Slit-scanning densitometry scan modes

Quantitative analysis by slit-scanning densitometry is not too successful for 2D TLC because standards can be applied only after the first development and will not have the same zone configuration as the doubly developed analyte zones. Alternatively, standards and samples must be developed and scanned on different plates under conditions that have to be assumed identical. Best results are expected to be obtained in the fluorescence mode, for which zone shape has less effect on scan area, or by use of a flying spot (zigzag) scanner that can represent the chromatogram as a contour map or three-dimensional image (Poole... 

Fig. 1 TLC and visible absorption spectra of synthetic colors extracted from a pickled vegetable under TLC/scanning densitometry. (A) Standards of tartrazine (Y-4), orange I (Or-I), and orange RN (Or-RN). (B) Standard of orange H (Or-II). (C) Extract of the sample. TLC/scanning densitometric conditions. Plate RP-18 (E. Merck). Solvent system methyl ethyl ketone-methanol-5 % sodium sulfate (1 1 1). Apparatus Shimadzu CS-9000. Wavelength scanning range 370 700 nm. Slit size 0.4 X 0.4 mm. Measuring mode reflecting absorption.

Pindolol enantiomers separated on C-8 silica gel (Figure 3.7) were quantified by densitometry [52]. Samples and standards (9 pil) were applied by means of a Linomat IV instrument (Camag) in 5 mm bands, developed as described in Section 3.4.2, and scanned at 256 nm in the absorbance mode with a slit 4 mm long and 3 mm wide (aliquot scanning method). To determine the amount of each enantiomer in each band of a drug substance or dosage form, the assay utilized... 

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