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A systematic toxicological analysis procedure using high-performance thin layer chromatography in combination with fibre optical scanning densitometry for identification of drugs in biological samples is presented. Two examples illustrate the practicability of the technique. First, the identification of a multiple intake of analgesics: codeine, propyphenazone, tramadol, flupirtine and lidocaine, and second, the detection of the sedative diphenhydramine. In both cases, authentic urine specimens were used. The identifications were carried out by an automatic measurement and computer-based comparison of in situ UV spectra with data from a compiled library of reference spectra using the cross-correlation function. The technique allowed a parallel recording of chromatograms and in situ UV spectra in the range of 197–612 nm. Unlike the conventional densitometry, a dependency of UV spectra by concentration of substance in a range of 250–1000 ng/spot was not observed.
Vorgestellt wird die Dioden-Array-Dünnschichtchromatographie als eine moderne und preiswerte Messmethode zur densitometrischen Erfassung von Substanzen auf einer DC- oder einer HPTLC-Platte. Sicher identifizierbar sind auch Substanzen mit schwachem Chromophor. Die Kubelka-Munk-Gleichung beschreibt einen linearen Zusammenhang zwischen Remissionslicht und lichtabsorbierender Stoffmenge auf der Platte. Die Auswertung im Spektralbereich von 316 bis 334 nm zeigt den Zusammenhang zwischen transformiertem Messsignal und aufgetragener Substanzmasse. Die schnelle Aufnahme von UV/vis-Spektren eröffnet der HPTLC den gesamten Bereich der Methodenvalidierung auf dem Niveau, auf welchem heute die HPLC-Analytik durchgeführt wird.
HPTLC (High Performance Thin Layer Chromatography) is a well known and versatile separation method which shows many advantages when compared to other separation techniques. The method is fast and inexpensive and does not need time-consuming pretreatments. For visualisation of the sample distribution on a HPTLC-plate we developed a new and sturdy HPTLC-scanner. The scanner allows simultaneous registrations of spectra in a range from 198 nm to 612 nm with a spectral resolution of better than 0.8 nm. The on-plate spatial resolution is better than 160 μm. The measurement of 450 spectra in one separation track does not need more than two minutes. The new diode-array scanner offers a fast survey over a TLC-separation and makes various chemometric applications possible. For compound identification a cross-correlation function is described to compare UV sample spectra with appropriate library data. The cross-correlation function herein described can also be used for purity testing. Unresolved peaks can be virtually separated by use of a least squares fit algorithm. In summary, the diode arry system delivers much more information than the commonly used TLC-scanner.