Simultaneous determination of insecticides, acaricides and fungicides by thin-layer chromatography

A method is described for the determination of residual amounts of some insecticides, acaricides and fungicides in fresh and processed fruits. Optimum conditions were established for the extraction of eighteen pesticides, purification of the extracts by column chromatography and subsequent two-dimensional thin-layer chromatography on silica gel GF254 with cyclohexane-acetone (10:1) and light petroleum-benzene-ethanol (65:30:5) as solvents and with detection under UV light at 254 and 366 nm followed by a 0.1% solution of bromophenol blue.     

Determination of organophosphorus pesticides by thin-layer chromatography

Analysis for 13 common organophosphorus pesticides by thin-layer chromatography is described; 17 solvent systems were examined. With channel thin-layer chromatography, linear calibration graphs were obtained for the range 1-10 mug.     

A method for the determination of some organophosphorus insecticides in human serum

Summary A simple and rapid method for the determination of organophosphorus insecticides in serum of poisoned patients is described. The compounds are extracted with benzene and the extraction residue is gas chromatographed on a glass capillary column with alkali flame ionisation detection. Concentrations from 2 ng cm⁻³ can be determined. As an example, results of the analysis of serum samples of three patients, poisoned with parathion and methylparation, are given.     

Low-temperature clean-up method for the determination of organophosphorus insecticides in olive oil

A simple, extremely low-cost method using low-temperature lipid precipitation has been developed for the rapid analysis of virgin olive oil for organophosphorus insecticides and triazine herbicides commonly used in olive groves. The method gives good clean-up for GC analysis with nitrogen-phosphorus detection and recoveries between 77 and 104%, with RSD values of 7-16%. Matrix enhancement was observed for some pesticides and metabolites.     

Simplified method for the determination of chlorinated fungicides and insecticides in fruits by gas chromatography

A fast, reliable method for the determination of more than twenty chlorinated fungicides and insecticides in a variety of fruit samples is presented. The pesticides are extracted from chopped samples with magnetic stirring, after adding 13 ml of acetone-phosphate buffer-brine solution (12:1, v/v) with 5 ml of n-hexane. The continuous module employed allows sequential decolourization of the organic phase, solvent changeover and solid-phase extraction for clean-up and preconcentration purposes. A 1-microl aliquot of the pesticides in ethyl acetate (eluent) is finally injected into the gas chromatograph for separation and identification. The method provides excellent clean-up despite the complexity of the matrices involved. Fruit samples (5-20 g) containing 0.1-1250 ng/g pesticides were analysed with a high precision (4-6%). After contamination of the fruit samples for 12 h, average recoveries >90% at fortification levels of 5-25 ng/g were obtained for most of the pesticides. Positive findings of these pesticides in fruits purchased at local markets were confirmed by GC-MS.     

Semiquantitative determination of anions by circular thin-layer chromatography

Summary A semiquantitative method for the determination of 11 anions (chromate, chloride, bromide, iodide, bromate, chlorate, ferrocyanide, ferricyanide, thiocyanate, arsenite and sulphite) by making circular spots on chromatoplate with the circular thin layer Chromatographic apparatus and their comparison with sensitivity standards has been developed. The accuracy is ±5% and the procedure is rapid, simple and economical.

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Zusammenfassung Ein semiquantitatives Verfahren zur Bestimmung von elf Anionen (Cr₄ ^2–, Cl^–, Br^–, J^–, BrO₃ ^–, C1O₃ ^–, [Fe(CN)₆]^4–, [Fe(CN)₆]^3–, CNS^–, AsO₃ ^3– und SO₃ ^2–) durch Ringchromatographie auf Dünnschichten und Vergleich mit Standardringen wurde ausgearbeitet. Die Genauigkeit beträgt ± 5%.

     

Semiquantitative determination of alkaloids by circular thin-layer chromatography

Summary A semiquantitative method for the determination of 13 alkaloids (nicotine, quinine, strychnine, brucine, ephedrine, pilocarpine, narcotine, cinchonine, ajmaline, atropine, cocaine, papaverine and morphine) from a single drop of solution by making circular spots on chromatoplate with the circular thin-layer Chromatographic apparatus and their comparison with sensitivity standard has been developed. The accuracy is ±5% and the procedure is rapid, simple and economical.

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Zusammenfassung Ein halbquantitatives Verfahren zur Bestimmung von 13 Alkaloiden (Nikotin, Chinin, Strychnin, Brucin, Ephedrin, Pilokarpin, Narkotin, Cinchonin, Aimalin, Atropin, Kokain, Papaverin und Morphin) in 1 Tropfen Lösung durch zirkuläre Dünnschichtchromatographie und Vergleich mit Standard-Ringen wurde ausgearbeitet. Die Genauigkeit des Verfahrens beträgt ±5%.

     

Disposable potentiometric enzyme sensor for direct determination of organophosphorus insecticides

A potentiometric disposable enzyme sensor for the direct and fast determination of organophosphorus (OP) insecticides was developed by using an organophosphorus hydrolase (OPH) immobilized on an ion-selective electrode. The disposable screen-printed transducer was based on double matrix membrane technology which allows easy mass production. The potentiometric device consisted of a H(+)-sensitive electrode with integrated Ag/AgCl reference electrode. The electrodes were prepared with N,N-dioctadecylmethylamine as H(+)-sensitive ionophore and pH calibration resulted in slopes of 55 mV decade-1 over a pH range from 11 to 6. OPH was isolated from recombinant Escherichia coli DH5 alpha and immobilized within poly(carbamoyl sulfonate) prepolymer on the surface of the H(+)-sensitive electrode without any further fixation membrane. OPH catalyzes the hydrolytic cleavage of OP compounds which releases protons in a concentration proportional to hydrolyzed substrate. Sensor performance was investigated with regard to enzyme load, concentration, pH and temperature of the measuring buffer using paraoxon as analyte. Best sensitivity and response time were obtained with sensors prepared with 250 U of OPH and measuring at 37 degrees C in 1.0 mM HEPES buffer, pH 9.3, containing 100 mM NaCl. The enzyme sensor exhibited a linear calibration range of 0.01-0.15 mM chlorpyrifos, 0.05-0.35 mM diazinon, 0.05-0.4 mM paraoxon and 0.007-0.05 mM parathion, respectively. For all these analytes response times to reach 95% of maximum change in potential did not exceed 5 min. Sensors stored under dry conditions at 4 degrees C still showed 60% of initial hydrolytic rate after 70 d. The sensors even when stored dry were ready for measurements after 5 min incubation in measuring buffer. A range of putative interfering substances did not influence sensor response, and suitability of measuring OPs in soil extracts was ascertained.     

Kinetic detection method for thin-layer chromatography

The feasibility of using kinetic detection and simultaneous kinetic methods for the determination of species separated on thin-layer chromatographic plates has been explored. The proposed method was tested by monitoring the reaction of ninhydrin with leucine, isoleucine, and phenylalanine. The results obtained using three instruments (two scanning instruments and an imaging instrument) were compared. Although none of the instruments provided ideal results, the premise of the kinetic approach for the in situ quantification of analytes was shown to be valid. The possibility of using kinetic methods to resolve responses from overlapped species was also investigated, and shows promise for improving the overall resolution of thin-layer chromatographic methods. A discussion of the instrumental requirements for successful utilization of the kinetic detection method is also given.