11/11/11 1 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Capillary Electrophoresis 1- Principles 2- Instrumentation Sections 30 A, B Suggested exercises: 30-1, 30-3, 30-4, 30-5, 30-6 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-4, Sections 30A and B Net electrophoretic mobility € µ =q6πηrv = µe x E = µe x V/L (Eq. 30-1, 30-2) € tM=µe( )E=Lµe( )V(Eq. 30-6) Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-4, Sections 30A and B Total electrophoretic mobility v = µEOF x E (Fig 30-2, Eq. 30-4) v = (µEOF + µe) x E (Eq. 30-5) € tM=µe+ µeof( )E=Lµe+ µeof( )V(Eq. 30-6) neutral11/11/11 2 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Development of the Electroosmotic Flow Negatively charged fused silica surface (Si-O ¯ ) Hydrated cations accumulate near the surface Bulk flow is towards the cathode upon application of the electric field Lecture 28- Nov 14 Chem 4101 – Fall 2011 Capillary Zone Electrophoresis (CZE) Migration Superimposed on EOF EOF Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-9, Section 30C Capillary zone electrophoresis11/11/11 3 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-1, Section 30B Instrumentation Advantages 1. Sampled volume (nanoliters) 2. Theoretical plates 3. Separation time Lecture 28- Nov 14 Chem 4101 – Fall 2011 Methods of Sample Injection Pressure Hydrodynamic Sample Vacuum Siphoning Electrokinetic Sample vial is replaced with a vial containing running buffer after the injection Running buffer Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-3, Section 30B Electroosmotic flow benefits – Theoretical plates CE HPLC Eqs. 30-3, 30-7 € N =µeV2DTheory Experimental € N =16tmW 2 € N =24DMLπr2uEq. 28-111/11/11 4 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-6, Section 30B Electropherogram 1- bromide 2- chloride 3- sulfate 4-nitrate 5-fluoride phosphate Lecture 28- Nov 14 Chem 4101 – Fall 2011 Effective and Total Capillary Lengths Total length Effective length to detector Inlet reservoir Detector Exit reservoir Lecture 28- Nov 14 Chem 4101 – Fall 2011 Section 30B11/11/11 5 Lecture 28- Nov 14 Chem 4101 – Fall 2011 Figure 30-5, Section 30B UV
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