BACKGROUND: Analyte annotation confidence in untargeted liquid chromatography mass-spectrometry (LC-MS) based chemical analysis can be enhanced by leveraging retention time information. For this, the chromatographic characteristics of the analytical system used should be well characterized. In this study, we measured 604 diverse chemical standards to characterize a dual LC setup consisting of pentabromobenzyl (PBr) and type-C silica hydride (SiH) columns operating in reversed-phase (RP) and aqueous normal-phase (ANP) mode, respectively. RESULTS: ANP and RP separations individually retained 40 % and 64 % of standards in cLogP range from -6.60 to 8.67 and -3.34 to 12.95, respectively. Using both columns, the coverage increased to 79 % of standards with cLogP range from -6.60 to 12.95 (median cLogP = 1.63). Retention selectivity follows the number of basic nitrogen atoms in the molecule on SiH column and polarity (cLogP) on PBr column. Column repeatability and reproducibility were tested in triplicate using a chemically diverse subset of 108 standards. Repeatability of retention times, peak widths and peak areas was 0.3 %, 14 %, 4 % for SiH column and 0.2 %, 12 %, 4 % for PBr column. Similarly, reproducibility was 15 %, 34 %, 30 % for SiH column and 9 %, 18 % and 34 % for PBr column. Predictive RT models were developed based on experimental RT data, achieving R2 values of 0.92 and 0.96, with mean absolute errors of 0.29 min and 0.27 min for SiH and PBr columns, respectively. SIGNIFICANCE: As proof of concept, 129 metabolites were annotated in pooled human serum and plasma by matching standard or predicted RT on one or both columns. The RT models and MS2 spectra of standards are openly available, facilitating uptake of this well-characterized chromatographic system to increase confidence in analyte annotation.

• Klíčová slova
• Aqueous normal-phase, Chemicals, Exposome, Metabolomics, Non-targeted, Retention time prediction,
• MeSH
• chromatografie kapalinová MeSH
• hmotnostní spektrometrie * MeSH
• knihovny malých molekul * MeSH
• lidé MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• knihovny malých molekul * MeSH

The Black Sea is a permanently anoxic, marine basin serving as model system for the deposition of organic-rich sediments in a highly stratified ocean. In such systems, archaeal lipids are widely used as paleoceanographic and biogeochemical proxies; however, the diverse planktonic and benthic sources as well as their potentially distinct diagenetic fate may complicate their application. To track the flux of archaeal lipids and to constrain their sources and turnover, we quantitatively examined the distributions and stable carbon isotopic compositions (δ13 C) of intact polar lipids (IPLs) and core lipids (CLs) from the upper oxic water column into the underlying sediments, reaching deposits from the last glacial. The distribution of IPLs responded more sensitively to the geochemical zonation than the CLs, with the latter being governed by the deposition from the chemocline. The isotopic composition of archaeal lipids indicates CLs and IPLs in the deep anoxic water column have negligible influence on the sedimentary pool. Archaeol substitutes tetraether lipids as the most abundant IPL in the deep anoxic water column and the lacustrine methanic zone. Its elevated IPL/CL ratios and negative δ13 C values indicate active methane metabolism. Sedimentary CL- and IPL-crenarchaeol were exclusively derived from the water column, as indicated by non-variable δ13 C values that are identical to those in the chemocline and by the low BIT (branched isoprenoid tetraether index). By contrast, in situ production accounts on average for 22% of the sedimentary IPL-GDGT-0 (glycerol dibiphytanyl glycerol tetraether) based on isotopic mass balance using the fermentation product lactate as an endmember for the dissolved substrate pool. Despite the structural similarity, glycosidic crenarchaeol appears to be more recalcitrant in comparison to its non-cycloalkylated counterpart GDGT-0, as indicated by its consistently higher IPL/CL ratio in sediments. The higher TEX86 , CCaT, and GDGT-2/-3 values in glacial sediments could plausibly result from selective turnover of archaeal lipids and/or an archaeal ecology shift during the transition from the glacial lacustrine to the Holocene marine setting. Our in-depth molecular-isotopic examination of archaeal core and intact polar lipids provided new constraints on the sources and fate of archaeal lipids and their applicability in paleoceanographic and biogeochemical studies.

• Klíčová slova
• archaea, core lipids, intact polar lipids, lipid sources, lipid turnover, lipidomics, stable carbon isotope,
• MeSH
• Archaea * chemie   MeSH
• geologické sedimenty chemie   MeSH
• glycerol MeSH
• glycerylethery * MeSH
• lipidy chemie   MeSH
• mořská voda chemie   MeSH
• voda * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Černé moře MeSH
• Názvy látek
• crenarchaeol MeSH Prohlížeč
• glycerol MeSH
• glycerylethery * MeSH
• lipidy MeSH
• voda * MeSH

Derivatized cyclofructans have been recently introduced as a new class of chiral selectors with great application potential. In this study, a R-naphthylethyl-functionalized cyclofructan 6 based chiral stationary phase (RN CF6 CSP) was used for separation of substituted binaphthyl catalysts in the normal phase HPLC mode. Dominant interaction types that play a role in the separation mechanism were revealed by a linear free energy relationship (LFER) method. In order to evaluate the contribution of the substituent on the cyclofructan structure to retention, the R-naphthylethyl-functionalized β-cyclodextrin (RN CD) CSP was chosen for comparison. Retention factors of 46 widely different solutes, with known solvation parameters, were determined on each of the columns under the same mobile phase compositions used for the enantiomeric separations. The LFER results showed that hydrogen bond acidity and polarity/polarizibility have the greatest impact on retention and enantioresolution on the RN CF6 CSP. The equal influence of the naphthylethyl substituent on the both CSPs was also confirmed while the effects of the basic cyclofructan versus cyclodextrin structures were different. The addition of trifluoroacetic acid to the hexane/propane-2-ol mobile phase was negligible on the RN CF6 CSP for the majority of atropoisomers except for one with ionizable functional groups. The RN CF6 column was shown to be more suitable for enantioseparation of the binaphthyl catalysts than the RN CD column. Higher retention offered by the latter CSP had no positive effect on the enantioresolution.

• MeSH
• beta-cyklodextriny chemie   MeSH
• chemické modely MeSH
• chromatografie kapalinová metody   MeSH
• fruktany chemie   MeSH
• naftaleny chemie   MeSH
• regresní analýza MeSH
• stereoizomerie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• beta-cyklodextriny MeSH
• cyclofructan 6 MeSH Prohlížeč
• fruktany MeSH
• naftaleny MeSH

In this work, two mixed-mode columns from a different manufacturers and one marketed as a reversed-phase column were characterized and compared in the terms of their interaction abilities, retentivity, peak symmetry, and applicability for peptide separation. All the tested columns contain octadecyl ligand and positively charged modifier, i.e. pyridyl group for the reversed-phase column XSelect CSH C18, quaternary alkylamine for mixed-mode column Atlantis PREMIER BEH C18 AX, and permanently charged moiety (details not available from the manufacturer) for mixed-mode column Luna Omega PS C18. For detailed characterization and comparison of their interaction potential, several approaches were used. First, a simple Walters test was performed to estimate hydrophobic and silanophilic interactions of the tested columns. The highest values of both parameters were observed for column Atlantis PREMIER BEH C18 AX. To investigate the effect of pH and buffer concentration on retention, mobile phases composed of acetonitrile and buffer (ammonium formate, pH 3.0; ammonium acetate pH 4.7 and pH 6.9) in various concentrations (5mM; 10mM; 15mM and 20mM) were used. The analysis of permanently charged compounds was used to describe the electrostatic interaction abilities of the stationary phases. The most significant contribution of electrostatic interactions to the retention was observed for Atlantis PREMIER BEH C18 AX column in the mobile phase with buffer of pH 3.0. A set of ten dipeptides, three pentapeptides and one octapeptide was used to investigate the effects of pH and buffer concentration on retention and peak symmetry. Each of the tested columns provides the optimal peak shape under different buffer pH and concentration. The gradient separation of the 14 tested peptides was used to verify the application potential of the tested columns for peptide separation. The best separation was achieved within 4 minutes on column Atlantis PREMIER BEH C18 AX.

• Klíčová slova
• Mixed-mode chromatography, Mixed-mode columns, Peptide separation, RP/anion-exchange mechanism, Reversed-phase column,
• MeSH
• chromatografie s reverzní fází přístrojové vybavení   MeSH
• hydrofobní a hydrofilní interakce MeSH
• koncentrace vodíkových iontů MeSH
• peptidy izolace a purifikace   MeSH
• pufry MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• peptidy MeSH
• pufry MeSH

This study introduces a silica-based monolith in a capillary format (0.1 mm × 100 mm) as a support for immobilization of liposomes and its characterization in immobilized liposome chromatography. Silica-based monolithic capillary columns prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea were modified by (3-aminopropyl)trimethoxysilane, whereby amino groups were introduced to the monolithic surface. These groups undergo reaction with glutaraldehyde to form an iminoaldehyde, allowing covalent binding of pre-formed liposomes containing primary amino groups. Two types of phospholipid vesicles were used for column modification; these were 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphatidyl choline with and without 1,2-diacyl-sn-glycero-3-phospho-L-serine. The prepared columns were evaluated under isocratic separation conditions employing 20mM phosphate buffer at pH 7.4 as a mobile phase and a set of unrelated drugs as model analytes. The liposome layer on the synthesized columns significantly changed the column selectivity compared to the aminopropylsilylated monolithic stationary phase. Monolithic columns modified by liposomes were stable under the separation conditions, which proved the applicability of the suggested preparation procedure for the synthesis of capillary columns dedicated to study analyte-liposome interactions. The column efficiency originating from the silica monolith was preserved and reached, e.g., more than 120,000 theoretical plates/m for caffeine as a solute.

• Klíčová slova
• Analyte–membrane interaction, Capillary liquid chromatography, Drugs, Immobilized liposome chromatography, Monolithic silica column,
• MeSH
• chromatografie kapalinová přístrojové vybavení   metody   MeSH
• léčivé přípravky chemie   izolace a purifikace   MeSH
• liposomy chemie   MeSH
• oxid křemičitý chemie   MeSH
• sloučeniny síry chemie   izolace a purifikace   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• léčivé přípravky MeSH
• liposomy MeSH
• oxid křemičitý MeSH
• sloučeniny síry MeSH

In the scope of the present review, the current status of high-performance liquid chromatography/ultra-high performance liquid chromatography and supercritical fluid chromatography is briefly provided. These techniques and their retention mechanisms are compared. Various alternative approaches utilized for the determination and description of the retention processes in these two systems are mapped. Two frequently used concepts, linear-free energy relationships, and hydrophobic subtraction models, used for the characterization of the retention interactions, are discussed. Principles and selected applications of the both methods are also covered. Then the models applied for the prediction of retention behavior of solutes on stationary phases are outlined. The procedures utilized for the sorbent/column classification are also covered. Simple chromatographic tests frequently used for the basic characterization and mutual comparison of stationary phases are summarized and briefly commented on. The importance of a statistical evaluation of complex retention data obtained from the chromatographic measurements is outlined. Finally, computer simulations aiming at the facilitation of the quest to optimize separation conditions for a given mixture of analytes are touched upon.

• Klíčová slova
• Characterization, Retention mechanisms, Retention models, Stationary phases,
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

HEMA, the copolymer of 2-hydroxyethyl methacrylate and ethylene dimethacrylate, has proven to be a suitable stationary phase for the size-exclusion chromatographic (SEC) characterization of humic substances in a wide pH range. The SEC measurements were performed typically with alkaline borate-based mobile phase: 0.025 mol/l Na2B4O7, 0.025 mol/l NaCl, 0.001 mol/l Na4P2O7, pH 9.1. After calibrating with globular protein standards, apparent molecular weights of typical peat- and coal-derived humic acids were estimated. The average molecular weights determined with the aid of the HEMA column were quite comparable with the values obtained previously by the method of low-pressure gel-permeation chromatography on the Sephadex column.

• MeSH
• časové faktory MeSH
• gelová chromatografie metody   MeSH
• huminové látky analýza   MeSH
• kalibrace MeSH
• koncentrace vodíkových iontů MeSH
• methakryláty chemie   MeSH
• molekulová hmotnost MeSH
• osmolární koncentrace MeSH
• půda analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• huminové látky MeSH
• hydroxyethyl methacrylate MeSH Prohlížeč
• methakryláty MeSH
• půda MeSH

Separation systems with a zirconia-based polystyrene HPLC column were characterized by different approaches, which allowed the recognition of interactions participating in the separation environments. Zirconia-based HPLC columns as an alternative to silica-based ones offer unique interaction mechanism based on Lewis acid-base theory. Besides hydrophobic interactions with the modified surface of the zirconia carrier it includes ion-exchange and ligand-exchange interactions that are helpful in the separation of many bioactive compounds. Three distinct approaches were applied for description of the complex separation mechanism. General chromatographic tests by Walters, Engelhardt and Galushko were applied to evaluate the fundamental properties of the systems - hydrophobicity and polarity. The complex model of linear free energy relationship described the interactions from the qualitative and quantitative points of view more in detail. Application of a set of basic compounds revealed the contribution of ion-exchange interactions participating in the separation systems.

• Publikační typ
• časopisecké články MeSH

Selectivity of phase system is of primary concern when designing a 2-D separation, as it affects the 2-D system orthogonality and consequently the peak capacity controlling the number of peaks that can be separated in the available 2-D retention space limited by the time of analysis. Possibilities for characterization of LC phase system selectivity with respect to different polar and nonpolar structural units are compared, with special attention to multidimensional samples with various types of repeat groups, such as homopolymers, (co)polymers, fatty acid esters with various acyl lengths and number and position of double bonds, etc. Possibilities of the 2-D LC separations of these and other sample types, including pharmaceuticals, natural phenolic compounds, biopolymers, etc., using various combinations of separation modes are reviewed. Rules for design of comprehensive 2-D LC x LC systems are discussed, with respect to mobile phase compatibility in the two systems and modulation techniques suppressing band broadening connected with the sample fraction transfer from the first to the second dimension. Pitfalls connected with online connection of normal-phase and RP LC systems and their possible practical solutions are addressed and illustrated by practical examples.

• MeSH
• časové faktory MeSH
• chromatografie kapalinová přístrojové vybavení   metody   MeSH
• design vybavení MeSH
• estery chemie   MeSH
• mastné kyseliny chemie   MeSH
• membrány umělé * MeSH
• polymery chemie   MeSH
• povrchové vlastnosti MeSH
• senzitivita a specificita MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• estery MeSH
• mastné kyseliny MeSH
• membrány umělé * MeSH
• polymery MeSH

Laccase-producing fungus (MY3) was successfully isolated from soil samples collected from Mansoura Governorate, Egypt. This fungal isolate has shown a high laccase production level over other isolated fungi. The identity of this isolate was determined by the molecular technique 18SrRNA as Curvularia lunata MY3. The enzyme purification was performed using ammonium sulfate precipitation followed by Sephacryl S-200 and DEAE-Sepharose column chromatography. The denatured enzyme using SDS-PAGE had a molar mass of 65 kDa. The purified laccase had an optimum temperature at 40 °C for enzyme activity with 57.3 kJ/mol activation energy for 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) oxidation. The enzyme had an optimum pH of 5.0, and it has shown a high stability at the acidic range (4.5 to 5.5). Mn2+ and Mg2+ ions enhanced the enzyme activity, while most of the enzyme activity was inhibited by Hg2+. Some compounds such as 2-mercaptoethanol, L-cysteine, and sodium azide at a concentration of 10 mmol/L had shown a high suppression effect on the enzyme activity. The enzyme strongly oxidized ABTS and syringaldazine and moderately oxidized DMP and guaiacol. The antimicrobial activity of the purified enzyme towards three pathogenic strains (Escherichia coli ATCC-25922, Staphylococcus aureus NRRLB-767, and Candida albicans ATCC-10231) was evaluated for the potential use as an antimicrobial therapeutic enzyme.

• Klíčová slova
• Characterization, Curvularia lunata, Laccase, Purification,
• MeSH
• antiinfekční látky * MeSH
• azosloučeniny * MeSH
• benzothiazoly * MeSH
• Curvularia * MeSH
• koncentrace vodíkových iontů MeSH
• kyseliny sulfonové * MeSH
• lakasa * metabolismus   MeSH
• stabilita enzymů MeSH
• substrátová specifita MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid MeSH Prohlížeč
• antiinfekční látky * MeSH
• azosloučeniny * MeSH
• benzothiazoly * MeSH
• kyseliny sulfonové * MeSH
• lakasa * MeSH
• mordant yellow 3 MeSH Prohlížeč