Sensitivity of pig liver esterase in detecting twelve carbamate pesticides on thin-layer chromatograms

Coupling of In Vitro Bioassays with Planar Chromatography in Effect-Directed Analysis

Modern analytical test methods increasingly detect anthropogenic organic substances and their transformation products in water samples and in the environment. The presence of these compounds might pose a risk to the aquatic environment. To determine a possible (eco)toxicological risk, aquatic samples are tested using various bioassays, including sub-organismic assays such as the luminescent bacteria inhibition test, the acetylcholinesterase inhibition test, and the umu-test. The effect-directed analysis (EDA) combines physicochemical separation methods with biological (in vitro) tests. High-performance thin-layer chromatography (HPTLC) has proved to be particularly well suited for the separation of organic compounds and the subsequent analysis of effects by the application of the biotests directly on the surface of the HPTLC plate. The advantage of using HPTLC in comparison to high-performance liquid chromatography (HPLC) for EDA is that the solvent which is used as a mobile phase during chromatography is completely evaporated after the separation and therefore can no longer influence the applied bioassays.A prioritization during the complex identification process can be achieved when observed effects are associated with the separated zones in HPTLC. This increases the probability of identifying the substance responsible for an adverse effect from the multitude of organic trace substances in environmental samples. Furthermore, by comparing the pattern of biological effects of a separated sample, it is possible to track and assess changes in biological activity over time, over space, or in the course of a process, even without identifying the substance. HPTLC has already been coupled with various bioassays.Because HPTLC is a very flexible system, various detection techniques can be used and combined. In addition to the UV/Vis absorption and fluorescence measurements, TLC can also be coupled with a mass spectrometer (MS) for compound identification. In addition, detection of functional groups by means of derivatization reagents can support this identification. It is also possible to combine derivatization and HPLC-MS.Two case studies are used to illustrate the significance of HPTLC-EDA in investigating water quality: Study on a wastewater treatment plant Possible influence of an artificial turf surface on ground water.

Determination of the insecticide promecarb by fluorogenic labelling with dansyl chloride

The use of spectrofluorimetry to determine the fluorescent derivative of the insecticide promecarb, following hydrolysis to the corresponding phenol in basic media and subsequent coupling with the labelling agent dansyl chloride, is described and discussed. A study of media of different basicity and of different temperatures for both reactions gave optimum conditions of 20 min for the hydrolysis reaction and 10 min for the labelling reaction at 55 degrees C in 0.05 mol dm-3 sodium hydrogen carbonate solution with a reagent to insecticide ratio of 12:1. The effect of the solvent on the formation of the dansyl derivative and on the extraction process was studied using nine and seven solvents, respectively. The use of a mixture of acetone and water (50 + 50, v/v) and an extraction into cyclohexane gave the best results. The minimum detectable concentration of promecarb in the experimental assays was 100 ng ml-1. The error and relative standard deviation at a concentration level of 0.6 micrograms ml-1 were 9.7 and 10.9%, respectively. Air samples containing promecarb at different concentration levels were analysed.

Chromatographic analysis of chemical warfare agents

The usefulness and applications of the particular types of chromatography in the analysis of chemical warfare agents have been reviewed. A major problem in the chromatographic analysis of chemical warfare agents is the collection and preparation of the samples. The importance of this problem differs for the various types of chromatography. Significant differences occur in the way in which samples are collected from air, water, soil, vegetables or animal organisms. The analyses are characterized by the main groups of chemical warfare agents, e.g., organophosphorus, vesicants, irritants, etc. Account has been taken of the relationships between their properties and the possibilities of their chromatographic analysis. The advantages and disadvantages of particular types of chromatography in the analysis of the particular groups and individual agents have been considered. The detectability of particular chemical warfare agents has been assessed, together with the separating efficiency for their mixtures. Examples of applications of chromatographic systems and conditions of chromatographing are summarized in tables. It is concluded that chromatography is a very useful tool in the analysis of chemical warfare agents; GC and TLC have the most advantageous properties, HPLC being slightly inferior.

Na+-coupled D-glucose uptake and membrane order of enterocyte brush border membrane vesicles, under the effect of a series of N-phenylcarbamates

The importance of the hydrophobic effect of exogenous substances and of modifications of membrane order on D-glucose uptake are still poorly defined. Our results show that the concentrative Na+ -coupled D-glucose uptake of rat enterocyte brush border membrane vesicles is inhibited by N-phenylcarbamates increase the membrane order. However, since the concentrations required for membrane order increase are much greater than those active on D-glucose uptake, the effects on lipid order cannot be responsible for the inhibition of D-glucose uptake. Measurements of D-glucose uptake under conditions of Na+ equilibrium show that these carbamates do not act directly on the carrier but indirectly by favouring the dissipation of the Na+ gradient.

[Enzymatic detection of carbamate pesticides on impregnated cellulose plates]

The detection of carbamate pesticides by an enzyme-inhibition method on impregnated (ethylene glycol, triethylene glycol, beta,beta'-oxydipropionitrile) cellulose thin layer plates is described. The enzyme-substrate combination: pig liver esterase-indophenylacetate (chromogenic substrate) was the most sensitive. The following parameters concerning the sensitivity of the method were investigated: enzyme source, substrate, pH, inhibition time, inhibition temperature, thickness of the cellulose layer, stationary phase.