Atefeh Sadat Zarabadi (Ati) Electroanalytical Chemistry-728August 6, 2010 Introduction & Background CE Detection UV absorbance spectroscopy Laser-induced fluorescence (LIF) Mass spectroscopy with electrospray ionization (MS-ESI) Electrochemichal detection (EC) EC Avdantages Suitable for small dimensions Construction Analytical performance Economic Available well-characterized electrode/analyte systems Introduction & Background Applicable EC modes for CE systems Amperometric Potentiometric CEEC instrumentation Electrical decoupling Separation voltage 5-30 kV, EC detection potential 1 V Physical alignment Capillary ID m, EC electrode thickness m Handling Instrumental Difficulties Approaches to CEEC decoupling Off-colunm detection End-column detection Off-colunm detection An electrically conducting fracture inside the capillary before EC electrodes End-column detection Sensing electrode is placed in CE buffer reservoir at the end of capillary CEEC systems 5) Cell: CE cathode, capillary outlet, and working, reference, and auxiliary electrodes 6) CE anode reservoir for decoupled system 7) Cell: detection capillary outlet and working, reference, and auxiliary electrodes End-column configuration Off-column configuration power supply reservoir capillary potentiostat Handling Instrumental Difficulties Procedures for effective alignment In-capillary Wall-jet On-capillary In-capillary Electrode is physically inserted into the exit opening of the capillary Wall-jet Disk- shaped electrode is placed across from the capillary outlet On-capillary Capillary and electrode are physically integrated into a single fixed unit Alignment methods used in CEEC in-capillary optimized in-capillary Wall-jet configuration On-capillary configuration current generation of potentiometric CEEC devices Sensing electrodes are typically miniaturized coated-wire electrodes which consist of a metal wire whose exposed surface is covered with a thin polymer film containing the ionophore of interest. dvantages of the coated-wire approach Simpler (no internal reference electrode) More rugged construction Potentiometric Detection & Applications Potentiometric CEEC applications Variety of inorganic and organic species Neurotransmitters Alkylamines, amino acids, fatty acids, and alkylsulfonates In coated wire ISEs, the potentiometric response is determined by the properties of the particular ionophore incorporated into the coating The detection provided is relatively nonspecific as well, generally allowing broad cation or anion detection. Potentiometric Detection & Applications Dual electrode CEEC simultaneously employing two (or more) independent sensing electrodes Dual-Parallel Dual-series Microfabricated CEEC devices (lab-on-a-chip) Highly efficient separations Integration of the CE process speed, cost, portability sample consumption Extremely compatible with microfabrication technologies Amperometric Detection & Applications Amperometricapplications Important CEEC targets; catechols, thiols, and carbohydrates A wide variety of specific organic and inorganic species DNA sequencing and analysis Direct assays of drugs of varying chemical structure Amperometric Detection & Applications the compatibility of electrode design and construction with standard microfabrication methods The complexity of an associated EC detection system can be increased as needed with relatively little additional difficulty Difficulties with capillary/ electrode alignment and CE/EC decoupling is rendered with microfabricated systems CEEC Applications in Microfabricated Analysis Devices Conclusions CEEC equipment is assembled in-house that makes it harder than other competing CE detection methods Perspective: new electrode materials and electrode configurations and the further increase in variety of samples Incorporation of EC detection schemes onto lab-on-a- chip platforms is an area of intense research and development activity Thanks for Your Attention!