A simple and rapid spectrophotometric method for determination of thiophanate-methyl in commercial formulations and its residues in foodstuffs

A new, simple, rapid, and sensitive spectrophotometric method for the determination of thiophanate-methyl, based on its reaction with cobalt(II) in the presence of triethylamine, has been developed. The yellowish green color that develops instantaneously on mixing the fungicide with the reagents in dimethylformamide is stable for at least 2 h and has maximum absorbance at 360 nm. The method has been successfully applied to the determination of thiophanate-methyl in its commercial formulations and residues on grains and apples. A photometric titration procedure for formulation analysis of the fungicide has also been developed.     

Colorimetric method for the determination of captafol (difolatan) in commercial formulations and residues on grains and apples.

A simple and rapid colorimetric method for the microdetermination of captafol (difolatan), based on its reaction with a dithiocarbamate, has been developed. The bright yellow colour which develops instantaneously on mixing the fungicide with the reagent is stable for at least 12 h. The method has been successfully adapted to the determination of captafol in its formulated products and residues on grains and apples.     

An oxidimetric method for the determination of thiophanatemethyl in commercial formulations

A simple, accurate and reliable titrimetric method is described for the determination of thiophanate-methyl, an important commercial fungicide. The method is based on its direct titration at room temperature with ammonium hexanitratocerate(IV) in sulphuric acid medium in the presence of potassium iodate as catalyst. The method permits detection of the end-point visually, potentiometrically or spectrophotometrically. The proposed method is recommended for routine determination of the fungicide in its commercial formulations.     

Nonplanar property study of antifungal agent tolnaftate-spectroscopic approach

Vibrational analysis of the thionocarbamate fungicide tolnaftate which is antidermatophytic, antitrichophytic and antimycotic agent, primarily inhibits the ergosterol biosynthesis in the fungus, was carried out using NIR FT-Raman and FTIR spectroscopic techniques. The equilibrium geometry, various bonding features, harmonic vibrational wavenumbers and torsional potential energy surface (PES) scan studies have been computed using density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of VEDA.4 program. Vibrational spectra, natural bonding orbital (NBO) analysis and optimized molecular structure show the clear evidence for electronic interaction of thionocarbamate group with aromatic ring. Predicted electronic absorption spectrum from TD-DFT calculation has been compared with the UV-vis spectrum. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy were also calculated. Vibrational analysis reveals that the simultaneous IR and Raman activation of the C-C stretching mode in the phenyl and naphthalene ring provide evidence for the charge transfer interaction between the donor and acceptor groups and is responsible for its bioactivity as a fungicide.     

Residues analysis of post-harvest imidazole fungicides in citrus fruit by HPLC and GLC

The determination of imazalil and prochloraz fungicide residues has been carried out by HPLC with an UV detector at 204 nm and by GLC with an electron capture detector (ECD). In both cases fungicide residues were extracted with hexane/acetone (90:10, v/v) after pH adjustment and purified by a liquid-liquid partitioning process. When HPLC was used for prochloraz and imazalil analysis, it was necessary to eliminate the interfering substances with a further clean-up process. This was also required when samples with low residue levels were analyzed by GLC. Recovery was always higher than 70%. The detection limit was 0.04 ppm for the HPLC method and 0.02 for the GLC method. Imazalil and prochloraz residues in "Washington Navel" oranges and "Hernandina" clementine fruits, dipped in a 1000 ppm fungicide solution, are reported.     

HPLC Analysis of Sodium 2-Pyridinethiol-1-oxide in Aqueous Metalworking Fluids via Derivatization with NBD-C1

Abstract

A method is described for the analysis of the fungicide, 2-pyridinethiol-1-oxide, in aqueous metalworking fluids. Derivatization is extremely rapid with NBD-C1 using minimal sample preparation. HPLC analysis is complete within a 10 minute run and has shown to have minimal interferences at 425 nm in the absorbance mode.     

Residues Analysis of Post-Harvest Imidazole Fungicides in Citrus Fruit by H PLC and GLC

Abstract

The determination of imazalil and prochloraz fungicide residues has been carried out by HPLC with an UV detector at 204 nm and by GLC with an electron capture detector (ECD).

In both cases fungicide residues were extracted with hexane/acetone (90:10, v/v) after pH adjustment and purified by a liquid-liquid partitioning process. When HPLC was used for prochloraz and imazalil analysis, it was necessary to eliminate the interfering substances with a further clean-up process. This was also required when samples with low residue levels were analyzed by GLC.

Recovery was always higher than 70%. The detection limit was 0.04 ppm for the HPLC method and 0.02 for the GLC method.

Imazalil and prochloraz residues in “Washington Navel” oranges and “Hernandina” clementine fruits, dipped in a 1000 ppm fungicide solution, are reported.     

Molecularly imprinted capillary electrochromatography for selective determination of thiabendazole in citrus samples

In this work, the suitability of the combination of molecular imprinting and capillary electrochromatography (MIP-CEC) to be used as powerful tool in environmental or food analysis has been for the first time studied and successfully demonstrated. A molecularly imprinted monolith (MIM) has been synthesised and evaluated as stationary phase for the selective determination of the fungicide thiabendazole (TBZ) in citrus samples by non-aqueous capillary electrochromatography. The influence of the mobile phase composition, the voltage of the power supply and the separation temperature on the recognition of TBZ by the imprinted polymer has been evaluated, and the imprint effect in the MIM was clearly demonstrated. Once optimum recognition conditions were established, other variables affecting mechanical properties and chromatographic performance of MIM were adjusted using computational approach. The high selectivity achieved by the MIP-CEC developed procedure allowed unambiguous detection and quantification of TBZ in citrus samples by direct injection of the crude sample extracts, without any previous clean-up, in less than 6 min. The developed method was properly validated and the calculated detection limits were below the established maximum residue limits (MRLs), clearly demonstrating the suitability of the method to be used for the control of the selected fungicide.     

Specific determination of ferbam residues in fog-water

A specific method for the determination of a fungicide, i.e. iron(III) dimethyldithiocarbamate (ferbam) in fog-water samples is described. The method is based on the releasing of equivalent amount of iron from the fungicide and subsequently determination by spectrophotometrically or by flame-atomic absorption spectrometrically (flame-AAS). The fungicide was extracted with chloroform/toluene from the samples and digested with nitric acid. For spectrophotometric determination, the solution was then treated with ammonium thiocyanate solution in presence of the surfactants and absorbance was measured at 475 nm. Whereas, the digested solution was directly applied for flame-AAS determination of ferbam. The molar absorptivity in terms of ferbam was determined to be (3.49)×10⁴ l mol⁻¹ cm⁻¹. The detection limits for spectrophotometric and flame-AAS methods were calculated to be 62 and 111 ppb ferbam (R.S.D. <1 and <3%), respectively. Whereas, the optimum concentration ranges for the analysis of ferbam are 4–120 and 1.5–55 μg in final volume, respectively. The methods are freed from interference of almost all ions [including Fe(II) and Fe(III)], which can commonly associate with ferbam in fog-water. The methods have been successfully applied to fog samples collected from agriculture sites of Raipur (central India).     

液相色谱–串联质谱法测定草莓中二噻农残留

采用盐酸酸化乙腈提取草莓中二噻农残留,提取溶液经无水硫酸钠和PSA净化后,利用安捷伦Poroshell120 EC–C18色谱柱进行分离,以甲醇–水(体积比20∶80,含5 mmol/L乙酸铵溶液)作为流动相,ESI负离子模式下进行液相色谱–四极杆串联质谱分析。结果表明,在10~200μg/L浓度范围内,线性关系良好,r20.999 8,平均回收率为71.8%~78.3%,相对标准偏差小于5%(n=6),方法定量限为5μg/kg。该方法简单快速,可满足新鲜草莓中二噻农残留检测工作的需要。     

Liquid chromatographic determination of benomyl in water samples after dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method combined with solvolysis reaction for extraction of the carbamate fungicide benomyl as carbendazim from water samples is described. The method is based on the extraction of benomyl from acidified sample solution and its conversion into carbendazim via solvolysis reaction with DMF as organic solvent. The proposed DLLME method was followed by HPLC with fluorimetric detection for determination of benomyl. The proposed method has good linearity (0.998) with wide linear dynamic range (0.01–25 mg/L) and low detection limit (0.0033 mg/L), making it suitable for benomyl determination in water samples.     

Verfahren zur Bestimmung des Fungicids Dithianon auf ?pfeln

Zusammenfassung Es werden spezifische Verfahren zur Aufreinigung und Bestimmung von Dithianon auf der OberflÄche bzw. im Homogenisat von Äpfeln beschrieben. Der Wirkstoff wird mit Dichlormethan oder Chloroform extrahiert, von pflanzlichen Begleitstoffen durch Verteilung in einem zweiphasigen Lösungsmittelsystem und — bei der Untersuchung des Homogenisats — durch prÄparative Schicht-Chromatographie an Kieselgel abgetrennt und nach Farbreaktion mit Morpholin bei 510 nm colorimetriert. Die in Zusatzversuchen ermittelte Standardabweichung betrÄgt für OberflÄchenrückstÄnde 5,1% (8,7% für RückstÄnde im Homogenisat), die untere Bestimmungsgrenze 0,06 ppm (0,05 ppm), die Wiederfindung 95% (61%). Eine selektive Identifizierung und halbquantitative Bestimmung des Wirkstoffes gelingt nach dünnschicht-chromatographischer Trennung durch eine empfindliche Farbreaktion mit, o-Aminothiophenol. — An Äpfeln und Sauerkirschen erstellte Abbaukurven werden diskutiert.

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Procedures for the determination of the fungicide dithianon on apples

Specific methods are described for clean-up and determination of dithianon on the surface and in the fruit pulp of apples. The compound is extracted with dichloromethane or chloroform and separated from interfering vegetable substances by distribution in a two-phase solvent system and—for the fruit pulp—by chromatography on silica gel. Determination is carried out photometrically at a wavelength of 510 nm after colour reaction with morpholin. The relative standard deviation is 5.1% for surface residues (8.7% for the fruit pulp), the limit of determination is 0.06 ppm (0.05 ppm) and the recovery is 95% (61%). A selective identification and half quantitative determination can be performed by thin-layer chromatography combined with a sensitive colour reaction with o-aminothiophenol.—Degradation curves on apples and cherries are discussed.

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Herrn Prof. Dr. K. G. Krebs zum 60. Geburtstag gewidmet.

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Die experimentellen Arbeiten wurden von Frl. G. Kissel und Herrn K. Hallstein durchgeführt.     

Spectrophotometric determination of mercury in environmental sample and fungicides based on its complex with o-carboxy phenyl diazoamino p-azobenzene

In the present method a new reagent o-carboxyphenyl diazoamino p-azobenzene has been synthesised for the determination of mercury spectrophotometrically. The method is based on the reaction of mercury with the reagent in alkaline medium where the reagent is in the aci-form. The purple violet coloured dye-mercury complex showed an absorption maxima at 540 nm. Beer's law is valid over the concentration range of mercury from 0.08 to 0.8 mug ml(-1) (0.08-0.8 ppm). The molar absorptivity and Sandell's sensitivity were found to be 2.22x10(5) mol(-1) cm(-1) and 0.0009 mug cm(-2), respectively. The method has been successfully applied to the determination of mercury in air, water, soil and fungicide samples.     

Liquid chromatographic determination of novel aminithiazolecarboxamide fungicide residues in soil and crops using online solid-phase extraction

A simple and convenient liquid chromatographic method has been developed and applied to the analysis of the novel aminothiazolecarboxamide fungicide, ethaboxam, in soil and crops. After the isolation and concentration of analyte from soil and crops, clean-up and separation of sample solutions are performed by high-performance liquid chromatography with online solid-phase extraction. Good linearity (r2 > 0.9995), recovery [for soil, 95.3-98.4%, and crops (grape, red pepper), 92.9-95.9%], and repeatability are achieved in the calibration range of 0.1-10.3 microg/mL. The limit of detection is the 2.5 parts per billion (ppb) (40 g of soil) and the 20 ppb (25 g of crops), respectively. This assay method shows the suitability for the residual analysis of ethaboxam in soil and crops.     

Inclusion of the fungicide chlozolinate in a multiresidue method.

A multiresidue GC method for the monitoring of electron-capturing compounds has been validated for the fungicide chlozolinate in the four crops with uses to be supported during re-evaluation procedures within the European Union. The method was also tested for a further eight crops. Matrix-matching of standards was found to be desirable to avoid the random occurrence of artificially high recoveries. The high accuracy and precision of the method, with a mean recovery of 94% and an RSD of +/-5%, shows it to be suitable for routine residue control in a wide range of crops.     

Multiresidue analysis of fungicides in soil by sonication-assisted extraction in small columns and gas chromatography

A rapid multiresidue method for the simultaneous determination of 14 fungicides in soil was developed. Fungicides were exacted from soil, placed in small columns, by sonication-assisted extraction with ethyl acetate. The effect of residue residence time and soil moisture content on the fungicide recovery was studied. Residue levels in soil were determined by gas chromatography with electron-capture and nitrogen-phosphorus detection. Residue identities were confirmed by gas chromatography coupled with mass spectrometry, in the selected ion monitoring mode. Recovery studies were carried out at 0.5, 0.1 and 0.05 microg/g fortification levels for each fungicide, and average recoveries obtained for these compounds ranged from 80 to 104% with relative standard deviations between 1 and 8%. The method is linear over the range assayed, 0.5-0.05 microg/g, and the detection limit for the fungicides studied varied from 2 to 10 microg/kg.     

A rapid pyrolytical method for the determination of wood preservatives in treated wood

Analytical laboratories are often confronted with the question whether a board of wood has been treated with an insecticide or fungicide or not at all. Generally this question is difficult to answer in the case of organic wood preservatives and requires considerable time for analytical procedures. Therefore, a simple and rapid method for determining the most common organic wood preservatives in a one-step procedure has been developed. They were measured by gas chromatography after thermal treatment by a Curie-point pyrolyser, directly attached to the GC. Under these conditions the specific compounds tended to be predominatly vaporised rather than pyrolysed. For analysis, a mass-selective detector (MSD) was used in selected ion mode (SIM). In one analytical step, up to eight different preservatives can be identified. Detection limits were in the range between 0.01 and 0.7 g/m².     

Behaviour studies of the fungicide cymoxanil in two strains of the fungus Botrytis cinerea and in haemolymph of locust and lobster. I. In situ monitoring by internal surface reversed-phase high-performance liquid chromatography

A method for following the metabolism of the fungicide cymoxanil in various biological media is described. By using a recently developed high-performance liquid chromatographic method, with an internal surface reversed-phase column, it is unnecessary to clean up the sample before analysis. Thus this technique makes monitoring in fungi as well as in arthropod haemolymph easier and faster.     

A Clean-up Method by Photocatalysis for HPLC Analysis of Iprodione in Dry Basil

Titanium dioxide was used as a photocatalyst to decompose interfering substances for a quantitative analysis of a fungicide (iprodione) in dry basil by HPLC. A quartz vial containing basil extract and titanium dioxide was irradiated with black light. The interfering substances were almost completely decomposed by 180 min of irradiation, whereas 88.3% of iprodione remained. The recovery of iprodione was 102.6% by the proposed method in basil extracts. This may have been due to different decomposition rates of the analyte and interfering substances.     

Solid-liquid-liquid extraction as an approach to the sensitive detection of a hydrophobic pollutant through surface-enhanced Raman spectroscopy

Surface-enhanced Raman scattering (SERS) spectra of thiram (tetramethylthiuram disulfide), a dimethyl dithiocarbamate fungicide, were recorded after the adsorption on plasmonic silver nanowires from a system of water, organic solvent and nanoparticles. As organic solvents dichloromethane and 1-octanol were involved. A method for measuring the adsorption constant of thiram as a model molecule to the silver surface by studying its partition phenomena in a binary solvent system is presented. The method is based on the extraction of a hydrophobic molecule from an organic solvent by an aqueous suspension of silver anisotropic nanoparticles. The obtained results demonstrate the effectiveness of SERS methodology for the sensitive analysis of compounds with low aqueous solubility, and a reliable SERS spectrum of thiram was obtained with excellent signal/noise ratio at low concentrations. In addition, for vibrational assignments, Density Functional Theory (DFT) was used for the simulation of the Raman and SERS spectra of thiram and its complexes with silver considering the following two models: a single silver atom and an Ag₂₀ cluster.