Thin layer technique

The thin-layer technique (CA 60, 6691) utilizes aliquots of proplnt ether extract (I) and the ether soln (II) of a known mixt. II consists of nitrates of glycerol and glycol, di-Bu or di-Et phthalates, Et or Me centralites, DNT, and diphenylamine. The chromatoplates are made of 85 15 silica gel and plaster of Paris. These plates, containing spots of I and 11, are developed with 1 1 C6H6-petroleum ether, then sprayed with specific detectors by color. The method is much quicker and easier than chemical analysis and simpler than infrared spectroscopy and column chromatography... 

Fermentation tests are based on the ability of yeast to oxidize the sugar to yield ethanol and carbon dioxide, although only the D-isomers are fermentable and only relatively few of these. Modem chromatographic techniques are, however, much more acceptable and paper and thin-layer techniques are useful for routine separation and semi-quantitation of carbohydrate mixtures, although GLC or HPLC techniques may be necessary for the more complex samples or for quantitative analysis. 

Paper chromatography has been used successfully for many years and is still a useful tool despite the fact that thin-layer techniques, especially with readily available commercially prepared plastic or foil-backed plates, offer advantages of speed, resolution and easier handling. Larger volumes of sample can be applied to paper, permitting the subsequent elution of a particular amino... 

Note The conventional co-crystallization is usually termed dried droplet preparation. The original thin layer technique involves preparation of a thin HCHA layer from solution in acetone on top of which the analyte is placed in a second step without re-dissolving the matrix. [95,97]... 

The student in the later stages of his training will certainly be required to recrystallise quantities of solid material within the range of 1 g to fractions of a milligram. These small quantities could arise from (i) small-scale preparations involving very expensive materials (ii) preparations of derivatives of small amounts of natural products (iii) by-products isolated from a reaction process (iv) chromatographic separation procedures (column and thin-layer techniques), etc. For convenience the experimental procedure to be adopted for recrystallisation of small quantities may be described under three groups ... 

The history, theory, and applications of paper and thin-layer techniques are described in several books. " The first report on the subject of thin-layer chromatography was by Izmailov and Shraiber, who applied the technique to the separation of pharmaceutical tinctures. 

You are now to apply the thin-layer technique to a group of colorless compounds. The spots may be visualized under an ultraviolet light if the plates have been coated with a fluorescent indicator, or chromatograms may be developed in a 4-oz bottle containing crystals of iodine. During development, spots appear rapidly, but remember that they cilso disappear rapidly. Therefore, outline each spot with a pencil immediately on withdrawal of the plate from the iodine chamber. Solvents suggested are as follows ... 

Rotation planar chromatography (RPC), as with OPLC, is another thin-layer technique with forced... 

As examples, experimental F(E) isotherms at = constant for Pb and T1 UPD in acidic perchlorate electrolyte on AgQikl) single crystal faces with Qtkl) = (111) and (100) are shown in Figs. 3.9 and 3.10, respectively [3.97, 3.105]. These isotherms were measured stepwise, waiting for equilibrium conditions according to polarization routines illustrated in Fig. 3.11 using the twin-electrode thin-layer technique" (TTL) for Pb UPD and the flow-through thin-layer technique" (FTTL) for T1 UPD. 

Both thin-layer techniques were developed by Schmidt, Siegenthaler et al. [3.55, 3.67, 3.68] and allow an independent and precise measurement of q(E,p) and iXE.fi) isotherms. From the q-T plot, the electrosorption valency can be directly determined as illustrated in Fig. 3.12 [3.97, 3.105]. The electrosorption valency was found to be Y = z m both UPD systems indicating the absence of cosorption and competitive sorption processes in the systems studied. 

In early Me UPD studies on single crystal substrates S [3.89, 3.98, 3.122], classical electrochemical techniques such as cyclic voltammetry, r(E,ju) isotherm measurements using thin-layer techniques ( PlL, FTTL), transient techniques in the time domain, and electrochemical impedance spectroscopy (EIS) in the frequency... 

FTTL flow-through thin layer technique... 

Currently, most planar chromatography is based on the thin-layer technique, which is faster, has better resolution, and is more sensitive than its paper counterpart. This section is devoted to thin-layer methods. Capillary electrochromatography is described in Section 33D. 

Preparative agar gel electrophoresis can be done both in columns and thick layers. Most of the column equipment used for polyacrylamide gel electrophoresis can also be used for agar or agarose gel separations [226-268]. With the thin-layer technique... 

Sternberg et al. (31) reported a thin layer chromatographic procedure which afforded separation and quantitation of LAL. Sternberg s technique allowed the detection of as little as 3 ng of LAL. High standard deviations and relatively long separation times tend to limit practical application of the thin layer technique (60-62), imporved the technique and shortened the time to 4 hrs. 

From the thin-layer technique, Kamai and colleagues found partial resolution of racemic [(Bz)(Et)(pentyl)(Ph)As]Br on vibro-crushed t/-quartz powder the (-)-enantiomer adsorbed preferably. Chemyaev and coworkers obtained partial resolution of the racemic complex [Pt(Hal)(NH3)N02]. On /-quartz the (+)-complex was adsorbed preferentially and exhibited only (+) 0.02-0.05° at 579 nm, even so, this rotation proved to be enough for identification of the spatial structure of the complex. 

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