Thin layer chromatograph

The nonquantitative detection of radioactive emission often is required for special experimental conditions. Autoradiography, which is the exposure of photographic film to radioactive emissions, is a commonly used technique for locating radiotracers on thin-layer chromatographs, electrophoresis gels, tissue mounted on sHdes, whole-body animal sHces, and specialized membranes (13). After exposure to the radiolabeled emitters, dark or black spots or bands appear as the film develops. This technique is especially useful for tritium detection but is also widely used for P, P, and 1. 

Inhalation of high concentrations of monochlorotoluenes will cause symptoms of central nervous system depression. Inhalation studies produced an LC q (rat, 4 h) of 7119 ppm for o-chlorotoluene (68). o- and Chlorotoluene are both considered moderately toxic by ingestion (Table 2). A study of the relationship between the electronic stmcture and toxicity parameters for a series of mono-, di-, and tri-chlorotoluenes has been reviewed (72). A thin-layer chromatographic method has been developed to assess the degree of occupational exposure of workers to chlorotoluenes by determining j -cblorobippuric... 

A simple, rapid, precise and economical High Performance Thin Layer Chromatographic (HPTLC) method has been developed and validated for determination of Alprazolam and Melatonine in its pharmaceutical preparation. It was performed on silica gel 60 Thin Layer... 

Crude methyl 2-bromostearate (33 g, 0 087 mol) is dissolved in 200 mL of acetonitrile containing 0 5 mL of water, and silver(I) fluonde (50 g, 0 393 mol) is added rapidly in one portion The slurry is stirred vigorously for 20 h in an oil bath at 80 C At the end ot this time thin-layer chromatographic analysis (petroleum... 

Unquestionably, most practical planar chromatographic (PC) analytical problems can be solved by the use of a single thin-layer chromatographic (TLC) plate and for most analytical applications it would be impractical to apply two-dimensional (2-D) TLC. One-dimensional chromatographic systems, however, often have an inadequate capability for the clean resolution of the compounds present in complex biological samples, and because this failure becomes increasingly pronounced as the number of compounds increases (1), multidimensional (MD) separation procedures become especially important for such samples. 

E. Menziani, B. Tosi, A. Bonora, P. Reschiglian and G. Eodi, Automated multiple development high-performance thin-layer chromatographic analysis of natural phenolic compounds , 7. Chromatogr. 511 396-401 (1990). 

Figure 9. Infrared spectrum of pyrethrin I decomposition product isolated from thin-layer chromatographic plate...

Ito30 determined Tedion through the difference between absorption at 250 and 277 nm after thin-layer chromatographic separation and elution with methanol. 

The checkers found that a fraction, b.p. 45-71° (18 mm.), had the following spectral properties infrared (carbon tetrachloride) no absorption in the 3300-1600 cm.-1 region attributable to OH, C=0, or C=C vibrations proton magnetic resonance (chloroform-d) <5, multiplicity, number of protons, assignment 3.1-4.2 (multiplet, 4, CH—Cl, CH—O, and C//2—O), 1.0-2.5 (multiplet, 7, GH3 and 2 x C//2)-Thin layer chromatographic analysis of this fraction on silica gel plates using chloroform as eluent indicated the presence of a major component (the cis- and fraus-isomers), Rf = 0.60, and a minor unidentified component, Rf = 0.14. 

Funk et al. have used a low-pressure mercury lamp without filter to liberate inorganic tin ions from thin-layer chromatographically separated organotin compounds these were then reacted with 3-hydroxyflavone to yield blue fluorescent chromatogram zones on a yellow fluorescent background [22]. Quantitative analysis was also possible here (XoK = 405 nm, Xji = 436 nm, monochromatic filter). After treatment of the chromatogram with Triton X-100 (fluorescence amplification by a factor of 5) the detection limits for various organotin compoimds were between 200 and 500 pg (calculated as tin). 

The reactions described above also explain reactions that occasionally occur during TLC and are frequently regarded as interferences. Of course, they can also be deliberately employed for photochemical activation of applied or thin-layer chromatographically separated samples. 

Note When combined with thin-layer chromatographic separation the reagent provides a specific detection method for nitrate and nitrite. The color development is often completed within a few minutes on silica gel plates. In the absence of ammonia vapor traces of oxides of nitrogen in the laboratory atmosphere can slowly cause the background to become reddish-brown. The simultaneous presence of the following ions in the chromatogram zones interferes with the detection of nitrate/nitrite I , 10J, IO4, MoO and H2PO2. 

Fodor-Csorba K, Dutka F. 1986. Selectivity and sensitivity of some thin-layer chromatographic detection systems. J Chromatogr 365 309-314. 

Udaya Bhaskar S, Nanda Kumar NV. 1981. Thin layer chromatographic determination of methyl parathion as paraoxon by cholinesterase inhibition. J AOAC 64 1312-1314. 

The balloon was removed briefly while aliquots were taken. The flask was flushed again with nitrogen and the balloon was then replaced. Thin-layer chromatographic analyses were carried out on glass plates coated with silica gel G which were purchased from Analtech, Newark, Delaware. With a 10 2 3 (v/v/v) solution of 1-butanol, acetic acid, and water as developing solvent, the Rf values for the product and L-cysteine hydrochloride are 0.19 and 0.25, respectively. 

Gossdij JA.W. Modifled Thin-Layer Chromatographic Separation of Preservatives , JL Ouvmatogr. 1971, 63, 433-437. 

Figure 39, A lipid pattern from normal serum which has been scanned for density of the thin-layer chromatograph, showing the various peaks, P, phospholipids C, cholesterol F, free fatty acids S, internal standard, T, triglycerides CE, cholesterol esters.

Century, B. Vorkink, W. P. and Natelson, S. Thin layer chromatographic screening of aminoacids in plasma and urine of newborns. Clin. Chem. (1974), 20,... 

TABLE II. Thin-Layer Chromatographic Rf values on Silica Gel ... 

Standard open column and thin-layer chromatographic methods have been gradually replaced by HPLC, which is faster, more reliable, more accurate and highly reproducible for analyzing plant pigments and for opening new perspectives in chlorophyll... 

AOAC Official Method 988.13, FD C Color Additives in Foods, Rapid Cleanup for Spectrophotometric and Thin-Layer Chromatographic Identification, AOAC Official Method of Analysis, 46.1.05, 3, 2000. 

Smith RV et al. (1975) Gas-liquid and thin-layer chromatographic determinations of xylenols in microbial extracts. J Chromatogr 106(l) 235-237... 

However, mostly because of the intuitive, trial-and-error approach of thin-layer chromatographers, long ago the technique split into two subtechniques, one bene-fiting from the hnear range of the adsorption isotherm and the other udlizing the... 

From the general framework of the Snyder and Soczewinski model of the linear adsorption TLC, two very simple relationships were derived, which proved extremely useful for rapid prediction of solute retention in the thin-layer chromatographic systems employing binary mobile phases. One of them (known as the Soczewinski equation) proved successful in the case of the adsorption and the normal phase TLC modes. Another (known as the Snyder equation) proved similarly successful in the case of the reversed-phase TLC mode. 

FIGURE 2.4 Three types of concentration profiles encountered among the thin-layer chromatographic bands (a) symmetrical (Gaussian) without tailing, (b) skewed with front tailing, and (c) skewed with back tailing [14],... 

With a growing implementation of the thin-layer chromatographic laboratories with densitometric scanners and particularly in the case of PLC, it seems quite important to reconsider definition of the Rp coefficient and the ways of its determination. Further, it seems strongly advisable to recommend the retardation factor in its i P(max) form as a more practical one for the preparative layer chromatographic usage. 

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