Central composite design, analytical methods

Several studies have employed chemometric designs in CZE method development. In most cases, central composite designs were selected with background electrolyte pH and concentration as well as buffer additives such as methanol as experimental factors and separation selectivity or peak resolution of one or more critical analyte pairs as responses. For example, method development and optimization employing a three-factor central composite design was performed for the analysis of related compounds of the tetracychne antibiotics doxycycline (17) and metacychne (18). The separation selectivity between three critical pairs of analytes were selected as responses in the case of doxycycline while four critical pairs served as responses in the case of metacychne. In both studies, the data were htted to a partial least square (PLS) model. The factors buffer pH and methanol concentration proved to affect the separation selectivity of the respective critical pairs differently so that the overall optimized methods represented a compromise for each individual response. Both methods were subsequently validated and applied to commercial samples. 

Carlson R (1992) Design and optimization of organic synthesis. Elsevier, Amsterdam Box GEP (1952) Statistical design in the study of analytical methods. Analyst 77 879-889 Cochran WG, Cox GM (1957) Experimental designs. WUey, New York Small TS, Fell AF, Coleman MW, Berridge JC (1995) Central composite design forthe rapid optimisation of ruggedness and chiral separation of amlodipine in capillary electrophoresis. Chirahty 7 226-234... 

Fundamental understanding of structure-function relationships is central for the design of improved selox catalysts, and has been greatly assisted by the development of new analytical tools with which to probe active sites at subnanometer spatial resolution [36] and subsecond time resolution. X-ray-based methods in particular can provide detailed insight into chemical composition and environment of active components and reacting adsorbates [140-142]. Quick and dispersive XAS have the capabihty to monitor dynamic changes in catalyst structure under reaction conditions (so-caUed operando spectroscopy) and have been applied to alcohol selox over Pd [96, 143-146], Pt [67, 147], and Ru [147] nanoparticles. 

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