Solvent Systems and Detection

Lipophilic compounds such as alkyl amides are separated over silica gel in the solvent system toluene-ethyl acetate (70 30) and detected with vanillin-sulphuric acid reagent (VS No. 42), vis. 

angustifoliae radix (narrow-leaved) coneflower root Echinacea angustlfolia DC Asteraceae Herba 

7% echinacoside 6-0-caffeoyl-verbascoside Caffeic acid derivatives alkyl amides Desrhamnosyl-verbascoside rutin 

Cutting almond, wiki quinine Missouri snake root Parthenium inlegrifolium L. Asteraceae 

Sesquiterpene esters Echi nadiol-, epoxyechin adiol-echinaxantliol- and dihydroxynardol-dnnamale Caffeic acid derivatives 

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Silica gel GF absorbents are used with all the solvent systems and detection is with short wave UV light (v254 nm) or with exposure to iodine vapor. 

The same adsorbent (silica gel 60 Fz-,., precoated plates, 20 X 20 cm Merck, Darra,stadt), the solvent systems and detection methods can be used a.s described for ascending I LC. Good. separations are obtained by solvent migrations of 5 cm only. 

The three drug extracts can be distinguished by their different flavonoid and phenol carboxylic acid content when separated in the polar solvent system and detected with NP/PEG reagent in UV-355iim. 

For analysis of sennoside,s in. Sennae folium or fructus, the. solvent. system and detection method descriped in Fig, 7, 8, chap, 2) should be used. 

Opiates can be identified by thin-layer chromatography (TLC) with many different combinations of mobile-phase solvent systems and detection reagents. A solvent system prepared with ethyl ace-tate-methanol-ammonium hydroxide (85 10 5) is commonly used to resolve heroin, codeine, acetylco-deine, morphine, and acetylmorphine. After development, opiates can be visualized by spraying or dipping the chromatogram in Dragendorff, iodoplatinate, or Marquis reagent. 

Many alkaloids are derivatives of tertiary amines and, as the name implies, are alkaline in nature. Numerous drugs of abuse as well as abused drugs are alkaloids. An extensive list of alkaloids, their sample preparation, solvent systems, and detection reagents have been given by Wagner et al. (1984). 

Other solvent systems and detection reagents are recommended for the identification and confirmation of drugs and their metabolites. These include ethyl acetate-methanol-concentrated ammonium hydroxide (90 7 3) with detection by fluorescamine, diphenylcarbazone, and iodoplatinate reagents for D-amphet-amine, barbiturates, and acidic drugs (e.g., phenobarbital, Dilantin, Mellaril, Valium, chlorpromazine, Lomotil, and Talwin) and ethyl acetate-methanol-concentrated ammonium hydroxide-water (85 13.5 0.5 1.0) with detection by... 

Heinisch et al. described methods for detecting drugs containing chlorine, bromine, or iodine that can be extracted from acidic solutions with ether, then identified with TLC using 12 solvent systems and silica gel F254 plates [66]. 

A comparison of ELISA, HPLC, and HPLC-ELISA methods was published for the determination of SAL in chicken liver tissue. Samples were homogenized with MeOH and extracted with methylenechloride. Some samples were analyzed by HPLC using the isocratic solvent system and postcolumn derivatization (vanillin in MeOH containing sulphuric acid), with the eluent monitoring at 520 nm. The HPLC-ELISA system was used to characterize nonspecific effects analyzing column fractions by ELISA, since this detection is over 1000 times more sensitive than the spectrophotometric one. This alleviated the need to derivatize the drug prior to the detection (104). 

Several TLC systems are available for the analysis of disopyramide phosphate. Solvent, adsorbent, and detection parameters are summarized in Table 3. 

Strelyuk described a thin-layer chromatographic method for the qualitative detection of dipyridamole [62], Data were presented on the use of various reagents for the detection by solution color change and precipitate formation in the thin-layer chromatography of dipyridamole. Thin-layer chromatography was on silica gel-calcium sulfate dihydrate, with methanol aqueous ammonia or benzene-dioxane being used as the mobile phase with detection at 270-330 nm. The Rvalues were 0.7-0.75 and 0.5-0.55 for the two solvent systems, and the detection limit was... 

For further identification of the separated steroid alkaloids, Bushway et al. used UV absorption ratios at 215, 225, 235 and 245 nm. For the detection, a wavelength of 215 nm was preferred to 208 nm because of a more stable baseline, and with sufficient sensitivity. The sensitivity could be increased by using acetonitrile - water as mobile phase. Such a solvent system allowed detection at 200 nm. 

C Variation of the solvent system and the detection with pyridine reagent reveals a broad band of red zones in the Rf range 0.5-0.6 (Tl). Red zones at R, 0.9-0.95 show chlorophyll coniponnds. 

Fig. 1 This solvent system and the AS reagent are suitable for the separation and the detection of triterpene-saponins, e.g. senegins in Senegae radix (1), as well as steroid (ester) saponins, e.g. Smilax saponins in Sarsaparillae radix (2).

In practice, P.c. consists of the physical separation, followed by spraal detection methods for the location of the individual substances. It may be performed on an analytical or preparative scale. With respect to the movement of the solvent system and position of the paper, P.c. can be ascending, descending or horizontal. Single or two dimensioi procedures, and radial P. c. (circular filter paper technique) are commonly used. Additional useful techniques are multiple development (the first solvent is removed by dryi and a different solvent is run in the same dimension) and flow-through or run-off (the solvent is allowed to run for a prolonged period by dripping from the edge of the paper). 

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