Column coupling Dotaz Zobrazit nápovědu
- Publikační typ
- abstrakt z konference MeSH
A method utilising isotachophoresis and capillary zone electrophoresis in the column coupling configuration with UV detection at 320 nm was developed for separation and determination of five phenolic acids (rosmarinic, p-coumaric, ferulic, caffeic and chlorogenic) and flavonoid quercitrin in a methanolic extract of Melissae herba. The proposed method has been validated with correlation coefficients from 0.9842 to 0.9988, RSD values between 0.39% and 0.83% for migration times and between 0.40% and 2.05% for peak areas.
- MeSH
- antioxidancia analýza chemie MeSH
- elektroforéza kapilární metody přístrojové vybavení MeSH
- elektroforéza metody přístrojové vybavení MeSH
- financování organizované MeSH
- flavonoidy analýza MeSH
- hydroxybenzoáty analýza MeSH
- koncentrace vodíkových iontů MeSH
- meduňka chemie MeSH
- methanol chemie MeSH
- odběr biologického vzorku metody přístrojové vybavení metody MeSH
- reprodukovatelnost výsledků MeSH
- rostlinné extrakty analýza MeSH
- senzitivita a specificita MeSH
- spektrofotometrie ultrafialová MeSH
The presented paper deals with a new methodology for direct determination of propranolol in human plasma. The methodology described is based on sequential injection analysis technique (SIA) coupled with solid phase extraction (SPE) column based on restricted access materials (RAM). Special RAM column containing 30 microm polymeric material-N-vinylacetamide copolymer was integrated into the sequential injection manifold. SIA-RAM system was used for selective retention of propranolol, while the plasma matrix components were eluted with two weak organic solutions to waste. Due to the acid-basic and polarity properties of propranolol molecule and principles of reversed-phase chromatography, it was possible to retain propranolol on the N-vinylacetamide copolymer sorbent (Shodex MSpak PK-2A 30 microm (2 mm x 10 mm)). Centrifuged plasma samples were aspirated into the system and loaded onto the column using acetonitrile-water (5:95, v/v), pH 11.00, adjusted by triethylamine. The analyte was retained on the column while proteins contained in the sample were removed to waste. Interfering endogenous substances complicating detection were washed out by acetonitrile-water (15:85), pH 11.00 in the next step. The extracted analyte was eluted by means of tetrahydrofuran-water (25:75), pH 11.00 to the fluorescence detector (emission filter 385 nm). The whole procedure comprising sample pre-treatment, analyte detection and column reconditioning took about 15 min. The recoveries of propranolol from undiluted plasma were in the range 96.2-97.8% for three concentration levels of analyte. The proposed SIA-RAM method has been applied for direct determination of propranolol in human plasma.
- MeSH
- financování organizované MeSH
- kalibrace MeSH
- koncentrace vodíkových iontů MeSH
- lidé MeSH
- molekulární struktura MeSH
- on-line systémy přístrojové vybavení MeSH
- propranolol chemie krev MeSH
- průtoková injekční analýza metody přístrojové vybavení MeSH
- senzitivita a specificita MeSH
- Check Tag
- lidé MeSH
The coupling of columns in sub/supercritical fluid chromatography presents a great opportunity for influencing the separation efficiency and extending the selectivity of the separation system. Combinations of different types of chiral stationary phases could positively affect the enantioresolution if single ones are complementary to each other. In this work, two superficially porous particle (2.7 μm) macrocyclic glycopeptide-based columns, namely TeicoShell and NicoShell, were serially coupled and tested in sub/supercritical fluid chromatography for the first time. The influence of the column arrangement on the enantioseparation of structurally diverse biologically active compounds was examined. The obtained results showed how the column order crucially affected the enantioresolution of compounds tested, but the retention was negligibly affected in most cases. We also demonstrated that single TeicoShell and NicoShell columns are very promising towards the development of highly efficient and fast/ultrafast sub/supercritical fluid chromatography methods for structurally different chiral compounds. The optimized methods for sub-minute enantioselective separation of certain biologically important compounds were proposed.
Capillary isotachophoresis with coupled columns provides efficient means for rapid electrophoretic analysis of sample volumes of up to 10microl or more. Commercially available instruments are commonly equipped with conductivity and UV absorbance detectors; however, their on-line coupling with electrospray mass spectrometry is highly desirable. In this work we have modified the commercial coupled column isotachophoresis system for direct connection to an ion trap mass spectrometer. The design included attachment of an elution block with a short capillary transfer line directing the separated zones towards the mass spectrometer. The modification further included separation of the injection and electrode blocks from the separation columns by semipermeable membranes eliminating unwanted fluid movements in the wide bore fluoropolymer separation capillaries. Fused silica capillaries with varying internal diameter were connected as a transfer line between the elution block and mass spectrometer. The transfer line served also as the ESI tip of the sheathless electrospray interface. During the analysis the first, wide bore preseparation capillary with 0.8mm internal diameter served for removal of the bulk sample components and preseparation of the potentially interfering analytes. After the electronic column switching the separation was finished in a 0.3mm internal diameter capillary and the separated ITP zones were transferred in-line by a spray liquid towards the mass spectrometer. The instrumentation was tested for determination of vitamins in whole blood analysis and separation of tryptic peptides.
Isomers and stereoisomers are always challenging to separate. Column coupling may provide improved chromatographic selectivity, necessary for the separation of the compounds with similar chemical and structural properties. The relatively low viscosity of supercritical fluids, used as mobile phases allows for the coupling of several columns in series in supercritical fluid chromatography (SFC), without exceeding the pressure limits of the system. The aim of this study is to propose reliable prediction of the retention behaviour of analytes on a coupled column system, based on a limited number of initial analyses. The chiral compounds atenolol, ephedrine, propranolol, mianserin, labetalol and nadolol, besides the diastereomers quinine and quinidine, and the structural isomers of aminophenol and aminocresol were used as model analytes. The retention behaviour of the analytes was determined on the individual chiral columns Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3, Lux Cellulose-4, Lux Amylose-2 and the achiral columns Luna NH2, Luna Silica, Synergi RP and FluoroSep RP. The mobile phase was composed of CO2 mixed with 20% (v/v) MeOH, which contained 0.1% (v/v) trifluoroacetic acid and 0.1% (v/v) isopropylamine. The retention factors of the analytes on coupled stationary phases were predicted, and subsequently compared to the experimentally obtained ones. Relative deviations of predicted and experimental retention factors were in range from 0.00% to 51.91%. Flow rate and back pressure of the screening conditions were adjusted to improve prediction precision on four column combinations, with varying success rates. The average relative deviations of retention factors were reduced to 2.84% - 6.59% by adjusting flow rate, and to 2.30% - 8.57% by adjusting back pressure. The most successful approach, flow rate adjustment, was then applied to select a column combination providing improved resolution of the structurally similar components of silymarin extract.
The presented review provides comprehensive and detailed characteristics on microcolumn separation techniques off-line coupled to mass spectrometry. Major attention is paid to the classification of junctions between the separation column and the deposition needle and to the process by which the liquid is transferred onto the target. Both contact and non-contact deposition techniques are covered. In order to emphasize the significance of the topic of off-line separations, current commercially available devices have been compared in terms of their potential utilization in analytical chemistry with a summarization of applications used over the past few years.
