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 1,135 records · Page 63Linked to original sources
PubMed1995

Reliable and sensitive method for determination of microcystins in complicated matrices by frit-fast atom bombardment liquid chromatography/mass spectrometry.

A reliable and sensitive method for determination of hepatotoxic microcystins in complicated matrices by frit-fast atom bombardment liquid chromatography/mass spectrometry (Frit-FAB LC/MS) is described. Immonium ions of constituent amino acids, which were obtained together with molecular ion species by FAB mass spectral analysis of standard microcystins RR, YR, LR, and [D-Asp3] and [Dha7]microcystins LR using flow injection system composed of Frit-FAB probe, showed potential for reliable identification of microcystins by Frit-FAB LC/MS. Frit-FAB LC/MS using a microbore column provided not only the baseline separation of standard microcystins RR, YR, and LR but 200-fold higher sensitivity than that using conventional column. Furthermore, when a selected ion monitoring (SIM) technique was used, the detection limits of microcystins RR, YR, and LR were 300, 350, and 400 pg, respectively, at a signal-to-noise ratio of 5:1, and calibration curves of each microcystin showed a linear relationship from 2 ng to 50 ng. Finally, identification and quantitative analyses of microcystins in water samples were carried out.

Chromatography, Liquid↗
PubMed2003

Development of a displacement immunoassay for human heart-type fatty acid-binding protein in plasma: the basic conditions.

To risk-stratify patients with chest pain who are admitted to emergency rooms and for whom initial evaluation is not conclusive, the use of cardiac markers has become a standard procedure. A recently introduced early plasma marker for acute myocardial infarction (AMI) is the 14.5-kDa cytoplasmic heart-type fatty acid-binding protein (FABP). To fully exploit its early release from injured myocardium, a rapid method for repeated measurements or continuous monitoring of FABP in plasma is desirable. Such an on-line method could be an immunosensor based on displacement. The aim of the present study was to further investigate the principles underlying the displacement assay of FABP, both in buffer and in plasma. Batches of sepharose-bound FABP were loaded with an antibody-horseradish peroxidase (HRP) conjugate (anti-FABP). Continuous measurement of FABP was mimicked by repeated addition of FABP containing solutions followed by several washing steps. In the presence of free FABP the antibody-HRP complex dissociated and was subsequently quantified. Significant displacement in the presence of free FABP was observed in both buffer and human plasma. Anti-FABP could be intermittently displaced in the same batch, for at least 9 h, and the displacement was concentration-dependent. These results show the feasibility of a sensor based on the displacement principle to be used for the diagnosis of AMI in emergency medicine.

Biosensing Techniques↗
PubMed2005

Determination of active ingredient within pharmaceutical preparations using flow injection mass spectrometry.

Two separate pharmaceutical blends, one containing 2% caffeine by weight, the other containing 2% creatine by weight, and 200 mg caffeine tablets were examined in this study. The purpose of the analyses was to determine the feasibility of using flow injection mass spectrometry for the quantitative analysis of active ingredient within a drug product or other form of pharmaceutical preparation. For more precise and accurate measurements, it was necessary to incorporate an internal reference within the samples. Further, flow injection analysis showed to provide quicker, more facile method development than the application of chromatographic separation. Samples were analyzed over an analyte concentration range of 5.0-15.0 microg/mL. Analyte selectivity was obtained through the observance of the (M+H)(+) ions generated by positive electrospray ionization of each of the analytes (m/z 195 for caffeine and m/z 132 for creatine), and accurate quantitation was achieved by determining the ratio of the analyte response versus the response of the incorporated reference compound. Sample-to-sample precision in these measurements was less than 3%, recovery values were shown to be accurate to within +/-3% of the actual values, and both analytical methods proved to be linear over the assay range (R(2)> or =0.999). Due to the excellent selectivity and low detection limits available to mass spectrometric detection, flow injection mass spectrometric analysis could be particularly applicable for analysis of formulations that contain either low doses of active ingredient, active ingredient with low solubility, or active ingredient that does not possess a strong chromophore. Additionally, this type of methodology shows to be conducive for rapid method development.

Amino Acids↗
PubMed2006

Development of sequential injection-lab-at-valve (SI-LAV) micro-extraction instrumentation for the spectrophotometric determination of an anionic surfactant.

The development of instrumentation for sequential injection analysis with a "lab-at-valve" (SIA-LAV) micro-extraction system is presented. The extractive determination of an anionic surfactant using methylene blue was selected as a model. Sample, reagents and organic solvent were sequentially aspirated into an extraction coil connected to the center of a selection valve, where extraction took place by flow reversal. The aqueous and organic phases were separated in a LAV unit attached to one port of the valve. The LAV unit situated a fiber-optic spectrophotometer to monitor the absorbance change of the extract product in the organic phase. The developed SIA-LAV system offers an alternative micro-total analysis system for automated micro-extraction.

Anions↗
PubMed1997

Equilibrium and kinetic study of the conformational transition toward the active state of p21Ha-ras, induced by the binding of BeF3- to the GDP-bound state, in the absence of GTPase-activating proteins.

Hitherto ras-related GTP-binding proteins have been considered not to bind phosphate analogs (Kahn, R. A. (1991) J. Biol. Chem. 266, 15595-15597), at least in the absence of activating proteins (Mittal, R., Reza, M., Goody, R., and Wittinghofer, A. (1996) Science 273, 115-117). In this work, we have used a fluorescent active mutant (Y32W) of p21(Ha-)ras to demonstrate that BeF3- binds to the GDP. p21(Ha-ras) complex in the absence of activating proteins. It induces a conformational change leading to a state with fluorescence properties similar to those of the active state. The binding has a low affinity (Kd at 25 degrees C = 8.1 +/- 0.3 mM) and is endothermic (DeltaH = 22.3 +/- 1.6 kJ mol-1). The similarity between the GTP-bound form and the GDP.BeF3--bound form has been confirmed using lifetime analysis of the tryptophan fluorescence. The kinetic analysis of the process indicates that the binding can be divided into a first bimolecular step, which accounts for the association of the anion with its binding site, and a second step, which corresponds to an internal conformational transition of the GDP. BeF3-.p21(Ha-)ras complex to its final state. Both steps are endothermic (DeltaH1 = 15 +/- 2 kJ mol-1 and DeltaH2 = 8 +/- 2 kJ mol-1). The kinetically determined enthalpy change of 23 +/- 4 kJ mol-1 is in excellent agreement with the equilibrium analysis.

Anions↗
PubMed2006

Flow-injection solvent extraction without phase separation. Fluorimetric determination of thiamine by the thiochrome method.

Two modes of liquid-liquid extraction in flow-injection systems were compared and applied to the fluorimetric determination of thiamine (Vitamin B(1)). The first included phase segmentation, but fluorescence was measured without phase separation. In this mode, thiamine was detected at concentrations higher than 8 microg/l with a linear application range of 30-2,000 microg/l, an R.S.D. of 1.9% (150 microg/l, n=10) and a sampling frequency of 60/h. In the second mode, a single segment of organic solution was injected into the aqueous stream and fluorescence was also measured without phase separation. Using this mode, concentrations of thiamine higher than 1 microg/l were detected, with a linear application range between 5 and 280 microg/l, an R.S.D. of 2.4% (150 microg/l, n=10) and a sampling frequency of 60/h. The two forms were applied to the analysis of thiamine in pharmaceuticals.

Flow Injection Analysis↗
PubMed2005

The use of turbulent flow chromatography and the isocratic focusing effect to achieve on-line cleanup and concentration of neat biological samples for low-level metabolite analysis.

The use of turbulent flow chromatography in conjunction with column switching isocratic focusing was used to perform on-line sample cleanup and concentration of neat rat plasma for the identification of low-level metabolites. The concentration was achieved by focusing multiple injections, which were cleaned by a turbulent flow column, onto an analytical column prior to elution into the mass spectrometer. In addition, the first application of turbulent flow chromatography for on-line sample cleanup of neat bile samples is reported. The on-line cleanup and concentration method extracts and concentrates a sample 20-fold in 1 h, and is completely automated.

Anatomy, Comparative↗
PubMed2002

Chemiluminescence flow-through sensor for the determination of vitamin B2 using controlled-reagent-release technology.

AIM: To establish a simple and novel method for the determination of vitamin B2 rapidly in pharmaceutical preparations. METHODS: Vitamin B2 was determined by a chemiluminescence (CL) sensor combined with flow-injection (FI) technology. The analytical reagents involved in the CL reaction, luminol and hexacyanoferrate (III), were both immobilized on an anion-exchange resin column in FI system. The CL signal produced by the reaction between luminol and hexacyanoferrate (III), which were eluted from the column through sodium phosphate injection, decreased in the presence of vitamin B2. RESULTS: The decreased CL intensity was linearly correlated with the vitamin B2 concentration in the range of 0.01-1.0 microgram.mL-1, the detection limit was 4.0 ng.mL-1 vitamin B2 (3 sigma). At a flow rate of 2.0 mL.min-1, the procedure including sampling and washing could be performed in 2 min with a relative standard deviation of less than 3.0%. CONCLUSION: The flow sensor exhibited both good sensitivity and stability. It could be reused more than 450 times and has been applied successfully to the analysis of vitamin B2 in pharmaceutical preparations.

Flow Injection Analysis↗
PubMed2003

Theoretical and experimental study of binary perturbation peaks with focus on peculiar retention behaviour and vanishing peaks in chiral liquid chromatography.

The perturbation peak theory was recently developed for acquiring binary isotherm data using the perturbation method (PM) and it was applied for some chiral systems. However, the binary plateaus of these systems were only weakly to moderately nonlinear. In this article the perturbation theory for LC, is developed for both retention times and peak areas and is verified by systematic experiments over the whole range of non-linearity. Attention is focused on non-linear effects that complicate the proper use of the PM method under moderately to strongly non-linear conditions. A serious complication was that the second perturbation peak vanished already at moderate plateau concentrations. A solution to this problem based on a firm theoretical basis and verified experimentally is presented. We also investigated a peculiar retention dependence on the binary plateau concentration, as the retentions of the two perturbation peaks of the binary plateau was compared with the single plateau peak of the more retained enantiomer.

Analysis of Variance↗
PubMed2001

Flow-injection spectrophotometric determination of certain cephalosporins based on the formation of dyes.

A flow-injection spectrophotometric method is described for the determination of cefadroxil (I) and cefotaxime (II). The method is based on the hydrolysis of the cephalosporin with sodium hydroxide whereby the sulfide ion is produced. The latter is allowed to react with N,N-diethyl-p-phenylenediamine sulfate (N,N-DPPD) and Fe (III), and the blue color produced is measured at 670 nm (method A). Linear calibration graphs are obtained in the range 36.34-109.2 and 95.48-477.4 microgml(-1) for I and II, respectively. The experimental limits of detection (three times the noise signal) are 0.036 and 0.048 microgml(-1) for I and II, respectively. The total flow-rate is 5.3 ml min(-1) for both drugs. Alternately, the sulfide ion produced is allowed to react with p-phenylenediamine dihydrochloride (PPDD) and Fe (III), and the violet color produced is measured at 597 nm (method B). Linear calibration graphs are obtained in the range 0.5-400 and 0.5-450 microg ml(-1) for I and II, respectively. The limits of detection are 0.4 and 0.2 microg ml(-1) for I and II, respectively. The total flow-rate is 3 ml min(-1) for both drugs. The methods have been successfully applied to the analysis of some pharmaceutical formulations, particularly of the injection and capsule types. The relative standard deviation (RSD) (n = 10) at the 50 and 100 microg ml(-1) levels of I and II were 0.83-0.77 and 0.9-0.8% with N,N-DPPD and PPDD as reagents, respectively. Recoveries were quantitative; the results obtained agreed with those obtained by other reported methods.

Cefadroxil↗
PubMed2001

A rapid method for peroxide value determination in edible oils based on flow analysis with Fourier transform infrared spectroscopic detection.

The development of an automated, rapid and highly precise method for determination of the peroxide value in edible oils based on a continuous flow system and Fourier transform infrared (FTIR) spectroscopic detection is described. The sample stream was mixed with a solvent mixture consisting of 25% (v/v) toluene in hexanol which contained triphenylphosphine (TPP). The hydroperoxides present in the sample reacted stoichiometrically with TPP to give triphenylphosphine oxide (TPPO) which has a characteristic and intense absorption band at 542 cm-1. A 10% (m/v) TPP solution in the solvent mixture and a 100 cm reaction coil were necessary for complete reaction. FTIR transmission spectra were recorded using a flow cell equipped with CsI windows having an optical pathlength of 100 microns. By using tert-butyl hydroperoxide spiked oil standards and evaluation of the band formed at 542 cm-1 a linear calibration graph covering the range 1-100 PV (peroxide value; mequiv O2 kg-1 oil) was obtained. The relative standard deviation was 0.23% (n = 11) and the throughput 24 samples h-1. The developed system was also applied to the determination of PV in olive, sunflower and corn oils, showing good agreement with the official reference method of the European Community which is based on titration using organic solvents. The results obtained clearly show that the developed method is superior to the standard wet chemical method, hence suggesting its application in routine analysis and quality control.

Flow Injection Analysis↗
PubMed2005

A micro-chemiluminescence determination of cyanide in whole blood.

A reactant volume self-controlled micro-device was presented and applied to the flow injection chemiluminescence (CL) for determination of cyanide in whole blood. A mini distiller was fabricated for cyanide extraction from the blood samples with the extraction efficiencies of cyanide > or = 98%. A fluidic control platform with air driving was fabricated. The described system showed the features of easy fabrication, undiluted sample injection, safe analysis operation, and suitability for automatic cyanide analysis. The calibration curve showed linearity in the cyanide concentration range of 5.0 x 10(-7) to 5.0 x 10(-5) mol l(-1) with the detection limits (3sigma) of 2.3 x 10(-7) mol l(-1). CL peak-height precision was 1.9% R.S.D. (n = 11) at the 1.0 x 10(-6) mol l(-1) cyanide level. The new devices were applied to the analysis of cyanide in rabbit whole blood samples and the results agreed well with those obtained from official method.

Animals↗
PubMed2006

Electrochemical immunoassay for vitellogenin based on sequential injection using antigen-immobilized magnetic microbeads.

A rapid and sensitive immunoassay for the determination of vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with an amperometric detector and a neodymium magnet. Magnetic beads, onto which an antigen (Vg) was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of magnetic beads in an immunoreaction cell were controlled by means of the neodymium magnet and by adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an alkaline phosphatase (ALP) labeled anti-Vg monoclonal antibody between the fraction of Vg immobilized on the magnetic beads and Vg in the sample solution. The immobilization of Vg on the beads involved coupling an amino group moiety of Vg with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactate film. The Vg-immobilized magnetic beads were introduced and trapped in the immunoreaction cell equipped with the neodymium magnet; a Vg sample solution containing an ALP labeled anti-Vg antibody at a constant concentration and a p-aminophenyl phosphate (PAPP) solution were sequentially introduced into the immunoreaction cell. The product of the enzyme reaction of PAPP with ALP on the antibody, paminophenol, was transported to an amperometric detector, the applied voltage of which was set at +0.2 V vs. an Ag/AgCl reference electrode. A sigmoid calibration curve was obtained when the logarithm of the concentration of Vg was plotted against the peak current of the amperometric detector using various concentrations of standard Vg sample solutions (0-500 ppb). The time required for the analysis is less than 15 min.

Antibodies, Monoclonal↗
PubMed1996

Colorimetric determination of astemizole in bulk and in its pharmaceutical dosage forms using flow injection.

A continuous flow spectrophotometric method for determining 0.5-100 micrograms ml-1 of astemizole in pure and in dosage forms is suggested. It depends on forming a pinkish orange product which can be quantified spectrophotometrically at 495 nm. The coloured product was due to the action of N-bromosuccinimide on astemizole in alkaline medium and in the presence of a cetyltrimethylammonium bromide micellar medium. The procedure is automated and solutions can be analysed at a rate of 167 h-1 with a relative error of about 1.25%. The limit of detection is 0.5 microgram ml-1 (approximately 1.09 x 10(-6) M). The method is evaluated by a recovery study and by the analysis of commercial formulations.

Astemizole↗
PubMed2003

Quantitative liquid chromatography-mass spectrometry determination of catechins in human plasma by automated on-line extraction using turbulent flow chromatography.

A simple, fast and sensitive liquid chromatography-mass spectrometry (LC-MS) method with automated on-line extraction using turbulent flow chromatography (TFC) for the determination of five catechins in human plasma was developed. In this method, after on-line extraction by its injection onto an extractor column at turbulent flow, five catechins were backwashed onto a reversed phase column via on-line column switching and separated chromatographically at a laminar flow of 1 ml min(-1). Using this tandem LC-LC-MS system, the extraction, the separation and the quantitation of five catechins in human plasma could be achieved with satisfactory selectivity and sensitivity. The limit of detection (S/N = 3) ranged from 0.6 to 2 ng ml(-1). The described procedure was very simple and rapid since no off-line sample preparation was required, total analysis time being 18.5 min.

Catechin↗