An improved design of the fused silica capillary flow cell for absorbance detection in microcolumn liquid chromatography.

Efficient absorbance detection of a low-volume chromatography peak is a difficult task. In this work, an improved design of the fused silica capillary flow cell for absorbance detection in microcolumn liquid chromatography is described. The cell was fabricated from 0.

Compact optical detector utilizing light emitting diodes, 50 nL L-shaped silica capillary cell and CCD spectrometer for simultaneous multi-wavelength monitoring of absorbance and fluorescence in microcolumn liquid chromatography.

Optical detection setup utilizing light emitting diodes (LEDs), 50 nL L-shaped silica capillary detection cell (L-cell), and low-cost CCD spectrometer is described in this work. Experimental configuration can be equipped with two different LEDs for absorbance measurement and other two LEDs for fluorescence excitation. This setup is capable of simultaneous multi-wavelength monitoring of absorbance and fluorescence when light produced by the individual LEDs and light emitted by the fluorescent analytes is resolved in the spectrum outputted by the CCD spectrometer.

Nanolitre-scale cell based on L-shaped silica capillary and optical fibre for absorption photometric detection in capillary liquid chromatography.

Miniaturised photometric detection cell based on the 150 μm I. D. L-shaped fused silica capillary (L-cell) and silica optical fibre is discussed in this paper.

Capillary electrophoresis in a fused-silica capillary with surface roughness gradient.

The electro-osmotic flow, a significant factor in capillary electrophoretic separations, is very sensitive to small changes in structure and surface roughness of the inner surface of fused silica capillary. Besides a number of negative effects, the electro-osmotic flow can also have a positive effect on the separation. An example could be fused silica capillaries with homogenous surface roughness along their entire separation length as produced by etching with supercritical water.

Instrument platforms for nano liquid chromatography.

The history of liquid chromatography started more than a century ago and miniaturization and automation are two leading trends in this field. Nanocolumn liquid chromatography (nano LC) and largely synonymous capillary liquid chromatography (capillary LC) are the most recent results of this process where miniaturization of column dimensions and sorbent particle size play crucial role. Very interesting results achieved in the research of extremely miniaturized LC columns at the end of the last century lacked distinctive raison d'être and only advances in mass spectrometry brought a real breakthrough.

A portable device for fast analysis of explosives in the environment.

A novel portable device for fast and sensitive analysis of explosives in environmental samples is presented. The developed system consists of miniaturized microcolumn liquid chromatograph, photolytic converter and chemiluminescence detector. The device is able to determine selectively nitramine- and nitroester- and most of nitroaromates-based explosives as well as inorganic nitrates at trace concentrations in water or soil extracts in less than 8 min.

Constant pressure mode extended simple gradient liquid chromatography system for micro and nanocolumns.

Performing gradient liquid chromatography at constant pressure instead of constant flow rate has serious potential for shortening the analysis time and increasing the productivity of HPLC instruments that use gradient methods. However, in the constant pressure mode the decreasing column permeability during a long period of time negatively affects the repeatability of retention time. Thus a volume-based approach, in which the detector signal is plotted as a function of retention volume, must be taken into consideration.

Combination of micropreparative solution isoelectric focusing and high-performance liquid chromatography for differentiation of biofilm-positive and biofilm-negative Candida parapsilosis group from vascular catheter.

This study utilizes the high-performance liquid chromatography technique in combination with the new micropreparative solution isoelectric focusing fractionation on non-woven fabric strip for the characterization and differentiation of biofilm-positive and biofilm-negative forms of Candida parapsilosis sensu stricto on the basis of the changes in the composition of their cell-surface. Treatment of yeasts by boiling in distilled water relased surface substances from yeasts cells. Consequently, the optimized procedure has been used for fast identification of the highly pathogenic biofilm-positive Candida parapsilosis group in real clinical material - sonicate from vascular catheters.

Simple automated liquid chromatographic system for splitless nano column gradient separations.

A simple splitless gradient liquid chromatographic system for micro and nano column separations has been assembled and tested. It consists of an OEM programmable syringe pump equipped with a glass microsyringe and ten-port selector valve. Gradient of mobile phase was created in the syringe barrel due to turbulent mixing.

Zwitterionic silica-based monolithic capillary columns for isocratic and gradient hydrophilic interaction liquid chromatography.

This study introduces zwitterionic monolithic capillary columns intended for isocratic and gradient HILIC separations. Silica-based monolithic capillary columns (100 μm × 150 mm) prepared by acidic hydrolysis of tetramethoxysilane in the presence of polyethylene glycol and urea were modified by a sulfoalkylbetaine zwitterion ([2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide) to HILIC stationary phase. The prepared columns were evaluated under the isocratic and gradient separation conditions using a standard mixture containing nucleic acid bases, nucleosides, and 2-deoxynucleosides.

Divergent-flow isoelectric focusing for separation and preparative analysis of peptides.

A divergent-flow isoelectric focusing (DF IEF) technique has been applied for the separation and preparative analysis of peptides. The parameters of the developed DF IEF device such as dimension and shape of the separation bed, selection of nonwoven material of the channel, and separation conditions were optimized. The DF IEF device was tested by the separation of a peptide mixture originating from the tryptic digestion of BSA, cytochrome c, and myoglobin.

Silica-based monolithic capillary columns-Effect of preparation temperature on separation efficiency.

The temperature effects during the sol-gel process and ageing of the silica-based monolith on the structure and separation efficiency of the capillary columns (100microm i.d., 150mm) for HPLC separations were studied.

Capillary electromigration separation of proteins and microorganisms dynamically modified by chromophoric nonionogenic surfactant.

A chromophoric nonionogenic surfactant poly(ethylene glycol) 3-(2-hydroxy-5-n-octylphenylazo)-benzoate, HOPAB, has been prepared and used as a buffer additive for a dynamic modification of proteins and/or microorganisms including Escherichia coli , Staphylococcus epidermidis (biofilm-positive and biofilm-negative), and the strains of yeast cells Candida albicans and Candida parapsilosis (biofilm-positive and biofilm-negative) during a capillary electrophoresis and a capillary isoelectric focusing (CIEF) with UV detection at 326 nm. Values of isoelectric points of labeled proteins and microorganisms have been calculated using UV-detectable pI markers and have been found comparable with pI of the native compounds. Minimum detectable amount has been assessed lower than picograms of proteins and lower than a hundred cells injected into a separation capillary.

Short monolithic columns for purification and fractionation of peptide samples for matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry analysis in proteomics.

This study records a novel application of methacrylate-based monolithic columns for MALDI-TOF/TOF MS analyses in proteomics for pre-concentration and separation of peptides derived from protein digestion. Reversed-phase monolithic capillary columns (30mm x 0.32mm i.

Miniaturized liquid core waveguide-based fluorimetric detection cell for capillary separation methods: application in CE of amino acids.

A miniaturized post-column fluorimetric detection cell for capillary separation methods based on optical fibers and liquid core waveguides (LCWs) is described. The main part of the detection cell is a fused-silica capillary coated with Teflon AF serving as an LCW. The optical fibers are used both for coupling the excitation source with the detection domain in the LCW and for the axial fluorescence collection from the LCW end.

Separation of microcystins by capillary electrochromatography in monolithic columns.

Contribution on microcystin variant analysis by capillary electrochromatography (CEC) with easily affordable spectrophotometric detection is presented. Two types of reversed-phase capillary columns formed by inorganic or organic polymer monoliths were prepared for this purpose. The analyses were performed isocratically by means of tris(hydroxymethyl) aminomethane (TRIS) buffers of mildly alkaline pH containing 30% (v/v) acetonitrile as the mobile phases.

Preliminary study on the monitoring of glutathione S-tranferase activity toward styrene oxide by electromigration methods.

A new method has been developed for the monitoring of glutathione S-tranferase (GST) detoxification activity toward styrene oxide (SO). The enzymatic reaction was carried out directly in a thermostatted autosampler vial and the formation of conjugates between glutathione (GSH) and SO was monitored by sequential MEKC runs. The determinations were performed in a 50-microm fused silica capillary using 50 mM SDS in 20 mM phosphate 20 mM tetraborate buffer (pH 8.

Fluorescence detection system for capillary separations utilizing a liquid core waveguide with an optical fibre-coupled compact spectrometer.

A fluorescence detection system for capillary liquid separation methods is described. The system is based on a silica capillary coated with a low refractive index fluoropolymer Teflon AF that serves both as a separation channel and as a liquid core waveguide (LCW). A fibre-coupled laser excites separated analytes in a detection point and arising fluorescence is collected at one end of the LCW capillary into the other optical fibre which brings it to a compact charge-coupled device (CCD) array spectrometer installed in a desktop computer.

Sample injection in capillary electrochromatography by heart-cut technique.

The splitter working in heart-cut regime was used for sample injection in capillary electrochromatography. The principle was implemented in an automated microgradient system allowing to inject from microlitre down to nanolitre volumes with high repeatability and minimal extra-column band broadening. The apparatus is able to deliver discrete volumes of liquids at a preset volumetric flow rate and to stop and restore the flow at any moment.

Automated microgradient system for capillary electrochromatography.

A microprocessor controlled gradient elution system suitable for capillary electrochromatography has been developed and tested. It is based on a liquid handling device described previously which is capable of liquid transport with both low and high fluid dispersion. The low dispersion region formed by stainless steel needle 250 microm I.