Densitometry

SIMULTANEOUS DETERMINATION OF LEVONORGESTREL AND ETHINYL ESTRADIOL IN LOW-DOSE ORAL CONTRACEPTIVES BY HPTLC-DENSITOMETRY... 

J C Touchstone and J Sherma (Eds), Densitometry in Thin-Layer Chromatography — Practice and Applications, Wiley-Interscience, New York, 1979... 

The resolution of infra-red densitometry (IR-D) is on the other hand more in the region of some micrometers even with the use of IR-microscopes. The interface is also viewed from the side (Fig. 4d) and the density profile is obtained mostly between deuterated and protonated polymers. The strength of specific IR-bands is monitored during a scan across the interface to yield a concentration profile of species. While in the initial experiments on polyethylene diffusion the resolution was of the order of 60 pm [69] it has been improved e.g. in polystyrene diffusion experiments [70] to 10 pm by the application of a Fourier transform-IR-microscope. This technique is nicely suited to measure profiles on a micrometer scale as well as interdiffusion coefficients of polymers but it is far from reaching molecular resolution. 

Figure 41, The principle of the tape system of analysis. The three tapes are the reagent tape on the bottom, cellopnarie in the center, and sample tape on top. The sample placed on the top tape folds over and is pressed by the press plate and warmed so that the material dialyses through the membrane. The stain is then formed and is read by reflecting densitometry on the reagent tape.

In Chapter 7, approaches for visualization of zones in chromatograms are discussed, including use of nondestructive and destructive dyeing reagents, fluorescence quenching on layers with a fluorescent indicator, and densitometry. In Chapter 8, additional detection methods, such as those used for biologically active and radioactive zones, as well as the recovery of separated, detected zones by scraping and elution techniques are covered. 

In the two figures (Figure 2.15 and Figure 2.16), examples of the densitometri-cally recorded concentration profiles of 5-phenyl-l-pentanol, chromatographed on the two different types of chromatographic paper are shown. 

Contemporary evaluation of the chromatographic plate is often performed by the localization of spots in UV light or densitometry scanning. After this procedure is performed, the adsorbent layer structure is not destroyed. The problem is how to remove the separated component mixture from the plate to make it ready to use for the next separation. 

Location of Separated Zones by Use of Visualization Reagents, UV Absorbance on Layers Containing a Fluorescent Indicator, and Densitometry... 

Measurement of optical density directly on the layer (i.e., in situ densitometry)... 

In situ densitometry has been the most preferred method for quantitative analysis of substances. The important applications of densitometry in inorganic PLC include the determination of boron in water and soil samples [38], N03 and FefCNfg in molasses [56], Se in food and biological samples [28,30], rare earths in lanthanum, glass, and monazite sand [22], Mg in aluminum alloys [57], metallic complexes in ground water and electroplating waste water [58], and the bromate ion in bread [59]. TLC in combination with in situ fluorometry has been used for the isolation and determination of zirconium in bauxite and almnimun alloys [34]. The chromatographic system was silica gel as the stationary phase and butanol + methanol + HCl -H water -n HF (30 15 30 10 7) as the mobile phase. 

Another interesting TLC method for the isolation and determination of bromate ion in flour dough and breads has been developed [59]. It involves extraction of BrOj from foodstuff, purification on alumina column, TLC separation on silica gel layer developed with water -1- -butanol + n-propanol (1 1 3), and quantification by densitometry. Bromate ion down to 0.1 pg in bread (1.0 g) was detected with tohdin-FIQ reagent. 

B. Jaillard, L. Ruiz, and J. C. Arvicu, pH mapping in transparent gel using colour indicator video-densitometry. Plant Soil /83 85 (1996). 

MS2 NiSAl-91 < X < 2.1) Nii j,CUySi.93 (0.03 < y < 0.1) Investigation of structural, electronic, and magnetic properties by means of X-ray diffraction, densitometry, resistivity, susceptibility, and Ni Mossbauer spectroscopy as function of x temperature of phase transition from semimetalhc to metallic state as function of x different Ni sites with different (l/f l) and different angle between H and EFG axis effect of Cu impurities... 

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