REVIEW Chemometric experimental design based optimization techniques in capillary electrophoresis: a critical review of modern applications Grady Hanrahan & Ruthy Montes & Frank A. Gomez Received: 31 July 2007 / Revised: 6 September 2007 / Accepted: 10 September 2007 / Published online: 2 October 2007 # Springer-Verlag 2007 Abstract A critical review of recent developments in the use of chemometric experimental design based optimization techniques in capillary electrophoresis applications is presented. Current advances have led to enhanced separa- tion capabilities of a wide range of analytes in such areas as biological, environmental, food technology, pharmaceuti- cal, and medical analysis. Significant developments in design, detection methodology and applications from the last 5 years (2002–2007) are reported. Furthermore, future perspectives in the use of chemometric methodology in capillary electrophoresis are considered. Keywords Capillary electrophoresis . Chemometrics . Optimization . Experimental design . Response surface methodology Introduction Over the past two decades capillary electrophoresis (CE) has become the technique of choice in many analytical laboratories where analysis of small quantities of materials must be accurately, efficiently, and expeditiously assessed. CE is a powerful analytical separation technique that brings speed, quantitation, reproducibility, and automation to the inherently highly resolving but labor-intensive methods of electrophoresis [1–5]. It is an excellent tool in the analysis of biological materials and is an unparalleled experimental tool for examining interactions in biologically relevant media. CE differentiates charged species on the basis of mobility under the influence of an applied electric field gradient. Selectivity can be manipulated by the alteration of electrolyte properties such as pH, ionic strength, and electrolyte composition, or by the incorporation of electro- lyte additives. CE offers a number of advantages as a separation technique: (1) it requires only small quantities of material; (2) it is applicable to water-soluble, nonvolatile, high molecular weight species in aqueous buffer solution; (3) it is readily automated and has good reproducibility; and (4) various separation modes make it applicable for the analysis of a variety of biological and nonbiological species. CE also suffers from several weaknesses as an analytical technique. Adsorption of charged species to the capillary wall can occur in the absence of efforts to minimize adsorption and can change the magnitude of electroosmotic flow. The presence of Joule heating and other effects of using high voltage create variances in electroosmotic flow some- times yielding irreproducible migration times for analytes, making comparison from run to run problematic. This disadvantage can be especially troubling in the pharmaceu- tical industry, where quality control is a priori and where method development is critical in product manufacture, analysis, and marketing. Hence, it is important to be able to determine optimal conditions in CE method development. Fortunately, various chemometrics-based techniques in- cluding multivariate experimental design and response surface methodology (RSM) have been devised to aid in optimizing the performance of a system. The importance of, and theoretical concepts behind, experimental design and optimization methodology in research and development Anal Bioanal Chem (2008) 390:169–179 DOI 10.1007/s00216-007-1619-y G. Hanrahan : R. Montes : F. A. Gomez (*) Department of Chemistry and Biochemistry, California State University, Los Angeles, Los Angeles, CA 90032, USA e-mail: fgomez2@calstatela.edu Present address: G. Hanrahan Department of Chemistry, California Lutheran University, Thousand Oaks, CA 91360, USA ghanraha@clunet.edu (*) e-mail: ghanraha@clunet.edu