Development of a fritless packed column for capillary electrochromatography-mass spectrometry

Capillary Electrophoresis Mass Spectrometry: Developments and Applications for Enantioselective Analysis from 2011–2020

It is now more than 25 years since the first report of enantioselective analysis by capillary electrophoresis-mass spectrometry (CE-MS) appeared. This article reviews the power of chiral CE-MS in resolving issues on the use of chiral selector incompatibility with MS and poor detectability encountered for chiral compounds by UV detection. The review begins with the general principles, requirements, and critical aspects of chiral CE-MS instrumentation. Next, the review provides a survey of MS-compatible chiral selectors (CSs) reported during the past decade, and the key achievements encountered in the time period using these CSs. Within the context of the strategies used to combine CE and MS, special attention is paid to the approaches that feature partial filling technique, counter-migration techniques, and direct use of CS, such as molecular micelles. In particular, the development and application of moving and fixed CS for EKC-MS, MEKC-MS, and CEC-MS demonstrate how various chiral compounds analyses were solved in a simple and elegant way during the 2010–2020 review period. The most noteworthy applications in the determination of chiral compounds are critically examined. The operating analytical conditions are detailed in the Tables, and the authors provide commentary on future trends of chiral separations by CE-MS.

Advances in chiral separation and analysis by capillary electrophoresis-mass spectrometry

目前使用的绝大多数药物为手性化合物,它们具有相似的物理和化学性质,但药理活性不同,且常以外消旋混合物的形式存在,因此对手性化合物的分离在生物、环境、食品和医药等领域一直备受关注。与广泛使用的液相色谱-质谱(LC-MS)相比,毛细管电泳-质谱(CE-MS)作为一种新型分离分析技术,具有分离效率高、样品和试剂消耗量低、选择性高和分离模式多样化等诸多优势,已经发展成为手性分析领域中有广阔应用前景的分析方法之一。CE-MS结合了CE的高分离效率和低样品消耗以及MS的高灵敏度和强结构解析能力,在蛋白质组学和代谢组学等领域发挥了重要作用。CE杰出的手性拆分能力与MS优势的结合,亦使CE-MS成为实现手性化合物高效分离分析的完美组合。在过去的十几年里,基于不同CE-MS分离模式的高性能手性分析体系层出不穷,如电动色谱-质谱(EKC-MS)、胶束电动色谱-质谱(MEKC-MS)和毛细管电色谱-质谱(CEC-MS)等,并成功应用于医药、生物、食品和环境科学等领域的手性化合物分析。该文主要综述了2011~2021年,CE-MS在手性化合物分析领域的技术、手性选择剂(如改性环糊精和聚合物表面活性剂等)的使用以及在医药等领域应用方面的研究进展,并讨论了不同手性分析模式的局限性,为未来的CE-MS手性分离分析技术发展及应用提供借鉴。

Sol-gel technique for the preparation of β-cyclodextrin gold nanoparticles as chiral stationary phase in open-tubular capillary electrochromatography

A novel open-tubular capillary electrochromatography column coated with β-cyclodextrin was prepared using the sol-gel technique. In the sol-gel approach, owing to the three-dimensional network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating enantiomers were shown. The influences of capillary inner diameter, coating time, organic modifier, buffer pH, and buffer concentration on separation were investigated. The sol-gel-coated β-cyclodextrin column has shown improved enantioseparation efficiency of chlorphenamine, brompheniramine, pheniramine, zopiclone in comparison with the sol-gel matrix capillary column. The migration time relative standard deviation of the separation of the enantiomers was less than 0.89% over five runs and 2.9% from column to column. This work confirmed that gold nanoparticles are promising electrochromatographic support to enhance the phase ratio of open-tubular capillary electrochromatography column in capillary electrochromatography.

Enantiomers separation by capillary electrochromatography using polysaccharide-based stationary phases

The separation of chiral compounds is an interesting and important topic of research because these compounds are involved in some biological processes, fundamentally in human health. Among the various application fields where enantiomers are remarkable, drug analysis has to be considered. Most of the drugs contain enantiomers and very often one of the two isomers could be pharmacologically more active or even dangerous. Therefore, the separation of these compounds is very important. Among the different analytical techniques usually employed, capillary electrochromatography has demonstrated great capability in enantiomers resolution. The great potential of this electromigration technique stands mainly in its high efficiency due to the use of an electrosmotic flow (flat flow profile) and on the high selectivity because of the use of a stationary phase. Chiral separation can be obtained utilizing several chiral stationary phases including a polysaccharide derivative. The aim of this review paper is to summarize the main features of capillary electrochromatography and polysaccharide derivatives of chiral stationary phase. It also report examples of practical applications utilizing this approach.

Chiral Capillary Electrophoresis-Mass Spectrometry: Developments and Applications in the Period 2010-2015: A Review

The sensitive detection of chiral compounds by capillary electrophoresis (CE) in biological samples remains a significant challenge and is currently considered a bottleneck in many chiral analysis projects. Chiral CE-MS can significantly improve the limit of detection and provide high sensitivity compared with chiral CE-UV. Chiral selectors such as modified cyclodextrins (CDs) and polymeric surfactants (a.k.a. molecular micelles, M_oM_s) in electrokinetic chromatography (EKC), micellar electrokinetic chromatography (MEKC) and capillary electrochromatography (CEC) have been developed to address the need for high sensitivity by CE-MS. However, several problems remain to be investigated to fully understand the potential of these hyphenation modes. This review provides introduction to major chiral CE-MS modes for the novice and highlights the important working principles of each mode of chiral CE-MS. Next, recent practical developments and progress in chiral CE-MS dating from January 2010 to September 2015 are described. The achievements in clinical and biomedical sciences using a variety of chiral selectors such as CDs and M_oM_s in EKC-MS, MEKC-MS and CEC-MS are discussed. Finally, conclusions and future prospects of CE-MS in chiral analysis are drafted.

Chiral capillary electromigration techniques-mass spectrometry-hope and promise

Analytical methods for chiral compounds require a separation step prior to mass spectrometric detection. CE can separate enantiomers by the use of a chiral selector and can be hyphenated with MS. The chiral selector can be either embedded inside the capillary (electrochromatography) or added into the background solution (EKC). This review describes the fundamentals and highlights the recent developments (September 2009-May 2013) of chiral CEC and EKC with detection using MS. There were 20 research and more than 30 review papers during this period. The research efforts were driven by fundamental studies, such as the development of novel chiral selectors in electrochromatography and of advanced partial filling techniques in EKC in order to optimise separation. Other developments were in application studies, such as in food analytics and metabolomics.

Enantioselectivity of mass spectrometry: challenges and promises

With the fast growing market of pure enantiomer drugs and bioactive molecules, new chiral-selective analytical tools have been instigated including the use of mass spectrometry (MS). Even though MS is one of the best analytical tools that has efficiently been used in several pharmaceutical and biological applications, traditionally MS is considered as a "chiral-blind" technique. This limitation is due to the MS inability to differentiate between two enantiomers of a chiral molecule based merely on their masses. Several approaches have been explored to assess the potential role of MS in chiral analysis. The first approach depends on the use of MS-hyphenated techniques utilizing fast and sensitive chiral separation tools such as liquid chromatography (LC), gas chromatography (GC), and capillary electrophoresis (CE) coupled to MS detector. More recently, several alternative separation techniques have been evaluated such as supercritical fluid chromatography (SFC) and capillary electrochromatography (CEC); the latter being a hybrid technique that combines the efficiency of CE with the selectivity of LC. The second approach is based on using the MS instrument solely for the chiral recognition. This method depends on the behavioral differences between enantiomers towards a foreign molecule and the ability of MS to monitor such differences. These behavioral differences can be divided into three types: (i) differences in the enantiomeric affinity for association with the chiral selector, (ii) differences of the enantiomeric exchange rate with a foreign reagent, and (iii) differences in the complex MS dissociation behaviors of the enantiomers. Most recently, ion mobility spectrometry was introduced to qualitatively and quantitatively evaluate chiral compounds. This article provides an overview of MS role in chiral analysis by discussing MS based methodologies and presenting the challenges and promises associated with each approach.

Tunnel frit: a nonmetallic in-capillary frit for nanoflow ultra high-performance liquid chromatography-mass spectrometryapplications

In this study, an easy method to fabricate a durable in-capillary frit was developed for use in nanoflow liquid chromatography (nanoLC). A small orifice was tunneled into the sol-gel frit during the polymerization process resulting in the simple fabrication of a tunnel frit. A short packing tunnel frit column (2 cm, C(18) particles) was able to sustain over 10,000 psi continuous liquid flow for 10 days without observation of particle loss, and back pressure variation was less than 5%. The tunnel frit was successfully applied to the fabrication of nanoflow ultra high-performance liquid chromatography (nano-UHPLC) trap and analytical columns. In the analysis of tryptic peptides, the tunnel frit trap and analytical columns were demonstrated to have high separation efficiency and sensitivity. In analysis of phosphopeptides, the use of the nonmetallic tunnel frit column showed better sensitivity than the metallic frit column. This design can facilitate the preparation of nano-HPLC and nano-UHPLC columns and the packing material can easily be refilled when the column is severely contaminated or clogged.