Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
2000-11-27
2002-11-26
Ludlow, Jan (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S070000, C422S082080, C422S082090, C422S082110
Reexamination Certificate
active
06485687
ABSTRACT:
The present invention relates to a thin-layer chromatography apparatus according to the generic term of claim
1
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Thin-layer chromatography is a widespread process for the separation and analysis of substance mixtures. There, a stationary phase is provided as a thin layer on a suitable carrier made of glass, polyester, aluminum or the like. The substance mixture to be investigated is applied at a starting point or a starting line on the stationary phase. The thin-layer plate is then developed. For this a mobile phase is brought as eluant (Eluens) onto the starting line or the starting point, say by placing the thin-layer plate in a trough chamber from where the mobile phase begins-to run, especially by the capillary action of the stationary phase on the thin-layer. The mobile phase there can carry along over the thin-layer plate constituents of the substance mixture to be investigated and that are soluble in that phase. The less-well-soluble components remain on the stationary phase. If the individual components of the applied substance mixture, by reason of substance-specific retention values, show different distributions between mobile and stationary phase, this leads to a breaking-up of the substance mixture over the thin-layer plate. There is obtained a spatial distribution of the components over the thin-layer plate that is substance-specific. The analysis of the distribution pattern, therefore of a chromatogram, makes possible qualitative and quantitative statements about the components of the substance mixture.
The required analysis of the developed thin-layer chromatography plates occurs ordinarily optically with thin-layer chromatography apparatuses, in which the thin-layer plate is irradiated with light, and with which it is possible to investigate how the irradiated light is altered by the thin-layer plate.
The present invention concerns itself more precisely with such an optical thin-layer chromatography apparatus, and it is not relevant whether the application and development proper of the thin-layer plate also occur in the apparatus itself; further, it is insignificant whether the carrier is rigid or flexibly formed from glass, polyester or the like, so long as it is accessible to an optical investigation of the developed chromatogram.
The optical determination as to which substances are present in the chromatogram can be supported, on the one hand, by the place which a certain component of the substance mixture has reached on the thin-layer plate in the development, and, on the other hand, by its optical properties, i.e. the absorption capacity of the substance, its fluorescent properties, etc. An exact investigation requires, therefore, both a high local resolution and also an exact spectral investigation.
It has been proposed (“Development of a system for measuring the UV spectra of components separated by TLC” by S. Ebel and W. Windmann in J. Planar Chromatography, 1991, pp. 171 ff), to conduct light from a deuterium lamp over a fiber-optic bundle onto a thin-layer plate and to feed it from there to a photo diode array detector. The fiber-optic bundle consists of a “Y” fiber which is used to conduct the light of the deuterium lamp onto the thin-layer plate, and to conduct it from there to the optical examination arrangement.
Measures with such systems are described in a large number of publications, for example A. N. Diaz and F. Garcia Sanchez in “Fiber optic fluorescence scanning in thin-layer chromatography” in “Instrumentation Science and Technology, 22 (3), 273-281 (1994)”; A. N. Diaz “Fiber-optic remote sensor for in situ fluorimetric quantification in thin-layer chromatography” in Analytica Chimica Acta, 255 (1991) 297-303.
A further device is known from “Determination of Reflectance of Pesticide Spots on Thin-Layer chromatograms Using Fiber Optica” by M. Beroza, K. R. Hill and K. H. Norris in Analytical Chemistry, vol. 40, 1608-1613 (1968). There it is proposed to scan a thin-layer plate with stochastically arranged Y-light conductors. The foot of the Y-fibers is led to the thin-layer plate, its first arm to a light source and its other arm to an optical investigation device. A reading head is required for the plate scanning and a head for the reference measurement on an adjacent free path.
In the article “A versatile Spectrophotometric Scanner for Large TLC Plates” by B. L. Hamman and M. L. Martin in Analytical biochemistry vol. 15, 305-312 (1966) it is proposed to install in a light-proof housing a plate scanner which comprises a driven slide piece, with which a fiber bundle is moved over a thin-layer plate. Sending and receiving photo-conductors are arranged facing one another lying opposite on the slide piece. The light spot size can be determined by the sliding of slots of suitable size in front of the sending photo-conductor.
A problem with such thin-layer chromatography apparatuses lies in the uneven distribution of the substances over the regions to which they are carried on the thin-layer plate during the development. The concentration is highest in the center of a zone and decreases toward the edges of the spot.
A known possibility for avoiding such faults lies in illuminating a large spot. In a further known arrangement (S. Bayerbach and G. Gaulitz “Spectral detection in thin-layer chromatography by linear photo diode array spectrometry” in Fresenius Z. Anal. Chem. (1989) 335:370-374) there is proposed, therefore a light spot size of one to two millimeters dependent on the distance from the thin-layer plate. This takes place also in use of unordered fiber light bundles.
It was further proposed (S. Ebel, E. Geitz and J. Hocke in “Fully automatic, computer-controlled evaluation of thin-layer chromatograms” in GIT Fachz. Lab, 24th year, pp. 660 ff) to lead the light spot in meander pattern over the substance spots on the thin-layer plate. It has further been proposed to deflect the thin-layer plate by a definite amount over an eccenter?, in order to avoid the point-form measuring of a thin-layer chromatogram spot, cf. vol. 5 “Dünnshicht-chromatographie” of Ullmans encyclopedia of technical chemistry.
What is disadvantageous with the previously described measurements by means of which the uneven substance distribution over the spot is supposed to be compensated for, is regularly the reduced local resolution. It leads with a given amount of substance to a worsened separating performance, or with limited amounts of substance to worsened detection sensitivity.
From WO 93/14392 there is known an analysis device with a polychromatic light source. The light source can comprise a glow lamp light source with a small opening or, preferably, a semiconductor light source, for example an LED.
From EP 0 060 709 B1 there is known a process and a device for multidimensional real-time chromatography. The prior known system has first means for the chromatographic separating of a sample of an unknown composition into a first grouping of components, in which these first means can be a matter of a chromatographic thin-layer plate; second means for the further separating of the components mentioned into a higher-dimensional second group of components; third means for the recognizing of the components mentioned. The third means can be a linear multi-photodiode array which detects how a light source illuminates the eluting solvent on the thin-layer plate. The illumination can use a plurality of light sources which are used successively and emit at different wavelengths that are specific for the unknown components sought. The publication concerns itself also with the problem that the analysis is not very accurate because of the spreading of the spots. The known process proposes the real-time investigation during the separation, but allows there in particular no subsequent evaluation of already developed thin-layer plates. It is therewith not possible to draw upon the prior-known system for the investigation of filed thin-layer plates, as required, say, for the documentation of charge qualities in the pharmaceutical industry.
The dissertation “Remission spectra:
Klein Karl-Friedrich
Spangenberg Bernd
Baker & Daniels
Ludlow Jan
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