Method development of enantiomeric separations in capillary electrophoresis (CE) is a time-consuming task, since finding the appropriate chiral selector is usually a "trial and error" process. It is impossible to predict the selectivity of a selector towards a certain enantiomer. Therefore, the affinity of all selectors has to be examined one at a time. In order to speed up this process, a strategy is proposed based on simple experimental design methodology. The approach includes first a screening in function of the pH to determine the optimal migration conditions followed by a selection of the right chiral selector by means of Taguchi designs. In the approach several variables, such as the type and concentration of cyclodextrin, the concentration of buffer electrolyte, and the percentage of organic modifier, are varied simultaneously to find initial separation conditions rapidly. The resulting initial separation conditions can be optimized in further steps to be more reproducible. We discuss the results of the approach when applied on a number of selected compounds that are recently in development at Johnson & Johnson--Pharmaceutical Research and Development. Parameters, such as quality of the separation and analysis time, are evaluated to determine initial separation conditions for each compound.

Generally reversed-phase high-performance liquid chromatography (RP-HPLC) methods are extensively applied during quality control of pharmaceutical products. Since capillary electrophoresis (CE) is based on a different separation principle and consequently results in a unique selectivity compared to RP-HPLC, it can advantageously be used as an orthogonal technique. CE equipped with a mass spectrometer detector provides even more information that can be helpful for identification and structural elucidation purposes. CE-MS was recently implemented in the method development approach to support impurity profiling of pharmaceutical products. In this paper the application of CE-electrospray ionization (ESI)-MS/MS to the impurity profiling of galantamine hydrobromide in stressed Reminyl Extended Release (ER) capsules is discussed. Reminyl ER samples were stressed at different storing conditions. The impurity profile of these samples was compared with the current RP-HPLC and chiral CE method, but also with CE-ESI-MS/MS. The combination of these three methods provided valuable data that allowed understanding comprehensively the impurity profile of these samples. Two impurities were detected at concentrations lower than 0.05%, which did not occur in nonstressed samples. Chromatographic data and the fragmentation patterns of galantamine and related compounds were also examined for identification of these two degradation products.

Highly selective capillary electrophoresis (CE) screening methods were applied to find a satisfactory separation of a chiral drug with eight stereoisomeric compounds. The initial separation conditions were further optimized using response surface modelling by applying a Box-Behnken experimental design. This approach resulted in a rapid and efficient optimization of the buffer concentration, the concentration of two cyclodextrins, and the run voltage, in order to obtain final separation conditions of the method. Further optimization and validation of the system in terms of sensitivity and robustness resulted in a method that is suitable for quality control release purposes.

Analyses of statistical variance were applied to evaluate the precision and practicality of a CD-based NACE assay for R-timolol after enantiomeric separation of R- and S-timolol. Data were collected in an interlaboratory study by 11 participating laboratories located in Europe and North America. General qualitative method performance was examined using suitability descriptors (i.e. resolution, selectivity, migration times and S/N), while precision was determined by quantification of variances in the determination of R-timolol at four different impurity levels in S-timolol maleate samples. The interlaboratory trials were designed in accordance with the ISO guideline 5725-2. This allowed estimating for each sample, the different variances, i.e. between-laboratory (s2(Laboratories)), between-day (s2(Days)) and between-replicate (s2(Replicates)). The variances of repeatability (s2r) and reproducibility (s2R) were then calculated. The estimated uncertainty, derived from the precision estimates, seems to be concentration-dependent above a given threshold. This example of R-timolol illustrates how a laboratory can evaluate uncertainty in general.

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