Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 112
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
Artigo em Inglês | MEDLINE | ID: mdl-32004941

RESUMO

Despite the development of an off-line packed fiber solid phase extraction procedure (PFSPE) for urinary catecholamines, automation remains a challenge. Here, we propose an on-line PFSPE-HPLC procedure for automated sample processing and analysis of urinary catecholamines, with good recovery and precision, to avoid manual operation errors. The on-line PFSPE-HPLC procedure has been thoroughly optimized concerning the gradient, valve switch timing, the effects of complexing reagent and buffer solution, and the stability of the nanofibers. Validation of the developed on-line PFSPE-HPLC protocol in urine yielded satisfactory accuracies of 99.6-104.2%, precision below 7.0%, as well as a linear range from 1 ng/mL to 100 ng/mL with a correlation coefficient of 0.999. The developed protocol is herein presented as a potential technology for automated sample pretreatment for the determination of urinary catecholamines.


Assuntos
Catecolaminas/urina , Cromatografia Líquida de Alta Pressão/métodos , Extração em Fase Sólida/métodos , Automação Laboratorial , Catecolaminas/química , Catecolaminas/isolamento & purificação , Éteres de Coroa/química , Humanos , Limite de Detecção , Modelos Lineares , Nanofibras/química , Reprodutibilidade dos Testes
2.
J Chromatogr Sci ; 57(8): 758-765, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31318022

RESUMO

The ability to detect catecholamines (CAs) and their metabolites is vital to understand the mechanism behind the neuronal diseases. Neurochemistry aims to provide an improved pharmacological, molecular and physiological understanding of complex brain chemistries by analytical techniques. Capillary electrophoresis (CE) is one such analytical technique that enables the study of various chemical species ranging from amino acids and peptides to natural products and drugs. CE can easily adapt the changes in research focus and in recent years remains an applicable technique for investigating neuroscience and single cell neurobiology. The prepared phenylalanine-based hydrophobic monolithic column, Polymethacryloyl-L-phenylalanine [PMAPA], was used as a stationary phase in capillary electrochromatography to separate CAs that are similar in size and shape to each other including dopamine (DA) and norepinephrine (NE) via hydrophobic interactions. Separation carried out in a short period of 17 min was performed with the electrophoretic mobility of 5.54 × 10-6 m2 V-1 s-1 and 7.60 × 10-6 m2 V-1 s-1 for DA and NE, respectively, at pH 7.0, 65% acetonitrile ratio with 100 mbar applied pressure by the developed hydrophobic monolithic column without needing any extra process such as imprinting or spacer arms to immobilize ligands used in separation.


Assuntos
Eletrocromatografia Capilar/métodos , Catecolaminas/isolamento & purificação , Metacrilatos/química , Fenilalanina/química , Eletrocromatografia Capilar/instrumentação , Catecolaminas/química , Dopamina/química , Dopamina/isolamento & purificação , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Norepinefrina/química , Norepinefrina/isolamento & purificação
3.
J Chromatogr A ; 1561: 48-55, 2018 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-29801939

RESUMO

In the present study, we developed a simple and high-throughput solid phase extraction (SPE) procedure for selective extraction of catecholamines (CAs) in urine samples. The SPE adsorbents were electrospun composite fibers functionalized with 4-carboxybenzo-18-crown-6 ether modified XAD resin and polystyrene, which were packed into 96-well columns and used for high-throughput selective extraction of CAs in healthy human urine samples. Moreover, the extraction efficiency of packed-fiber SPE (PFSPE) was examined by high performance liquid chromatography coupled with fluorescence detector. The parameters affecting the extraction efficiency and impurity removal efficiency were optimized, and good linearity ranging from 0.5 to 400 ng/mL was obtained with a low limit of detection (LOD, 0.2-0.5 ng/mL) and a good repeatability (2.7%-3.7%, n = 6). The extraction recoveries of three CAs ranged from 70.5% to 119.5%. Furthermore, stable and reliable results obtained by the fluorescence detector were superior to those obtained by the electrochemical detector. Collectively, PFSPE coupled with 96-well columns was a simple, rapid, selective, high-throughput and cost-efficient method, and the proposed method could be applied in clinical chemistry.


Assuntos
Catecolaminas/isolamento & purificação , Catecolaminas/urina , Éteres de Coroa/química , Nanofibras/química , Poliestirenos/química , Extração em Fase Sólida/métodos , Cromatografia Líquida de Alta Pressão/métodos , Humanos , Limite de Detecção
4.
J Vis Exp ; (133)2018 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-29553566

RESUMO

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and related diseases, but their precise measurement is still a challenge. Many protocols have been described for neurotransmitter measurement by a variety of instruments, including high-pressure liquid chromatography (HPLC). However, there are shortcomings, such as complicated operation or hard-to-detect multiple targets, which cannot be avoided, and presently, the dominant analysis technique is still HPLC coupled with sensitive electrochemical or fluorimetric detection, due to its high sensitivity and good selectivity. Here, a detailed protocol is described for the pretreatment and detection of catecholamines with high pressure liquid chromatography with electrochemical detection (HPLC-ECD) in real urine samples of infants, using electrospun composite nanofibers composed of polymeric crown ether with polystyrene as adsorbent, also known as the packed-fiber solid phase extraction (PFSPE) method. We show how urine samples can be easily precleaned by a nanofiber-packed solid phase column, and how the analytes in the sample can be rapidly enriched, desorbed, and detected on an ECD system. PFSPE greatly simplifies the pretreatment procedures for biological samples, allowing for decreased time, expense, and reduction of the loss of targets. Overall, this work illustrates a simple and convenient protocol for solid-phase extraction coupled to an HPLC-ECD system for simultaneous determination of three monoamine neurotransmitters (norepinephrine (NE), epinephrine (E), dopamine (DA)) and two of their metabolites (3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxy-phenylacetic acid (DOPAC)) in infants' urine. The established protocol was applied to assess the differences of urinary catecholamines and their metabolites between high-risk infants with perinatal brain damage and healthy controls. Comparative analysis revealed a significant difference in urinary MHPG between the two groups, indicating that the catecholamine metabolites may be an important candidate marker for early diagnosis of cases at risk for brain damage in infants.


Assuntos
Catecolaminas/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Neurotransmissores/isolamento & purificação , Extração em Fase Sólida/métodos , Catecolaminas/metabolismo , Humanos , Neurotransmissores/metabolismo
5.
Anal Bioanal Chem ; 409(17): 4215-4223, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28451718

RESUMO

Complexation-mediated electromembrane extraction (EME) of highly polar basic drugs (log P < -1) was investigated for the first time with the catecholamines epinephrine, norepinephrine, and dopamine as model analytes. The model analytes were extracted as cationic species from urine samples (pH 4), through a supported liquid membrane (SLM) comprising 25 mM 4-(trifluoromethyl)phenylboronic acid (TFPBA) in bis(2-ethylhexyl) phosphite (DEHPi), and into 20 mM formic acid as acceptor solution. EME was performed for 15 min, and 50 V was used as extraction voltage across the SLM. TFPBA served as complexation reagent, and selectively formed boronate esters by reversible covalent binding with the model analytes at the sample/SLM interface. This enhanced the mass transfer of the highly polar model analytes across the SLM, and EME of basic drugs with log P in the range -1 to -2 was shown for the first time. Meanwhile, most matrix components in urine were unable to pass the SLM. Thus, the proposed concept provided highly efficient sample clean-up and the system current across the SLM was kept below 50 µA. Finally, the complexation-mediated EME concept was combined with ultra-high performance liquid chromatography coupled to tandem mass spectrometry and evaluated for quantification of epinephrine and dopamine. Standard addition calibration was applied to a pooled human urine sample. Calibration curves using standards between 25 and 125 µg L-1 gave a high level of linearity with a correlation coefficient of 0.990 for epinephrine and 0.996 for dopamine (N = 5). The limit of detection, calculated as three times signal-to-noise ratio, was 5.0 µg L-1 for epinephrine and 1.8 µg L-1 for dopamine. The repeatability of the method, expressed as coefficient of variation, was 13% (n = 5). The proposed method was finally applied for the analysis of spiked pooled human urine sample, obtaining relative recoveries of 91 and 117% for epinephrine and dopamine, respectively.


Assuntos
Catecolaminas/urina , Técnicas Eletroquímicas/instrumentação , Microextração em Fase Líquida/instrumentação , Membranas Artificiais , Compostos de Boro/química , Catecolaminas/isolamento & purificação , Humanos , Limite de Detecção , Urinálise/instrumentação
6.
ACS Nano ; 11(4): 3446-3455, 2017 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-27997789

RESUMO

We report an approach to spatially resolve the content across nanometer neuroendocrine vesicles in nerve-like cells by correlating super high-resolution mass spectrometry imaging, NanoSIMS, with transmission electron microscopy (TEM). Furthermore, intracellular electrochemical cytometry at nanotip electrodes is used to count the number of molecules in individual vesicles to compare to imaged amounts in vesicles. Correlation between the NanoSIMS and TEM provides nanometer resolution of the inner structure of these organelles. Moreover, correlation with electrochemical methods provides a means to quantify and relate vesicle neurotransmitter content and release, which is used to explain the slow transfer of dopamine between vesicular compartments. These nanoanalytical tools reveal that dopamine loading/unloading between vesicular compartments, dense core and halo solution, is a kinetically limited process. The combination of NanoSIMS and TEM has been used to show the distribution profile of newly synthesized dopamine across individual vesicles. Our findings suggest that the vesicle inner morphology might regulate the neurotransmitter release event during open and closed exocytosis from dense core vesicles with hours of equilibrium needed to move significant amounts of catecholamine from the protein dense core despite its nanometer size.


Assuntos
Dopamina/análise , Nanoestruturas/química , Nanotecnologia , Animais , Catecolaminas/química , Catecolaminas/isolamento & purificação , Portadores de Fármacos/química , Eletrodos , Exocitose , Microscopia Eletrônica de Transmissão , Neurotransmissores/química , Neurotransmissores/metabolismo , Células PC12 , Tamanho da Partícula , Ratos , Espectrometria de Massa de Íon Secundário , Propriedades de Superfície
7.
J Chromatogr A ; 1468: 23-32, 2016 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-27667649

RESUMO

Nonhydrolytic sol-gel (NHSG) route was used for the creation of novel zirconia-polypropylene oxide (ZrO2-PPO) sol-gel hybrid sorbents in the form of surface coatings for the extraction and preconcentration of catecholamine neurotransmitters and molecules structurally related to their deaminated metabolites. In comparison to other sorbents made of inorganic transition metal oxides, the presented hybrid organic-inorganic sorbents facilitated reversible sorption properties that allowed for efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The presented sol-gel hybrid sorbents effectively overcame the major drawbacks of traditional silica- or polymer-based sorbents by providing superior pH stability (pH range: 0-14), and a variety of intermolecular interactions. Nonaqueous sol-gel treatment of PPO with ZrCl4 was employed for the derivatization of the terminal hydroxyl groups on PPO, providing zirconium trichloride-containing end groups characterized by enhanced sol-gel reactivity. NHSG ZrO2-PPO sorbent provided excellent microextraction performance for catecholamines, low detection limits (5.6-9.6pM), high run-to-run reproducibility (RSD 0.6-5.1%), high desorption efficiency (95.0-99.5%) and high enrichment factors (∼1480-2650) for dopamine and epinephrine, respectively, extracted from synthetic urine samples. The presented sol-gel sorbents provided effective alternative to conventional extraction media providing unique physicochemical characteristics and excellent extraction capability.


Assuntos
Técnicas de Química Analítica/métodos , Neurotransmissores/isolamento & purificação , Zircônio/química , Catecolaminas/isolamento & purificação , Técnicas de Química Analítica/instrumentação , Géis/química , Reprodutibilidade dos Testes , Dióxido de Silício/química
8.
Analyst ; 141(8): 2568-73, 2016 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-27029966

RESUMO

We have developed an analytical method for the determination of catecholamines and related compounds in mouse urine by column-switching HPLC. Selective extraction of the catechol compounds was performed using a precolumn modified with phenylboronic acid, which has a pH dependent affinity for the catechol structures. The pretreatment buffer, which facilitated binding of the catechols to the precolumn, was optimized to ensure high analyte recoveries and good peak shapes. We found that using the same acetonitrile content in the pretreatment buffer and hydrophilic interaction liquid chromatography mobile phase was necessary to improve peak shapes. Eight catechol compounds were selectively extracted and separated using 100 mmol L(-1) ammonium formate/acetonitrile (20/80 v/v, pH 8.0) for the extraction step, and 20 mmol L(-1) ammonium formate (pH 2.5)/acetonitrile (20/80 v/v) for elution and separation. Native fluorescence of the separated catechol compounds was monitored, and the limits of detection, corresponding to a signal to noise ratio of 3, were 9-58 nmol L(-1). Five catechol compounds (dopamine, epinephrine, norepinephrine, 3,4-dihydroxyphenylglycol, and 3,4-dihydroxymandelic acid) were successfully quantified in mouse urine. Intra- and inter-day precisions were less than 10%, and performance was superior to that afforded by manual sample pretreatment.


Assuntos
Catecolaminas/urina , Cromatografia Líquida de Alta Pressão/métodos , Urinálise/métodos , Animais , Tampões (Química) , Catecolaminas/química , Catecolaminas/isolamento & purificação , Limite de Detecção , Camundongos , Reprodutibilidade dos Testes
9.
Yakugaku Zasshi ; 135(8): 955-60, 2015.
Artigo em Japonês | MEDLINE | ID: mdl-26234353

RESUMO

Measurement of biological compounds is important for the clarification of biological phenomena. For the quantification of trace amounts of biological compounds, efficient separation and sensitive analytical methods are necessary. The present author developed HPLC-fluorescence and chemiluminescence detection methods for biological compounds such as catecholamines, amino acids, and thiols. In this review article, two studies are summarized: one on the development of an on-chip liquid chromatography method using pillar array columns with low-dispersion turns; and another on the development of simultaneous analytical method of biothiols by HPLC with fluorescence detection under hydrophilic interaction chromatography conditions.


Assuntos
Aminoácidos/análise , Catecolaminas/análise , Cromatografia Líquida de Alta Pressão/métodos , Compostos de Sulfidrila/análise , Aminoácidos/isolamento & purificação , Animais , Catecolaminas/isolamento & purificação , Cromatografia Líquida/métodos , Fluorescência , Interações Hidrofóbicas e Hidrofílicas , Medições Luminescentes/métodos , Análise em Microsséries , Ratos , Compostos de Sulfidrila/isolamento & purificação
10.
J Sep Sci ; 38(16): 2857-64, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26017668

RESUMO

The levels of catecholamines, especially dopamine, epinephrine and norepinephrine in urine and plasma have been used to assist the diagnosis and treatment of psychosis. Due to their low endogenous concentrations, the determination of the three major catecholamines is very difficult. Boronate adsorbents are often employed to extract these cis-diol compounds from complex matrices. In this work, a novel type of magnetic nanoparticles modified with 4-formylphenylboronic named Fe3O4@PEI-FPBA was synthesized by a facile two-step approach. The abundant amino groups of polyethyleneimine provided the rich binding sites for boronate ligands. Herein, the adsorption capacity of Fe3O4@PEI-FPBA is greatly improved with a value of 3.45 mg/g towards epinephrine, which is much larger than that of analogous material without polyethyleneimine. The magnetic nanoparticles also exhibited high magnetization (72.25 emu/g) and specific selectivity towards the catecholamines. Finally, a liquid chromatography tandem mass spectrometry method based on Fe3O4@PEI-FPBA nanoparticles was successfully used to determine the three catecholamines from human urine samples. The linearity, limit of quantitation, recovery and precision of the method were satisfactory. Based on the method, it is found that the levels of dopamine, epinephrine and norepinephrine in depressive patients are higher than those in healthy controls.


Assuntos
Catecolaminas/isolamento & purificação , Depressão/urina , Óxido Ferroso-Férrico/química , Polietilenoimina/química , Adsorção , Ácidos Borônicos/química , Catecolaminas/urina , Cromatografia Líquida de Alta Pressão , Humanos , Magnetismo , Espectrometria de Massas , Nanopartículas/química
11.
Biomed Chromatogr ; 29(1): 103-9, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24917362

RESUMO

For the first time, electrospun composite nanofibers comprising polymeric crown ether with polystyrene (PCE-PS) have been used for the selective extraction of catecholamines - dopamine (DA), norepinephrine (NE) and epinephrine (E) - prior to their analysis by high-performance liquid chromatography-electrochemical detection. Using a minicartridge packed with PCE-PS composite nanofibers, the target compounds were extracted effectively from urine samples to which diphenylborinic acid 2-aminoethyl ester was added as a complexing reagent. The extracted catecholamines could be liberated from the fiber by the addition of acetic acid. A good linearity was observed for catecholamines in the range of 2.0-200 ng mL(-1) (NE, E and DA). The detection limits of catecholamines (signal-to-noise ratio = 3) were 0.5 ng mL(-1) (NE), 0.2 ng mL(-1) (E) and 0.2 ng mL(-1) (DA), respectively. Under the optimized conditions, the absolute recoveries of the above three catecholamines were 90.6% (NE), 88.5% (E) and 94.5% (DA). The repeatability of extraction performance was from 5.4 to 9.2% (expressed as relative standard deviation). Our results indicate that the proposed method could be used for the determination of NE, E and DA in urine.


Assuntos
Catecolaminas/isolamento & purificação , Éteres de Coroa/química , Nanofibras/química , Poliestirenos/química , Extração em Fase Sólida/métodos , Catecolaminas/urina , Cromatografia Líquida de Alta Pressão , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
12.
Biomacromolecules ; 15(4): 1204-15, 2014 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-24552290

RESUMO

Thermoresponsive anionic copolymer brushes, poly(N-isopropylacrylamide-co-acrylic acid-co-tert-butylacrylamide) [P(IPAAm-co-AAc-co-tBAAm)], were grafted onto a monolithic silica rod column through surface-initiated atom-transfer radical polymerization (ATRP) to prepare an effective thermoresponsive anionic chromatography matrix. An ATRP initiator was attached to the rod surface. N-Isopropylacrylamide (IPAAm), tert-butyl acrylate (tBA), tert-butylacrylamide (tBAAm), and the ATRP catalyst CuCl/CuCl2/tris[2-(N,N-dimethylamino)ethyl]amine were dissolved in 2-propanol, and the reaction mixture was pumped into the initiator-modified column. After grafting P(IPAAm-co-tBA-co-tBAAm) on the monolithic silica surfaces, deprotection of the tert-butyl group of tBA was performed. Chromatographic analysis showed that the prepared column was able to separate catecholamine derivatives and angiotensin subtypes within a shorter analysis time (5 min) than a silica-bead-packed column modified with the same copolymer brush could. These results indicated that the prepared copolymer-modified monolithic silica rod column may be a promising bioanalytical and bioseparation tool for rapid analysis of basic bioactive compounds and peptides.


Assuntos
Cromatografia/instrumentação , Peptídeos/isolamento & purificação , Polímeros/química , Acrilamidas/química , Adsorção , Angiotensinas/isolamento & purificação , Catecolaminas/isolamento & purificação , Cromatografia/métodos , Cromatografia em Gel , Espectroscopia Fotoeletrônica , Polimerização , Polímeros/síntese química , Dióxido de Silício/química , Propriedades de Superfície , Temperatura
13.
Electrophoresis ; 34(4): 552-6, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23172632

RESUMO

A capillary formed by connecting a 9.7 cm-long separation capillary with id 25 µm with an auxiliary 22.9 cm-long capillary with id 100 µm (coupled capillary) was tested for electrophoretic separation at high electric field intensities. The coupled capillary was placed in the cassette of a standard electrophoresis apparatus. It was used in the short-end injection mode for separation of a mixture of dopamine, noradrenaline, and adrenaline in a BGE of 20 mM citric acid/NaOH, pH 3.2. An intensity of 2.7 kV/cm was attained in the separation part of the capillary at a separation voltage of 30 kV, which is 2.9 times more than maximum intensity value attainable in a capillary with the same length with uniform id. At these high electric field intensities, the migration times of the tested neurotransmitters had values of 12.3-13.3 s and the attained separation efficiency was between 2350 and 2760 plates/s. It is thus demonstrated that an effective separation instrument - a coupled capillary - can be used for very rapid separation in combination with standard, commercially available instrumentation.


Assuntos
Eletroforese Capilar/instrumentação , Eletroforese Capilar/métodos , Catecolaminas/análise , Catecolaminas/química , Catecolaminas/isolamento & purificação , Ácido Cítrico/química , Modelos Químicos , Neurotransmissores/análise , Neurotransmissores/química , Neurotransmissores/isolamento & purificação , Hidróxido de Sódio/química , Fatores de Tempo
14.
Electrophoresis ; 34(2): 297-303, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23161197

RESUMO

This study examines the use of unmodified magnetite nanoparticles (Fe(3)O(4) NPs) for selective extraction and enrichment of the catecholamines dopamine (DA), noradrenaline (NE), and adrenaline (E), prior to analysis using capillary electrophoresis with UV detection. Coordination between Fe(3+) on-the-surface Fe(3)O(4) NPs and the catechol moiety of catecholamines enables Fe(3)O(4) NPs to capture catecholamines from an aqueous solution. We obtained maximum loading of catecholamines on the NP surface by adjusting the pH of the solution to 7.0. In addition, catecholamine loading on the Fe(3)O(4) NPs increased in conjunction with NP concentrations. H(3)PO(4) was found to be efficient for the removal of adsorbed catecholamines on the NP surface. Adding 1.2% poly(diallyldimethylammonium chloride) to the background electrolyte resulted in a baseline separation of the liberated catecholamines within 20 min. Under optimal extraction and separation conditions, the limit of detections at a S/N ratio of 3 for E, NE, and DA were 9, 8, and 10 nM, respectively. Significantly, the combination of a phenylboronate-containing spin column and the proposed method was successfully applied to the determination of NE and DA in human urine and NE in Portulaca oleracea L. leaves.


Assuntos
Catecolaminas/isolamento & purificação , Eletroforese Capilar/métodos , Nanopartículas de Magnetita/química , Adulto , Catecolaminas/análise , Catecolaminas/urina , Humanos , Masculino , Extratos Vegetais/química , Folhas de Planta/química , Portulaca/química , Reprodutibilidade dos Testes , Espectrofotometria Ultravioleta
15.
Artigo em Inglês | MEDLINE | ID: mdl-23270937

RESUMO

A rapid and sensitive liquid chromatography tandem mass spectrometry method for simultaneous quantification of catecholamine neurotransmitters in microdialysates was developed. The catecholamine neurotransmitters dopamine (DA) and norepinephrine (NE) were pre-column derivatized with dansyl chloride and analyzed. A gradient elution method was used to separate the analytes from the interferences on an Agilent Poroshell 120 EC-C18 outer porous micro particulate column. The method was robust and sensitive to determine with the lower limit of quantification value of 0.068pmol/mL and 0.059pmol/mL for DA and NE, respectively. It has acceptable precision and accuracy for concentrations over the standard curve range. The method was successfully applied for simultaneous quantitation of DA and NE in the prefrontal cortex (PFC) dialysates of rats obtained from a microdialysis study dosed with vehicle and atomoxetine through intra peritoneal (i.p.) route at a dose of 3mg/kg to monitor the change in extracellular concentrations. Thus, accomplishment of this method would facilitate the neurochemical monitoring for discovery of new chemical entities targeted for the treatment of attention deficit hyperactivity disorder (ADHD).


Assuntos
Catecolaminas/análise , Cromatografia Líquida/métodos , Compostos de Dansil/química , Microdiálise/métodos , Neurotransmissores/análise , Espectrometria de Massas em Tandem/métodos , Animais , Catecolaminas/líquido cefalorraquidiano , Catecolaminas/química , Catecolaminas/isolamento & purificação , Estabilidade de Medicamentos , Masculino , Neurotransmissores/líquido cefalorraquidiano , Neurotransmissores/química , Neurotransmissores/isolamento & purificação , Córtex Pré-Frontal/química , Ratos , Ratos Wistar , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
16.
J Chromatogr A ; 1272: 65-72, 2013 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-23261287

RESUMO

This study describes the ability of triallyl isocyanurate (TAIC)-co-methacrylate ester polymer monoliths as stationary phases for the separation of hydrophilic compounds (phenolic acids, amino acids and catecholamines) in capillary electrochromatography (CEC) and ultra high pressure liquid chromatography (UHPLC). Several TAIC-co-methacrylate ester polymer monoliths prepared by single-step in situ copolymerization of TAIC, ethylene dimethacrylate (EDMA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), with or without alkyl methacrylates were characterized by examining the SEM image, surface area, contact angle, and the thermal decomposition temperature. Compared to the conventional methacrylate ester-based monoliths, these proposed monoliths possessed hydrophilic character thus increased wettability which improved chromatographic separation selectivity of polar phenolic acids. Among the proposed TAIC-co-methacrylate monoliths, poly(TAIC-co-EDMA-AMPS-co-stearyl methacrylate (SMA)) showed separation selectivity with an increased analyte resolution from 0.0 to 0.92 for 4-hydroxybenzoic acid and vanillic acid, which were consistently difficult to resolve in the reversed-phase chromatographic mechanism of these monoliths in aqueous mobile phases. Moreover, stable ionization efficiencies were observed when this monolith was combined with ESI-MS detector possibly because an organic solvent-rich sheath liquid was used in the CEC-MS. This study demonstrates the potentiality of novel TAIC-co-methacrylate polymer monoliths in hydrophilic solute separation either in CEC or UHPLC mode.


Assuntos
Eletrocromatografia Capilar/métodos , Catecolaminas/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Metacrilatos/química , Triazinas/química , Aminoácidos/análise , Hidroxibenzoatos/isolamento & purificação , Microscopia Eletrônica de Varredura , Porosidade , Solventes , Temperatura
18.
Talanta ; 99: 897-903, 2012 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-22967640

RESUMO

A rapid and selective method for the extraction and determination of catecholamines (CLs) from urine samples has been successfully developed using a magnetic molecularly imprinted polymer (MMIP) as a sorbent material. The MMIP has been prepared using dopamine hydrochloride (DA) as template molecule, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as cross-linking agent and Fe(3)O(4) magnetite as magnetic component. The extraction was carried out by stirring urine samples with the magnetic polymer. When the extraction was completed, the MMIP, together with the captured analytes, was easily separated from the sample matrix by an adscititious magnet. The analytes desorbed from the MMIP were determined by capillary electrophoresis (CE). It was shown that the MMIP had high affinity and selectivity toward DA and other structurally related CLs such as 3-methoxytyramine hydrochloride (MT), DL-normetanephrine hydrochloride (NME), DL-norephinephrine hydrochloride (NE) and (±) epinephrine (E). Different parameters affecting the extraction efficiency were evaluated in order to achieve the optimal pre-concentration of the analytes and to reduce non-specific interactions. Under the optimal conditions, the CL limits of detection were at the 0.04-0.06 µM range. The relative standard deviations of migration time and response ranged from 0.7% to 1.4% and from 2.9% to 5.5%, respectively. The proposed method was successfully applied to determine CLs, including MT, NME, DA, NE and E in human urine samples.


Assuntos
Catecolaminas/isolamento & purificação , Catecolaminas/urina , Dopamina/química , Eletroforese Capilar/métodos , Imãs/química , Impressão Molecular/métodos , Polímeros/síntese química , Humanos , Nanopartículas de Magnetita/química , Metacrilatos/química , Fatores de Tempo
19.
Electrophoresis ; 33(2): 379-87, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22222982

RESUMO

The use of mixtures of ionic and zwitterionic surfactants in poly(dimethylsiloxane) (PDMS) microchips is reported. The effect of surfactant concentration on electroosmotic flow (EOF) was studied for a single anionic surfactant (sodium dodecyl sulfate, SDS), a single zwitterionic surfactant (N-tetradecylammonium-N,N-dimethyl-3-ammonio-1-propanesulfonate, TDAPS), and a mixed SDS/TDAPS surfactant system. SDS increased the EOF as reported previously while TDAPS showed an initial increase in EOF followed by a reduction at higher concentrations. When TDAPS was added to a solution containing SDS, the EOF decreased in a concentration-dependent manner. The EOF for all three surfactant systems followed expected pH trends, with increasing EOF at higher pH. The mixed surfactant system allowed tuning of the EOF across a range of pH and concentration conditions. After establishing the EOF behavior, the adsorption/desorption kinetics were measured and showed a slower adsorption/desorption rate for TDAPS than SDS. Finally, the separation and electrochemical detection of model catecholamines in buffer and reduced glutathione in red blood cell lysate using the mixed surfactant system were explored. The mixed surfactant system provided shorter analysis times and/or improved resolution when compared to the single surfactant systems.


Assuntos
Dimetilpolisiloxanos/química , Eletroforese em Microchip/instrumentação , Eletroforese em Microchip/métodos , Tensoativos/química , Adsorção , Adulto , Catecolaminas/análise , Catecolaminas/isolamento & purificação , Eletro-Osmose , Eritrócitos/química , Glutationa/sangue , Glutationa/isolamento & purificação , Humanos , Concentração de Íons de Hidrogênio , Compostos de Amônio Quaternário , Dodecilsulfato de Sódio
20.
J Chromatogr A ; 1218(48): 8715-7, 2011 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-22033108

RESUMO

Existing two-phase solvent systems for high-speed countercurrent chromatography cover the separation of hydrophobic to moderately polar compounds, but often fail to provide suitable partition coefficient values for highly polar compounds, such as sulfonic acids, catecholamines and zwitter ions. The present paper introduces a new solvent series which can be applied for the separation of these polar compounds. It is composed of 1-butanol, ethanol, saturated ammonium sulfate and water at various volume ratios and consists of a series of 10 steps which are arranged according to the polarity of the solvent system so that the two-phase solvent system with suitable K values for the target compound(s) can be found in a few steps. Each solvent system gives proper volume ratio and high density difference between the two phases to provide a satisfactory level of retention of the stationary phase in the spiral column assembly. The method is validated by partition coefficient measurement of four typical polar compounds including methyl green (basic dye), tartrazine (sulfonic acid), tyrosine (zwitter ion) and epinephrine (a catecholamine), all of which show low partition coefficient values in the polar 1-butanol-water system. The capability of the method is demonstrated by separation of three catecholamines.


Assuntos
Distribuição Contracorrente/instrumentação , Distribuição Contracorrente/métodos , Solventes/química , 1-Butanol/química , Sulfato de Amônio/química , Catecolaminas/isolamento & purificação , Etanol/química , Interações Hidrofóbicas e Hidrofílicas , Modelos Químicos , Concentração Osmolar , Reprodutibilidade dos Testes , Ácidos Sulfônicos/isolamento & purificação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA