Thin-Layer Chromatography and Detection

Standard compound allicin, diallylsulphide, dipropyl- and dimethylsiilphinate lOmgis Reference dissolved in 2 ml dichloromethane 15 pi is used for TLC. solutions 

Silica gel 60 Fj -precoated TLC plates (Merck, Germany). Adsorbent 

B Piperis nigri fructus (2) is characterized by the yellow piperine zone (T2) at U, 0.25. The essential oil compounds are seen as blue zones at R, 0.6 and at the solvent front. 

C Piperis albi (2) and Piperis nigri fructus (3) both contain piperine at Rf 0.5 (Tl) and dipiperine at R, 0.7. Piperis fructus mainly differs in the contribution of minor compounds, sucb as piperyline (R, 0.15), piperettine, piperine isomers (R, 0.55) and piperaesthin A at R, — 0.75. Different amounts of terpenes are detectable as violet-blue zones at the solvent front. 

B n-butanol-n-propanol-glacial acetic acid-water (30 10 10 10) 

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Traditional analysis for cyclodiene insecticides involves their extraction from rendered adipose fat followed by gas or thin layer chromatography and detection by electron capture or mass spectrometry (6z. 1). These methods are time consuming, require sophisticated equipment and highly trained personnel. Because of the persistence of cyclodiene insecti-... 

The first part of the book consists of a detailed treatment of the fundamentals of thin-layer chromatography, and of measurement techniques and apparatus for the qualitative and quantitative evaluation of thin-layer chromatograms. In situ prechromatographic derivatization techniques used to improve the selectivity of the separation, to increase the sensitivity of detection, and to enhance the precision of the subsequent quantitative analysis are summarized in numerous tables. 

Kavetskii et al. [224] developed a method for the simultaneous determination of pesticides in soil. A combination of thin layer chromatography and gas chromatography was used. The pesticides examined were 4,4 DDT, 4,4 DDD, 4,4 DDE, 2,4 DDT, GHCG, aGHCG, Metaphos, Phosphamidon, Phozalone, Atrazine, Prometryne, Simazine and 2,4 dichlorophenoxy acetic acid. Detection limits were in the range 0.5-5pg kgy1. 

If the compound shows no convenient intrinsic feature, it may be possible to develop a detectable characteristic by chemical modification and, particularly in thin-layer chromatography and electrophoresis, many locating reagents which are specific for various groups of compounds are available. 

The inclusion of a fluorescent dye into thin-layer plates can be used to detect substances that quench its fluorescence and so result in dark zones when the chromatogram is examined under ultraviolet radiation. Autoradiography can also be used in thin-layer chromatography and electrophoresis when samples are radio-labelled. 

DCA, 158. Reaction in solution affords numerous products, among which 158 and 164 were not formed in thin-layer chromatography (TLQ-detectable amounts. 

Cinnamyl anthranilate can be assayed by a method based on ester hydrolysis. Bulk samples of food-grade cinnamyl anthranilate have been analysed for purity by thin-layer chromatography and high-performance liquid chromatography. A method has been described for determining the content of this compound in food products by steam distillation followed by paper chromatography and examination under ultraviolet light it has a limit of detection of 1 pg (lARC, 1983). 

A Ibe, K Saito, M Nakazato, Y Kikuchi, K Fujinuma, Y Naoi, T Nishima. Detection and determination of aspartame in foods by thin layer chromatography and high performance liquid chromatography. J FoodHyg Soc Jpn 26(1) 1-6, 1985. 

A. Pelander, I. Ojanpera, K. Lahti, K. Niinivaara and E. Vuori, Visual detection of cyanobacterial hepatotoxins by thin-layer chromatography and application to water analysis, Water Res., 10 (2000) 2643-2652. 

Kiffe, M., Jehle, A., and Ruembeli, R. (2003). Combination of high-performance liquid chromatography and microplate scintillation counting for crop and animal metabolism studies A comparison with classical on-line and thin-layer chromatography radioactivity detection. Anal. Chem. 75 723-730. 

Fluorescence may by induced using labeled mono- or polyclonal antibodies raised against the compound of interest. This technique has been used successfully to detect the presence of okadaic acid in cultures of Prorocentrum lima, and, further, to estimate quantities of the compound in individual cells.110 Immunofluoresence in combination with thin layer chromatography and ELISA techniques have also been used to detect multiple haptens in mycotoxin families.111112... 

Waggon and Jehle [121,122] have reported on the quantitative detection of triphenyl and tri-, di-, and monobutyltin species in aqueous solution by a combination of liquid-liquid extraction, thin layer chromatography and anodic stripping voltammetry. 

The fatty/waxy products contained the lipophilic substances, including fatty oils, waxes, resins and colorants. Valuable pharmacological effects were proved for some minor constituents of these products (e.g. triterpenes, diterpenes, sterols and carotenoids). Thin layer chromatography and on-line UV-VIS spectroscopy were used for the quick identification and quantity determination of these compounds using authentic samples as standards. The SFE method proved favorable in terras of both extraction yield and speed of carotenoids. The CO2 extracts of the lavandin, clary sage and thyme have been enriched in triterpenic compounds (a-es P-amyrin, oleanic acid, ursolic acid, etc.) and phytosterols. Both free and esterified triterpenoids were present in the extracts of the different samples. Furthermore camosol and other diterpenes were detected in the SFE extract of Lamiaceae plants. The fatty acid composition was only slightly different for extracts obtained by SFE and conventional hexane extraction. 

The variety of sampling methods available in spectrofluorimetry makes it a very versatile technique. The most frequent mode of sample presentation is as a dilute solution, although gases, suspensions, and solid surfaces can also be examined. Combinations of spectrofluorimetry with thin-layer chromatography and high pressure liquid chromatography are particularly advantageous for sensitive and selective detection offluorophores. 

High Pressure Liquid Chromatography. In serum chlorpropamide or tolbutamide, sensitivity 7 pg/ml for chlorpropamide, UV detection—R. E. Hill and J. Crechiolo,/. Chromat.y 1978,145 Biomed. AppL, 2,165-168. In urine chlorpropamide and metabolites, using initial separation by thin-layer chromatography, UV detection—J. A. Taylor, Clin. Pharmac. Ther., 1972, 75,710-718. 

Thin-layer chromatography and HPTLC offer many possibilites for the determination of mycotoxins in plant or animal samples. Plant samples usually contain higher concentrations of mycotoxins, but analysis of animal tissues may be necessary either to confirm a suspected mycotoxicosis or to detect potential residues for human food. Many official methods are available, based on TLC, and the recent development of HPTLC also offers many possibilities for the detection and quantitation of several mycotoxins in various biological samples. 

Verpoorte and Svendson53) have compared thin-layer chromatography and high performance liquid chromatography when analysing alkaloids they found the detection limit in HPLC to be 1-100 ng and in TLC to be 10-100 ng. 

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