Recent developments in capillary isoelectric focusing.

The developments in capillary isoelectric focusing (cIEF) over the period 2003-2007 are reviewed. With the focus on technological aspects, cIEF papers published in the fields of methodology, new techniques, detection, multidimensional systems, miniaturization and applications are summarized. The methodology section covers recent research in ampholytes composition, detergents and other additives, carrier ampholyte free cIEF, coatings and other capillary modifications. In the section on new systems adjustments to the technique (e.g. dynamic IEF), different applications of cIEF (e.g. as injection system) and new devices are reported. Systems focusing on whole column imaging, fluorescence and chemiluminescence detection and coupling to mass spectrometers are discussed in the section on detection. Interfacing cIEF with MS via RPLC systems and hyphenation of cIEF with capillary electrochromatography and other capillary electrophoresis modes are also summarized. Papers focusing on miniaturization are reviewed in the section on microfluidic devices. The section on applications will show analysis of biopharmaceutical compounds and isolated proteins for metabolomic studies. For the analysis of complex biological matrices, generally multidimensional systems are needed, which are mentioned throughout this review.