain FA site may lie in the same region as a second major drug-binding site, the large warfarin-binding area. Thermodynamic parameters of the FA-BSA interactions are suggestive of primary binding being a combination of electrostatic and hydrophobic binding and secondary binding being purely hydrophobic in nature. Carbamate interactions with BSA show several primary sites and also suggest a disparity between the binding of ligands of ⩽ 7 and ⩾ 8 in total length, but there was no evidence of competition between FA and carbamates. A model is proposed to explain these observations, which includes the suggestion that several classes of hydrophobic binding areas exist, each of which is specific for ligands of a restricted range of chain lengths.

Fruit Thinning and Russeting Effects of Oxamyl on Apple1

Abstract Methyl N’N’-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxaminidate (oxamyl)-thinned fruit of ‘Golden Delicious’ and ‘Starkrimson Delicious’ apples (Malus domestica Borkh.), as did naphthaleneacetic acid (NAA) and 1-naphthyl N-methyl carbamate (carbaryl). At 12- and 13-mm diameter fruit size, an increase in concentration of oxamyl sprays increased thinning. Oxamyl produced increasingly severe russet on ‘Golden Delicious’ at concentrations above 300 ppm.

Spectrophotometric Determination of Carbaryl in Grains

Abstract A method has been developed for determining carbaryl (1-naphthyl N-methyl carbamate) in grains, based on hydrolysis of carbaryl with methanolic potassium hydroxide to 1-naphthol, reaction with 4-aminophenazone in the presence of alkaline oxidizing agent, and spectrophotometric measurement at the absorption maximum at 475 nm. The relationship between absorbance and concentration is linear in the range of 0.5-20 μg/mL. The method can be applied to levels as low as 0.3 ppm carbaryl in grains.