Automated Multiple Development Research Articles

Analysis of pesticide residues in drinking water by planar chromatography

Planar chromatography is described in the field of water analysis, The principle of automated multiple development (AMD) technique is mentioned, the strategy of the whole procedure which became a German standard is demonstrated and separations of pesticide mixtures, as well as water samples containing pesticides are presented. The suitability of this method was proved for 283 pesticides and the corresponding ISO Standard has been applied for.

Determination of 2,3-butanediol in high and low acetoin producers of Saccharomyces cerevisiae wine yeasts by automated multiple development (AMD).

High performance thin layer chromatography with automated multiple development was used to determine 2,3-butanediol levels in wine produced by high and low acetoin-forming strains of Saccharomyces cerevisiae. An inverse correlation between acetoin and 2,3-butanediol content was found suggesting a leaky mutation in acetoin reductase of the low 2,3-butanediol producing strains.

Application of AMD to the Determination of Crop Protection Agents in Drinking Water. Part IV: Fundamentals of a Confirmatory Test

AbstractA method is described for the determination of fifteen active ingredients of plant protecting products in ground‐, raw, and drinking water. After extraction and enrichment of the pesticides from the water sample with solid‐phase extraction, the extract is fractionated on silica‐coated TLC plates, first in a so‐called screening gradient by AMD (automated multiple development). The detection of the pesticides is performed by UV multidetection. Positive results from the first separation are confirmed by a second separation on silica in an AMD gradient of distinctly different selectivity, compared to the first separation. Following this strategy, it is possible to distinguish nearly all nonvolatile, from water extractable, active ingredients of plant protecting products in the market. UV spectra are taken for further confirmation of positive results. In most cases, this is possible even at the limit of determination.All chromatograms and spectra shown are raw data, resulting from the confirmatory test DIN 38407 part 11, in the laboratory of one participant*). The method is standardized in the meantime as DIN V 38407‐11.

Use of AMD-HPTLC for Carbohydrate Monitoring in Beers

Determination of malto-oligosaccharides and monosaccharides is important for controlling brewing processes and for characterization of final product taste by making a correlation between sensory impressions and quantitative measurement of the components. Amino-layer HPTLC (high-performance thin-layer chromatography) associated with AMD (automated multiple development ) has been evaluated for use in monitoring of maltotetraose, maltotriose, glucose, and fructose in different beers. The AMD-HPTLC system allows one to operate under gradient conditions and to separate complex mixtures of components within large intervals of polarity. In this case the gradient was based on acetonitrile-acetone-water. The results obtained show that the low detection limit, the absence of clean-up procedures, and the high sample throughout make this method suitable even for use on a large scale, thus making it possible to control the main fermentation components in commercial beers.

Computer-aided optimization of gradient multipledevelopment thin-layer chromatography: I. Two-stage development

A theoretical model of the simplest version of gradient multiple development, the technique of two-step development, is discussed as a preliminary stage to a general theory of planar multi-step development and automated multiple development (AMD). A computer program for the calculation of final R F values for two-step development in the gradient mode for known retention vs. eluent composition relationships is reported. Comparison of predicted and experimental R F values shows satisfactory agreement; still better agreement is observed for the consecutive Δ R F values.

Planar chromatography: Current status and future perspectives in pharmaceutical analysis (short review) — II. Special techniques and future perspectives in planar chromatography

The state of the art of various special analytical planar chromatographic methods is summarized especially for forced-flow planar chromatography (FFPC), overpressured-layer chromatography (OPLC) and rotation planar chromatography (RPC) as well as for the automated multiple development (AMD) technique. The connection between analytical planar and column liquid chromatographic methods and the identification of separated compounds with chromatographic and spectroscopic data are summarized. Some aspects of future perspectives, such as parallel connected multi-layer FFPC and long distance OPLC (LD-OPLC) are given. A combination of OPLC with the AMD method is predicted as the method of the future. Strategies using FFPC techniques are suggested in the form of a flow chart.

Application of high-performance thin-layer chromatography and automated multiple development for the identification and determination of pesticides in water

The combination of high-performance thin-layer chromatography (HPTLC) with automated multiple development (AMD) allows full automation of the separation step. This provides both a separation efficiency that is considerably better than that in conventional TLC and reproducible gradient elution on the thin layer. Reliable identification of trace amounts of pesticides ( e.g., 28 ppt of atrazine) in subsoil, surface and drinking water is clearly demonstrated by AMD-HPTLC using a polarity gradient based on dichloromethane. A second universal elution gradient with changed selectivity on which the substances have different relative migration distances, identification by the multi-wavelength response correlation and the option of recording UV spectra in situ constitute three independent methods for reliable and rapid verification. Using 100- instead of 200-μm HPTLC silica gel layers and reducing the running distance increments from 3 to 2 or 1 mm increase the sensitivity, the linearity and the speed of the method.