Quantification of ascorbic acid and acetylsalicylic acid in effervescent tablets by CZE-UV and identification of related degradation products by heart-cut CZE-CZE-MS

Recent applications and chiral separation developments based on stationary phases in open tubular capillary electrochromatography (2019–2022)

Capillary electrochromatography (CEC) plays a significant role in chiral separation via the double separation principle, partition coefficient difference between the two phases, and electroosmotic flow-driven separation. Given the distinct properties of the inner wall stationary phase (SP), the separation ability of each SP differs from one another. Particularly, it provides large room for promising applications of open tubular capillary electrochromatography (OT-CEC). We divided the OT-CEC SPs developed over the past four years into six types: ionic liquids, nanoparticle materials, microporous materials, biomaterials, non-nanopolymers, and others, to mainly introduce their characteristics in chiral drug separation. There also added a few classic SPs that occurred within ten years as supplements to enrich the features of each SP. Additionally, we discuss their applications in metabolomics, food, cosmetics, environment, and biology as analytes in addition to chiral drugs. OT-CEC plays an increasingly significant role in chiral separation and may promote the development of capillary electrophoresis (CE) combined with other instruments in recent years, such as CE with mass spectrometry (CE/MS) and CE with ultraviolet light detector (CE/UV).

Characterisation of a new online nanoLC-CZE-MS platform and application for the glycosylation profiling of alpha-1-acid glycoprotein

The ever-increasing complexity of biological samples to be analysed by mass spectrometry has led to the necessity of sophisticated separation techniques, including multidimensional separation. Despite a high degree of orthogonality, the coupling of liquid chromatography (LC) and capillary zone electrophoresis (CZE) has not gained notable attention in research. Here, we present a heart-cut nanoLC-CZE-ESI-MS platform to analyse intact proteins. NanoLC and CZE-MS are coupled using a four-port valve with an internal nanoliter loop. NanoLC and CZE-MS conditions were optimised independently to find ideal conditions for the combined setup. The valve setup enables an ideal transfer efficiency between the dimensions while maintaining good separation conditions in both dimensions. Due to the higher loadability, the nanoLC-CZE-MS setup exhibits a 280-fold increased concentration sensitivity compared to CZE-MS. The platform was used to characterise intact human alpha-1-acid glycoprotein (AGP), an extremely heterogeneous N-glycosylated protein. With the nanoLC-CZE-MS approach, 368 glycoforms can be assigned at a concentration of 50 μg/mL as opposed to the assignment of only 186 glycoforms from 1 mg/mL by CZE-MS. Additionally, we demonstrate that glycosylation profiling is accessible for dried blood spot analysis (25 μg/mL AGP spiked), indicating the general applicability of our setup to biological matrices. The combination of high sensitivity and orthogonal selectivity in both dimensions makes the here-presented nanoLC-CZE-MS approach capable of detailed characterisation of intact proteins and their proteoforms from complex biological samples and in physiologically relevant concentrations.

Rapid classification and identification of chemical constituents in Epimedium koreanum Nakai by UPLC-Q-TOF-MS combined with data post-processing techniques

INTRODUCTION

Epimedium koreanum Nakai (EKN), is a well-known Chinese herbal medicine for the treatment of osteoporosis, immunosuppression, tumours and cardiovascular diseases. Comprehensive component identification is essential for elucidation of its pharmacological mechanism and quality control. However, its complex chemical composition has caused certain difficulties in the analysis of this traditional Chinese medicine (TCM). Therefore, there is an urgent need to establish a method for rapid classification and identification of EKN chemical components.

OBJECTIVE

To establish a method for rapid classification and identification of the main components of flavonoids, organic acids and alkaloids in EKN.

METHODS

The samples were analysed by ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and data post-processing techniques. The UPLC system used a BEH C₁₈ column to separate the total extract of EKN. The mobile phase consisted of 0.1% formic acid in water and acetonitrile, and the EKN extract was analysed by gradient elution at a flow rate of 0.4 mL/min. In both the positive and negative ion modes, the fragment information was obtained and compared with those of the characteristic fragmentations and neutral losses described in the literature to quickly identify the target compounds.

RESULTS

Finally, we successfully screened out 51 chemical components, including 40 flavonoids, nine organic acids, and two alkaloids.

CONCLUSION

The established method not only comprehensively analysed the chemical compositions of EKN, solved the difficult problems of analysis and identification of the complex chemical compositions of the TCM, but also further promoted the development of the application of chemical compositions of TCM.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Improved CE(SDS)-CZE-MS method utilizing an 8-port nanoliter valve

Capillary sieving electrophoresis utilizing SDS (CE(SDS)) is one of the most applied methods for the analysis of antibody (mAb) size heterogeneity in the biopharmaceutical industry. Inadequate peak identification of observed protein fragments is still a major issue. In a recent publication, we introduced an electrophoretic 2D system, enabling online mass spectrometric detection of generic CE(SDS) separated peaks and identification of several mAb fragments. However, an improvement regarding system stability and handling of the approach was desired. Here, we introduce a novel 8-port valve in conjunction with an optimized decomplexation strategy. The valve contains four sample loops with increased distances between the separation dimensions. Thus, successively coinjection of solvent and cationic surfactant without any additional detector in the second dimension is enabled, simplifying the decomplexation strategy. Removal efficiency was optimized by testing different volumes of solvents as presample and cationic surfactant as postsample zone. 2D measurements of the light and heavy chain of the reduced NIST mAb with the 8-port valve and the optimized decomplexation strategy demonstrates the increased robustness of the system. The presented novel set-up is a step toward routine application of CE(SDS)-CZE-MS for impurity characterization of proteins in the biopharmaceutical field.

Comprehensive and quantitative stability study of ascorbic acid using capillary zone electrophoresis with ultraviolet detection and high-resolution tandem mass spectrometry

Ascorbic acid is a powerful antioxidant compound involved in many biological functions, and a chronic deficiency is at the origin of scurvy disease. A simple, rapid, and cost-effective capillary electrophoresis method was developed for the separation and simultaneous quantification of ascorbic acid and the major degradation products: dehydroascorbic acid, furfural, and furoic acid. Systematic optimization of the conditions was performed that enabled baseline separation of the compounds in less than 10 min. In addition to simultaneous quantification of ascorbic acid alongside to the degradation products, stability studies demonstrated the possibility using capillary electrophoresis to separate and identify the major degradation products. Thus, high-resolution tandem mass spectrometry experiments were conducted in order to identify an unknown degradation product separated by capillary electrophoresis and significantly present in degraded samples. Comparison of mass spectrometry data and capillary electrophoresis electropherograms allowed to identify unambiguously trihydroxy-keto-valeraldehyde. Finally, capillary electrophoresis was successfully applied to evaluate the composition of different pharmaceutical preparation of ascorbic acid. Results showed the excellent performance of the capillary electrophoresis method due to the separation of excipients from the compounds of interest, which demonstrated the relevance of using an electrophoretic separation in order to perform comprehensive stability studies of ascorbic acid.

Optimized Vortex-Assisted Dispersive Liquid–Liquid Microextraction Coupled with Spectrofluorimetry for Determination of Aspirin in Human Urine: Response Surface Methodology

Background:

A Vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) method is presented for the determination of aspirin (acetylsalicylic acid) in human urine by spectrofluorimetry.

Objective:

To determine trace levels of aspirin in biologic samples by using green and low-cost method development.

Methods:

For the microextraction procedure, chloroform and acetonitrile were used as extraction and disperser solvent, respectively. The factors affecting the efficiency of extraction such as volume of chloroform, volumes of acetonitrile, ionic strength, sample pH, centrifuging time, and extraction time were investigated. Then significant variables were optimized by the response surface method using the Box- Behnken design.

Results:

Under the optimum extraction conditions, a linear calibration curve in the range of 0.1 to 130 ng mL-1 with a correlation coefficient of R2 = 0.998 was obtained. The limits of detection (LOD) and limits of quantification (LOQ) were 0.031 and 0.103 ng mL-1, respectively. The relative standard deviations (RSD) were less than 4%.

Conclusion:

Enrichment factor and recoveries were achieved for the extraction of aspirin in human urine. This method gives a rapid, simple, sensitive and environmentally friendly for the measurement of trace amount aspirin.

Online mass spectrometry of CE (SDS)-separated proteins by two-dimensional capillary electrophoresis

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is the fundamental technique for protein separation by size. Applying this technology in capillary format, gaining high separation efficiency in a more automated way, is a key technology for size separation of proteins in the biopharmaceutical industry. However, unequivocal identification by online mass spectrometry (MS) is impossible so far, due to strong interference in the electrospray process by SDS and other components of the SDS-MW separation gel buffer. Here, a heart-cut two-dimensional electrophoretic separation system applying an electrically isolated valve with an internal loop of 20 nL is presented. The peak of interest in the CE (SDS) separation is transferred to the CZE-MS, where electrospray-interfering substances of the SDS-MW gel are separated prior to online electrospray ionization mass spectrometry. An online SDS removal strategy for decomplexing the protein-SDS complex is implemented in the second dimension, consisting of the co-injection of organic solvent and cationic surfactant. This online CE (SDS)-CZE-MS system allows MS characterization of proteoforms separated in generic CE (SDS), gaining additional separation in the CZE and detailed MS information. In general, the system can be applied to all kinds of proteins separated by CE (SDS). Here, we present results of the CE (SDS)-CZE-MS system on the analysis of several biopharmaceutically relevant antibody impurities and fragments. Additionally, the versatile application spectrum of the system is demonstrated by the analysis of extracted proteins from soybean flour. The online hyphenation of CE (SDS) resolving power and MS identification capabilities will be a powerful tool for protein and mAb characterization. Graphical abstract Two-dimensional capillary electrophoresis system hyphenated with mass spectrometry for the characterization of CE (SDS)-separated proteins. As first dimension, a generic and high MS-interfering CE (SDS) separation is performed for size separation. After heart-cut transfer of the unknown CE (SDS) protein peak, via a four-port nanoliter valve to a volatile electrolyte system as second dimension, interference-free mass spectrometric data of separated mAb fragments and soybean proteins are obtained.

Associations between personality traits and adequate home storage of drugs in older patients

The objective of this study was to investigate the association between personality traits of older patients and adequate home storage of drugs. Forty-four participating Dutch community pharmacists randomly selected each up to four community-dwelling elderly patients (≥65 years) who were using at least one prescription drug. The Big Five Inventory was used to assess the personality traits - 'openness', 'conscientiousness', 'extraversion', 'agreeableness' and 'neuroticism' - of patients. An assessment of adequate home storage of drugs was made using a summed composite score for each patient ranging from zero (adequate storage) to three (inadequate storage) was based on storage criteria representing quality, information and level of storage organization. A 51.2% of the patients stored drugs adequately in accordance with all quality ("Q") and information ("I") criteria. A high level of drug storage organization was found in 70.8% of patients. Forty-three patients (31.4%) stored their drugs adequately based on all storage criteria (composite storage score 0). No associations between personality dimensions and adequate drug storage were found. Having a lower number of drugs was associated with adequate drug home storage (OR_adjusted 0.86; 95% CI: 0.77-0.96). In conclusion, this study suggests that personality is not associated with adequate home storage of drugs in older patients.

Recent advances in capillary electrophoresis-mass spectrometry: Instrumentation, methodology and applications

Capillary electrophoresis (CE) offers fast and high-resolution separation of charged analytes from small injection volumes. Coupled to mass spectrometry (MS), it represents a powerful analytical technique providing (exact) mass information and enables molecular characterization based on fragmentation. Although hyphenation of CE and MS is not straightforward, much emphasis has been placed on enabling efficient ionization and user-friendly coupling. Though several interfaces are now commercially available, research on more efficient and robust interfacing with nano-electrospray ionization (ESI), matrix-assisted laser desorption/ionization (MALDI) and inductively coupled plasma mass spectrometry (ICP) continues with considerable results. At the same time, CE-MS has been used in many fields, predominantly for the analysis of proteins, peptides and metabolites. This review belongs to a series of regularly published articles, summarizing 248 articles covering the time between June 2016 and May 2018. Latest developments on hyphenation of CE with MS as well as instrumental developments such as two-dimensional separation systems with MS detection are mentioned. Furthermore, applications of various CE-modes including capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), capillary gel electrophoresis (CGE) and capillary isoelectric focusing (CIEF) coupled to MS in biological, pharmaceutical and environmental research are summarized.

Two-dimensional capillary electrophoresis-mass spectrometry (CE-CE-MS): coupling MS-interfering capillary electromigration methods with mass spectrometry

Electromigration separation techniques often demand certain compounds in the electrolyte to achieve the required selectivity and efficiency. These compounds, including the electrolyte itself, ampholytes, polymeric compounds for sieving, complexing agents, tensides, etc. are often non-volatile. Thus, interference with the electrospray ionization process is a common issue, impeding direct coupling of such electrolyte systems to mass spectrometry. Still, several options exist to obtain mass spectra after separation, including offline fractionation, alternative ionization, dilution, or the change to volatile constituents. In the first part of this article, these methods are discussed. However, all of these options are a compromise of separation performance and sensitivity of mass spectrometric detection. Two-dimensional capillary electrophoresis-mass spectrometry (CE-CE-MS) systems represent a promising alternative to the aforementioned challenges, as they allow the use of existing methods with best separation performance in combination with sensitive mass characterization. In this context, the second part of this article is dedicated to the advantages, limitations, and applications of this approach. Finally, an outlook towards future developments is given.

Two-Dimensional Capillary Electrophoresis with On-Line Sample Preparation and Cyclodextrin Separation Environment for Direct Determination of Serotonin in Human Urine

An advanced two-dimensional capillary electrophoresis method, based on on-line combination of capillary isotachophoresis and capillary zone electrophoresis with cyclodextrin additive in background electrolyte, was developed for effective determination of serotonin in human urine. Hydrodynamically closed separation system and large bore capillaries (300–800 µm) were chosen for the possibility to enhance the sample load capacity, and, by that, to decrease limit of detection. Isotachophoresis served for the sample preseparation, defined elimination of sample matrix constituents (sample clean up), and preconcentration of the analyte. Cyclodextrin separation environment enhanced separation selectivity of capillary zone electrophoresis. In this way, serotonin could be successfully separated from the rest of the sample matrix constituents migrating in capillary zone electrophoresis step so that human urine could be directly (i.e., without any external sample preparation) injected into the analyzer. The proposed method was successfully validated, showing favorable parameters of sensitivity (limit of detection for serotonin was 2.32 ng·mL⁻¹), linearity (regression coefficient higher than 0.99), precision (repeatability of the migration time and peak area were in the range of 0.02–1.17% and 5.25–7.88%, respectively), and recovery (ranging in the interval of 90.0–93.6%). The developed method was applied for the assay of the human urine samples obtained from healthy volunteers. The determined concentrations of serotonin in such samples were in the range of 12.4–491.2 ng·mL⁻¹ that was in good agreement with literature data. This advanced method represents a highly effective, reliable, and low-cost alternative for the routine determination of serotonin as a biomarker in human urine.