IEF in microfluidic devices.

IEF is one of the most powerful and prevalent techniques used in separation sciences. The power of IEF comes from the fact that it not only separates analytes based on their pI but also focuses them into highly resolved bands. In line with the miniaturization trend spurring the analytical community, the past decade has yielded a wealth of research focused on implementing IEF in microfluidic chip-based formats (microIEF). Scaling down the separation technique provides several advantages such as reduced sample sizes, assay automation, and significant improvements in assay speed without sacrificing separation performance. Besides presenting microscale adaptations of standard schemes, researchers have also developed improved detection techniques, demonstrated novel microIEF assays, and incorporated microIEF with other analytical methods for achieving on-chip multidimensional separations. This review provides a brief historical outline of IEF's beginnings, theoretical incentives driving miniaturization of the methodology, a thorough synopsis of microIEF publications to date, and an outlook to the future.