Microscale Separations Research Articles

Assessing Surface Adsorption in Cyclic Olefin Copolymer Microfluidic Devices Using Two-Dimensional Nano Liquid Chromatography-Micro Free Flow Electrophoresis Separations.

Surface interactions are a concern in microscale separations, where analyte adsorption can decrease the speed, sensitivity, and resolution otherwise achieved by miniaturization. Here, we functionally characterize the surface adsorption of hot-embossed cyclic olefin copolymer (COC) micro free-flow electrophoresis (μFFE) devices using two-dimensional nLC × μFFE separations, which introduce a 3- to 5 s plug of analyte into the device and measure temporal broadening that arises from surface interactions. COC is an attractive material for microfluidic devices, but little is known about its potential for surface adsorption in applications with continuous fluid flow and temporal measurements. Adsorption was minimal for three small molecule dyes: positively charged rhodamine 123, negatively charged fluorescein, and neutral rhodamine 110. Temporal peak widths for the three dyes ranged from 3 to 7 s and did not change significantly with increasing transit distance. Moderate adsorption was observed for Chromeo P503-labeled myoglobin and cytochrome c with temporal peak widths around 20 s. Overall, the COC surface adsorption was low compared to traditional glass devices, where peak widths are on the order of minutes. Improvements in durability, long-term performance, and ease of fabrication, combined with low overall adsorption, make the COC μFFE devices a practical choice for applications involving time-resolved continuous detection.

Proceedings of APCE-CECE-ITP-IUPAC 2022

In a demonstration of modern analytical chemistry at its best, the International Interdisciplinary Conference of Chemical Analysis, APCE-CECE-ITP-IUPAC 2022 was held after two years of COVID-19-related delays in Siem Reap, Cambodia. The quadruple meeting included: 18th Asia Pacific International Symposium on Microscale Separations and Analyses, 17th International Interdisciplinary Meeting on Bioanalysis, 28th International Symposium on Electro- and Liquid Phase-Separation Techniques, and IUPAC Special Symposia by Division of Chemistry and the Environment. While, under normal circumstances, these conferences would take place in different countries, we have decided to bring together analytical chemists from all over the world for a conference covering all aspects of modern analytical chemistry. Our goal remained the same: “bring together scientists from different disciplines who may not meet at other meetings”. With plenary and invited lectures delivered by distinguished scientists, this in-person meeting allowed to broaden our knowledge, meet new friends, and start new collaborations. The organizers want to thank all speakers, sponsors, and participants for their support. Please, check the conference web for more information about the history, programs, photos, and videos.

Differences between Colloidal and Crystalline Evaporative Deposits.

Evaporative deposits from drops are widely studied due to their numerous applications in low-effort self-assembly, including for inkjet printing, microscale separations, and sensing/diagnostics. This phenomenon has been broadly explored for drops containing suspended colloidal particles but has been less quantified for drops with dissolved solutes. When a drop of solute/solvent mixture is evaporated on a substrate, nonvolatile solutes become supersaturated as the solvent evaporates, which then leads to crystal nucleation at the substrate-drop contact line. Emerging crystals alter the local wettability and fundamentally alter the dynamics of evaporation, which, in turn, influences the resultant evaporative deposit. Here we investigate the role of interactions between the substrate, crystals, and solution by comparing the evaporative deposition of three different salts as solutes against an evaporating colloidal solution. We show that nucleation effects can cause crystalline deposits to have a temperature relationship that is opposite to that of colloidal deposits and demonstrate how a balance between the contact-line pinning force and nucleation controls the deposit size.

Electrochemical Multiplexing: Control over Surface Functionalization by Combining a Redox‐Sensitive Alkyne Protection Group with “Click”‐Chemistry

AbstractLocal functionalization of surfaces is a current technological challenge. An electrochemically addressable alkyne protection group is presented enabling the site‐selective liberation of alkynes exclusively on electrified electrodes. This controlled deprotection is based on a mendione chromophore which becomes a strong enough nucleophile upon reduction to intramolecularly attack the trialkylsilane alkyne protection group. The site‐selective liberation of the alkyne is demonstrated by immobilizing the protected alkyne precursor on a transparent TiO2 electrode and subsequently immobilizing red and blue azide dyes by azide‐alkyne “click” chemistry. While the proof‐of‐principle is based on colorations visible to the bare eye, the technique presented is generic also to nontransparent electrodes, microscale separations, and functional moieties other than dyes. It may open manifold applications where site‐selective functionalization is required but hardly realizable with conventional methods.

32nd International Symposium on Microscale Separations and Bioanalysis (MSB 2016).

32nd International Symposium on Microscale Separations and Bioanalysis, Niagara-on-the-Lake, Canada, 3-7 April 2016 The 32nd edition of the International Symposium on Microscale Separations and Bioanalysis (MSB) was held in Niagara-on-the-Lake, Canada, from 3 to 7 April 2016. This article outlines the aim and the main distinctive features of the MSB symposium. A selection of the scientific research presented at MSB 2016 is highlighted with a special focus on microscale separation developments in the fields of sample preparation, (glyco)proteomics and metabolomics.

Microsystems for Anion Exchange Separation of Radionuclides in Nitric Acid Media

An efficient and reproducible photopolymerized poly(ethylene glycol methacrylate methacrylate-co- allyl methacrylate) monolith was synthesized and a photografting process based on the ene-thiol click-chemistry has been performed to give anion exchange properties to the monolith. Since their introduction in the early 1990s polymethacrylate monoliths have emerged as a powerful alternative for microscale separations or sample treatment. Their relatively simple implementation in columns with small internal diameters makes them particularly attractive for the new chromatographic challenges of complex matrices analysis and on-chip separations. Despite their relatively poor ion-exchange capacity due to their highly porous structure, their use as anion exchangers is of large interest for nuclear analysis as numerous separations are based on this process. This paper presents a systematic study of the synthesis of the polymeric porous monolith and the versatile and robust functionalization method developed for the specific strong acidic media used in radiochemical procedures. The robustness of the stationary phase was tested in concentrated nitric acid.

Recent trends in analytical and structural glycobiology

The great complexity of glycosylated biomolecules necessitates a set of powerful analytical methodologies to reveal functionally important structural features. Mass spectrometry (MS), with its different ionization techniques, mass analyzers, and detection strategies, has become the most important analytical method in glycomic and glycoproteomic investigations. In combination with MS, microscale separations (based on capillary chromatography and electrophoresis) and carbohydrate microchemistry, we feature here conceptually important applications of the recent years. This review focuses on methodological advances pertaining to disease biomarker research, immunology, developmental biology, and measurements of importance to biopharmaceuticals. High-sensitivity determinations and sample enrichment/preconcentration are particularly emphasized in glycomic and glycoproteomic profiling.

A Fluorogenic Aromatic Nucleophilic Substitution Reaction for Demonstrating Normal-Phase Chromatography and Isolation of Nitrobenzoxadiazole Chromophores

Normal-phase chromatography is an essential technique for monitoring chemical reactions, identifying the presence of specific components, as well as the purification of organic compounds. An experiment to facilitate the instruction and understanding of the concepts behind normal-phase chromatography at the introductory and intermediate undergraduate organic chemistry levels is described. The experiment exploits a fluorogenic aromatic nucleophilic substitution (SNAr) reaction to allow thin-layer and flash chromatography to be performed using direct visualization and can also be used to demonstrate the influence of organic structure on observable bulk properties. Finally, the experiment provides an opportunity to teach microscale separations using flash chromatography and provides a convenient one-step nucleophilic aromatic substitution.

Recent progress of polar stationary phases in CEC and capillary liquid chromatography

The stationary phases including the nonpolar and polar stationary phases in microscale separations have been greatly developed. This review describes the recent progress of the polar stationary phases (PSPs) with the focus on their preparation and the interesting applications in the field of CEC and capillary liquid chromatography (CLC) covering the literatures from the middle of 2006 to the middle of 2008. The PSPs described herein were summarized into three types as open-tubular, particle-packed and monolithic stationary phases for either CEC or CLC, and the separation mechanisms are of hydrophilic interaction, chiral selection, ion-exchange and/or electrostatic interaction, etc. After overviewing the literatures published in the last 2 years, the research efforts on PSPs for CEC and CLC have been remaining in the fabrication of open-tubular and monolithic capillary columns; whereas, the research endeavor of PSPs on particulate-packed format seemed to decline most likely due to the commercial availability of various packing particles for CEC and CLC.

Micro-scale open-tube capillary separations of functional proteins

This article describes a novel technique whereby fully functional proteins or multiprotein complexes are efficiently extracted from biological samples to chemically derivatized walls of fused-silica open-tube capillary columns. Proteins are eluted with very high yields into elution volumes that are smaller in volume than the internal volume of the open-tube capillary column itself, thereby achieving 100-fold increases in target protein concentrations from starting samples of less than 1 ml. The open-tube capillary columns are designed for single use; combined with the physical and chemical characteristics of the open-tube capillary column, this provides exceptional purity to the eluted proteins. Affinity-based open-tube capillary columns are demonstrated here to purify, enrich, and maintain functionality for a monomeric and dimeric enzyme, a low-abundance HeLa nuclear complex, and a light-harvesting octadecameric membrane protein complex. The design of the open-tube capillary column allows for facile direction of the processed protein sample to any number of final detection techniques and is capable of generating final protein concentrations required for many structural biology experiments. The open-tube capillary columns are also characterized by exceptional ease of use. Current designs allow for up to 10 open-tube capillary columns to be applied simultaneously with no fundamental impediments to even greater parallel operation.

Meeting News: Protein digestion on-line with CE/MS

Katie Cottingham reports from the 17th International Symposium on Microscale Separations and Capillary Electrophoresis -- Salzburg, Austria

Meeting News: A new alternative to ICAT

Katie Cottingham reports from the 17th International Symposium on Microscale Separations and Capillary Electrophoresis -- Salzburg, Austria

Meeting News: isolated hydrogel valves

ADVERTISEMENT RETURN TO ISSUEPREVNewsNEXTMeeting News: isolated hydrogel valvesMichael Felton reports from the 16th International Symposium on Microscale Separations and Analysis (HPCE 2003)—San Diego, Calif.Michael FeltonCite this: Anal. Chem. 2003, 75, 7, 144 APublication Date (Web):April 1, 2003Publication History Published online1 April 2003Published inissue 1 April 2003https://doi.org/10.1021/ac0312763RIGHTS & PERMISSIONSArticle Views127Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (81 KB) Get e-AlertsSUBJECTS:Hydrogels Get e-Alerts

Meeting News: Brain chemistry with CE

Michael Felton reports from the 16th International Symposium on Microscale Separations and Analysis (HPCE 2003)—San Diego, Calif.

Meeting News: Portable CE

ADVERTISEMENT RETURN TO ISSUEPREVNewsNEXTMeeting News: Portable CEMichael Felton reports from the 16th International Symposium on Microscale Separations and Analysis (HPCE 2003)—San Diego, Calif.Michael FeltonCite this: Anal. Chem. 2003, 75, 7, 144 APublication Date (Web):April 1, 2003Publication History Published online1 April 2003Published inissue 1 April 2003https://doi.org/10.1021/ac031275aRIGHTS & PERMISSIONSArticle Views99Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (81 KB) Get e-Alerts Get e-Alerts

Method for immobilization of liposomes in capillary electrophoresis by electrostatic interaction with derivatized agarose.

A novel procedure for immobilization of liposomes inside fused-silica capillaries is demonstrated. First, the inner wall of the capillaries was coated with a positively charged polymer, composed of derivatized agarose. Subsequently, negatively charged liposomes were immobilized by electrostatic interaction on the polymer coating. The developed liposome coated capillaries were used as a nanoseparation tool for studying interactions between small drug compounds and liposomes. Part of this work was presented at the 15th International Symposium on Microscale Separations and Analysis, HPCE 2002, Stockholm, Sweden, April 2002.

Comprehensive two dimensional separation based on coupling micellar electrokinetic chromatography with capillary isoelectric focusing.

Concentrating properties of the Capillary Isoelectric Focusing (CIEF) system with continuous whole-column-imaging detection were investigated for application as a second dimension in a comprehensive two-dimensional (2D) separation process. The concentration/separation/detection was completed within 4 min in a 300 microm inner diameter capillary. As the key to the successful coupling of CIEF to a first dimension separation, a novel interface was developed. A 10-port valve with two conditioning loops was used to perform both comprehensive collection and dialysis desalting of the first dimensional effluent, and as an interface coupling Micellar Electrokinetic Chromatography (MEKC) to CIEF. In the loop, salt and other unwanted first dimension effluent components were eliminated by dialysis and carrier ampholytes (CAs) were added. Peak broadening during the dialysis did not have significant impact on the CIEF separation because of its concentrating effect. Protein digests were first separated by MEKC followed by isoelectric point (pI) using whole-column-imaged CIEF. The dialysis interface allows general coupling of the whole-column-imaged CIEF to microscale separations.

Meeting News: Rapid single-cell analysis on a microfluidic chip

ADVERTISEMENT RETURN TO ISSUEPREVNewsNEXTMeeting News: Rapid single-cell analysis on a microfluidic chipNews from the 15th International Symposium on Microscale Separations and Analysis (HPCE 2002)—Judith Handley reports from Stockholm, SwedenJudith HandleyCite this: Anal. Chem. 2002, 74, 13, 365 APublication Date (Web):July 1, 2002Publication History Published online1 July 2002Published inissue 1 July 2002https://doi.org/10.1021/ac022061gRIGHTS & PERMISSIONSArticle Views161Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (20 KB) Get e-AlertsSUBJECTS:Biotechnology,Fluid dynamics Get e-Alerts

15th International Symposium on Microscale Separations and Analysis, HPCE 2002 Stockholm, Sweden, April 14-18, 2002

Journal of Separation ScienceVolume 25, Issue 8 p. 547-548 Conference Report 15th International Symposium on Microscale Separations and Analysis, HPCE 2002 Stockholm, Sweden, April 14–18, 2002 Václav Kašička, Václav KašičkaSearch for more papers by this author Václav Kašička, Václav KašičkaSearch for more papers by this author First published: 13 June 2002 https://doi.org/10.1002/1615-9314(20020601)25:8<547::AID-JSSC547>3.0.CO;2-KAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume25, Issue8June 2002Pages 547-548 RelatedInformation

Principles for microscale separations based on redox-active surfactants and electrochemical methods.

We report principles for microscale separations based on selective solubilization and deposition of sparingly water-soluble compounds by an aqueous solution of a redox-active surfactant. The surfactant, (11-ferrocenylundecyl)trimethylammonium bromide, undergoes a reversible change in micellization upon oxidation or reduction. This change in aggregation is exploited in a general scheme in which micelles of reduced surfactant are formed and then put in contact with a mixture of hydrophobic compounds leading to selective solubilization of the compounds. The micelles are then electrochemically disrupted, leading to the selective deposition of their contents. We measured the selectivity of the solubilization and deposition processes using mixtures of two model drug-like compounds, o-tolueneazo-beta-naphthol (I) and 1-phenylazo-2-naphthylamine (II). By repeatedly solubilizing and depositing a mixture that initially contained equal mole fractions of each compound, we demonstrate formation of a product that contains 98.4% of I after six cycles. Because the aggregation states of redox-active surfactants are easily controlled within simple microfabricated structures, including structures that define small stationary volumes (e.g., wells of a microtiter plate) or flowing volumes of liquids (e.g., microfabricated channels), we believe these principles may be useful for the purification or analysis of compounds in microscale chemical process systems. When used for purification, these principles provide separation of surfactant and product.