A set of new mixed-mode ion-exchange stationary phases is presented. The backbone of organic selectors is formed by a linear hydrocarbon chain, which is divided into two parts of various lengths by a heteroatom (oxygen or nitrogen). In all studied cases, there is a sulfonic acid moiety as the terminal group. Therefore, selectors bearing oxygen gave rise to strong cation ion-exchange stationary phases, while selectors with an embedded nitrogen atom (inducing a weak anion exchange capacity) were used to create zwitterion ion-exchange stationary phases. The new mixed-mode stationary phases were chromatographically evaluated in high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) using isocratic elution conditions to disclose their chromatographic potential. In HPLC mode, aqueous-rich reversed phase chromatography, acetonitrile-rich hydrophilic interaction liquid chromatography and methanolic ion-exchange chromatography mobile phases were employed. In these chromatographic modes, retention factors and selectivity values for a test set of basic and zwitterionic analytes were determined. The results were compared and principal component analysis for each chromatographic mode was performed. For all chromatographic modes, the component 1 in the principal component analysis reflected the elution order. The application of different mobile phases on a particular column resulted not only in variation in retention, but also in modified selectivity, and different elution order of the analytes. The orthogonality of the elution order depending on the employed mobile phase conditions was especially reflected for structurally closely related analytes, such as melatonin and N-acetyl-serotonin, tryptamine and serotonin or noradrenalin and octopamine. However, ion-exchange interactions remain the main driving force for retention. From all investigated stationary phases, the SCX 2 (C5-linker and C4-spacer) seems to be the best choice for the separation of basic analytes using different mobile phase conditions.
- MeSH
- Acetonitriles chemistry MeSH
- Anions chemistry MeSH
- Biogenic Amines isolation & purification MeSH
- Chromatography methods MeSH
- Chemistry, Pharmaceutical methods MeSH
- Hydrophobic and Hydrophilic Interactions MeSH
- Ion Exchange MeSH
- Cations chemistry MeSH
- Pharmaceutical Preparations chemistry isolation & purification MeSH
- Methanol chemistry MeSH
- Water chemistry MeSH
- Publication type
- Journal Article MeSH
Glycoproteomics is a challenging branch of proteomics because of the micro- and macro-heterogeneity of protein glycosylation. Hydrophilic interaction liquid chromatography (HILIC) is an advantageous alternative to reversed-phase chromatography for intact glycopeptide separation prior to their identification by mass spectrometry. Nowadays, several HILIC columns differing in used chemistries are commercially available. However, there is a lack of comparative studies assessing their performance, and thus providing guidance for the selection of an adequate stationary phase for different glycoproteomics applications. Here, we compare three HILIC columns recently developed by Advanced Chromatography Technologies (ACE)- with unfunctionalized (HILIC-A), polyhydroxy functionalized (HILIC-N), and aminopropyl functionalized (HILIC-B) silica- with a C18 reversed-phase column in the separation of human immunoglobulin G glycopeptides. HILIC-A and HILIC-B exhibit mixed-mode separation combining hydrophilic and ion-exchange interactions for analyte retention. Expectably, reversed-phase mode successfully separated clusters of immunoglobulin G1 and immunoglobulin G2 glycopeptides, which differ in amino acid sequence, but was not able to adequately separate different glycoforms of the same peptide. All ACE HILIC columns showed higher separation power for different glycoforms, and we show that each column separates a different group of glycopeptides more effectively than the others. Moreover, HILIC-A and HILIC-N columns separated the isobaric A2G1F1 glycopeptides of immunoglobulin G, and thus showed the potential for the elucidation of the structure of isomeric glycoforms. Furthermore, the possible retention mechanism for the HILIC columns is discussed on the basis of the determined chromatographic parameters.
- MeSH
- Chromatography, Ion Exchange methods MeSH
- Chromatography, Reverse-Phase methods MeSH
- Glycopeptides isolation & purification MeSH
- Hydrophobic and Hydrophilic Interactions MeSH
- Immunoglobulin G isolation & purification MeSH
- Isomerism MeSH
- Humans MeSH
- Proteomics MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Comparative Study 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.
In this work we utilized basic and acidic analytes to investigate the ionic interaction participation in retention behavior of selected reversed-phase and polar columns. The test analytes included nitrate, benzenesulfonate and trimethylphenylammonium ions. The fully aqueous mobile phase comprising 10 mM dichloroacetic acid buffered with ammonia solution to desirable pH was used for retention experiments. Developed method was utilized to study the ionic interactions of stationary phases in pH range between 2.5 and 9.0. We demonstrate that selected sorbents used for reversed-phase and hydrophilic interaction chromatography separations exhibit cation- or anion-exchange interactions. We compare the results to novel Atlantis PREMIER BEH C18 AX mixed-mode column that combines reversed-phase and anion-exchange interaction modes. We evaluated the relative retention strength of selected columns for anionic and cationic analytes.
The selectivity for 15 biogenic amines and amino acids shown by three capillary cation-exchange columns, IonPac CS19, CS12A and CS17 (250 × 0.4 mm ID, all from Thermo Fisher Scientific), exhibiting medium, medium low and ultra-low hydrophobicity, and either carboxylic or mixed carboxylic/phosphonic acid functional groups, was investigated. A mixed mode retention mechanism was revealed with ion-exchange, hydrophobic and hydrogen bonding interactions contributing to retention of polar organic molecules on these phases. The relative impact of these interactions was evaluated via the effect of concentration and pH of the eluent (methanesulfonic acid) on the retention of fifteen structurally similar biogenic amines and amino acids. Strong hydrogen bonding interactions were observed between the solute amino acid carboxylic groups and cation-exchange groups from the ion-exchangers. This is the first time retention data correlated with logP data has revealed clustering of the solutes in two groups, according to the presence or absence of a carboxylic acid functional group. In addition, stronger retention behaviour was found for the IonPac CS12A cation-exchanger, containing both carboxylic and phosphonic functional groups. Further assessment of the orthogonality plots of retention factors for the three stationary phases revealed that the columns exhibited different complimentary selectivity that can be utilised to achieve specific separations.
In this work, we have investigated the predictive properties of mixed-mode retention model and oligomeric mixed-mode model, taking into account the contribution of monomeric units to the retention, in hydrophilic interaction liquid chromatography. The gradient retention times of native maltooligosaccharides and their fluorescent derivatives were predicted in the oligomeric series with number of monomeric glucose units in the range from two to seven. The maltooligosaccharides were separated on a packed column with carbamoyl-bonded silica stationary phase and 15 gradient profiles with different initial and final mobile phase composition were used with the gradient times 5; 7.5 and 10min. The predicted gradient retention times were compared for calculations based on isocratic retention data and gradient retention data, which provided better accuracy of the results. By comparing two different mobile phase additives, the more accurate retention times were predicted in mobile phases containing ammonium acetate. The acidic derivatives, prepared by reaction of an oligosaccharide with 2-aminobenzoic acid or 8-aminonaphthalene-1,3,6-trisulfonic acid, provided more accurate predictions of the retention data in comparison to native oligosaccharides or their neutral derivatives. The oligomeric mixed-mode model allowed prediction of gradient retention times using only one gradient profile, which significantly speeded-up the method development.
In this work, we have investigated retention of maltooligosaccharides and their fluorescent derivatives in hydrophilic interaction liquid chromatography using four different stationary phases. The non-derivatized maltooligosaccharides (maltose to maltoheptaose) and their derivatives with 2-aminobenzoic acid, 2-aminobenzamide, 2-aminopyridine and 8-aminonaphthalene-1,3,6-trisulfonic acid were analyzed on silica gel, aminopropyl silica, amide (carbamoyl-bonded silica) and ZIC-HILIC zwitterionic sulfobetain bonded phase. The partitioning of the analytes between the bulk mobile phase and adsorbed water-rich layer, polar and ionic interactions of analytes with stationary phase have been evaluated and compared. The effects of the mobile phase additives (0.1% (v/v) of acetic acid and ammonium acetate in concentration range 5-30 mmol L(-1)) on retention were described. The suitability of different models for prediction of retention was tested including linear solvent strength model, quadratic model, mixed-mode model, and empirical Neue-Kuss model. The mixed-mode model was extended to the parameter describing the contribution of monomeric glucose unit to the retention of non-derivatized and derivatized maltooligosaccharides, which was used for evaluation of contribution of both, oligosaccharide backbone and end-group to retention.
- MeSH
- 1-Naphthylamine chemistry MeSH
- Adsorption MeSH
- Aminopyridines chemistry MeSH
- Models, Chemical * MeSH
- Chemistry Techniques, Analytical * MeSH
- Chromatography, Liquid * MeSH
- Hydrophobic and Hydrophilic Interactions MeSH
- Oligosaccharides chemistry isolation & purification MeSH
- ortho-Aminobenzoates chemistry MeSH
- Silicon Dioxide chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The chromatographic behaviour of eleven synthetic cathinones and four phenylethylamines under supercritical/subcritical fluid conditions was investigated. Four stationary phases with sub-2μm particles (Waters Acquity UPC(2) BEH silica, BEH 2-ethylpyridine, CSH Fluoro-Phenyl, and HSS C18SB) were evaluated in terms of isomer resolution, chromatographic peak shape, and analysis time. Methanol, water, formic acid, ammonium hydroxide, ammonium acetate, and ammonium formate were mixed with carbon dioxide to test their influence on analyte retention and peak shapes. Methanol and ammonium cations were essential for successful separations. Efficient separations of four isomeric pairs (R>1), and most of the remaining analytes, were achieved in less than 3.3min on BEH and Fluoro-Phenyl columns with gradient of methanolic ammonium hydroxide in CO2. Drugs were detected by positive electrospray ionization-triple quadrupole mass spectrometry in selected reaction monitoring mode. Added detection specificity and faster separation of isomers on the BEH column using a steep gradient and high flow rate reduced analysis time of the mixture of 15 drugs to 1.6min.
Seven solid phase sorbent materials with reversed-phase, mixed-mode interactions (ion-exchange and reversed-phase), and molecularly imprinted polymers (MIP), namely Oasis HLB, Oasis MAX, Oasis MCX, Bond Elute Plexa, Bond Elute Plexa PAX, Bond Elute Plexa PCX, and SupelMIP sorbents, were investigated. The present study was focused on the retention and elution of pharmaceutically active substances based on several analyte-sorbent interaction properties. Basic drugs, such as β-blockers (i.e., atenolol, pindolol, acebutolol, metoprolol, labetalol, and propranolol) were selected as the model compounds for this study. These compounds are frequently encountered in anti-doping tests. The extraction efficiencies of the individual sorbents were compared based on the recovery of known amounts of the targeted analytes in a metered elution volume (500 μL) in three separate elution fractions. The elution efficiency of the total amount of the target analytes on various sorbents was not appreciably influenced by the volume of eluent required for complete elution. Based on the small matrix effects and clear baseline, SupelMIP was the most suitable sorbent for urine analysis. The relative analyte recoveries of the SPE-HPLC procedure proved satisfactory for the range from 94% to 105%, with an RSD ranging from 2% to 4%. The regression equations for all of the targeted compounds exhibited excellent linearity (r(2) > 0.9991) over the range of 10 to 1000 ng mL(-1). The limits of detection and quantification for the selected β-blocker compounds in urine were in the ranges of 0.6 to 2.0 ng mL(-1) and 2.0 to 6.7 ng mL(-1), respectively.
- MeSH
- Adsorption MeSH
- Adrenergic beta-Antagonists isolation & purification urine MeSH
- Solid Phase Extraction instrumentation methods MeSH
- Humans MeSH
- Molecular Imprinting MeSH
- Polymers chemical synthesis chemistry MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Evaluation Study MeSH
- Research Support, Non-U.S. Gov't MeSH
... Impression -- The Maxillary Impression -- Disinfection ol Impressions -- I ’arae I illicit I Procedures -- Mixing ... ... Procedures for Debanding 441 -- Clinical Procedures for Debonding 441 -- Post-Debonding Evaluation 443 -- Retention ... ... Calculus Removal 615 -- Manual Subgingival Scaling Steps 616 -- Ultrasonic and Sonic Scaling 621 -- Mode ... ... 712 -- Efficacy 71 3 -- Reversible Side Effects of Bleaching 716 -- Irreversible Tooth Damage 716 -- Modes ...
11th ed. xxiv, 1147 s. : il. ; 28 cm
- MeSH
- Clinical Medicine MeSH
- Oral Hygiene MeSH
- Dental Hygienists MeSH
- Dental Prophylaxis MeSH
- Publication type
- Monograph MeSH
- Handbook MeSH
- Outline MeSH
- Conspectus
- Stomatologie
- NML Fields
- zubní lékařství
- NML Publication type
- učebnice vysokých škol
