A new high-performance liquid chromatography (HPLC) method has been developed to detect ultra-low concentrations of bisphenol-A (BPA) (below 1 ng/L (ppt)) using column switching electrochemical detection (ECD). The results were superior to those obtained from manual pretreatment procedure with membrane stationary phase. BPA is inherently ubiquitous in the environment, including tools and solvents used for its analysis; to obtain meaningful results, therefore, the concentration of the overall BPA contamination must be below the detection limit for BPA using the analytical system. Therefore, purified water for preparing the standard BPA solution must be filtered with a hydrophobic membrane to suppress BPA background levels of contamination. In addition, we investigated methods for effectively preserving environmental water containing BPA. The addition of a small amount of ethylenediaminetetraacetic acid (EDTA) provided good recovery even after overnight storage. By employing these precautionary measures and procedures to reduce BPA contamination from the analytical procedure, we could accurately determine 1 - 10 ppt of BPA in environmental water samples using a column switching HPLC system.

Sample introduction method was studied to reduce the extra-column effect in reversed-phase HPLC. Slow transport of a sample band (SToSB) in the pre-column space followed by the introduction of the band into the column at a near-optimum flow rate resulted in larger plate counts for a 1.0 mmID, 5 cm long column as much as 1.4-1.6 times for solutes with a retention factor (k) of 0.5-1.8 compared to a conventional elution method. Further reduction of the extra-column effect was possible by orthogonally splitting the sample band (SplSB) by flow switching during its slow transport followed by the introduction of the leading part of the band into the column. In this case, increased plate counts of up to 2-3 times for solutes with k of 0.5-1.8 were observed for a 1.0 mmID, 5 cm column. The sample introduction method, SToSB in the injector and the pre-column tube of a few μL, was found to reduce the extra-column band variance by 0.4-0.5 μL2 for an UHPLC system with the extra-column volume (Vextra) of ca. 4.6 μL and the system variance (σextra2) of 1.1 μL2 at flow rate of 100 μL/min, while SToSB and subsequent SplSB were found to be more effective, reducing σextra2 by about 0.8 μL2. With an UHPLC instrument with Vextra of about 10 μL and σextra2 of ca. 3.6 μL2 at flow rate of 300 μL/min, 1.4-2.1 times as many plate counts were observed with SToSB and SplSB compared to the normal elution method for early-eluting solutes with k=0.25-1.7 for a column, 2.1 mmID, 5 cm long. With this UHPLC instrument, SToSB and/or SplSB resulted in the reduction of σextra2 by 1.2-2.2 μL2.

Increasing the separation efficiency and understanding the interactions associated with the columns and the stationary phases are some of the major objectives of fundamental studies on liquid chromatography. The separation of isotopic compounds is significant in separation science for how it illustrates the extremely high ability of high performance liquid chromatography systems, and has its own significance, too, as a longtime target of scientific curiosity. Isotopic separation is an interesting subject for separation science by itself because of the high similarity in the solute structure. Fundamental information on molecular interactions will be helpful for understanding the retention behaviors of various solutes in combination with diverse stationary phases and mobile phases. Difficult separations have often been carried out by recycle chromatography using a series of several columns to allow the solute mixture band to go through the columns many times before being eluted out.

Fast enantiomeric separation of amino acids was studied by liquid chromatography/mass spectrometry (LC/MS) on a chiral crown ether stationary phase. A chiral crown ether bonded silica column (3 mm internal diameter (i.d.), 5 cm long) packed with 3 mm particles was employed instead of a 15 cm column packed with 5 mu m particles used in our previous study. In addition, the extra-column variance, becoming more serious for smaller columns, was reduced by replacing 0.127 mm i.d. post-column tubes with shorter, smaller-diameter (0.0635 mm i.d.) tubes. The results demonstrated the benefits of using shorter columns packed with smaller particles and the reduction of the extra-column band broadening for fast enantiomeric separation. Finally, the enantiomeric separation of 18 pairs of proteinogenic amino acids was achieved within 2 min with a resolution (Rs) > 1.5 for each pair using an isocratic mobile phase of acetonitrile/water/trifluoroacetic acid (ACN/W/TFA) = 96/4/0.5, and a flow rate 1.2 mL/min at 30 degrees C. This is the highest throughput method for simultaneous chiral separation of all proteinogenic amino acids except proline to date. (C) 2020, The Society for Biotechnology, Japan. All rights reserved.

We report hydrogen/deuterium (H/D) isotope effects based on weak intermolecular interactions with polar functional groups and aromatic rings in liquid chromatography (LC). Various LC experiments with different aromatic analytes, separation media, and nonpolar mobile phases were conducted under normal phase LC conditions, where the hydrophobic interaction was completely suppressed. The separation media that had polar functional groups, such as silanol groups, allowed for higher separation efficiencies for the pairs of aromatic H/D isotopologues. In comparing the C-13 NMR spectra of protiated and deuterated aromatic analytes, the electron density of the deuterated analyte was found to be slightly higher than that of the protiated analytes. In the case of silanol functional groups, aromatic rings of the analyte acted as donors through the OH-pi interaction to hydrogen atoms in the silanol groups. Thus, the deuterated analytes were able to be greatly retained by the stronger OH-pi interactions. Furthermore, a C-70-fullerene bonded monolithic column (C70 column), which effectively provides CH-pi interactions, allowed the opposite isotope effect. Briefly, an electrostatic attraction based on the dipole(induced) dipole interaction dominated in the CH-pi interactions, according to a van't Hoff analysis. Hence, the bonding lengths of the C-H or D bonds were sensitively affected, such that we were able to conclude that the CH-pi interaction depended on the geometric effect. Applying these opposing H/D isotope effects, we were able to finally demonstrate effective H/D isotopologue separations by utilizing the complementary action of the OH-pi and CH-pi interactions.

•Pre-column dispersion is reduced by transporting the sample at low flow rates.•A general model of chromatography accounting for this effect is proposed.•Slow sample pre-column transport increases peak capacity by 20•Theoretical and experimental isocratic peak capacities are in excellent agreement.•Optimum slow pre-column flow rate is about 10–15

Ultrahigh-efficiency separations based on the presence of one deuterium in benzene, toluene, and naphthalene were achieved by recycle chromatography using C18 silica columns. Larger isotopic separation factors, alpha(H/D), were observed in methanol-water than in acetonitrile-water, when the mobile phases provided similar retention factors (k), or similar methylene selectivity, alpha(CH2). Isotopic resolutions between nondeuterated and perdeuterated aromatic hydrocarbons at long separation times were estimated by using the plate counts obtainable by recycle operation as a function of a cycle time, along with the retention factors and the separation factors experimentally observed. Methanol-acetonitrile-water ternary mobile phases were predicted to provide the greatest resolution per unit time, and actually enabled separation by the difference of one H/D substitution on the aromatic hydrocarbons with alpha(H/D) = 1.008 or less, and also the differentiation of the isomers of monodeuterated toluene with alpha(toluene-4-d/toluene-alpha-d) = 1.0016. The discrimination mechanism of H/D isotopic species is discussed based on the dispersion interactions of a CH/CD group of the solute with the stationary phase as well as the mobile phase.

•Chiral crown-ether bonded phase enabled fast separation of chiral amino acids.•All proteinogenic amino acids except proline were resolved within ten minutes.•Acidic, acetonitrile rich mobile phase reduced hydrophobic interaction.•Electrostatic repulsion reduced the contribution of hydrophilic partition mechanism.•Sample diluent and mobile phase were optimized to avoid peak distortion by water.

米国アルゴンヌ国立研究所の開発した高速炉と乾式サイクル施設を統合した統合型高速炉は受動的安全性，核不拡散性，放射性廃棄物の減容化において優れた核燃料サイクル方式である。またこのシステムは福島第一原子力発電所事故で生じた燃料デブリの処理に適用可能な技術と考えられる。実際にこの技術を使った場合，デブリ処理に要する時間，施設の安全性，建設コストを試算するとともに今後の技術的課題などの技術的可能性を検討した。

The kinetic performance of five chromatographic columns designed for fast liquid chromatography with different column packing materials - including fully porous (2.0 and 1.9μm particles), core-shell (2.6μm particles) or monolithic packings - with identical column dimensions (2.1×50mm) was tested. Since the tested monolithic column showed systematically better efficiency for early eluting compounds than the packed columns, an additional band broadening effect was suspected for the packed columns. The effects of the presence of the frits and the bed heterogeneity of the columns near the frits were characterized by a column-reversal method. It has been shown that significant differences - even 20-25% difference in efficiency - can exist between the two ends of the packed columns, while the monolithic column shows rather similar performance at either column end.

Monolithic silica columns have greater (through-pore size)/(skeleton size) ratios than particulate columns and fixed support structures in a column for chemical modification, resulting in high-efficiency columns and stationary phases. This review looks at how the size range of monolithic silica columns has been expanded, how high-efficiency monolithic silica columns have been realized, and how various methods of silica surface functionalization, leading to selective stationary phases, have been developed on monolithic silica supports, and provides information on the current status of these columns. Also discussed are the practical aspects of monolithic silica columns, including how their versatility can be improved by the preparation of small-sized structural features (sub-micron) and columns (1 mm ID or smaller) and by optimizing reaction conditions for in situ chemical modification with various restrictions, with an emphasis on recent research results for both topics.

Separation of diastereomers of DL--tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3 mmID, 20 cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic DL--tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0 oC, 536 bar, while three peaks were observed when the separation was carried out either at 12.0 oC at low pressure or at 20 oC at 488 bar. Higher temperature (30.0 oC) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0 oC and 441 bar, although the stationary phase afforded greater resolution for and -tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0 oC and 463 bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of DL--tocopherol.

Separation of diastereomers of dl-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3mmID, 20cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic dl-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0°C, 536bar, while three peaks were observed when the separation was carried out either at 12.0°C at low pressure or at 20°C at 488bar. Higher temperature (30.0°C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0°C and 441bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0°C and 463bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of dl-α-tocopherol.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTCore–Shell, Ultrasmall Particles, Monoliths, and Other Support Materials in High-Performance Liquid ChromatographyNobuo Tanaka* and David V. McCalley*View Author Information GL Sciences Inc., Iruma, Saitama 358-0032 Japan Centre for Research in Biosciences, University of the West of England, Frenchay, Bristol BS16 1QY, U.K.*E-mail: [email protected]*E-mail: [email protected]Cite this: Anal. Chem. 2016, 88, 1, 279–298Publication Date (Web):November 5, 2015Publication History Published online30 November 2015Published inissue 5 January 2016https://pubs.acs.org/doi/10.1021/acs.analchem.5b04093https://doi.org/10.1021/acs.analchem.5b04093review-articleACS PublicationsCopyright © 2015 American Chemical SocietyRequest reuse permissionsArticle Views4391Altmetric-Citations136LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Catalyst supports,Materials,Nanoparticles,Particulate matter,Silica Get e-Alerts

Fast Liquid Chromatography–Mass Spectrometry Methods in Food and Environmental Analysis, pp. 57-107 (2015) No AccessChapter 3: Monolithic Columns in Fast Liquid ChromatographyTakeshi Hara, Oscar Núñez, Tohru Ikegami, and Nobuo TanakaTakeshi HaraDepartment of Chemical Engineering, Vrije Universiteit Brussel, Belgium, Oscar NúñezDepartment of Analytical Chemistry, University of Barcelona, Spain, Tohru IkegamiDepartment of Biomolecular Engineering, Kyoto Institute of Technology, Japan, and Nobuo TanakaGL Sciences Inc., JapanUniversity of California, Davis, USAhttps://doi.org/10.1142/9781783264940_0003Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: The following sections are included: Features of Monolithic Silica Columns: Rapid Separation Using Monolithic Silica Columns in Rod and Capillary Formats Fabrication of columns The support structure regarding through-pores, skeletons, and amount of silica in a column Column permeability, column efficiency, and improvement of preparation method Current performance of monolithic silica columns Kinetic performance Functionalization of monolithic silica columns Advantages and disadvantages: roles of monolithic silica columns Features of Organic Polymer Monolithic Columns Food and Environmental Applications Summary and Conclusions References FiguresReferencesRelatedDetails Fast Liquid Chromatography–Mass Spectrometry Methods in Food and Environmental AnalysisMetrics History PDF download

Prototype small-size (1.0mm I.D., 5cm long) columns for reversed-phase HPLC were evaluated in relation to instrument requirements. The performance of three types of columns, monolithic silica and particulate silica (2μm, totally porous and 2.6μm, core-shell particles) was studied in the presence of considerable or minimal extra-column effects, while the detector contribution to band broadening was minimized by employing a small size UV-detector cell (6- or 90nL). A micro-LC instrument having small system volume (<1μL) provided extra-column band variance of only 0.01-0.02μL(2). The three columns generated about 8500 theoretical plates for solutes with retention factor, k>1-3 (depending on the column), in acetonitrile/water mobile phase (65/35=vol/vol) at 0.05mL/min, with the instrument specified above. The column efficiency was lower by up to 30% than that observed with a 2.1mm I.D. commercial column. The small-size columns also provided 8000-8500 theoretical plates for well retained solutes with a commercial ultrahigh-pressure liquid chromatography (UHPLC) instrument when extra-column contributions were minimized. While a significant extra-column effect was observed for early eluting solutes (k<2-4, depending on column) with methanol/water (20/80=vol/vol) as weak-wash solvent, the use of methanol/water=50/50 as wash solvent affected the column efficiency for most analytes. The results suggest that the band compression effect by the weak-wash solvent associated with partial-loop injection may provide a practical means to reducing the extra-column effect for small-size columns, while the use of an instrument with minimum extra-column effect is highly desirable.