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Journal of Chromatography. A Apr 2023A novel method for the determination of "true" free sulfur dioxide (SO) in wine and cider was developed using capillary electrophoresis with direct ultraviolet-visible...
A novel method for the determination of "true" free sulfur dioxide (SO) in wine and cider was developed using capillary electrophoresis with direct ultraviolet-visible spectrophotometric detection (CE-UV/vis). Free SO was measured in model solutions with different SO-binding agents present (α-ketoglutarate, pyruvate, acetaldehyde, glucose, fructose, and malvidin-3-glucoside) as well as a variety of white and red wines and ciders. The CE method was compared to three conventional methods for measuring free SO, the Ripper method, Aeration-Oxidation (AO), and pararosaniline by discrete analyzer (DA). While some statistically significant differences (p<0.05) were found between the four methods in unpigmented model solutions and samples, the values generally agreed. In the presence of anthocyanins in model solution and red wines, free SO values found by CE were significantly lower than the other three methods (p<0.05). The difference in values found by Ripper and CE correlated strongly with anthocyanin content (R = 0.8854) and even more strongly when accounting for polymeric pigments (R = 0.9251). The results in red ciders differed from those in red wines, while the CE measured significantly lower free SO2 values than the other three methods, the difference in free SO values measured by CE and Ripper correlated more closely with anthocyanin concentration (R = 0.8802) than absorbance due to bleachable pigment (R = 0.7770). The CE method was found to be rapid (4 min/injection), sensitive (LOD=0.5 mg/L, LOQ=1.6 mg/L free SO in wine, 0.8 and 2.8 mg/L, respectively, in cider), robust, and repeatable (average RSD = 4.9%) and did not suffer from the issue of over-reporting free SO in pigmented samples often observed with currently accepted methods.
Topics: Wine; Sulfur Dioxide; Anthocyanins; Electrophoresis, Capillary; Oxidation-Reduction
PubMed: 36966602
DOI: 10.1016/j.chroma.2023.463936 -
Analytical Chemistry Aug 2022Coupling capillary electrophoresis (CE) to mass spectrometry (MS) is a powerful strategy to leverage a high separation efficiency with structural identification....
Coupling capillary electrophoresis (CE) to mass spectrometry (MS) is a powerful strategy to leverage a high separation efficiency with structural identification. Traditional CE-MS interfacing relies upon voltage to drive this process. Additionally, sheathless interfacing requires that the electrophoresis generates a sufficient volumetric flow to sustain the ionization process. Vibrating sharp-edge spray ionization (VSSI) is a new method to interface capillary electrophoresis to mass analyzers. In contrast to traditional interfacing, VSSI is voltage-free, making it straightforward for CE and MS. New nanoflow sheath CE-VSSI-MS is introduced in this work to reduce the reliance on the separation flow rate to facilitate the transfer of analyte to the MS. The nanoflow sheath VSSI spray ionization functions from 400 to 900 nL/min. Using the new nanoflow sheath reported here, volumetric flow rate through the separation capillary is less critical, allowing the use of a small (i.e., 20 to 25 μm) inner diameter separation capillary and enabling the use of higher separation voltages and faster analysis. Moreover, the use of a nanoflow sheath enables greater flexibility in the separation conditions. The nanoflow sheath is operated using aqueous solutions in the background electrolyte and in the sheath, demonstrating the separation can be performed under normal and reversed polarity in the presence or absence of electroosmotic flow. This includes the use of a wider pH range as well. The versatility of nanoflow sheath CE-VSSI-MS is demonstrated by separating cationic, anionic, and zwitterionic molecules under a variety of separation conditions. The detection sensitivity observed with nanoflow sheath CE-VSSI-MS is comparable to that obtained with sheathless CE-VSSI-MS as well as CE-MS separations with electrospray ionization interfacing. A bare fused silica capillary is used to separate cationic β-blockers with a near-neutral background electrolyte at concentrations ranging from 1.0 nM to 1.0 μM. Under acidic conditions, 13 amino acids are separated with normal polarity at a concentration ranging from 0.25 to 5 μM. Finally, separations of anionic compounds are demonstrated using reversed polarity under conditions of suppressed electroosmotic flow through the use of a semipermanent surface coating. With a near-neutral separation electrolyte, anionic nonsteroidal anti-inflammatory drugs are detected over a concentration range of 0.1 to 5.0 μM.
Topics: Anions; Cations; Electroosmosis; Electrophoresis, Capillary; Spectrometry, Mass, Electrospray Ionization
PubMed: 35913997
DOI: 10.1021/acs.analchem.2c02074 -
Chemical Reviews Sep 2018Capillary electrophoresis has emerged as a powerful approach for carbohydrate analyses since 2014. The method provides high resolution capable of separating... (Review)
Review
Capillary electrophoresis has emerged as a powerful approach for carbohydrate analyses since 2014. The method provides high resolution capable of separating carbohydrates by charge-to-size ratio. Principle applications are heavily focused on N-glycans, which are highly relevant to biological therapeutics and biomarker research. Advances in techniques used for N-glycan structural identification include migration time indexing and exoglycosidase and lectin profiling, as well as mass spectrometry. Capillary electrophoresis methods have been developed that are capable of separating glycans with the same monosaccharide sequence but different positional isomers, as well as determining whether monosaccharides composing a glycan are alpha or beta linked. Significant applications of capillary electrophoresis to the analyses of N-glycans in biomarker discovery and biological therapeutics are emphasized with a brief discussion included on carbohydrate analyses of glycosaminoglycans and mono-, di-, and oligosaccharides relevant to food and plant products. Innovative, emerging techniques in the field are highlighted and the future direction of the technology is projected based on the significant contributions of capillary electrophoresis to glycoscience from 2014 to the present as discussed in this review.
Topics: Carbohydrate Conformation; Electrophoresis, Capillary; High-Throughput Screening Assays; Monosaccharides; Oligosaccharides; Polysaccharides; Pyrenes; Staining and Labeling
PubMed: 29528644
DOI: 10.1021/acs.chemrev.7b00669 -
Analytical Chemistry Feb 2020Capillary electrophoresis-mass spectrometry is a powerful technique for high-throughput and high efficiency separations combined with structural identification....
Capillary electrophoresis-mass spectrometry is a powerful technique for high-throughput and high efficiency separations combined with structural identification. Electrospray ionization is the primary interface used to couple capillary electrophoresis to mass analyzers; however, improved designs continue to be reported. A new interfacing method based on vibrating sharp-edge spray ionization is presented in this work to overcome the challenges of decoupling applied voltages and to enhance the compatibility with separations performed at near-neutral pH. The versatility and ease of use of this ionization source is demonstrated using β-blockers, peptides, and proteins. The cationic β-blocker pindolol was injected electrokinetically, and detected at concentrations ranging from 10 nM to 5 μM, with an estimated detection limit of 2 nM. The vibrating sharp-edge spray ionization functions with flow rates from 70 to 200 nL/min and did not perturb the capillary electrophoresis separation electroosmotic flow as evidenced by the observation that most migration times differed less than 7% ( = 3) across a lab-built system interfaced to mass spectrometry and a commercial system that utilizes absorbance detection. For cationic beta-blockers the theoretical plates achieved in the capillary electrophoresis-mass spectrometry setup were 80%-95% of that observed with a commercial capillary electrophoresis-UV absorbance detection system.
Topics: Electroosmosis; Electrophoresis, Capillary; Molecular Structure; Pindolol; Spectrometry, Mass, Electrospray Ionization
PubMed: 31971372
DOI: 10.1021/acs.analchem.9b03994 -
Molecules (Basel, Switzerland) Jun 2022It is now more than 25 years since the first report of enantioselective analysis by capillary electrophoresis-mass spectrometry (CE-MS) appeared. This article reviews... (Review)
Review
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.
Topics: Chromatography, Micellar Electrokinetic Capillary; Electrophoresis, Capillary; Mass Spectrometry; Micelles; Stereoisomerism
PubMed: 35807372
DOI: 10.3390/molecules27134126 -
Journal of Separation Science Sep 2022Protein profiling of major bovine milk proteins (i.e., whey and casein proteins) is of great interest in food science and technology. This complex set of protein...
Protein profiling of major bovine milk proteins (i.e., whey and casein proteins) is of great interest in food science and technology. This complex set of protein proteoforms may vary with breed, genetics, lactation stage, health, and nutritional status of the animal. Current routine methods for bovine milk protein profiling at the intact level are typically based on capillary electrophoresis-ultraviolet, which does not allow confirming unequivocally the identity of the separated proteins. As an alternative, in this study, we describe for the first time a novel and simple capillary electrophoresis-mass spectrometry method in positive electrospray ionization mode. Under the optimized conditions, capillary electrophoresis-mass spectrometry allowed the separation and identification at the intact level of major bovine milk whey and casein proteins in less than 15 min. Furthermore, high-resolution mass spectrometry confirmed its importance in the reliable characterization of bovine milk protein proteoforms, especially those with slight molecular mass differences, such as β-casein A1 and A2, which are relevant to unequivocally identify milk with specific β-casein compositions (e.g., A2A2 milk, which is widely known as A2 milk). This differentiation was not possible by matrix-assisted laser desorption/ionization mass spectrometry, which provided rapidly and easily a rich but less accurate fingerprint of bovine milk proteins due to the lower mass resolution.
Topics: Animals; Caseins; Electrophoresis, Capillary; Female; Milk; Milk Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
PubMed: 35866669
DOI: 10.1002/jssc.202200423 -
Expert Opinion on Drug Discovery Feb 2017Many screening platforms are prone to assay interferences that can be avoided by directly measuring the target or enzymatic product. Capillary electrophoresis (CE) and... (Review)
Review
Many screening platforms are prone to assay interferences that can be avoided by directly measuring the target or enzymatic product. Capillary electrophoresis (CE) and microchip electrophoresis (MCE) have been applied in a variety of formats to drug discovery. CE provides direct detection of the product allowing for the identification of some forms of assay interference. The high efficiency, rapid separations, and low volume requirements make CE amenable to drug discovery. Areas covered: This article describes advances in capillary electrophoresis throughput, sample introduction, and target assays as they pertain to drug discovery and screening. Instrumental advances discussed include integrated droplet microfluidics platforms and multiplexed arrays. Applications of CE to assays of diverse drug discovery targets, including enzymes and affinity interactions are also described. Expert opinion: Current screening with CE does not fully take advantage of the throughputs or low sample volumes possible with CE and is most suitable as a secondary screening method or for screens that are inaccessible with more common platforms. With further development, droplet microfluidics coupled to MCE could take advantage of the low sample requirements by performing assays on the nanoliter scale at high throughput.
Topics: Drug Discovery; Electrophoresis, Capillary; Electrophoresis, Microchip; High-Throughput Screening Assays; Humans; Microfluidic Analytical Techniques; Molecular Targeted Therapy
PubMed: 27911223
DOI: 10.1080/17460441.2017.1268121 -
Analytical Chemistry Aug 2023A novel concept for highly versatile automated analyses of dried blood spot (DBS) samples by commercial capillary electrophoresis (CE) is presented. Two interchangeable...
A novel concept for highly versatile automated analyses of dried blood spot (DBS) samples by commercial capillary electrophoresis (CE) is presented. Two interchangeable CE cartridges with different fused-silica capillaries were used for the DBS elutions and the DBS eluate analyses, respectively. The application of one CE cartridge with a wide-bore capillary reduced DBS processing times to a minimum (1-2 min per sample) while fitting the other CE cartridge with a narrow-bore capillary served for highly efficient CE analyses. A comprehensive investigation of major variables affecting liquid handling in CE (capillary length, internal diameter, and temperature) was carried out with the aim of optimizing both procedures and enabling their maximum flexibility. The application of two CE cartridges also enabled the employment of CE detectors with different instrumental set-ups and/or principles as was demonstrated by the optical detection of nonsteroidal anti-inflammatory drugs (NSAIDs) and the conductivity detection of amino acids (AAs). The presented methods were optimized for the automated CE analyses of 36 DBS samples formed by a volumetric collection of 5 μL of capillary blood onto Whatman 903 discs and processed by direct in-vial elution using the CE instrument. The precision of liquid transfers for the automated DBS elutions was better than 0.9% and the precision of CE analyses did not exceed 5.1 and 12.3% for the determination of NSAIDs and AAs, respectively. Both methods were linear ( ≥ 0.996) over the therapeutic (NSAIDs) and the endogenous (AAs) concentration ranges, had limits of quantification below the typical analyte concentrations in human blood, and achieved sample throughputs of more than 6 DBSs per hour.
Topics: Humans; Electrophoresis, Capillary; Amino Acids; Dried Blood Spot Testing; Electric Conductivity; Capillaries
PubMed: 37505089
DOI: 10.1021/acs.analchem.3c02474 -
Analytical Chemistry Mar 2021Single-cell capillary electrophoresis mass spectrometry (CE-MS) is a promising platform to analyze cellular contents and probe cell heterogeneity. However, current...
Single-cell capillary electrophoresis mass spectrometry (CE-MS) is a promising platform to analyze cellular contents and probe cell heterogeneity. However, current single-cell CE-MS methods often rely on offline microsampling processes and may demonstrate low sampling precision and accuracy. We have recently developed an electrospray-assisted device, , for low-volume sample extraction. With the spray-capillary, low-volume samples (pL-nL) are drawn into the sampling end of the device, which can be used directly for CE separation and online MS detection. Here, we redesigned the spray-capillary by utilizing a capillary with a <15 μm tapered tip so that it can be directly inserted into single cells for sample collection and on-capillary CE-MS analysis. We evaluated the performance of the modified spray-capillary by performing single-cell microsampling on single onion cells with varying sample injection times and direct MS analysis or online CE-MS analysis. We have demonstrated, for the first time, online sample collection and CE-MS for the analysis of single cells. This application of the modified spray-capillary device facilitates the characterization and relative quantification of hundreds of metabolites in single cells.
Topics: Electrophoresis, Capillary; Mass Spectrometry; Spectrometry, Mass, Electrospray Ionization
PubMed: 33646748
DOI: 10.1021/acs.analchem.0c04624 -
Current Opinion in Biotechnology Feb 2017Capillary electrophoresis-mass spectrometry has shown considerable potential for profiling polar ionogenic compounds in metabolomics. Hyphenation of capillary... (Review)
Review
Capillary electrophoresis-mass spectrometry has shown considerable potential for profiling polar ionogenic compounds in metabolomics. Hyphenation of capillary electrophoresis to mass spectrometry is generally performed via a sheath-liquid interface. However, the electrophoretic effluent is significantly diluted in this configuration thereby limiting the utility of this method for highly sensitive metabolomics studies. Moreover, in this set-up the intrinsically low-flow property of capillary electrophoresis is not effectively utilized in combination with electrospray ionization. Here, advancements that significantly improved the performance of capillary electrophoresis-mass spectrometry are considered, with a special emphasis on the sheathless porous tip interface. Attention is also devoted to various technical aspects that still need to be addressed to make capillary electrophoresis-mass spectrometry a robust approach for probing the polar metabolome.
Topics: Animals; Electrophoresis, Capillary; Humans; Metabolome; Metabolomics; Spectrometry, Mass, Electrospray Ionization
PubMed: 27455398
DOI: 10.1016/j.copbio.2016.07.002