Silica caffeine-impregnated

Fig. 42 Chromatogram of polycyclic aromatic hydrocarbons on caffeine-impregnated precoated silica gel 60 HPTLC plates with concentrating zone (Merck). The following can be recognized in increasing Rf value. — 1. benzo(ghi)perylene, 2. indeno(l,2,3-cd)pyrene, 3 benzo(a)pyrene, 4. benzo(b)fluoranthene, 5. benzo(k)fluoranthene, 6. fluoranthene.

Separation methods, multichromato-graphic la 56 Serine la 246,356 lb 132 Serotonin la 70,76,239,240,262,355, 380 lb 37-39,231,243,348 Serotonin metabolites lb 327 Serum lipids la 89 Serum proteins la 74 Sesquiterpene derivatives lb 239,446 Sesquiterpene esters lb 239 Sesquiterpene glucosides la 327 Sesquiterpene lactones lb 448 Sevin lb 387-389 Si 50 000, specific surface area la 91 Silica gel, caffeine-impregnated la 85 -, surface modified la 3 Silica gel 60, specific surface area la 91... 

In the determination of polycychc aromatic hydrocarbons (PAHs), the separation is performed either on caffeine-impregnated HPTLC silica gel 60 plates, on HPTLC-RP-18 plates with a concentration zone or on precoated HPTLC silica gel 60 plates with a concentration zone (Merck Item Nos. 1.15086,1.15037,1.13728). Subsequent dipping in paraffin/n-hexane (1 4) gives not only stabilization of the PAHs on the plate but also an increase in the fluorescence intensity by a factor of 4-5 [83a]. 

Determination of Banned Fat-Soluble Azo Dyes in Spices ON Caffeine-Impregnated Silica Gel Plates... 

During the TLC-MS experiments for confirmation purposes, the additional orthogonal separation selectivity of a short monolithic RP 18e column was used to separate the caffeine impregnation, also eluting from the silica layer, from the azo dyes. The column was integrated in the outlet capillary line of the TLC-MS interface, when a direct online HPTLC-HPLC-MS hyphenation was performed. 

Ready-to-use impregnated plates are also commercially available (i.e., caffeine- or ammonium-sulfate-impregnated silica for the separation of polynuclear aromatic hydrocarbons and surfactants, respectively). 

A,S.ergotamine,ergo tami nine,caffeine Butalbital.phenobarbital Separation on silver impregnated silica gel Lichrosorb Si 100 5iim,imp. with 1.09% Agl... 

Ergta.Ergtaine Butalbital, atropine,scopo- phenobarbital lamine,caffeine Separation on silver impregnated silica gel... 

Silica gel 60, impregnated with caffeine for PAH determination Charge transfer complexes Polycyclic aromatic hydrocarbons (PAH) acc. to German drinking water specification (TVO)... 

Ready-to-use impregnated plates are also commercially available [e.g., caffeine- or ammonium sulfate-impregnated silica for the separation of polycychc aromatic hydrocarbons (PAHs) and surfactants, respectively]. A large number of impregnating agents have been tested, the ones most frequently used in TLC being silver nitrate, metal ions, cationic and anionic surfactants, silicone, and paraffin oil. Boric acid-impregnated silica gel layers are suitable for the resolution of carbohydrates and lipids (see Table 2). 

Impregnating agents that are able to form charge transfer complexes. An example is the HPTLC precoated plate silica gel 60 impregnated with caffeine, which has been introduced in 1994. 

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