The retention behavior of several series of free α- and ω-amino acids and positional isomers of amino pentanoic acid in the hydrophilic interaction chromatography mode (HILIC) was studied. The study was carried out on three stationary phases followed by post-column derivatization with fluorescence detection in order to describe the retention mechanism of the tested amino acids. The effect of chromatographic conditions including acetonitrile content in the mobile phase, mobile phase pH (ranging from 3.5 to 6.5) and concentration of buffer in the mobile phase was investigated. The effect of the number of carbon atoms (nC) in aliphatic chains of the individual homologue of α- and ω-amino acids and the logarithm of the partition coefficient (logD) on retention was also a part of the presented study. A good correlation (r > 0.98) between the logk and logD values of amino acids or nC, respectively, was observed. The described linear relationships were subsequently applied to predict the retention behavior of individual members of the homologous series of amino acids and to optimize the mobile phase composition in HILIC. The obtained results confirmed that the retention mechanism of α-amino acids, ω-amino acids and positional isomers of amino acids was based on the logD values and the number of carbon atoms in the aliphatic chains of amino acids. The elution order of ω-amino acids and positional isomers of amino pentanoic acid was strongly dependent on the mobile phase pH in the investigated range whereas the retention factors of all α-amino acids remained essentially unchanged on all tested stationary phases.

• Klíčová slova
• Amino acids, HILIC, Homologous series, Retention behavior,
• MeSH
• aminokyseliny chemie   izolace a purifikace   MeSH
• hydrofobní a hydrofilní interakce MeSH
• koncentrace vodíkových iontů MeSH
• stereoizomerie MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• aminokyseliny MeSH

Reversed-phase ultrahigh-performance liquid chromatography (RP-UHPLC) method using two 15cm sub-2μm particles octadecylsilica gel columns is developed with the goal to separate and unambiguously identify a large number of lipid species in biological samples. The identification is performed by the coupling with high-resolution tandem mass spectrometry (MS/MS) using quadrupole - time-of-flight (QTOF) instrument. Electrospray ionization (ESI) full scan and tandem mass spectra are measured in both polarity modes with the mass accuracy better than 5ppm, which provides a high confidence of lipid identification. Over 400 lipid species covering 14 polar and nonpolar lipid classes from 5 lipid categories are identified in total lipid extracts of human plasma, human urine and porcine brain. The general dependences of relative retention times on relative carbon number or relative double bond number are constructed and fit with the second degree polynomial regression. The regular retention patterns in homologous lipid series provide additional identification point for UHPLC/MS lipidomic analysis, which increases the confidence of lipid identification. The reprocessing of previously published data by our and other groups measured in the RP mode and ultrahigh-performance supercritical fluid chromatography on the silica column shows more generic applicability of the polynomial regression for the description of retention behavior and the prediction of retention times. The novelty of this work is the characterization of general trends in the retention behavior of lipids within logical series with constant fatty acyl length or double bond number, which may be used as an additional criterion to increase the confidence of lipid identification.

• Klíčová slova
• Human plasma, Lipidomics, Lipids, Mass spectrometry, Retention behavior, Ultrahigh-performance liquid chromatography,
• MeSH
• časové faktory MeSH
• chromatografie s reverzní fází metody   MeSH
• erytrocyty chemie   MeSH
• hmotnostní spektrometrie s elektrosprejovou ionizací metody   MeSH
• lidé MeSH
• lipidy analýza   krev   chemie   moč   MeSH
• mozek - chemie MeSH
• prasata MeSH
• superkritická fluidní chromatografie MeSH
• tandemová hmotnostní spektrometrie metody   MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• lipidy MeSH

The retention behavior of a large group of analytes (35) with varied properties (pKa and logP) was studied on eight hydrophilic interaction LC columns with different surfaces, stationary phase chemistries, and types of particles. The acetonitrile content (5-95%), buffer concentration (0.5-200 mM), and pH of the mobile phase (3.8 and 6.8) were evaluated for their effects on the retention behavior. The type of stationary phase had a significant impact on the selectivity and retention time of the tested analytes. Completely different selectivity was observed on the aminopropyl stationary phase. In this study, the influence of the buffer concentration was similar for all tested columns, except for the aminopropyl stationary phase. Increasing the buffer concentration led to decreased retention times for the basic compounds and increased retention times for the acidic compounds, while the inverse behavior was observed on the aminopropyl stationary phase. The selectivity of the individual stationary phases was evaluated at pH 3.8 and 6.8. Much lower selectivity differences between the stationary phases were observed at pH 6.8 than pH 3.8. Bare silica stationary phases were used in the comparison of the particles (fused-core and fully porous particles of 3 and 1.7 μm) and the columns provided by different manufacturers.

• Klíčová slova
• Buffer concentration effects, Hydrophilic interaction liquid chromatography, Retention mechanisms, Stationary phases, pH effects,
• MeSH
• chromatografie kapalinová přístrojové vybavení   MeSH
• hydrofobní a hydrofilní interakce MeSH
• koncentrace vodíkových iontů MeSH
• organické látky chemie   MeSH
• oxid křemičitý chemie   MeSH
• poréznost MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• organické látky MeSH
• oxid křemičitý MeSH

OBJECTIVE: The present study aims to examine whether declarative memory dysfunction relates to impaired core memory mechanisms or attentional and executive dysfunction in idiopathic REM Sleep Behavior Disorder (iRBD). METHOD: In this observational, cross-sectional study, were enrolled 82 individuals with the diagnosis of iRBD according to the International Classification of Sleep Disorders and 49-matched healthy controls fulfilling inclusion criteria. All participants underwent two memory tasks, namely the Rey Auditory Verbal Learning Test (RAVLT) and Memory Binding Test (MBT), which include conditions of varying degrees of dependence on executive functioning, as well as different indicators of core memory processes (e.g., learning, retention, relational binding). RESULTS: We used Bayesian multivariate generalized linear model analysis to evaluate the effect of iRBD on memory performance controlled for effects of age and sex. Individuals with iRBD displayed worse memory performance in the delayed free recall task (b = -0.37, 95% PPI [-0.69, -0.05]), but not on delayed recognition of the same material. Their performance in cued recall tasks both in immediate and delayed conditions was in comparison to controls relatively spared. Moreover, the deficit in delayed free recall was mediated by attention/processing speed. CONCLUSIONS: In iRBD, we replicated findings of reduced free recall based on inefficient retrieval (retrieval deficit), which was small in terms of effect size. Importantly, the memory profile across measures does not support the presence of core memory dysfunction, such as poor learning, retention or associative binding.

• Klíčová slova
• RBD (rapid eye movement (REM) sleep behavior disorder), cued recall, free recall, iRBD (idiopathic rapid eye movement (REM) sleep behavior disorder), memory binding, memory impairment,
• MeSH
• Bayesova věta MeSH
• kognitivní dysfunkce * diagnóza   MeSH
• lidé MeSH
• neuropsychologické testy MeSH
• porucha chování v REM spánku * komplikace   MeSH
• poruchy paměti diagnóza   MeSH
• průřezové studie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• pozorovací studie MeSH

The chromatographic behavior was studied of a series of potential acetylcholinesterase reactivators, pyridinium oximes, bearing linear aliphatic chains of the length of the aliphatic bridge from 1 to 12 carbon atoms, on a pentafluorophenyl-modified stationary phase. The retention mechanisms and the dependence of the capacity factor on mobile phase composition, aliphatic chain bridge length and calculated log P were evaluated and discussed in detail. The separation of the studied oximes was found to be driven by hydrophobic interactions when a lower content of organic modifier was used in mobile phase; however, the ion-exchange mechanism was the leading one when a large portion of organic modifier was used. In addition, the lipophilicity was found to be a driving mechanism of the separation of oximes bearing a connecting chain of the length of 6-12 carbon atoms, whereas the retention of oximes with shorter connecting chains was significantly influenced by other separation mechanisms such as aromatic or π-π interaction. These results can be useful for the development of new, efficient acetylcholinesterase reactivators.

• MeSH
• fenoly chemie   MeSH
• fluorbenzeny chemie   MeSH
• oximy chemie   MeSH
• pyridinové sloučeniny chemie   MeSH
• regresní analýza MeSH
• vysokoúčinná kapalinová chromatografie přístrojové vybavení   metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2,3,4,5,6-pentafluorophenol MeSH Prohlížeč
• fenoly MeSH
• fluorbenzeny MeSH
• oximy MeSH
• pyridinové sloučeniny MeSH

A fundamental problem associated with the vertical transport of engineered nanomaterials (ENMs) in saturated porous media is the occurrence of nonexponential, for example, nonmonotonic or linearly increasing, retention profiles. To investigate this problem, we compiled an extensive database of ENMs transport experiments in saturated porous media. Using this database we trained a decision tree that shows the order of importance, and range of influence, of the physicochemical factors that control the retention profile shape. Our results help identify domains where current particle-transport models can be used, but also highlight, for the first time, large domains where nonexponential retention profiles dominate and new approaches are needed to understand ENM transport. Importantly, highly advective flow and high ENM influent mass can mask the influence of other physicochemical factors on the retention profile shape; notably, this occurs in 50% of the experiments investigated. Where the relationship between physicochemical factors and retention profile shape can be investigated in detail, our results agree with, and provide validation for, the current understanding of how these factors influence ENM transport.

• MeSH
• nanostruktury chemie   MeSH
• poréznost MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

A systematic study of the retention behavior of isomeric triacylglycerols (TGs) in silver-ion HPLC on a ChromSpher Lipids column has been performed between 10 to 40°C using the most widespread hexane- and dichloromethane-based mobile phases. The randomization of mono-acyl TG standards and the random esterification of glycerol with fatty acids are employed to produce mixtures of TG isomers. The mobile phase composition has no influence on the general retention pattern, but significant differences in the retention order of double bond (DB) positional isomers in hexane and dichloromethane mobile phases are described and compared with the previous literature data. Saturated TGs with fatty acyl chain length from C7:0 to C22:0 are partially separated using the hexane mobile phase but not at all with the dichloromethane mobile phase. The hexane mobile phase enables at least partial resolution of TG regioisomers with up to seven DBs, while the resolution of only ALA/AAL and ALnA/AALn isomers is achieved with the dichloromethane mobile phase. The effect of temperature differs significantly depending on the mobile phase composition. Retention times of TGs increase with increasing temperature in the hexane mobile phase, while an opposite effect is observed for the dichloromethane mobile phase.

• Klíčová slova
• Double bond positional isomers, Regioisomers, Silver-ion HPLC, Trans isomers, Triacylglycerol,
• MeSH
• stříbro chemie   MeSH
• teplota MeSH
• triglyceridy chemie   izolace a purifikace   MeSH
• vysokoúčinná kapalinová chromatografie metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• stříbro MeSH
• triglyceridy MeSH

OBJECTIVE: The aim of the present study was to investigate if prospective memory (PM) is impaired in idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD). RBD is a parasomnia characterized by dream enactment and by REM sleep without muscle atonia. iRBD is considered as the initial stage of neurodegeneration with pathological storage of alpha-synuclein. METHOD: Sixty iRBD patients with polysomnography-confirmed RBD without parkinsonism and dementia and 30 demographically matched normal controls (NC) were enrolled in the present study. Clinical assessment included Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), dopamine transporter single-photon emission computed tomography (DaT-SPECT) for imaging synapses of dopaminergic neurons in the striatum and a neuropsychological battery with embedded time-based and event-based PM measures. RESULTS: iRBD differed significantly from NC in event-based PM, a number of event-based failures to recall intention and total PM performance (all p < .001) but did not differ in time-based PM and recognition. PM did not contribute to impairment of instrumental activities of daily living in iRBD. Despite being preserved in iRBD in comparison to NC, time-based PM correlated significantly with dopaminergic neuronal loss measured by DaT-SPECT. CONCLUSIONS: We show evidence for a differential pattern of PM impairment in iRBD with severe impairment of event-based and concurrent preservation of time-based PM. We theorize that event-based PM impairment in iRBD is caused by severe impairment of retention and recognition mechanisms in episodic memory whereas time-based PM seems to be affected by reduced striatal dopaminergic synapses.

• Klíčová slova
• REM sleep behavior disorder, episodic memory, neurodegenerative disease, parasomnia, prospective memory, synucleinopathy,
• MeSH
• činnosti denního života psychologie   MeSH
• epizodická paměť * MeSH
• jednofotonová emisní výpočetní tomografie metody   MeSH
• lidé středního věku MeSH
• lidé MeSH
• neuropsychologické testy MeSH
• polysomnografie metody   MeSH
• porucha chování v REM spánku diagnostické zobrazování   epidemiologie   psychologie   MeSH
• poruchy paměti diagnostické zobrazování   epidemiologie   psychologie   MeSH
• senioři MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Seven retention models have been selected to describe a dual-retention behavior of ten dopamine-related compounds on polymer-based monolithic stationary phase with zwitterion sulfobetaine functionality. Regression quality, as well as a statistical significance of individual regression parameters, have been evaluated. Better regression performance showed two four-parameter models when compared to three-parameter models. On the other hand, limited number of experimental points disqualified statistical robustness of four-parameter models. Among three-parameter models, retention description introduced by Horváth and Liang provided comparable quality of regression at significantly improved robustness. Multivariate analysis of the best three-parameter models provided the description of physicochemical properties of dopamine precursors and metabolites. Principal component analysis and logistic regression allowed structural characterization of dopamine-related compounds based solely on regression parameters extracted from an isocratic elution data. Both polarity and type of functional groups has been correctly assigned for 3-methoxytyramine that has not been part of an evaluation study. Among applied dual-retention models, Horváth´s model, initially developed to describe a retention of ionic compounds on nonpolar stationary phases, provided robust regression of experimental data and allowed an extraction of structural characteristics of dopamine-related compounds.

• Klíčová slova
• Dopamine, Dual-retention, Polymer monolith, Regression analysis, Retention model,
• MeSH
• betain analogy a deriváty   chemie   MeSH
• chemické modely * MeSH
• dopamin analogy a deriváty   chemie   MeSH
• molekulární struktura MeSH
• polymery chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 3-methoxytyramine MeSH Prohlížeč
• betain MeSH
• dopamin MeSH
• polymery MeSH
• sulfobetaine MeSH Prohlížeč

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