A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometry

A New Strategy for the Software-Assisted LC Separations of Ketoconazole and Its Impurities

Analytical quality by design and the use of dissimilar chromatographic systems can be employed to accelerate chromatographic separations. Herein, a software (S-Matrix)-assisted platform was used to proficiently screen, optimize and select the optimal parameters for the chromatographic separation of ketoconazole and its related impurities. This approach evaluated the various chromatographic parameters in a stepwise manner based on the statistical tools and provided an in-depth understanding of the critical parameters influencing the peak selectivities and separations. It was demonstrated that dissimilar conditions, such as different stationary phases, mobile phase pH and organic modifiers (i.e., critical method variables), can improve the peak resolution, while the critical quality attributes can provide conditions appropriate for quantification purposes via a quality target analytical method. Furthermore, an orthogonal method was established to support the primary method. The orthogonality between the two methods was defined by the correlation matrix between the two systems using the Pearson correlation coefficient and was found to be 0.12. Using the optimized method, the primary method was validated as per International Council for Harmonization in the range of 0.05-1.0% for impurities and 80.0-120.0% for ketoconazole, thereby indicating the suitability of the method for use in quality control laboratories.

Mass spectrometry for small molecule pharmaceutical product development: a review

Developing a pharmaceutical product has become increasingly difficult and expensive. With an emphasis on developing project knowledge at an earlier stage in development, the use of information-rich technologies (particularly MS) has continued to expand throughout product development. Continued improvements in LC/MS technology have widened the scope of utilizing MS methods for performing both qualitative and quantitative applications within product development. This review describes a multi-tiered MS strategy designed to enhance and accelerate the identification and profiling of both process- and degradation-related impurities in either the active pharmaceutical ingredient (API) or formulated product. Such impurities can be formed either during chemical synthesis, formulation, or during storage. This review provides an overview of a variety of orthogonal-mass spectrometric methodologies, namely GC/MS, LC/MS, and ICP-MS, in support of product development. This review is not meant to be all inclusive; however, it has been written to highlight the increasing use of hyphenated MS techniques within the pharmaceutical development area.

Drug impurity profiling: Method optimization on dissimilar chromatographic systems: Part I: pH optimization of the aqueous phase

The use of dissimilar chromatographic systems in drug impurity profiling can be very advantageous. Screening a new-drug impurity mixture on those systems not only enhances the chance that all impurities are revealed, but also allows choosing a suited system for further method development. In this paper several strategies were evaluated to predict the optimal pH (of the buffer used in the mobile phase) from the screening results. Four or five dissimilar stationary phases were screened at four pH values (between 2.5 and 9.4), in order to obtain maximal information about the composition of the sample and to select one column for the subsequent optimization. Different linear models (straight lines, 2nd and 3rd degree polynomials) based on these experiments were tested for their ability to predict the retention times (t(R)) of the impurities at intermediate pH values. The predicted t(R) values were then used to calculate minimal resolutions and eventually to select an optimal pH at which the highest minimal resolution is predicted. None of the applied models is accurate enough to predict correctly which peaks are worst separated at the indicated optimal pH. However, the best strategy (applying a second degree polynomial describing the t(R) measured at 3 consecutive screening pH values) did succeed in indicating an optimal pH at which a good separation of the impurities is obtained. Unfortunately, the resulting separation quality is not or only slightly better than the best separation obtained during screening. Therefore, it can be concluded that the most (time-) efficient approach to develop an impurity profile of a new drug is to screen it on four or five dissimilar columns at four different pH values and to retain the best screening conditions (without making predictions for intermediate conditions) for further optimization of the organic modifier composition of the mobile phase, and occasionally the temperature and the gradient. This is at least the case when the profiles have a complexity similar to those studied.

Drug impurity profiling by capillary electrophoresis/mass spectrometry using various ionization techniques

Capillary electrophoresis/mass spectrometry (CE/MS) is predominantly carried out using electrospray ionization (ESI). Recently, atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) have become available for CE/MS. With the VUV lamp turned off, the APPI source may also be used for CE/MS by thermospray ionization (TSI). In the present study the suitability of ESI, APCI, APPI and TSI for drug impurity profiling by CE/MS in the positive ion mode is evaluated. The drugs carbachol, lidocaine and proguanil and their potential impurities were used as test compounds, representing different molecular polarities. A background electrolyte of 100 mM acetic acid (pH 4.5) provided baseline separation of nearly all impurities from the respective drugs. APPI yielded both even- and odd-electron ions, whereas the other ionization techniques produced even-electron ions only. In-source fragmentation was more pronounced with APCI and APPI than with ESI and TSI, which was most obvious for proguanil and its impurities. In general, ESI and TSI appeared the most efficient ionization techniques for impurities that are charged in solution achieving detection limits of 100 ng/mL (full-scan mode). APPI and APCI showed a lower efficiency, but allowed ionization of low and high polarity analytes, although quaternary ammonium compounds (e.g. carbachol) could not be detected. Largely neutral compounds, such as the lidocaine impurity 2,6-dimethylaniline, could not be detected by TSI, and yielded similar detection limits (500 ng/mL) for ESI, APPI and APCI. In many cases, impurity detection at the 0.1% (w/w) level was possible when 1 mg/mL of parent drug was injected with at least one of the CE/MS systems. Overall, the tested CE/MS systems provide complementary information as illustrated by the detection and identification of an unknown impurity in carbachol.

Capillary electrophoresis for the analysis of small-molecule pharmaceuticals

This paper reviews the application of CE to the analysis of small-molecule pharmaceuticals. The areas of pharmaceutical analysis covered are enantiomer separation, the analysis of small molecules such as amino acids or drug counter-ions, pharmaceutical assay, determination of related substances and physicochemical measurements such as log P and pK(a) of compounds. The different electrophoretic modes available and their advantages for pharmaceutical analysis are described. Recent applications of CE for each subject area are tabulated with electrolyte details.

Recent advances in the application of capillary electrophoresis with mass spectrometric detection

This review gives an overview of applications of CE coupled to MS detection published in the literature of the last three years. The works discussed in this paper comprise a wide range of different fields of application. These include important sections such as the analysis of biomolecules, the analysis of pharmaceuticals and their metabolites in different matrices, environmental analysis, and also investigations on the composition of technical products.