Báo cáo sắc ký bản mỏng TLC (1)

TLC Thin Layer chromatography Which method can be used to evaluate an analyte based on a titrant? T I T R A T I O N Principle TLC technology Rf value Application Outline Principle In TLC, components of the mixture are partitioned between an adsorbent (the stationary phase, usually silica gel, SiO2) and a solvent (the mobile phase) which flows through the adsorbent Individual components move up at different rates, depending on As the mobile phase rises up the TLC plate by capillary action, the intermolecular forces between the component and the silica gel components dissolve in the solvent and move up the TLC plate stationary phase and the mobile phase Principle Analyte Stationary phase mobile phase Stationary phase The stationary phase is a powdered adsorbent which is fixed to a aluminum, glass, or plastic plate  They are polar stationary phase Which conclusions can be drawn from the polarity of the stationary? Solution Rf (A) = 2/5 = 0.4 Rf (B) = 3/5 = 0.6 Rf (C) = 0.8/5 = 0.16 Rf (D) = 4/5 = 0.8 => The unknown contains compounds: C and B Application  Analyzing the purity of a compound  Following the course of a reaction  Identification of components of a mixture (using appropriate standards) Advantage & Disadvantage Advantage - Simple - Quick - Inexpensive - Small amount of the sample Disadvantage - Not exactly to quantify Summary  The more polar analyte, the shorter distance in the plate  Based on Rf , the compounds can be identified Distance run by the solute x Rf = = Distance run by the solvent front xo < Rf < Questions Predict what will happen when this plate is developed in the chamber ? Answer The samples were spotted too low on the plate, and the chamber is too full with the developing solvent Therefore, when the plate is placed into the chamber, the spots will bleed off of the plate and into the solvent The plate cannot be developed Questions What is wrong with the plate shown below? Answer The samples were spotted on the plate too closely together During the development of the plate, the spots will run together, causing inconclusive experimental results Questions A student removed this chromatogram from the development chamber and allowed the solvent to dry What did he forget to do? Answer The student forgot to trace the solvent front before allowing the solvent to dry on the chromatogram No Rf values can be calculated from this chromatogram Questions What is wrong with this student's paper chromatography chamber setup? Answer The chamber is uncovered, so it is not saturated with solvent vapor Questions Consider the following silica gel TLC plate of compounds A, B, and C developed in hexane Which compound, A, B, or C, is the most polar? Answer Compound A is the most polar because it does not travel as far as the other two compounds Thanks for your attention !!! ... evaluate an analyte based on a titrant? T I T R A T I O N Principle TLC technology Rf value Application Outline Principle In TLC, components of the mixture are partitioned between an adsorbent... mobile phase rises up the TLC plate by capillary action, the intermolecular forces between the component and the silica gel components dissolve in the solvent and move up the TLC plate stationary... very slowly up the TLC plate  More nonpolar analytes interact less strongly with the polar silica gel and more strongly with the less polar mobile phase and move higher up the TLC plate attached