Silica, thin-layer chromatograph

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... 

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. 

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. 

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. 

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

Isolation of Sesquiterpene Lactones. The ether extract was evaporated and dissolved in 952 ethanol. Then an equal volume of 42 aqueous lead acetate was added. After 1 hour the mixture was filtered to remove precipitated chlorophyll and phenolic products and the ethanol removed under vacuum. The aqueous layer was extracted with chloroform giving a dark colored oil from which the sesquiterpenes were isolated by a combination of chromatographic procedures, i.e., LH-20 gel permeation, silica gel using both packed columns and thin layer plates. A variety of solvents were also used to purify the individual sesquiterpene lactones, e.g., benzene-acetone (1 1), ethyl acetate, chloroform-methanol (9 1). On thin layer chromatographic plates, spots were visualized by spraying with 22 aqueous KMn04 solution. 

Van de Vaart et al. [45] used a thin-layer chromatographic method for the analysis of miconazole and other compounds in pharmaceutical creams. The drugs in creams were analyzed by thin-layer chromatography on silica gel plates with ether in pentane-saturated chamber or with butanol-water-acetic acid (20 5 2). Both active ingredients and vehicle components were detected and Rf values of 67 active ingredients are tabulated. Additional eluents may be needed to separate certain combinations of ingredients. 

Qian et al. [46] determined miconazole nitrate and benzoic acid in paint by a thin-layer chromatographic densitometric method. The drug was spotted on a GF254 silica gel plate, developed with a 42 21 13 5 w-hexane-chloroform-methanol-... 

Zheng and Sun [67] used a thin-layer chromatographic method for the analysis of primaquine and other quinoline derivatives. The drug and other compounds were chromatographed on silica gel GF254 plate, with methanol aqueous 25 28% ammonia (200 3) and chloroform dichloromethane diethylamine (4 3 1), as mobile phases. Spots were located under ultraviolet radiation. The detection limit was 12 pg/mL. Total separation could be achieved by the use of two plates and the respective mobile phase. 

Most of the parallel reactions described in Schemes 4.23 and 4.24 were performed as dry-media reactions, in the absence of any solvent. In many cases, the starting materials and/or reagents were supported on an inorganic solid support, such as silica gel, alumina, or clay, that absorbs microwave energy or acts as a catalyst for the reaction (see also Section 4.1). In this context, an interesting method for the optimization of silica-supported reactions has been described [83], The reagents were co-spotted neat or in solution onto a thin-layer chromatographic (TLC) plate. 

Mix 0.01 M dimethyltryptamine, 0.02 M phosphate buffer pH 7.2 containing 5 mM ascorbic acid, 0.02 M disodium EDTA and 0.01 M ferrous sulfate (CuCI may substitute) and add with stirring at 20-22° 0.02 M H202 (0.01 M may increase yield). Let reaction proceed to completion (2 hours or less) and extract with ethyl acetate. Dry and evaporate in vacuum to get about 30% yield of psilocin. The product, which contains the other OH-DMT s as well, can be chromatographed on silica thin layer with t-butanol-acetic acid-water (ACS 22,1210 (1968)) or on a 5% alumina-Nickel... 

A variety of procedures were utilized to analyze this reaction mixture and to characterize a,10-diaminopolystyrene. Thin layer chromatographic analysis using toluene as eluent exhibited three spots with Rf values of 0.85, 0.09, and 0.05 which corresponded to polystyrene, poly(styryl)amine and a,w-diaminopolystyrene (see Figure 1). Pure samples of each of these products were obtained by silica gel column Chromatography of the crude reaction mixture initially using toluene as eluent [for polystyrene and poly(styryl)amine] followed by a methanol/toluene mixture (5/100 v/v) for the diamine. Size-exclusion chromatography could not be used to characterize the diamine since no peak was observed for this material, apparently because of the complication of physical adsorption to the column packing material. Therefore, the dibenzoyl derivative (eq. 5) was prepared and used for most of the analytical characterizations. 

TLC Analysis. For experiment 2, thin layer chromatographic analysis was carried out by reducing solvent volumes to less than 250 pi under a nitrogen stream, spotting on activated silica gel plates, and developing in chloroform acetone (20 1, v v). Autoradiographs of these plates were prepared by exposing them to X-ray film for 3 or 4 days at -20 C. 

Indinavir sulfate may be analyzed by TLC using E. Merck silica gel 60F-254 high performance thin layer chromatographic plates, and eluted with a mobile phase of 8 1 1 (v/v/v) ethyl acetate methanol ammonium hydroxide [8], Visualization was performed by developing the plate with iodine stain, and viewing under short-wave UV (254 nm) light. When using this method, the Rf of indinavir sulfate is approximately 0.6 [8]. 

After removal of solvent in vacuo, the yellow residue is chromatographed on silica thin layer chromatography (TLC) plates using hexane-CH2Cl2(85 15) as eluent. The major product, 2, is a nearly colorless band observed at Rf = 0.17. This band can be seen better by using an UV lamp and UV sensitized TLC plates (precoated TLC plates, silica gel 60 F-254, layer thickness 0.25 mm, Merck). This band is separated from the starting material (Rf = 0.47) and several minor bands and the products are eluted from the silica gel with CH2C12. An analytically pure sample can be obtained by recrystallization from hexane at - 20 °C. Yield 0.053-0.070 g (30-40%). 

In thin-layer chromatographic methods, sulfonamide residues were first separated on commercially available silica gel plates using various solvent mixtures as mobile phase, and subsequently detected by fluorometry after spraying... 

Thin-layer chromatographic methods are limited to the determination of hygromycin B and have been carried out on commercially available silica gel... 

A more comprehensive approach was reported in 1975 by Brabander and Verbeke (612). In this method, tissue samples were extracted with methanol and the acidified extract defatted with petroleum ether to be loaded onto a Dowex 50W-X8 anion-exchange resin. Following elution with aqueous methanol, the concentrated buffered extract was further defatted with diethyl ether. The sample was derivatized with 7-chloro-4-nitrobenzo-2-oxa-l,3-diazole (NBD-Cl) to be further spotted on a silica high-performance thin-layer chromatographic plate developed in two dimensions using chloroform/ethanol and chloroform/propionic acid consecutively as eluents. Detection of the propylthiouracil, phenylthiouracil, and tapazole residues was carried out on the basis of the fluorescence induction of the NBD derivatives of the drugs with an alkaline cysteine solution. 

Bhushan and Parsad [65] resolved dansyl amino acids on erythromycin impregnated thin-layer chromatographic (TLC) silica plates. The mobile phase used was different ratios of 0.5 M aqueous NaCl-acetonitrile-methanol. Further, Bhushan and Thiong o [66] achieved the chiral resolution of dansyl amino acids on silica TLC plates impregnated with vancomycin chiral selector. The mobile phase used for this study was acetonitrile-0.5 M aqueous NaCl (10 4 and 14 3, v/v). The chiral recognition mechanisms of antibiotic CSPs in sub-SFC, SFC, CEC, and TLC modes of chromatography were found to be similar to HPLC. 

Thin layer chromatographic analysis of 4-acetoxyazetid1n-2-one was carried out on E. Merck Silica gel F254 plates by elution with ethyl acetate. The hexane-soluble impurity (Rf 0.67) was detected by shortwave UV. 4-Acetoxyazetidin-2-one (Rf 0.38) was detected by exposure of the plate for 5 min to chlorine gas followed by spraying with TDM solution (Note 9) and heating with a hot air gun. 

C. F. Poole and M. T. Belay, The influence of layer thickness on the chromatographic and optical properties of high performance silica gel thin layer chromatographic plates , J. Planar Chromatogr. 4 345-359 (1991). 

Peak from Sephadex LH-20 column chromatography (see Fig. 4.6) Polyamide thin-layer chromatographic method (3-dimensional) Silica gel thin-layer chromatographic method0 (one-dimensional )... 

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