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PubMed2006

Development of enzyme flow calorimeter system for monitoring of microbial glycerol conversion.

Glycerokinase from Cellulomonas sp. was used to develop biosensor based on flow calorimetry for quantitative analysis of glycerol during bioconversion process. An automatic flow injection analysis device with the glycerol biosensor was built and tested during growth on glycerol of 1,3-propanediol-producing bacteria. The biosensor exhibited an extreme storage and operational stability enabling us to use it for more than 2 years without significant loss of sensitivity. No interference with 1,3-propanediol and fermentation medium was observed. The linear range of glycerol concentration up to 70 mM was extended by developed automatic dilution technique with the aim of automatic online monitoring of microbial process. The analytical system was able to monitor the bioconversion process in a fully automatic way during the whole run with sampling frequency of one sample per 10 min.

Bacteria↗
PubMed1991

Development of a turbidimetric immunoassay for on-line monitoring of proteins in cultivation processes.

An on-line assay for a thermostable pullulanase and antithrombin III (AT III) is described. The assay is based on the formation of aggregates between the protein to be measured and antibodies raised against this protein. Assay automation was achieved by utilizing the flow injection analysis (FIA) principles. The apparatus, a stopped-flow, merging-zone manifold, is described in detail. Since the reaction used in an FIA system does not have to reach equilibrium, it was possible to reduce the time for an assay cycle to 2.5 min. A method for simulating cultivation conditions was developed for assay optimization. Using this method, a detection limit of 1 mg l-1 together with a standard deviation of 1.5 was found. A sandwich ELISA was used as reference assay in the case of AT III and an enzymatic activity assay in the case of pullulanase. Correlation coefficients of 0.988 (AT III) and 0.976 (pullulanase) were determined. The turbidimetric assay was successfully used for pullulanase monitoring during a 240-h cultivation of Clostridium thermosulfurogenes.

Antigen-Antibody Complex↗
PubMed1989

Coronaspray nebulization and ionization of liquid samples for ion mobility spectrometry.

Ion mobility spectrometry after electrospray nebulization and ionization was investigated as a method for the detection of components dissolved in liquids. While electrosprary operating conditions proved promising, greater sensitivity was achieved when the electric potential applied to the sample introduction needle was increased above breakdown potential and a corona discharge was established. Passing the liquid through the corona discharge established a "coronaspray" that efficiently nebulized and ionized the solvent and analytes. In this initial investigation of coronaspray ion mobility spectrometry (CIMS), ion current as a function of potential, temperature, and liquid flow rate was studied; several IMS spectra were obtained; and a continuous monitoring mode of operation was demonstrated. The results from this study indicated that CIMS has potential as a versatile and sensitive detection method for a variety of analytical procedures involving liquid flowing streams such as flow injection analysis, liquid chromatography, capillary zone electrophoresis, and field flow fractionation.

Electrochemistry↗
PubMed1997

Microfabricated flow chamber for fluorescence-based chemistries and stopped-flow injection cytometry.

A microfabricated flow chamber (MFC) suitable for performing liquid-based fluorimetric assays is introduced. Precision delivery of microliter volumes of sample and reagent to the MFC is accomplished by a double-syringe-pump flow injection analysis (FIA) apparatus. The FIA-MFC system also combines the 'sheath flow' technique (traditionally used in flow cytometry) and stopped-flow FIA as a way to allow sample and reagent streams to be mixed reproducibly. The applicability of this FIA-MFC system to bioanalytical assays is demonstrated by performing an enzymatic assay with an artificial fluorigenic substrate to determine the activity of Savinase, a proteolytic enzyme. When coupled to a fluorescence microscope platform, quantitative analysis of the reaction product is possible. Experiments showed that the FIA-MFC system was capable of performing the assay with good reproducibility of injection (1.5%), and linearity of response (r2 = 0.9997) in activity ranges of analytical interest. Owing to the incorporation of flow cytometry sheath flow principles into an FIA format, the FIA-MFC system is a suitable tool for cytometric studies.

Detergents↗
PubMed2000

Fractionation of nickel species from airborne aerosols: practical improvements and industrial applications.

Presently recommended methods for fractionation of airborne nickel dusts are laborious and time-consuming. A new method has been developed based on existing procedures of leaching nickel fractions from sample filters, and based on the principles of flow-injection analysis. A special sample filter holder has been constructed to be used in conjunction with the flow-injection system. In this system, soluble nickel compounds are extracted from the filter with ammonium citrate buffer, sulphidic nickel by peroxycitric acid, and metallic nickel by CuCl2/KCl. The final dissolution of the filter by HNO3/HCl results in the oxidic fraction. Endpoint determination of these fractions is performed by use of graphite-furnace atomic absorption spectrometry (GF-AAS). The analytical criteria of this method have been established, and the suitability of the method for application in the practice of industrial hygiene has been demonstrated.

Aerosols↗
PubMed2005

[Determination of nitrite in water samples by sequential injection analysis with chemiluminescence detection on chip flow cell].

A sequential injection chemiluminescence's system using a chip flow cell was described for the determination of trace amount of nitrite in water samples. Nitride reacted with hydrogen peroxide to form peroxynitrous acid in sulfuric acid medium, which was an unstable in acid medium and subsequently was quenched into peroxynitrite in basic solution. During the composition of peroxynitrite the chemiluminescence intensity was enhanced with the presence of uranin and ethyldimethylcetylammonium bromide. The reaction coil (flow cell) and holding coil was combined for tracking the emission signal. The experimental parameters including physical and chemical parameter were optimized. The interference of cations in water samples was eliminated by passing previously the sample solution through a cation-exchange column. The linear range of the calibration graph was obtained from 1 x 10(-6) to 1 x 10(-4) mol x L(-1) with a correlation coefficient of 0.9998. The detection limit at 95% confidence was 6.8 x 10(-7) mol x L(-1). The relative standard deviation at 1 x 10(-5) mol x L(-1) nitrite level was 2.7%, and the recovery of 90%-99% and the sampling frequency of 80 h(-1) were obtained.

Calcium↗
PubMedDate not supplied

Inorganic, organic, and total mercury in blood and urine: cold vapor analysis with automated flow injection sample delivery.

A cold vapor atomic absorption technique for blood or urine mercury analysis that uses persulfate oxidation to prepare samples for total mercury analysis and acid permanganate oxidation to prepare samples for inorganic mercury analysis is described. The linearity of the procedures ranged from 0.5 to 25 micrograms/L. Precision ranged from 20% at 1 microgram/L to 7% at 20 micrograms/L. Documentation of accuracy is based on analysis of samples prepared by an international proficiency survey program. The development of a two-step digestion procedure followed by automated flow-injection mercury analysis was a necessary precursor to the assessment of inorganic and alkylmercury exposure in a large unexposed human population. Application of this technique to 902 blood and 902 urine samples collected from a normal human population who had no extraordinary mercury exposure generated mean plus two standard deviation skewed confidence-limit ranges of results as follows: blood total mercury, 0-8.4 micrograms/L; blood inorganic mercury, 0-1.7 micrograms/L; blood organic mercury, 0-7.5 micrograms/L; urine total mercury, 0-9.9 micrograms/L; urine inorganic mercury, 0-8.6 micrograms/L; and urine organic mercury, 0-1.8 micrograms/L.

Autoanalysis↗
PubMed2006

Flow injection amperometric determination of procaine in pharmaceutical formulation using a screen-printed carbon electrode.

A rapid and simple method for procaine determination was developed by flow injection analysis (FIA) using a screen-printed carbon electrode (SPCE) as amperometric detector. The present method is based on the amine/hydroxylamine oxidation from procaine monitored at 0.80 V on SPCE in sodium acetate solution pH 6.0. Using the best experimental conditions assigned as: pH 6.0, flow rate of 3.8 mL min(-1), sample volume of 100 microL and analytical path of 30 cm it is possible to construct a linear calibration curve from 9.0x10(-6) to 1.0x10(-4) mol L(-1). The relative standard deviation for 5.0x10(-5) mol L(-1) procaine (15 repetitions using the same electrode) is 3.2% and detection limit calculated is 6.0x10(-6) mol L(-1). Recoveries obtained for procaine gave a mean values from 94.8 to 102.3% and an analytical frequency of 36 injections per hour was achieved. The method was successfully applied for the determination of procaine in pharmaceutical formulation without any pre-treatment, which are in good accordance with the declared values of manufacturer and an official method based on spectrophotometric analysis.

Anesthetics, Local↗
PubMed1999

Cyclodextrin-based optosensor for the determination of warfarin in waters.

A flow-through optosensor for warfarin is described. The sensor is developed in conjunction with flow analysis systems and uses a commercial bound beta-cyclodextrin material as the sensing phase. A strong fluorescence signal was observed as a result of the formation of an inclusion complex between warfarin and beta-cyclodextrin. The analytical performance characteristics of the proposed sensor for analysis of low levels of warfarin were as follows: the detection limits for continuous and flow injection analysis systems were 2 and 19 ppb, respectively; the observed relative standard deviations at 0. 5 ppm warfarin level were less than 2.3%. A study of the interference of other naphthalenic toxic substances was carried out. The continuous flow method was satisfactorily applied to the determination of the rodenticide in natural waters.

Agriculture↗
PubMedDate not supplied

Rapid optimization of the post-column fluorogenic ninhydrin reaction for the HPLC-based determination of bradykinin and related fragments.

A flow injection analysis scheme is demonstrated for the rapid optimization of reagent concentrations, flow rates, delay time and temperature using the guanidino moiety specific fluorogenic ninhydrin reaction. Using the amino acid arginine, non-arginine containing peptides, and the arginine-containing peptides, bradykinin and related fragments, specificity is demonstrated. These results serve to extend previous descriptions of the post-column reaction by offering a time efficient approach for the optimization of newly assembled post-column reactors using this chemistry. The reactor is subsequently added to a gradient elution HPLC system with the separation of bradykinin and bradykinin fragments demonstrated. Detection sensitivity in the high femtomole-low picomole mass range was achieved for these substances.

Bradykinin↗
PubMed1991

Monitoring and control of biotechnological production processes by Bio-FET-FIA-sensors.

Single and multisensor field effect transistors (FET) with a pH-sensitive Si/SiO2/Si3N4/Ta2O5-gate and reference electrode (for single sensor) were developed and used for manufacturing the following biological (Bio)-FETs: for glucose analysis, glucose oxidase-FET (GOD-FET); for urea analysis, urease-FET; and for cephalosporin C analysis, cephalosporinase-FET. The GOD-FETs were integrated into flow injection analysis (FIA) of the Eppendorf variables analyser (EVA) system and used for monitoring the glucose concentration in microbial cultivation and production processes with recombinant Escherichia coli K12 MF, recombinant E. coli JM103, Saccharomyces cerevisiae H620, and Candida boidinii. Urease-FET-FIA was used to monitor the urea concentration in a simulated cultivation of Cephalosporium acremonium and urease-FET-FIA and GOD-FET-FIA for the monitoring of urea and glucose concentrations in simulated S. cerevisiae cultivations.

Acremonium↗
PubMed1994

Immobilized enzymes as tools in food analysis.

A lot of publications described the possibilities of using selective enzymatic reactions in analysis, but not much authors described applications for the analysis of real samples. In this paper important publications, which described different applications in food analysis, are reviewed. In the first section the use of biosensors for food analysis, in the second section the combination of immobilized enzymes and flow injection analysis and in the last section the use of immobilized enzymes in combination with HPLC are described. Most of the applications described used enzymes for the determination of sugars mainly glucose, but also methods for the determination of inhibitors in foods are described.

Amino Acids↗
PubMed2002

Modified carbon paste electrodes for flow injection amperometric determination of isocitrate dehydrogenase activity in serum.

A carbon paste electrode modified with the adsorbed products of the electrochemical oxidation of adenosine triphosphate is described. The electrode was applied to the amperometric electrocatalytic detection of the reduced form of both nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate. The catalytic oxidation current shows a linear dependence on the concentration of the reduced form of nicotinamide adenine dinucleotide up to 1x10(-4)M, with a detection limit of 5x10(-9)M. Modified carbon paste electrodes were coated with an electrogenerated film of nonconducting poly(o-phenylenediamine) to obtain a stable amperometric response for at least 150h. In addition to static measurements, determination of both reduced cofactors was carried out in a flow injection analysis system with a thin-layer amperometric detection cell. The electrocatalytic monitoring of reduced nicotinamide adenine dinucleotide phosphate was applied to flow injection measurement of isocitrate dehydrogenase activity in serum. The results were in good agreement with those for the standard spectrophotometric test kit. The proposed method consumed less time and reagents and provided better precision than the standard method.

Adenosine Triphosphate↗
PubMedDate not supplied

Postcolumn chemiluminescence as a detection technique in the liquid chromatographic analysis of beta-lactam ring containing compounds.

A broad range of compounds containing the beta-lactam ring were screened for enhancement of luminol chemiluminescence. A selection of these compounds were found to enhance the chemiluminescence of luminol. A high-performance liquid chromatographic method for the analysis of some beta-lactams employing postcolumn chemiluminescence was developed via flow injection analysis studies.

Calibration↗
PubMed2003

Development and application of a robust speciation method for determination of six arsenic compounds present in human urine.

Six arsenic species [arsenate, arsenite, arsenocholine, arsenobetaine, monomethyl arsonic acid, and dimethyl arsinic acid] present in human urine were determined using ion-exchange chromatography combined with inductively coupled plasma mass spectrometry (IC-ICP-MS). Baseline separation was achieved for all six species as well as for the internal standard (potassium hexahydroxy antimonate V) in a single chromatographic run of less than 30 min, using an ammonium carbonate buffer gradient (between 10 and 50 mM) at ambient temperature, in conjunction with cation- and anion-exchange columns in series. The performance of the method was evaluated with respect to linearity, precision, accuracy, and detection limits. This method was applied to determine the concentration of these six arsenic species in human urine samples (n = 251) collected from a population-based exposure assessment survey. Method precision was demonstrated by the analysis of duplicate samples that were prepared over a 2-year analysis period. Total arsenic was also determined for the urine samples using flow injection analysis coupled to ICP-MS. The summed concentration of the arsenic species was compared with the measured arsenic total to demonstrate mass balance.

Arsenic↗
PubMed2006

Plasma nitrite reserve and endothelial function in the human forearm circulation.

Attenuation of endothelium-derived nitric oxide (NO) synthesis is a hallmark of endothelial dysfunction. Early detection of this disorder may have therapeutic and prognostic implications. Plasma nitrite mirrors acute and chronic changes in endothelial NO-synthase activity. We hypothesized that local plasma nitrite concentration increases during reactive hyperemia of the forearm, reflecting endothelial function. In healthy subjects (n = 11) plasma nitrite and nitrate were determined at baseline and during reactive hyperemia of the forearm using reductive gas-phase chemiluminescence and flow-injection analysis, respectively. Endothelium-dependent dilation of the brachial artery was measured as flow-mediated dilation (FMD) using high-resolution ultrasound. Results were compared to patients with endothelial dysfunction as defined by reduced FMD (n = 11). Reactive hyperemia of the forearm increased local plasma nitrite concentration from 68 +/- 5 to 126 +/- 13 nmol/L (p < 0.01), whereas in endothelial dysfunction nitrite remained unaffected (116 +/- 12 to 104 +/- 10 nmol/L; n.s.), corresponding to nitrite reserves of 94 +/- 21 and -8 +/- 4%. This was accompanied by a significantly greater increase in brachial artery diameter (FMD: 8.5 +/- 0.4% vs 2.9 +/- 0.5%, for healthy subjects and endothelial dysfunction, respectively; p < 0.001). This observation suggests that nitrite changes reflect endothelial function. Assessment of local plasma nitrite during reactive hyperemia may open new avenues in the diagnosis of vascular function.

Adult↗
PubMed2002

Ion suppression effects in liquid chromatography-electrospray-ionisation transport-region collision induced dissociation mass spectrometry with different serum extraction methods for systematic toxicological analysis with mass spectra libraries.

Ion suppression effects during electrospray-ionsation mass spectrometry (ESI-MS) caused by different sample preparation procedures for serum were investigated. This topic is of importance for systematic toxicological analysis for which LC-ESI-MS has been developed with transport-region collision-induced dissociation (ECI-CID) and mass spectra library searching. With continuous postcolumn infusion of two test compounds-codeine and glafenine-the ion suppression effects of extracted biological matrix obtained after a standard liquid-liquid extraction, a mixed-mode solid-phase extraction (SPE) method, a protein precipitation method and a combination of precipitation with polymer-based mixed-mode SPE have been investigated. Extracted ion chromatograms of codeine ([M+H](+), m/z 300) and glafenine ([M-H](-), m/z 371) were used for monitoring ion suppression. Severe ion suppression effects for codeine and glafenine were detected in positive and in negative ionisation modes, respectively, in the LC-front peak after serum clean-up with SPE (acid/neutral fraction) and protein precipitation as well as with protein precipitation combined with SPE. Less ion suppression of codeine in positive mode was found with liquid-liquid extraction of serum samples. No ion suppression was detected with the second fraction of the mixed-mode SPE (using RP-C(8) and cation-exchange phase) in both ionisation modes. All suppression effects were caused by polar and unretained matrix components, which were present after extraction and/or protein precipitation. However, no specific ion suppression was seen after elution of the polar LC-front throughout the whole gradient. It could be demonstrated, that ion suppression is not generally present at any retention time when using reversed-phase HPLC with rather long gradient programs, but may play an important role in case of high-throughput LC-MS analysis, when the analyte is not separated from the LC-front, or in flow injection analysis without chromatographic separation.

Chromatography, Liquid↗
PubMed1991

Coaxial continuous flow fast atom bombardment for higher-molecular-weight peptides: comparison with static fast atom bombardment and electrospray ionization.

A comparison of coaxial continuous flow fast atom bombardment (FAB) with static FAB and with electrospray ionization (ESI) for the analysis of 'high'-mass peptides (Mr = 3000-4000) is presented. Sensitivities of the peptides by coaxial continuous flow FAB is nearly an order of magnitude better than by static FAB. Single-scan spectra with good signal-to-noise can be obtained from as little as 200 fmol (by flow injection analysis). Detection limits by ESI mass spectrometry were found to be equivalent to 20 times higher than by coaxial continuous flow FAB on a per mole basis, but 4-20 times lower on a concentration basis, owing to the greater flow per unit time employed in the ESI mass spectrometric experiments.

Mass Spectrometry↗