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level: Level 5

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TLC

level questions: Level 5

QuestionAnswer
inert supports (glass, plastic, aluminium) with a THIN VENEER of chromatographic media (silica,etc…)TLC plates
SP : solid in plate MP: liquid In planar surface Mobile phase flow by capillary actionThin Layer Chromatography
TLC Adsorbents:Silica – acidic Alumina (aluminum oxide) – basic surface
Preparation of PLATES:1 Plate (made of glass, stainless steel or aluminum) 2 Particles are mixed w/ water or organic solvent to form slurry 3 Coated on plates using spreader 4 dried
Modifications of TLC adsorbant 1 for analysis of basic compounds e.g. antihistamines nacortics. 1 Silica gel with KOH
Modifications of TLC adsorbant 1 silica gel rendered nonpolar by reaction with dichlorodimethylsilane (ODS), e.g. identity test for penicillins. 1 Silanised silica gel
Modifications of TLC adsorbant 1 coated with a liquid PARAFFIN OR WAXY stationary phase, pharmacopeial test for triglycerides and FA in fixed oils. 1 Kieselguhr
TLC DETECTION METHODS1 Iodine vapor -> aminoglycosides 2 Ninhydrin -> fixed oils 3 Potassium permanganate -> sugars 4 Alkaline tetrazolium blue -> corticosteroids 5 Ethanol/ Sulphuric acid 20% -> fluorescent corticosteroids
produce fluorescent (amines and amino acids), used to detect presence of aminoglycosides, pink spots for primary amine, yellow spots for tertiary amineNinhydrin
derivatizing agents – produce brown spots, used to detect Fixed oilsIodine vapor
detect sugars and sugar-like molecules, aliphatic double bondsPotassium permanganate
specific for corticosteroids - blue spotsAlkaline tetrazolium blue
produce fluorescent spots from corticosteroidsEthanol/ Sulphuric acid 20%
Quantitative analysis:1 Area of adsorbent containing the substance can be removed from plate by scraping or by aspirating it into a PASTEUR PIPET 2 The compound is eluted from adsorbent using solvent and the stationary phase is removed by centrifugation or filtration 3 The solute is quantified using spectrometric or chromatographic methods