Standard Methods for the Examination of Water and Wastewater, 21 st Ed. (APHA AWWA 2005). Gravimetric Analysis. Sulfate precipitation SO 4 2- + BaCl 2 -> BaSO 4 (s) + 2Cl - BaSO 4 is highly insoluble and can be isolated on filter paper Watch for imprurities: Confounding effect: Fe.
SO42- + BaCl2 -> BaSO4(s) + 2Cl-
BaSO4 is highly insoluble and can be isolated on filter paper
Watch for imprurities: Confounding effect: Fe
BBC Bitesize, 2011
Gravimetric Analysis of SO42-
BaSO4 (g) / F.W. of BaSO4(g/mol) = ______ (mol)
______(mol) / initial vol. (L) = ___________ (mol/L)
_____ (mol/L) * F.W. of SO42- (g/mol) = ______ (g/L)
= ______ (mg/L)
“Chromatography” is the general term for a variety of physico-chemical separation techniques, all of which have in common the distribution of a component between a mobilephase and a stationary phase.
Paper chromatography. Image: Membrane Solutions, 2011
Ion Exchange Chromatography
A resin (stationary solid phase) is used to covalently attach anions or cations onto it. Solute ions of the opposite charge in the mobile liquid phase are attracted to the resin by electrostatic forces.
Different Types of Ion Exchange Resin Beads
SEM of Resin Coating
Ion Exchange Resin Beads are packed into Columns for inline flow of Mobile Phase.
Utilizes a mobile liquid or gaseous phase that is adsorbed onto the surface of a stationary solid phase. The equilibriation between mobile and stationary phases produces separation of solutes.
Based on a thin film formed on the surface of a solid support by a liquid phase. Solute equilibriates between the mobile phase and the stationary phase.
Normal: Polar stationary phase (e.g. silica gel), non-polar mobile (org. solvents)
Reverse: Non-polar stationary phase, polar mobile phase (e.g., aqueous, alc.)
Molecular Exclusion Chromatography
This type of chromatography lacks an attractive interaction between the stationary phase and solute. The liquid or gaseous phase passes through a porous gel which separates the molecules according to its size.
Most selective type of chromatography employed. It utilizes the specific interaction between one kind of solute molecule and a second molecule that is immobilized on a stationary phase. The ion or protein is later extracted by changing ionic strength or pH.
High Performance Liquid Chromatography (HPLC) is similar to reverse phase, only in this method, the process is conducted at a high velocity and pressure drop. The column is shorter and has a small diameter, but it is equivalent to possessing a large number of equilibrium stages.
An Electrical Conductivity Detector Sensing Cell
Proxy for concentration is measured by specific conductance
Eluent – The mobile phase that is mixed with the sample to carry it past the stationary phase
Analyte – An analyte is a substance or chemical constituent that is determined in an analytical procedure
Matrix – In chemical analysis, matrix refers to the components of a sample other than the analyte. The matrix can have a considerable effect on the way the analysis is conducted and the quality of the results obtained; such effects are called matrix effects.
Suppressor – A device which suppresses signals or ions that are not analytes of interest, or may interfere with analyte analysis.
Ion suppression is necessary when the mobile phase has a high conductivity and the contribution of the eluted ions are relatively so small that their signal is swamped by the background signal from the mobile phase.
Gas chromatography makes use of a pressurized gas cylinder and a carrier gas, such as helium, to carry the solute through the column. The most common detectors used in this type of chromatography are thermal conductivity and flame ionization detectors.
Gas adsorption chromatography involves a packed bed comprised of an adsorbent used as the stationary phase. Common adsorbents are zeolite, silica gel and activated alumina. This method is commonly used to separate mixtures of gases.
Gas-liquid chromatography is a more common type of analytical gas chromatography. In this type of column, an inert porous solid is coated with a viscous liquid which acts as the stationary phase. Diatomaceous earth is the most common solid used. Solutes in the feed stream dissolve into the liquid phase and eventually vaporize. The separation is thus based on relative volatilities.
Capillary gas chromatography is the most common analytical method. Glass or fused silica comprise the capillary walls which are coated with an absorbent or other solvent. Because of the small amount of stationary phase, the column can contain only a limited capacity. However, this method also yields rapid separation of mixtures.