1 Chemical Separations Somsak Sirichai Lecturer Semester 1/2002

2 Lecturer: Somsak Sirichai Office: Chemistry building, room c307 Phone: ext Office Hours: Tuesday 8-10 am Code: Subject: Chemical Separations Credits: 2(2-0-4) Lecture: Chemistry building, room c310

3 Course Description: Study chemical separations. Topics: Volatilization, Distillation, Extraction, Ion Exchange, Chromatography and Electroseparation Grading: Midterm exam40% Final exam40% Assignments10% Quizzes10%

4 Text:None Primary References: Karger, Snyder & Horvath; An Introduction to Separation Science Meloan; Chemical Separations Principles, Techniques, and Experiments J ö nsson; Chromatographic Theory and Basic Principles Ahuja; Trace and Ultratrace Analysis by HPLC Khaledi; High Performance Capillary Electrophoresis

5 What is separation? ‘ a process whereby the compounds of interest are removed from the other compounds in the sample that may react similarly and interfere with a quantitative determination ’ important in the preparation of pure compounds often complex and may require several different methods and much time before the final determinative step

6 Terms common to chemical separations cleanup spiking a practical term used to describe the handling of a sample before the measuring step the addition of a known amount of a standard to a sample so that recoveries can be determined and to calibrate the signal for quantitation

7 Percent recovery: The amount of a spike that can be recovered when processed through the entire analysis procedure values of % are desired. if <80%, modify the method.

8 Separation Methods: phase changes extraction ion exchange resins chromatography electric field flotation membranes miscellaneous techniques separations involving

9 Phase changes sample no vacuum appliedvacuum applied solid to gas or vapor solid to liquid to vapor liquid to vapor solid to vapor volatilization zone melting (batch, azeotropic, extractive, steam, immiscible solvents) distillation (vacuum, molecular, sublimation) distillation Lyophilization

10 Extraction sample liquidsolid liquid to liquid Liquid to liquid countercurrent liquid to solid to liquid solid to vapor Batch, Continuous solvent heavier, Continuous solvent lighter countercurrent SPE Continuous (soxhlet) Supercritical fluid (SFE)

11 Ion exchange resins sample Ionic molecules Ionic or polar molecules Neutral molecules Ion exchange Ion chromatography Ion retardation Ion exclusion Ligand Exchange

12 Chromatography sample Liquid mobile phase gas mobile phase Liquid mobile phase columnflat gravity flow pressure applied displacement multicolumn affinity size exclusion flash high performance gas-liquid paper thin layer

13 Electric fields sample Ions deposited as metal electrodeposition Gel type matrix required yesno electrophoresis Capillary zone electrophoresis Field flow fractionation horizontal immunoelectrophoresis disc ion focusing yes no

14 Volatilization ‘ the conversion of all or part of solid or a liquid to a gas ’ The gas may be produced by: 1. direct heating 2. applying the principle that strong acids displace weaker acids and strong bases displace weaker bases

15 Example: the evolution of CO 2 (g), weak acid, from solid CaCO3 by adding HCl, a strong acid the removal of NH 3 (g), a weak base, from solid (NH 4 ) 2 SO4 by adding NaOH

16 3. by oxidation burning a sulfide in air to produce SO 2 4. by reduction, or converting the elements to hydrides, such as AsH 3, H 2 Se

17 Techniques 1. Moisture determination Fig. Microwave oven for drying food

18 2. Determination of Mercury in the Environment by Volatilization Fig. Apparatus for flameless AAS

19 Next lecture: Distillation