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We will present the first example of a two-dimensional scanned TLC-plate, measured by use of a diode-array scanner. A spatial resolution of 250 µm was achieved on plate. The system provides real 2D fluorescence and absorption spectra in the wavelength-range from 190 to 1000 nm with a spectral resolution of greater than 1 nm. A mixture of 12 sulphonamides was separated by using a cyanopropyl-coated silica gel plate (Merck, 1.16464) with the solvent mix of methyl tert-butyl ether-methanol-dichloromethane-cyclohexane-NH3 (25%) (48:2:2:1:1, v/v) in the first and with a mixture of water-acetonitrile-dioxane-ethanol (8:2:1:1, v/v) in the second direction. Both developments were carried out over a distance of 70 mm. A separation number (spot capacity) of 259 was calculated. We discussed a new formula for its calculation in 2D-TLC separations. The drawback of this method is that measuring a 2D-TLC plate needs more than 3 h measurement time.
Quantification of astaxanthin in salmons by chemiluminescence and absorption after TLC separation
(2018)
Astaxanthin is a keto-carotenoid, belongs to the chemical class of terpenes and is a yellow lipid soluble compound. The compound is present in marine animals like salmons and crustacean. Its colour is due to conjugated double bonds and these double bonds are responsible for its antioxidant effect. Its antioxidant activity is ten times stronger than other carotenoids and nearly 500 fold stronger than vitamin-E. We present a new thin layer chromatography (TLC) method to measure astaxanthin on TLC-plates (Merck, 1.05554) in the visible absorption range as well as by using chemiluminescence. For separation a solvent mixture of cyclohexane and acetone (10 + 2.4, v/v) was used. The RF-value of astaxanthin is 0.14.The limit of detection in vis-absorption is 64 ng / band and the limit of quantification is 92 ng/band. In chemiluminescence the values are 90 ng / band and 115 ng/band. The method offers two independently working measurement modes on a single plate which increase the accuracy of the quantification.
Two solvent mixtures for high-performance thin-layer chromatographic (HPTLC) separation of some compounds showing estrogenic activity in the yeast estrogen screen (YES) assay are presented. The new method, planar yeast estrogen screen (pYES) combines the YES assay and a chromatographic separation on silica gel HPTLC plates with the performance of the YES assay. For separation, the analytes were applied bandwise to HPTLC plates (10 × 20 cm) with fluorescent dye (Merck, Germany). The plates were developed in a vertical developing chamber after 30 min of chamber saturation over a separation distance of 70 mm, using cyclohexane‒methyl-ethyl ketone (2:1, V/V) or cyclohexane‒CPME (3:2, V/V) as solvents. Both solvents allow separation of estriol, daidzein, genistein, 17β-estradiol, 17α-ethinyl estradiol, estrone, 4-nonylphenol and bis(2-ethylhexyl) phthalate.
High-performance thin-layer chromatography (HPTLC), as the modern form of TLC (thin-layer chromatography), is suitable for detecting pharmaceutically active compounds over a wide polarity range using the gradient multiple development (GMD) technique. Diode-array detection (DAD) in conjunction with HPTLC can simultaneously acquire ultraviolet‒visible (UV‒VIS) and fluorescence spectra directly from the plate. Visualization as a contour plot helps to identify separated zones. An orange peel extract is used as an example to show how GMD‒DAD‒HPTLC in seven different developments with seven different solvents can provide an overview of the entire sample. More than 50 compounds in the extract can be separated on a 6-cm HPTLC plate. Such separations take place in the biologically inert stationary phase of HPTLC, making it a suitable method for effect-directed analysis (EDA). HPTLC‒EDA can even be performed with living organism, as confirmed by the use of Aliivibrio fischeri bacteria to detect bioluminescence as a measure of toxicity. The combining of gradient multiple development planar chromatography with diode-array detection and effect-directed analysis (GMD‒DAD‒HPTLC‒EDA) in conjunction with specific staining methods and time-of-flight mass spectrometry (TOF‒MS) will be the method of choice to find new chemical structures from plant extracts that can serve as the basic structure for new pharmaceutically active compounds.
A Simple and Reliable HPTLC Method for the Quantification of the Intense Sweetener Sucralose®
(2003)
This paper describes a simple and fast thin layer chromatography (TLC) method for the monitoring of the relatively new intense sweetener Sucralose® in various food matrices. The method requires little or no sample preparation to isolate or concentrate the analyte. The Sucralose® extract is separated on amino‐TLC‐plates, and the analyte is derivatized “reagent‐free” by heating the developed plate for 20 min at 190°C. Spots can be measured either in the absorption or fluorescence mode. The method allows the determination of Sucralose® at the levels of interest regarding foreseen European legislation (>50 mg/kg) with excellent repeatability (RSD = 3.4%) and recovery data (95%).