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Advanced Analytical Methods in Chemistry: Chromatography, Electrophoresis, Potentiometry, and Titration

This resource provides an in-depth exploration of advanced analytical methods utilized in chemistry, including chromatography, electrophoresis, potentiometry, titration, and spectrophotometry. Each method is discussed with focus on its principles, mechanisms, and practical applications. Key chromatography techniques are compared based on physical states and separation mechanisms. Potentiometry is detailed with equations and electrode types, while titration is outlined with various endpoint detection methods. The significance of each technique in quantitative analysis is emphasized. **Relevant

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Advanced Analytical Methods in Chemistry: Chromatography, Electrophoresis, Potentiometry, and Titration

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  1. Analytic methods II. part Jana Švarcová

  2. Chromatography • Electrophoresis • Potentiometry • Titration • Spectrophotometry

  3. Chromatography methods • Basic theory – separation of mixtures  distributed between two phases • stationary phase (SF)  • mobile phase (MF) – carries the mixtures • The separation is based on differential partitioning between the mobile and stationary phases • Differential rates of migration as the mixture moves over adsorptive materials provide separation • Various components of mixtures have different affinities for the stationary phase

  4. Chromatography methods chromatography • Chromatography techniques by: • physical state of mobile phase • layout of stationary phase (column/planar) • separation mechanism liquid (LC) gas (GC) Gas-solid distributive adsorption ion-exchange gel affinity Gas-liquid paper thin layer

  5. Basic term Typical chromatographic separation of substance tR w – width of peak h substance w1/2 – half-width tR – retention time tM w1/2 absorbance (AU) tR w time (min)

  6. Liquid chromatography • MF - a liquid of low viscosity which flows through the stationary phase bed column Computer data - results Reservoir of mobile phase sample detector pump waste http://www.pharmacelsus.de/hplc/

  7. HPLC • High Performance Liquid Chromatography • higher flow rate of mobile phase (high pressure ∼ 107 Pa) • the better separation

  8. Gaschromatography • The mobile phase in gas chromatography is generally an inert gas

  9. TLC - thin layer chromatography • Plane layout of SF - layer of solid particles spread on a support • Compounds in the sample mixture travel different distances according to how strongly they interact with the stationary phase a - distance the spot traveled a b b – maximum distance the eluent traveled start start http://web.natur.cuni.cz/~pcoufal/tlcpc.html Retention factor RF - RF = a/b

  10. Electrophoresis • A class of separation techniques - analytes are separated by their ability to move in gel in response to an applied electric field • Separation – size of charge, shape and size of molecule • Migration – cations migrate towards the cathode (-), anions towards the anods (+)

  11. Electrophoresis Electroforeogramofserumproteins proteins – fraction%

  12. Potentiometry • Anlytical method – analytes are studied by measuring the potential (volts) in the electrochemical galvanic cell (the difference in electrode potentials)

  13. Potentiometry – basic terms • Two electrodes (acording potential stability) • Indicator electrode • Reference electrode • The potential is related to the concentration of one or more analytes

  14. Potentiometry • Nernstequation – calculation of the electrode potential E R – theuniversalgasconstant (8,314 J.K-1.mol-1) T – absolutetemperature F – the Faraday constant, the number of coulombs per mole of electrons (96 500 C.mol-1) a – the chemical activity for the relevant species; ox/redforms Eo –  the standard reduction potential

  15. Potentiometry – analyticalapplication • Potentiometrictitrationcurve Potential (V) Volume oftitrant (ml)

  16. Electrodes • Referent electrodes: • calomel • Ag/AgCl • Indicatorelectrodes: • Ion-selective Potential in turn is described by theNernstequationand is directly proportional to the pH difference between solutions on both sides of the glass.

  17. Titration • laboratory method of quantitative chemical analysis - is used to determine the unknown concentration of an identified analyte • the titrant – reagent (is prepared as a standard solution) • A known concentration and volume of titrant reacts with a solution of analyte to determine concentration • Titre – the volume of titrant reacted • Detection of the equivalence point • appropriate pH indicator is added (reflecting the pH range of the equivalence point) • Different methods to determine the endpoint include • Spectroscopy • Potentiometer • Conductivity Burette

  18. Acid–base titration • Indicators – organicchemicalcompoundwhich causes the colour of the solution to change depending on the pH (sensitivity to differentconcentrationof H+ions)

  19. Acid-base titration • Calculate the mass of sulfuric acid in the sample solution when theconsumptionofstandard titrantsolutionNaOH was 24.22 ml at a concentration of 0.1022 mol/l.

  20. Spectrophotometry - VIS • Analyticalapplications - measure concentrations of absorbing (coloured) materials based on developed calibration curves • To obtainedthe unknown concentrationof sample – calibrationcurve (graph of the transmittance or absorbance versus the wavelength) • Absorption of VIS light by a sample • 390 – 750 nm

  21. Spectrophotometry - measurement • the absorbance of a sample will be proportional to the number of absorbing molecules in the spectrometer light beam  • transmittance T • absorbance A l beamof monochrom. radiationΦo beam of radiation leaving the sample Φ • Lambert-Beerlow: A = ε × c × l ε – Molar absorptivity c - sample concentration (mol/L) l – length of light path through the sample (cm)

  22. Absorptionspectroscopy •  performed across the electromagnetic spectrum→ choiceofwavelengthmaxabsorption sample

  23. VIS – analytical applications • Blank • Lambert-Beerlow – unknownconcentrations • Calibartioncurve

  24. Basic structureofspectrophotometers

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