Electrophoresis 2012, 33, 893–898 893 Lucas Blanes 1 Wendell Karlos Tomazelli Coltro 2 Renata Mayumi Saito 3 Amanda Van Gramberg 1 Claudimir Lucio do Lago 3 Philip Doble 1 1 Centre for Forensic Science, University of Technology, Sydney (UTS), Broadway, NSW, Australia 2 Instituto de Qu´ ımica, Universidade Federal de Goi ´ as, Goi ˆ ania, GO, Brazil 3 Instituto de Qu´ ımica, Universidade de S ˜ ao Paulo, S ˜ ao Paulo, SP, Brazil Received September 14, 2011 Revised November 9, 2011 Accepted November 15, 2011 Review High-voltage power supplies to capillary and microchip electrophoresis Over the past years, the development of capillary electrophoresis (CE) and microchip elec- trophoresis (ME) systems has grown due to instrumental simplicity and wide application. In both CE and ME, the application of a high voltage (HV) is a crucial step in the electroki- netic (EK) injection and separation processes. Particularly on ME devices, EK injection is often performed with three different modes: gated, pinched, and unpinched. In all these cases, different potential values may be applied to one or multiple channels to control the injection of small sample volumes as well as the separation process. For this reason, the construction of reliable HV power supplies (HVPS) is required. This review covers the advances of the development of commercial and laboratory-built HVPS for CE and ME. Moreover, it intends to be a guide for new developers of electrophoresis instrumentation. Keywords: Analytical instrumentation / High-voltage power supplies / Lab-on-a-chip / Miniaturization DOI 10.1002/elps.201100490 1 Introduction Capillary electrophoresis (CE) and microchip electrophoresis (ME) require the use of a high voltage (HV) for perform- ing electrokinetic (EK) sample injection and separation. After injection, separation of the sample components occurs due to the electric field with the application of a high potential difference across the capillary or channel extremities. Conse- quently, the components present in the injected sample plug are driven toward the detector with a velocity that depends on the electroosmotic flow, mass-to-charge ratios, solution conditions, temperature, and the magnitude of the applied potential [1]. Due to the numerous factors that affect separa- tion, a reliable HV power supply (HVPS) eliminates further complications and ensures reproducible separations. Electrophoretic separations can be carried out by using constant voltage (CV) or constant current (CC) modes. Kurosu et al. [2] reported a comparative study of injection repeatability under CV and CC modes. The repeatability of the migration time was better for the CC mode. However, the CC mode is not always available in a HVPS. Moreover, as researchers are more familiar with employing CV modes of separation, most experiments are performed in the CV mode. The first reports of CE described the use of a regulated HV DC power supply Correspondence: Professor Philip Doble, Department of Chem- istry and Forensic Science, University of Technology Sydney, PO Box 123 Broadway, NSW 2007, Australia E-mail: Philip.Doble@uts.edu.au Fax: + 61-2-9514-1460 Abbreviations: HV, high-voltage; HVPS, high-voltage power supply; PEPS, programmable eight-path-electrode power supply; USB, universal serial bus (Megavolt Model RDC-30-10, Hackensack, NJ, USA) with ca- pability of delivering 0 to +30 kV to drive the electrophoretic separations [3, 4]. In order to avoid accidental current and voltage leakage, the HV end of the system was enclosed in a Plexiglass box which automatically cut off the HV when opened. Since these first reports, the analytical instrumenta- tion has received significant attention and nowadays many companies offer commercial HVPS for CE applications. In addition, due to the impressive growth in the last two decades, the capabilities of ME devices have made the lab-on-a-chip platform accessible to most researchers with full or limited access to sophisticated instrumentation. However, as indi- cated by Collins et al. in 2004, there are sparse descriptions of HVPS that can be utilized to control these devices [5]. The same occurs with conventional CE. There are a myr- iad of HVPS—both commercial and laboratory built. Careful consideration of advantages and disadvantages of each de- vice provides insights for successfully incorporating HVPS during the development of new instruments. Felhofer et al. published a paper in 2010 dedicated to instrumentation in CE showing for the first time a brief overview on HVPS [6]. The main goal of this review is to cover the main in- strumental advances regarding the development of HVPS for CE and ME. Examples of commercial and homemade HVPS are described for guidance of new developers of CE and ME instrumentation. 2 Commercial HVPS To ensure reproducible and robust results after assembling an electrophoresis device, it is imperative that the power supply delivers a CV or CC. Such ideal conditions are of- ten only available through the use of a commercial HVPS (Glassman High Voltage Inc., http://www.glassmanhv.com, C  2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.electrophoresis-journal.com