Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Flow Injection Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed2000

Electrode coatings based on chitosan scaffolds.

Thin films of a biopolymer chitosan (CHIT) were cast on glassy carbon electrodes, modified by grafting Lucifer Yellow VS dye (LYVS) onto chitosan chains, and cross-linked with glutaric dialdehyde (GDI). The ion-transport and ion-exchange properties of such polymeric structures (CHIT, CHIT-LYVS, CHIT-LYVS-GDI) were studied using cyclic voltammetry, rotating disk electrode, and flow injection analysis. The results showed that the chitosan matrix supported a fast ion transport as demonstrated by aqueous-like values of the apparent diffusion coefficients of Ru(NH3)6(3)+ and dopamine in the films. Anionic LYVS dye introduced a permselectivity against anions (e.g., Fe(CN)6(4)-, ascorbate) into the CHIT-LYVS films. The cross-linking of such films with GDI further increased their permselectivity as well as their stability. A unique combination of high permselectivity and fast ion transport in the CHIT-LYVS-GDI films is discussed in terms of the mixed-transport mechanism involving both pore and membrane diffusion in a highly hydrated chitosan matrix. The results indicate that the chemically modified chitosan is an attractive new coating for the development of fast, selective, and reversible sensors.

Carbohydrate Sequence↗
PubMed2000

Thermometric sensing of peroxide in organic media. Application to monitor the stability of RBP-retinol-HRP complex.

The stability of horseradish peroxidase (HRP) in aqueous and organic solvents is applied to develop a simple thermometric procedure to detect the binding of retinoic acid-HRP conjugate to retinol binding protein (RBP). Butanone peroxide (BP) in organic phase and hydrogen peroxide in aqueous phase is detected thermometrically on a HRP column, immobilized by cross-linking with glutaraldehyde on controlled pore glass (CPG). Acetone, acetonitrile, methanol, and 2-butanol are used for detection of BP, in the flow injection analysis (FIA) mode. A linear range between 1 and 50 mM BP is obtained in all the organic solvents with a precision of 5-7% (CV%). The magnitude and nature of the thermometric response is significantly different in each organic solvent. The stability of HRP in the organic phase is used to study the stability of a retinoic acid-HRP conjugate bound to immobilized RBP. The response of HRP (to 20 mM BP) in the retinoic acid-HRP conjugate is used as an indicator of the stability of the RBP-retinoic acid-HRP complex, after challenges with various organic/aqueous solvents. Both immobilized HRP and RBP are stable at least for 6 months. The effect of o-phenylene diamine on the thermometric response of HRP is also investigated. A scheme for the design of a thermometric retinol (vitamin A) biosensor is proposed.

Calibration↗
PubMed2006

Association of methanol and water in ionic liquids elucidated by infrared spectroscopy using two-dimensional correlation and multivariate curve resolution.

Water and methanol associations in ionic liquids (ILs) have been studied by means of FTIR spectroscopy. Spectra at different concentrations of water or methanol in ILs were obtained by means of on-line dilution using a flow injection analysis system. Spectral features in the OH stretching region revealed that most of the water and methanol molecules tended to be isolated from each other and to interact with the anion of the IL via H bonding. By means of two-dimensional correlation spectroscopy, the formation of methanol and water dimers was also detected. Multivariate curve resolution was used to recover pure spectra and concentration profiles of the different species. Methanol dimers form at concentrations higher than 0.8% (w/w) in the three studied ILs, 1-ethyl-3-methylimidazolium tetrafluoroborate (emimBF4), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). Self-association of water molecules takes place in emimBF4 and bmimBF4 at a molar ratio similar to that of methanol molecules; however, water dimers cannot be detected in bmimPF6, the most hydrophobic IL studied. No evidence was found that bigger water clusters are formed in these ILs at the studied cosolvent concentrations.

Journal Article↗
PubMed2005

Optically fabricated three dimensional nanofluidic mixers for microfluidic devices.

This paper describes a simple technique for fabricating complex, but well defined, three-dimensional (3D) networks of nanoscale flow paths in the channels of microfluidic systems. Near field scanning optical measurements reveal the optics associated with the fabrication process and the key features that enable its application to the area of microfluidics. Confocal studies of microfluidic devices that incorporate 3D nanostructures formed using this approach show that they function as efficient passive mixing elements, particularly at low Reynolds numbers. This application and others such as separation and extraction inmicrofluidic total analysis systems or lab on a chip devices represent promising areas for 3D nanostructures of this general type.

Equipment Design↗
PubMed2006

Zeptogram-scale nanomechanical mass sensing.

Very high frequency (VHF) nanoelectromechanical systems (NEMS) provide unprecedented sensitivity for inertial mass sensing. We demonstrate in situ measurements in real time with mass noise floor approximately 20 zg. Our best mass resolution corresponds to approximately 7 zg, equivalent to approximately 30 xenon atoms or the mass of an individual 4 kDa molecule. Detailed analysis of the ultimate sensitivity of such devices based on these experimental results indicates that NEMS can ultimately provide inertial mass sensing of individual intact, electrically neutral macromolecules with single-Dalton (1 amu) resolution.

Equipment Design↗
PubMed2006

Microfluidic system for planar patch clamp electrode arrays.

We present a microfluidic system integrated with disposable cell interface partitions for simultaneous patch clamp recordings. Glass-supported poly(dimethylsiloxane) (PDMS) partitions, having a 2 microm air-blown aperture, were reversibly sealed to a microfluidic system including PDMS channels with isolation valves and microfabricated Ag/AgCl electrodes. Gigaseal recordings from RBL-1 cells were obtained with a 24% success rate. Simultaneous whole cell recordings from valve-isolated electrodes were obtained.

Animals↗
PubMed2004

Electrowetting (EW)-based valve combined with hydrophilic teflon microfluidic guidance in controlling continuous fluid flow.

Electrowetting (EW)-based techniques have been widely used in manipulating discrete liquid. However, few articles discussed the controlling of continuous fluid flow by using EW-based techniques. In this paper, an EW-based valve combined with plasma-modified Teflon surface, which serves as a microfluidic guidance, in controlling continuous fluid flow has been demonstrated. The plasma-modified Teflon surface is firstly demonstrated for confining continuous fluid flow. The EW-based microfluidic device possesses the functions of a valve and a microchannel without complex moving parts and grooved microchannels. The quantitative characteristics of the EW-based valve are also studied. Propylene carbonate (PC) is firstly demonstrated as the working liquid in the EW-based device because of its applications in parallel oligonucleotide synthesis. It is found that lower valve actuation voltage reduces the deterioration of the valve and improves the valve stability.

Electrochemistry↗
PubMed2005

Microfabricated arrays of femtoliter chambers allow single molecule enzymology.

Precise understanding of biological functions requires tools comparable in size to the basic components of life. Single molecule studies have revealed molecular behaviors usually hidden in the ensemble- and time-averaging of bulk experiments. Although most such approaches rely on sophisticated optical strategies to limit the detection volume, another attractive approach is to perform the assay inside very small containers. We have developed a silicone device presenting a large array of micrometer-sized cavities. We used it to tightly enclose volumes of solution, as low as femtoliters, over long periods of time. The microchip insures that the chambers are uniform and precisely positioned. We demonstrated the feasibility of our approach by measuring the activity of single molecules of beta-galactosidase and horseradish peroxidase. The approach should be of interest for many ultrasensitive bioassays at the single-molecule level.

Biological Assay↗
PubMed2005

A microfluidic culture platform for CNS axonal injury, regeneration and transport.

Investigation of axonal biology in the central nervous system (CNS) is hindered by a lack of an appropriate in vitro method to probe axons independently from cell bodies. Here we describe a microfluidic culture platform that polarizes the growth of CNS axons into a fluidically isolated environment without the use of targeting neurotrophins. In addition to its compatibility with live cell imaging, the platform can be used to (i) isolate CNS axons without somata or dendrites, facilitating biochemical analyses of pure axonal fractions and (ii) localize physical and chemical treatments to axons or somata. We report the first evidence that presynaptic (Syp) but not postsynaptic (Camk2a) mRNA is localized to developing rat cortical and hippocampal axons. The platform also serves as a straightforward, reproducible method to model CNS axonal injury and regeneration. The results presented here demonstrate several experimental paradigms using the microfluidic platform, which can greatly facilitate future studies in axonal biology.

Animals↗
PubMed1997

Acoustic waves and the real-time study of biochemical macromolecules at the liquid/solid interface.

The adsorption of the proteins, bovine serum albumin, fibrinogen, avidin and neutravidin (non-glycosylated form of avidin) to a variety of surfaces imposed on thickness shear mode sensors in examined in a flow-injection analysis format. In all cases, adsorption of these moieties was essentially irreversible, although the magnitude of adsorption was dependent on surface free energy and functional group chemistry. Also described is the direct, real-time detection of the binding of peptides to HIV-1 TAR RNA bound on a thickness-shear mode (TSM) sensor surface. The results clearly indicate that responses are discriminatory for two different peptides. In order to provide a theoretical backcloth for the experimental measurements, a new model for the operation of the TSM in liquids is presented.

Acoustics↗
PubMed1997

Microbial detection by a glucose biosensor coupled to a microdialysis fibre.

The use of a glucose biosensor coupled to microdialysis sampling in a flow injection analysis system is described to follow the growth of Escherichia coli in a glucose-containing liquid culture medium. The experimental set-up permitted a throughput rate of 25 samples h-1. Growth curves were modelled by a modified Gompertz equation, which permitted the determination of lag time and maximum specific growth rate. The time required to produce an appreciable variation in the biosensor response (minimum detection time, MDT) was determined. A plot of MDT versus microbial concentration was found to be linear in the range 10(6)-10(10) colony forming units (cfu) ml-1. A microbial concentration of 10(6) cfu ml-1 can be detected after about 5 h.

Bacteriological Techniques↗
PubMed1998

Photochemically induced fluorimetric detection of tianeptine and some of its metabolites. Application to pharmaceutical preparation.

The photochemically induced fluorescence (PIF) properties of tianeptine and some of its metabolites were investigated in acidic (pH 2.3) water-alcohol mixtures at room temperature. Two PIF methods were developed, including bulk solution and flow injection analysis (FIA). Linear calibration plots were established over a concentration range of more than one order of magnitude. Limits of detection ranged from 15 ng ml-1 for FIA-PIF to 25 ng ml-1 in bulk solution. The RSDs were between 3 and 5%. The PIF methods were applied to the determination of tianeptine in a pharmaceutical preparation with recoveries varying from 96 to 106% in bulk solutions and from 98 to 106% for FIA-PIF.

Antidepressive Agents, Tricyclic↗
PubMed1999

Evaluation of the 'antioxidant power' of olive oils based on a FIA system with amperometric detection.

A new method for the evaluation of the 'total antioxidant power' of olive oils, based on a flow injection analysis system with electrochemical detection, is described. It represents a attractive alternative to the mostly used Rancimat method since it is based on the chemical structure of antioxidants and does not require the manipulation of several parameters, such as temperature and oxygen pressure, to accelerate oil oxidation. The proposed procedure is simple, rapid, allows a throughput of 90 samples h-1 and provides a good precision: an RSD of 3.5% was obtained for caffeic acid at the concentration level of 5 mg L-1 (n = 12). A comparison of the proposed was obtained for caffeic acid at the concentration level of 5 mg L-1 (n = 12). A comparison of the proposed procedure with two other methods (Rancimat method and ABTS.+ decoloration assay) was performed to investigate the applicability and limitations of the proposed method.

Antioxidants↗
PubMed2000

Trace level determination of perchlorate in water matrices and human urine using ESI-FAIMS-MS.

High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates perchlorate from interfering isobaric ions of bisulfate and dihydrogenphosphate in the gas-phase. The use of a new FAIMS prototype and waveform generator, along with the use of a mixed carrier gas, in this electrospray ionisation (ESI)-FAIMS-mass spectrometry (MS) study gave a detection limit for perchlorate in a relatively "clean" matrix of tap water of 0.050 ppb. Flow injection analysis (FIA) of dilutions of fortified waste water, a fortified river water certified reference material (CRM; SLRS-4, National Research Council of Canada), and a fortified human urine Standard Reference Material (SRM; 2381, National Institute of Standards and Technology) gave detection limits of 0.37 ppb, 0.50 ppb, and 4.8 ppb, respectively, in the undiluted matrices.

Environmental Monitoring↗
PubMed2001

Speciation of nickel in airborne particulate matter by means of sequential extraction in a micro flow system and determination by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

A four-stage sequential extraction procedure for the speciation of nickel has been applied to ambient aerosol samples. The determination of the soluble, sulfidic, metallic and oxidic Ni fractions in particulate matter was carried out by graphite furnace (electrothermal) atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). An EDTA solution, a mixture of diammonium citrate and hydrogen peroxide, and a KCuCl3 solution were used as leaching agents for the determination of the soluble, sulfidic and metallic species, respectively, and nitric acid was used for the determination of oxidic compounds after microwave digestion of particulate matter sampled on filters. A new micro scale filter holder placed in a closed flow injection analysis (FIA) system for use in nickel speciation by means of sequential extraction, and the results of the optimisation of the extraction conditions are described. The temperature program for ETAAS was optimised for all extraction solutions with the aid of temperature curves. Pyrolysis temperatures of 900. 600 and 1,000 degrees C were found to be optimum for EDTA, hydrogen peroxide plus ammonium citrate and KCuCl3-containing solutions, respectively. Airborne dust was sampled on lilters at two locations near to a metallurgical plant in Dortmund, Germany. Concentrations in the low ng m(-3) range down to the detections limits (0.1-0.3 ng m(-3)) and various nickel species were found to be present in the collected dust. The mean fractions of total nickel (sampling period of one month) were found to contain 36+20% of soluble, 6 +/- 4% of sulfidic, 11 +/- 15% of metallic and 48 +/- 18% of oxidic nickel.

Air Pollutants↗
PubMed2002

Selective determination of hydrogen peroxide by adduct formation with a dinuclear iron(III) complex and flow injection analysis/tandem mass spectrometry.

A highly selective method for the determination of hydrogen peroxide is presented. In a flow injection analysis (FIA) instrument, the analyte is brought into contact with a dinuclear heptadentate iron(III) complex. The formation of the peroxide adduct is quantified using electrospray tandem mass spectrometry (ESI-MS/MS). Selected reaction monitoring (SRM) based on the transition from the triply charged peroxide adduct with m/z = 251.2 to the triply charged fragment ion of m/z = 240.5 is performed. The limit of detection for hydrogen peroxide is 10(-7) mol dm(-3), limit of quantification is 3 x 10(-7) mol dm(-3), and a linear range of 2.5 decades starting at the limit of quantification is observed.

Journal Article↗
PubMed2004

Automated, controlled deposition of nanoparticles on polyelectrolyte-coated silicon from chemomechanically patterned droplet arrays.

This paper describes three advances in lab on a chip technology. First, it is shown that chemomechanical surface patterning can be performed using a commercially available liquid handler that has undergone only minor modifications. These capabilities are demonstrated by making and then characterizing smaller hydrophobic corrals, made with a diamond tip, than have previously been reported. Hydrophobic corrals are small enclosures on a surface that are ringed by hydrophobic lines. They hold droplets of high surface tension solutions. They allow a surface to be subdivided into individually addressable elements, thus providing a platform for conducting many simultaneous surface experiments with small (down to ca. 1 microL) liquid volumes. An important consequence of this work is that it makes chemomechanical surface patterning, which is a valuable and straightforward method for surface modification, much more accessible to the technical community. Second, it is shown that an entire array of hydrophobic corrals can be simultaneously coated with polyelectrolyte multilayers, but that the hydrophobic corrals still retain the ability to hold liquids after this deposition. The robotic arm of the liquid handler is again employed to manufacture this ultrathin film. Finally, as a demonstration of the capability of this technology to create complex patterned arrays on surfaces from solution for biological or nanostructured materials applications, and again employing the liquid handler, polyelectrolyte-coated hydrophobic corrals are individually addressed and loaded with a solution containing gold nanoparticles for independently specified times. The density and morphology of deposited nanoparticle monolayers were studied by scanning electron microscopy. The deposition of gold nanoparticles onto a chip occurred at a constant rate (0.5% min(-1)) over the range of times studied.

Adsorption↗
PubMed2004

Rapid PCR in a continuous flow device.

Continuous flow polymerase chain reaction (CFPCR) devices are compact reactors suitable for microfabrication and the rapid amplification of target DNAs. For a given reactor design, the amplification time can be reduced simply by increasing the flow velocity through the isothermal zones of the device; for flow velocities near the design value, the PCR cocktail reaches thermal equilibrium at each zone quickly, so that near ideal temperature profiles can be obtained. However, at high flow velocities there are penalties of an increased pressure drop and a reduced residence time in each temperature zone for the DNA/reagent mixture, that potentially affect amplification efficiency. This study was carried out to evaluate the thermal and biochemical effects of high flow velocities in a spiral, 20 cycle CFPCR device. Finite element analysis (FEA) was used to determine the steady-state temperature distribution along the micro-channel and the temperature of the DNA/reagent mixture in each temperature zone as a function of linear velocity. The critical transition was between the denaturation (95 degrees C) and renaturation (55 degrees C-68 degrees C) zones; above 6 mm s(-1) the fluid in a passively-cooled channel could not be reduced to the desired temperature and the duration of the temperature transition between zones increased with increased velocity. The amplification performance of the CFPCR as a function of linear velocity was assessed using 500 and 997 base pair (bp) fragments from lambda-DNA. Amplifications at velocities ranging from 1 mm s(-1) to 20 mm s(-1) were investigated. The 500 bp fragment could be observed in a total reaction time of 1.7 min (5.2 s cycle(-1)) and the 997 bp fragment could be detected in 3.2 min (9.7 s cycle(-1)). The longer amplification time required for detection of the 997 bp fragment was due to the device being operated at its enzyme kinetic limit (i.e., Taq polymerase deoxynucleotide incorporation rate).

Bacteriophage lambda↗