Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition

This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.

An interlaboratory capillary zone electrophoresis-UV study of various monoclonal antibodies, instruments, and ε-aminocaproic acid lots

Capillary zone electrophoresis ultraviolet (CZE-UV) has become increasingly popular for the charge heterogeneity determination of mAbs and vaccines. The ε-aminocaproic acid (eACA) CZE-UV method has been used as a rapid platform method. However, in the last years, several issues have been observed, for example, loss in electrophoretic resolution or baseline drifts. Evaluating the role of eACA on the reported issues, various laboratories were requested to provide their routinely used eACA CZE-UV methods, and background electrolyte compositions. Although every laboratory claimed to use the He et al. eACA CZE-UV method, most methods actually deviate from He's. Subsequently, a detailed interlaboratory study was designed wherein two commercially available mAbs (Waters' Mass Check Standard mAb [pI 7] and NISTmAb [pI 9]) were provided to each laboratory, along with two detailed eACA CZE-UV protocols for a short-end, high-speed, and a long-end, high-resolution method. Ten laboratories participated each using their own instruments, and commodities, showing excellence method performance (relative standard deviations [RSDs] of percent time-corrected main peak areas from 0.2% to 1.9%, and RSDs of migration times from 0.7% to 1.8% [n = 50 per laboratory], analysis times in some cases as short as 2.5 min). This study clarified that eACA is not the main reason for the abovementioned variations.

Sixteen capillary electrophoresis applications for viral vaccine analysis

A broad range of CE applications from our organization is reviewed to give a flavor of the use of CE within the field of vaccine analyses. Applicability of CE for viral vaccine characterization, and release and stability testing of seasonal influenza virosomal vaccines, universal subunit influenza vaccines, Sabin inactivated polio vaccines (sIPV), and adenovirus vector vaccines were demonstrated. Diverse CZE, CE-SDS, CGE, and cIEF methods were developed, validated, and applied for virus, protein, posttranslational modifications, DNA, and excipient concentration determinations, as well as for the integrity and composition verifications, and identity testing (e.g., CZE for intact virus particles, CE-SDS application for hemagglutinin quantification and influenza strain identification, chloride or bromide determination in process samples). Results were supported by other methods such as RP-HPLC, dynamic light scattering (DLS), and zeta potential measurements. Overall, 16 CE methods are presented that were developed and applied, comprising six adenovirus methods, five viral protein methods, and methods for antibodies determination of glycans, host cell-DNA, excipient chloride, and process impurity bromide. These methods were applied to support in-process control, release, stability, process- and product characterization and development, and critical reagent testing. Thirteen methods were validated. Intact virus particles were analyzed at concentrations as low as 0.8 pmol/L. Overall, CE took viral vaccine testing beyond what was previously possible, improved process and product understanding, and, in total, safety, efficacy, and quality.

Recent advances in the capillary electrophoresis analysis of antibiotics with capacitively coupled contactless conductivity detection

This review describes briefly the high rate of counterfeiting of antimicrobial drugs with focus upon its immediate health consequences. The major part of this review encompasses accounts of the improvements achieved in the domain of miniaturization of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D). The application of this principle into the development of portable devices as well as its application to counter the health-system-crippling phenomenon of counterfeit antibiotic formulations, are discussed in the context of developing countries.

Recent advances in capillary electrophoretic migration techniques for pharmaceutical analysis

Since the introduction about 30 years ago, CE techniques have gained a significant impact in pharmaceutical analysis. The present review covers recent advances and applications of CE for the analysis of pharmaceuticals. Both small molecules and biomolecules such as proteins are considered. The applications range from the determination of drug-related substances to the analysis of counterions and the determination of physicochemical parameters. Furthermore, general considerations of CE methods in pharmaceutical analysis are described.

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.

Quantification in capillary electrophoresis-mass spectrometry: long- and short-term variance components and their compensation using internal standards

Different approaches were chosen to examine ionization reproducibility of analytes after separation by capillary electrophoresis-mass spectrometry (CE-MS) in a commercially available sheath-flow electrospray interface. For this task three different standard samples were examined. Sample 1 contained neostigmine bromide (cationic), paracetamol (PCM) (neutral) and nicotinic acid (anionic component). Results were evaluated using internal standard (IS) calculations. Sample 2 represented an isotopically labelled IS of the quantified substance (PCM/D4-PCM), while sample 3 (neostigmine bromide/scopolamine hydrobromide) provided an IS closely migrating to the tested substance. Furthermore, short-time variations inside the interface were examined by multiple injections of the same substance. For sample 1, the relative standard deviations (RSD%s) were between 8 and 25% (n at least 58) for the peak area ratios. Multiple injected samples gave 5.5-19.4% (n = 25) for peak area RSD%. Using a closely migrating IS, sample 3, RSD%s between 6.5 and 10% (n at least 63) were achieved. With isotopically labelled IS, sample 2, an RSD% of 3-4% was achieved for peak area ratios over long periods (n = 25), for shorter periods (n = 9) even 1-2% RSD% was obtained. Keeping the instrument settings constant, the influence on the ionization efficiency and reproducibility was tested, varying the buffer pH, the organic buffer modifier and the sample concentration. Repeatabilities of migration time and peak area were measured and compared. Two 10 mM ammonium acetate buffers with pH 4.0 and 8.5 were investigated. No influence of buffer pH on peak area reproducibility was found. Isopropanol as organic buffer modifier significantly improved the ionisation leading to larger peak areas, but reduced reproducibility. The basic buffer produced slightly better RSD%s for migration times (2.5-4.0%) (n = 180) and faster analysis for the different test analytes of sample 1, while with the acetic buffer, RSD%s from 3.9 to 6.0% were obtained (n at least 163). The positioning of the capillary turned out to be the crucial parameter to ensure reproducible results. Thus, a procedure was established to ensure a defined ion-intensity level after capillary changes. The investigation of the different sample concentrations gave negligible differences in RSD%, showing that the signal-to-noise ratio was not the crucial parameter for reproducibility here, in contrast to CE-UV detection.

Electroosmotic flow variations caused by the volatility of buffer components: diagnosis and therapy

In order to separate a polar amine pharmaceutical and its potential impurities, a micellar electrokinetic chromatography method was developed. The main compound and 11 other substances were completely separated using a 20 mM Tris buffer, pH 8.0, containing 50 mM sodium dodecylsulfate (SDS) and 24% (v/v) acetonitrile. However, a strong, continuous reduction in the EOF occurred and quantification was not possible. The EOF reproducibility could not be improved by suitable rinsing procedures. Surface effects or interactions did not cause the EOF changes, but the evaporation of acetonitrile was identified as the major source for EOF instability. However, a high concentration of acetonitrile was decisive for selectivity. Thus a reliable protection against the evaporation of this buffer constituent had to be found. Paraffin and various silicon oils were tested as covering film. In order to quickly test buffer systems if the evaporation of electrophoresis solutions is acceptable, an alternative experimental design without doing CE experiments had to be found. Electrical conductivity was chosen as parameter, because it can be determined simply and fast. The buffers under investigation were placed in a 50-ml beaker with a magnetic stirring rod, placed on a magnetic stirrer. The buffer solution was kept in motion at 120 rev./min. The beaker was covered around the measuring head with laboratory film and in addition to this with paraffin or silicon oil. An acetonitrile content up to 10% (v/v) was acceptable if a coverage was used. The various cover liquids had a similar effect. A content of 15% (v/v) already increased the evaporation effect significantly. Higher acetonitrile contents are not acceptable. A buffer similar to the originally transferred method, 20 mM Tris (pH 8.0), 50 mM SDS containing 10% (v/v) acetonitrile as well as 10% (v/v) isopropanol showed an acceptably low evaporation in the conductivity experiments. With this buffer, a stable EOF was also obtained. Conductivity measurements are generally applicable to quickly test buffers that contain organic solvents.