Densitometric chromatogram evaluation

Samples applied with the ATS 4 can be positioned for normal, double-sided, or circular chromatographic development. Analyses performed with this applicator, combined with densitometric chromatogram evaluation controlled by the same PC with Windows-based WinCats software, comply with good manufacturing practices/ good lab practices (GMP/GLP), installation qualification (IQ)/operational qualification (OQ), and 21 Code of Federal Regulations (CFR) Part 11 (drug analysis) requirements. 

Quantitative TLC is the subject of Chapter 10 of Ref. I. The theory and techniques of densitometric TLC are elaborated in Chapter 10 of this Handbook, and general considerations and instrumental aspects of densitometric chromatogram evaluation are presented in Chapter 5. Quantification of 1 ipids and other types of compounds on quartz rods coated with an immobilized layer of silica gel or other sorbent with direct interfacing to a flame ionization detector (the Chromarod system) was reviewed by Shantha (188) and Ackman et al. (189) and is described in Chapter 13. 

The Automatic TLC Sampler III is the latest version of this kind. It applies samples automatically from a rack of sample vials. The samples are dispensed from a steel capillary, spotwise by contact transfer or bandwise using the spray-on technique. The capillary which delivers the samples moves according to the plotter principle at a lateral speed of 25 cm/s. The sample dispensing speed is selectable between 10 and 1(X)0 nL/s. The application module is controlled by an IBM-compatible PC, normally the same computer that controls densitometric chromatogram evaluation. 

V. DENSITOMETRIC CHROMATOGRAM EVALUATION A. General, Methodological Considerations... 

CAMAG Chromatogram Immersion Device III Immerses and withdraws chromatograms at a selected speed to avoid tide lines which may interfere with densitometric chromatogram evaluation. 

Finally, an officially updated definition of the retardation factor, R, issued by lUPAC is important to the whole field of planar chromatography (the linear and the nonlinear TLC mode included). The importance of such a definition has two reasons. First, it is promoted by the growing access of planar chromatography users for densitometric evaluation of their chromatograms and second, by the vagueness of the present definition in the case of skewed concentration profiles with the samples developed under mass overload conditions. 

The spectrodensitometric analysis allows the separation and quantitation of zaleplon from its degradate on silica gel plates using chloroform-acetone-ammonia solution (9 1 0.2, v/v/v) as a mobile phase. This method depends on quantitative densitometric evaluation of thin-layer chromatogram of zaleplon at 338 nm over a concentration range of 0.2-1 yg/band, with mean percentage recovery 99.73 1.35.7%. 

The book accompanying InCom 1996 includes an example of the Video-Densitometric Evaluation of Thin-Layer Chromatograms [124]. Thomas Mall concluded that, compared with the usual TLC evaluation methods, the video-densi-tometric method was... 

Documentation of a TLC chromatogram as an image is conveniently possible. Traditionally photographs have been taken but the availability of electronic devices such as flatbed scanners or digital cameras have simplified the process. The principal advantage of electronic images is their durability. Added benefit is the possibility of qualitative and quantitative densitometric evaluation. 

In OPLC, the development, the detection and quantitative evaluation of chromatograms may be performed in off-line and on-line mode. The off-line detection and densitometric determination of analyte are performed by the same manner in OPLC as in classical TLC/HPTLC. 

Figure 22 Densitometric evaluation of (a) TLC and (b) OPLC chromatograms of same quaternary ammonium compounds CHROMPRES 25 development chamber, 2.0 MPa Schimadzu CS-930 scanner eluent, isopropanol methanol-0.9 M sodium acetate (20 3 30, v/v) reagent, Dragendorff S, origin 1, N -trimethyl-L-lisyne 2, choline 3, carnitine 4, trigonelline 5, betaine. (Reproduced by permission from Ref. 85.)...

Conventional TLC is simple in instrumentation and in practice. The mobile phase can be easily prepared from organic solvents of conventional purity. The chromatograms can be visually evaluated after color reaction or under UV light. However, to yield quantitative results, densitometric evaluation is usually required. Although great efforts have been made to completely automate, this is difficult and not widely used. 

Linder K, Juries E W 1965 Direct densitometric methods for evaluating paper chromatograms of malic, tartaric, and citric acid of fruits. Z Lebensm-Unters Forsch 128 65-70... 

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