Electrolyte systems for on-line CE-MS: Detection requirements and separation possibilities

Capillary Electrophoresis-Mass Spectrometry with Multisegment Injection and In-Capillary Preconcentration for High-Throughput and Sensitive Determination of Therapeutic Decapeptide Triptorelin in Pharmaceutical and Biological Matrices

A capillary electrophoresis-tandem mass spectrometry method with a multisegment injection and an in-capillary field-enhanced sample stacking for determination of therapeutic peptide triptorelin in pharmaceutical and biological matrices was developed. The CE separation conditions were optimized in order to obtain maximal separation efficiency, analytical signal intensity and stability, and minimal adsorption of the analyzed peptide onto the capillary wall (1 M formic acid-HFo, pH 1.88). The implementation of the field-enhanced sample injection into CE improved the value of limit of detection 50 times while the multisegment injection increased the sample throughput three times in comparison to a conventional CE approach. The proposed method was characterized by favorable performance parameters, such as linearity (r2 ≥ 0.99), limit of detection (5 ng mL-1 in water matrix, 25 ng mL-1 in plasma matrix), precision (relative standard deviation, 1.5-9.4% for intraday and 2.3-11.9% for interday reproducibility), or accuracy (relative errors in the range of 80-109%). The FDA-validated method was successfully applied to the analysis of triptorelin in the commercial drug Diphereline® 0.1 mg (powder for injection) and in spiked human plasma samples. Favorable performance parameters along with proven application potentialities indicate the usefulness of the proposed method for its routine use in drug quality control laboratories and for clinical analysis, such as determination of triptorelin levels in plasma (for pharmacokinetic study).

CE-MS for Proteomics and Intact Protein Analysis

This chapter aims to explore various parameters involved in achieving high-end capillary electrophoresis hyphenated to mass spectrometry (CE-MS) analysis of proteins, peptides, and their posttranslational modifications. The structure of the topics discussed in this book chapter is conveniently mapped on the scheme of the CE-MS system itself, starting from sample preconcentration and injection techniques and finishing with mass analyzer considerations. After going through the technical considerations, a variety of relevant applications for this analytical approach are presented, including posttranslational modifications analysis, clinical biomarker discovery, and its growing use in the biotechnological industry.

Ultrasensitive determination of serotonin in human urine by a two dimensional capillary isotachophoresis-capillary zone electrophoresis hyphenated with tandem mass spectrometry

A two-dimensional capillary isotachophoresis-capillary zone electrophoresis method hyphenated with tandem mass spectrometry was developed and validated for ultrasensitive quantification of serotonin in real human urine samples. Under optimal conditions, the separation was achieved within 12 min (including on-line sample preparation) with the limit of detection of 34 pg mL^-1 (due to a large volume sample injection, here 10 µL, and isotachophoretic preconcentration). This concentration limit represents the lowest value for serotonin in comparison to other previously published separation methods employing mass spectrometry detection and applied to urine matrices. Thanks to high orthogonality, on-line concentration and clean-up effects of this approach, other excellent validation parameters such as linearity (coefficient of determination > 0.99), inter-day and intra-day precision (relative standard deviations 3.5-12.2%), accuracy (relative errors within 99-109.4%), and recovery (96-102%) could be easily obtained too. To demonstrate applicability of the method, we monitored serotonin levels in various real samples (from a healthy volunteer and clinical ones). The determined levels, normalized on the creatinine concentrations, were in the range of 6.81-12.86 ng mmol^-1 creatinine This advanced method is suggested for an effective, reliable, high sample throughput, and low cost routine clinical screening or targeted metabolomic studies of serotonin in urine samples.

A simple and rapid LC-MS/MS and CE-MS/MS analytical strategy for the determination of therapeutic peptides in modern immunotherapeutics and biopharmaceutics

Modern therapy of metabolic, neurodegenerative, inflammation, or cancer diseases is recently based on an immunotherapeutic approach. The peptide conjugates represent innovative and effective therapeutics that are better tolerated and are much more specific than small molecule-based medicines. The nature and manufacturing process of these therapeutics make their analysis very challenging. Here, two robust analytical methods based on an on-line combination of ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) and capillary electrophoresis with tandem mass spectrometry (CE-MS/MS) were developed for fast determination of immunogenic synthetic peptide (peptide sequence CADNLHKVVGQST) in a conjugate with bovine serum albumin (BSA) as a carrier protein and is a peptide, conjugate formulated with a vaccine adjuvant - Alhydrogel® 2 %. An effective non-enzymatic release step of the peptide from the final peptide conjugate based on acid hydrolysis with the use of 2% formic acid was successfully tested and implemented. The proposed methods were validated according to the ICH guideline and parameters such as linearity, precision, and accuracy, the limit of detection (LOD) or limit of quantification (LOQ) were assessed. Calibration curves were linear within the range of 1-30 μg.mL^-1 and the correlation coefficients were higher than 0.99. The intraday and interday precisions were 3.2-8.1 % (UHPLC-MS/MS), 1.6-9.3 % (CE-MS/MS) and 3.6-10.3 % (UHPLC-MS/MS), 4.1-10.2 % (CE-MS/MS), respectively. The recovery ranged in the interval of 98.4-107.4 % for UHPLC-MS/MS method and 100.3-103.2 % for CE-MS/MS method. The presented approaches represent an effective tool for simple, rapid and robust quantification of immunogens in modern immunotherapeutics and other biopharmaceuticals with appropriate peptide sequences.

Classical MALDI-MS versus CE-based ESI-MS proteomic profiling in urine for clinical applications

Human urine is an attractive and informative biofluid for medical diagnosis, which has been shown to reflect the (patho)-physiology of not only the urogenital system, but also others such as the cardiovascular system. For this reason, many studies have concentrated on the study of the urine proteome, aiming to find relevant biomarkers that could be applied in a clinical setting. However, this goal can only be achieved after reliable quantitative and qualitative analysis of the urinary proteome. In the last two decades, MS-based platforms have evolved to become indispensable tools for biomarker research. In this review, we will present and compare two of the most clinically relevant analytical platforms that have been used for the study of the urinary proteome, namely CE-based ESI-MS and classical MALDI-MS. These platforms, although not directly comparable, have been extensively used in proteomic profiling and therefore their comparison is fundamentally relevant to this field.

Nonaqueous CE ESI-IT-MS analysis of Amaryllidaceae alkaloids

The Amaryllidaceae are widely distributed medical plants. Lycorine, lycoramine, lycoremine, and lycobetaine are the major active alkaloids in Amaryllidaceae plants. A nonaqueous CE ESI-IT-MS method for separation, identification, and quantification of the Amaryllidaceae alkaloids has been developed. The MS(1-3) behavior has been studied and the fragmentation pathways of main fragment ions have been proposed. The effects of several factors such as composition and concentration of buffer, applied voltage, composition, and flow rate of the sheath liquid, nebulizing gas pressure, flow rate, and temperature of drying gas were investigated. Under the optimal conditions, the linear concentration range of these compounds was wide with the correlation coefficient (R(2) ) >0.99. RSDs of migration time and peak areas were <10%. The LODs were <240 ng/mL. The proposed method can be successfully applied to the determination of the related alkaloids in the Lycoris radiata roots.

Separation of isomeric bavachin and isobavachalcone in the fructus Psoraleae by capillary electrophoresis-mass spectrometry

Bavachin and isobavachalcone are the isomeric compounds in the fructus Psoraleae. The ion trap mass spectrometric fragmentation pathways of the bavachin and isobavachalcone in negative ion mode were elucidated for the identification. A novel method for determination of isomeric bavachin and isobavachalcone has been developed by capillary electrophoresis coupled with mass spectrometric detection. The effects of several factors such as concentration, pH of ammonium acetate buffer, separation voltage, composition and flow rate of the sheath liquid were investigated. Under optimal conditions, the linear concentration range for bavachin and isobavachalcone were 0.8-100 μg/mL with the correlation coefficient of 0.996 and 0.995, respectively. Relative standard deviations of migration time and peak areas were lower than 5%. The limits of detection (signal/noise = 3) were 60 ng/mL. The proposed method can be successfully applied to the determination of bavachin and isobavachalcone in the fructus Psoraleae and six fructus Psoraleae-containing preparations.

Capillary electrophoresis/mass spectrometry relevant to pharmaceutical and biotechnological applications

Advanced analytical techniques play a crucial role in the pharmaceutical and biotechnological field. In this context, capillary electrophoresis/mass spectrometry (CE/MS) has attracted attention due to efficient and selective separation in combination with powerful detection allowing identification and detailed characterization. Method developments and applications of CE/MS have been focused on questions not easily accessible by liquid chromatography/mass spectrometry (LC/MS) as the analysis of intact proteins, carbohydrates, and various small molecules, including peptides. Here, recent approaches and applications of CE/MS relevant to (bio)pharmaceuticals are reviewed and discussed to show actual developments and future prospects. Based on other reviews on related subjects covering large parts of previous works, the paper is focused on general ideas and contributions of the last 2 years; for the analysis of glycans, the period is extended back to 2006.

On-line CE/ESI/MS interfacing: recent developments and applications in proteomics

After shining as the ultimate separation - sequencing technique used for the successful completion of the Human Genome Project, in the early 2000s CE experienced lowered popularity among separation scientists. The renewed interest in recent years relates to the separation needs, especially in proteomics, metabolomics, and glycomics, where CE complements liquid chromatography techniques. This interest is further boosted by the regulators requiring additional separation techniques for characterization of newly developed pharmaceuticals. This paper gives a short overview of recent developments in the on-line interfacing of CE separation techniques with electrospray ionization/mass spectrometric analysis. Both the instrumentation and selected CE/ESI/MS applications including analyses of peptides, proteins, and glycans are discussed with the stress on research published in the past 3 years. Techniques related to the proteomic and glycomic analyses such as sample preconcentration, on-line protein digestion, and analyte derivatization prior CE/ESI/MS analysis are also included.

Analysis of drugs of forensic interest with capillary zone electrophoresis/time-of-flight mass spectrometry based on the use of non-volatile buffers

The present work is aimed at investigating the influence of the background electrolyte composition and concentration on the separation efficiency and resolution and mass spectrometric detection of illicit drugs in a capillary zone electrophoresis-electrospray ionization-time of flight mass spectrometry (CZE-ESI-TOF MS) system. The effect of phosphate, borate and Tris buffers on the separation and mass spectrometry response of a mixture of 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, methadone, cocaine, morphine, codeine and 6-monoacetylmorphine was studied, in comparison with a reference ammonium formate separation buffer. Inorganic non-volatile borate and Tris buffers proved hardly suitable for capillary electrophoresis-mass spectrometry (CE-MS) analysis, but quite unexpectedly ammonium phosphate buffers showed good separation and ionization performances for all the analytes tested. Applications of this method to real samples of hair from drug addicts are also provided.

Glycan analysis by modern instrumental methods

The oligosaccharides attached to proteins or lipids are among the most challenging analytical tasks due to their complexity and variety. Knowing the genes and enzymes responsible for their biosynthesis, a large but not unlimited number of different structures and isomers of such glycans can be imagined. Understanding of the biological role of structural variations requires the ability to unambiguously determine the identity and quantity of all glycan species. Here, we examine, which analytical strategies - with a certain high-throughput potential - may come near this ideal. After an expose of the relevant techniques, we try to depict how analytical raw data are translated into structural assignments using retention times, mass and fragment spectra. A method's ability to discriminate between the many conceivable isomeric structures together with the time, effort and sample amount needed for that purpose is suggested as a criterion for the comparative assessment of approaches and their evolutionary stages.

Recent advances in CE-MS: Synergy of wet chemistry and instrumentation innovations

CE with MS detection is a hyphenated technique which greatly improves the ability of CE to deal with real samples, especially with those coming from biology and medicine, where the target analytes are present as trace amounts in very complex matrices. CE-MS is now almost a routine technique performed on commercially available instruments. It faces currently a tremendous development of the technique itself as well as of its wide application area. Great interest in CE-MS is reflected in the scientific literature by many original research articles and also by numerous reviews. The review presented here has a general scope and belongs to a series of regularly published reviews on the topic. It covers the literature from the last 2 years, since January 2008 till June 2010. It brings a critical selection of related literature sorted into groups reflecting the main topics of actual scientific interest: (i) innovations in CE-ESI-MS, (ii) use of alternative interfaces, and (iii) ways to enhance sensitivity. Special attention is paid to novel electrolyte systems amenable to CE-MS including nonvolatile BGEs, to advanced CE separation principles such as MEKC, MEEKC, chiral CE, and to the use of preconcentration techniques.

Simplified capillary electrophoresis nanospray sheath-flow interface for high efficiency and sensitive peptide analysis

We report a simple nanospray sheath-flow interface for capillary electrophoresis. This interface relies on electrokinetic flow to drive both the separation and the electrospray; no mechanical pump is used for the sheath flow. This system was interfaced with an LCQ mass spectrometer. The best results were observed with a 2-microm diameter emitter tip and a 1-mm spacing between the separation capillary tip and the emitter tip. Under these conditions, mass detection limits (3sigma) of 100 amol were obtained for insulin receptor fragment 1142-1153. The separation efficiency exceeded 200,000 plates for this compound. The relative standard deviation generated during continual infusion of a 50 microM solution of angiotensin II was 2% for the total ion count and 3% for the extracted ion count over a 40-min period. Finally, the interface was also demonstrated for negative ion mode.

Investigation of commercial sorbents for the analysis of opioid peptides in human plasma by on-line SPE-CE

In this study, we investigated the performance of several commercial sorbents (Sep-pack) C18, (t)C18, C8 and (t)C2, Oasis HLB, Isolute ENV+, Strata-X and Oasis MCX) for the determination of opioid peptides by solid-phase extraction coupled on-line to capillary electrophoresis (SPE-CE). First, standard solutions were analyzed in order to achieve the lowest LOD and the best electrophoretic separations using UV detection. The best results were obtained using C18, C8 and (t)C2 sorbents, which were examined for the analysis of spiked human plasma samples. A double-step sample clean-up pretreatment, which consisted of precipitation with acetonitrile and filtration, was needed to prevent saturation of the on-line SPE microcartridge. The filtration step was critical to obtain optimum analyte recovery and to clean up the sample matrix. A range of centrifugal filters and filtration conditions were tested and the recoveries of the sample pretreatment were evaluated by CE-ESI-MS. The LODs attained through SPE-CE-UV were approximately ten-fold better with C18 than with C8 and (t)C2. The 0.1 microg/mL LODs achieved by C18-SPE-CE-UV were further improved until we could detect 1 ng/mL concentrations of opioid peptides in plasma samples by C18-SPE-CE-ESI-MS, due to the outstanding selectivity of the MS detection.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics

The use of capillary electromigration methods to analyze foods and food components is reviewed in this work. Papers that were published during the period April 2007 to March 2009 are included following the previous review by García-Cañas and Cifuentes (Electrophoresis, 2008, 29, 294-309). These works include the analysis of amino acids, biogenic amines, peptides, proteins, DNAs, carbohydrates, phenols, polyphenols, pigments, toxins, pesticides, vitamins, additives, small organic and inorganic ions and other compounds found in foods and beverages, as well as those applications of CE for monitoring food interactions and food processing. The use of microchips, CE-MS, chiral-CE as well as other foreseen trends in food analysis are also discussed including their possibilities in the very new field of Foodomics.

Advanced CE for chiral analysis of drugs, metabolites, and biomarkers in biological samples

An analysis of recent trends indicates that CE can show real advantages over chromatographic methods in ultratrace enantioselective determination of biologically active compounds in complex biological matrices. It is due to high separation efficiency and many applicable in-capillary electromigration effects in CE (countercurrent migration, stacking effects) enhancing significantly (enantio)separability and enabling effective sample preparation (preconcentration, purification, analyte derivatization). Other possible on-line combinations of CE, such as column coupled CE-CE techniques and implementation of nonelectrophoretic techniques (extraction, membrane filtration, flow injection) into CE, offer additional approaches for highly effective sample preparation and separation. CE matured to a highly flexible and compatible technique enabling its hyphenation with powerful detection systems allowing extremely sensitive detection (e.g. LIF) and/or structural characterization of analytes (e.g. MS). Within the last decade, more as well as less conventional analytical on-line approaches have been effectively utilized in this field and their practical potentialities are demonstrated on many new application examples in this article. Here, three basic areas of (enantioselective) drug bioanalysis are highlighted and supported by a brief theoretical description of each individual approach in a compact review structure (to create integrated view on the topic), including (i) progressive enantioseparation approaches and new enantioselective agents, (ii) in-capillary sample preparation (preconcentration, purification, derivatization), and (iii) detection possibilities related to enhanced sensitivity and structural characterization.