Development of TLC plates

TLC is used to determine copper in aluminum alloys. The process involves the sampling of the investigated material by anodic dissolution, development of TLC plate with acetone -f HCl -f HjO (70 15 15), and the identification of analyte by 1-(2-pyridylazo)-2-naphthol [70]. A TLC system comprising silica gel as stationary... 

After development of TLC plates, the next important step is to detect the separated components so as to determine their respective Rf values. 

Antibiotics, 445-480 aminoglycosides, 457-461 cephalosporins, 452-457 macrolides, 463—468 miscellaneous antibiotics, 473-478 poiicillins, 446-452 pqnides, 461-463 tetracyclines, 468-473 Anticircular development of TLC plate, 27 Antioxidants, 803... 

Circular development of TLC plate, 27 Classical preparative layer chromatography (CPLC), 307,308-317 applicability of, 317... 

Linear analyzers, 350-352.357 Linear development of TLC plate, 25-27 Lipids. 683-714 advantages of TLC. 683 chromatographic systems. 691-698 one-dimensional solvent systems, 692-b94 mobile phase, 692 stationary phases, 691-692... 

With regard to the line 1, the development eould be noted for the following methods those, where peroxide derivatives of earboxylie aeids are used methods of multiple-wavelength speetrophotometrie analysis methods of quantitative aeeounting of a priori information methods of liquid ehromatography (a Unified adsorption eenter model and a Mobile phase effeetive eoneentration eoneeption an applieation of mieellar ehromatography standardization of TLC-plates). 

For preparative separation, the mobile phase can be selected by performing preliminary analytieal TLC experiments. In PLC, the chromatographic chamber has to be saturated within 2 h beeause the development of preparative plates is much slower than the analytical development. In the analytical preassay during the selection of mobile phase composition, the chromatographic chamber must be hned with a sheet of filter paper to obtain a saturated atmosphere with mobile phase vapor. Then, the optimized analytical mobile phase can be transferred imchanged to preparative separations in the saturated developing chamber. 

Preparation of TLC Plates The Plate Spotter Spotting the Plates Developing a Plate Visualization Interpretation Multiple Spotting Preparative TLC... 

Flexible and versatile dissolving solvent and mobile phase The choice of the sample solvent is not as critical in TLC as in HPLC because it is removed by evaporation before development of the plate. On the contrary, in HPLC the dissolving solvent chosen must be compatible in terms of composition and strength with the column and mobile phase. The same logic applies to the TLC mobile phase that is completely evaporated before detection. Therefore, the UV-absorbing properties, purity, or acid and base properties of the mobile phase are not as crucial as with HPLC. In addition, there is less solvent waste in TLC than in HPLC. 

Samples (3 mL) of substrate containing cultures were taken at 24, 48 and 120 h after substrate addition and extracted with equal volumes of ethyl acetate. The organic phases were separated by centrifugation for 3 min in a desktop centrifuge and used for TLC analysis. 30 0 pL of sample extracts were spotted onto TLC plates that were developed with ethyl acetate hexane (v/v). Visualization of TLC plates was done by fluorescence quenching under 254 nm UV light. 7 f values were naphthalene, 0.90 ... 

HPTLC is conducted on TLC plates which are coated with purified silica gel with a particle range of 2-10 fjm as opposed to 2-25 jum for standard commercial TLC plates. The narrower particle size range means that a greater number of theoretical plates are available for separation and thus the spots on the TLC plate remain tighter. These type of plates may be run in a standard type of TLC tank but optimal performance is obtained from horizontal development of the plates using apparatus of the type shown in Figure 13.10. 

Fluorography of TLC Plates. TLC plates were developed in the appropriate solvent system and dried at 50° for 10-15 minutes. 

TLC Analysis. Two-dimensional TLC was carried out on Anasil-OF silica-on-glass plates. An ether solution of the crude sample was spotted on a plate, and the plate was developed twice with heptane to carry nonpolar components to the top edge of the plate. The acids remained at the origin and were separated by development of the plate perpendicular to the original direction with hep-... 

Analytical TLC differs from PLC in that larger weights and volumes of samples are applied as a band across the entire layer width to thicker (0.5-2 mm) and sometimes larger layers, the purpose of which is the isolation and purification of 10-1000 mg of sample for further analysis. Multiple development of the plate is commonly used, and the separated substances are detected by a non-destructive method (e.g., under UV light and iodine vapors), and recovered by extraction from scraped layer material. PLC can be used to isolate sufficient pure drug compounds for confirmation by spectrometry in cases where analytical TLC is not adequate for identification. Examples of pharmaceutical applications of PLC include a new sesquiterpene trimer and phenylpropanoid glycosides. ... 

Thin layer chromatography is carried out by using 20 x 20-cm preparative TLC plates made with silica [Kieselgel 60G (EM Science) or Silica Gel GF (lO/im, Analtech)] to an approximate thickness of 0.S mm. The mixtures are applied as dichloromethane solutions using a drawn-out Pasteur pipet. Development of the plates is conducted in air. The capacity of each plate is lOOmg. 

For consistent application of solutions to a TLC plate, gently touch a microcapillary containing the analyte solution to the surface of the plate and allow a small portion of the aliquot to flow out. Moving parallel to the baseline of the plate, apply the solution in a narrow band about 0.5 cm long. Upon development of the plate, tight, narrow bands are formed, making visualization of trace impurities easier [2]. 

The steps involved in preparative TLC are (1) application of the sample onto the plates, (2) development of the plates, (3) detection and location of the compound of interest, and (4) extraction of the compound of interest. Detection is usually by ultraviolet light. When the separated compound of interest is located on the plate, the band is scraped and the impurity is extracted from the stationary phase (i.e., silica gel) with an appropriate solvent. The extracted material is filtered or centrifuged, and the solvent collected is evaporated to yield the isolated material. It is essential to remove silica gel and other interfer-ent that may inhibit the identification of the compound. The isolated material is submitted for LC-MS analysis. 

After development on TLC plates, amino-substituted 1,3,5-triazines can be revealed by use of the chloro-toluidine reaction <83JC97>. This is a sensitive method developed for the detection of amino and imino compounds on paper chromatograms. The method depends on the formation of chloramines which are then detected by liberation of iodine from a starch-potassium iodide reagent. 

Levarato has developed a series of quantitative methods for the determination of prednisolone along other corticoids after extraction from preparations and separation by TLC on silica gel plates and determination by spectrophotometric (absorption at 240 nm) or colorimetric methods (INH-hydrazone formation, tetrazolium reaction) (81). A simple, fast and quantitative TLC-method for the determination of prednisolone in tablets is described. The method is stability-indicating with respect to accuracy, specificity, sensitivity and precision. The coefficient of variation was between 1.26 and 1.96 % and the sensitivity was about 25 ng. The chromatographic separation was performed on a silicagel plate using two step development of the plate (82). A simple TLC method of separation of prednisolone from other corticosteroids is reported (83). Prednisolone and the dephosphorylated D-homosteroid can be separated on silanised silica gel TLC plates (36). 

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