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PubMed1991

On-line determination of intracellular beta-galactosidase activity in recombinant Escherichia coli using flow injection analysis (FIA).

A flow injection analysis (FIA) system was developed for the determination of cytoplasmic beta-galactosidase activity in recombinant Escherichia coli. The FIA system and its application for on-line monitoring of beta-galactosidase production during cultivation of recombinant E. coli in a 60-l airlift tower loop reactor is described. The results demonstrate that an FIA assay in conjunction with a cell disintegration step can be applied successfully for on-line monitoring of intracellular protein formation.

Colorimetry↗
PubMed1991

On-line determination of glucose concentration throughout animal cell cultures based on chemiluminescent detection of hydrogen peroxide coupled with flow-injection analysis.

A flow-injection analysis (FIA) system for the on-line determination of glucose in animal cell cultures is described. The system is based on immobilized glucose oxidase (GOD). The hydrogen peroxide generated in the enzyme reaction is determined via a highly sensitive chemiluminescent reaction with luminol. Based on the measurement of the maximum emitted light intensity, the system was able to analyse hydrogen peroxide over the concentration range of 10(-7) to 10(-2) M. For glucose determination, the system has a linear range of 10(-5) to 5 x 10(-2) M glucose, with an r.s.d. of 3% at the 1 mM level (5 measurements). The influence of luminol and buffer concentrations, pH and temperature on the chemiluminescent reaction were investigated. The enzyme reactor used was stable for more than 4 weeks in continuous operation, and it was possible to analyse up to 20 samples per h. The system has been successfully applied to on-line monitoring of glucose concentration during an animal cell culture, designed for the production of human antithrombin III factor. Results obtained with the FIA system were compared with off-line results, obtained with a Yellow Springs Instrument Company Model 27 (YSI).

Animals↗
PubMedDate not supplied

On-line determination of biomass in a microalga bioreactor using a novel computerized flow injection analysis system.

A flow injection analysis (FIA) device has been developed, which is able to assay successfully for biomass in a microalga bioreactor. The device is fully computerized and is operated via diluting small aliquots of the culture followed by measuring optical density (OD); this figure is then accurately correlated with biomass, in terms of both cell number and ash-free dry weight, during the entire culture time. Furthermore, the device is not expensive, is highly versatile, and is easy to operate owing to specifically developed, user-friendly software. The growth rate and biomass productivity of Pavlova lutheri, cultivated under batch and semicontinuous modes, were monitored as experimental testing model.

Biomass↗
PubMed1999

The determination of busulphan in dissolution samples by flow injection analysis.

A robust colourimetric flow injection analysis (FIA) procedure is described for the determination of busulphan in dissolution samples of a 2 mg tablet formulation. The sample solution is injected directly into a reagent stream containing 4-(4-nitrobenzyl)pyridine/potassium hydrogen phthalate. An on-line heating stage allows the formation of a coloured pyrridinium salt species, which following stabilisation is detected spectrophotometrically at 570 nm. The method has been fully validated and is linear over the concentration range 0.004-0.024 mg of busulphan ml(-1). The method can also been applied to uniformity of content and bulk assay testing.

Busulfan↗
PubMedDate not supplied

Chemiluminescence inhibition assay for folic acid using flow injection analysis.

A new flow injection method for the determination of folic acid is described. A fast oxidation reaction occurred when folic acid was mixed with potassium ferricyanide generating ferrocyanide which then inhibited the chemiluminescent reaction of ferricyanide and luminol in alkaline medium. The decrease of chemiluminescence intensity was correlated with the folic acid concentration in the range 0.1-21 microg/mL; the detection limit for the assay was 0.03 microg/mL (3sigma). A complete analysis of folic acid, including sampling and washing, could be performed within 2 min with a relative standard deviation of less than 4.0%. The proposed method has been applied successfully to the determination of folic acid in pharmaceutical preparations.

Ferricyanides↗
PubMed2001

Selective trace level analysis of phenolic compounds in water by flow injection analysis--membrane introduction mass spectrometry.

Flow injection analysis coupled with membrane introduction mass spectrometry (FIA-MIMS) with on-line derivatization is shown to allow fast, accurate, nearly interference-free, and sensitive (low microgram/L) quantitation of phenolic compounds in water. On-line FIA derivatization of the phenolic compounds is performed by acetic anhydride acetylation in a K2CO3-buffered alkaline medium. The phenol acetates so formed efficiently permeate a silicone membrane and are directly transferred to the mass spectrometer, in which they are analyzed with selectivity and high sensitivity via selected ion monitoring. FIA-MIMS analysis was performed for aqueous solutions of phenol, 2-methylphenol, 4-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, and detection limits in the 0.5-20 micrograms/L (ppb) range were observed for an analytical frequency of six samples/h. FIA-MIMS for phenolic compound analysis is considerably less time-consuming and labor intensive than most chromatographic methods based on liquid-liquid extraction and preconcentration procedures and is therefore applicable for on-line and in-situ monitoring of phenols in wastewaters and in the environment. FIA-MIMS employing acetic anhydride derivatization is also virtually free of interferences since it combines chemical, membrane, and enhanced MS selectivity; hence quantitation of phenolic compounds can be performed in the presence of congeners.

Acetates↗
PubMed2002

Evaluation of the temporal effect to the peak tailing in flow injection analysis.

The deformation of a flow injection analysis peak from a Gaussian shape has two components: spatial and temporal. The former is mainly attributed to the Poisseulie effect in the tubular flow, whereas the latter is related to the observing position (of a fixed detector) at which signal is measured. The combination of the two makes a skewed peak track on the recorder chart. Therefore, an observed peak may imply a substantial fraction of a "false" tail due to the effect of non-simultaneous detection. An expanding-Gaussian model is proposed to simulate the purely temporal effect, and the asymmetric factors were compared with that of the experimental peak shapes. In most cases the peak deformation occurring in flow injection analysis should be regarded as "temporal". The contribution of the spatial effects (Poisseulie profile and others) might not be as significant as it was thought previously.

Flow Injection Analysis↗
PubMed2002

A rapid assay method for catechol-O-methyltransferase activity by flow injection analysis.

A rapid assay employing flow injection analysis (FIA) to determine the activity of purified catechol-O-methyltransferase (COMT) from porcine liver is described. The method was based on the determination of normetanephrine, the 3-O-methyl metabolite of the substrate norepinephrine. Excess norepinephrine was removed from the incubation mixture by alumina extraction twice to allow normetanephrine to be subjected to flow injection analysis, coulometrical oxidation, fluorogenic reaction with ethylenediamine and fluorescence detection. K(m) and V(max) values for COMT obtained with the system were 503 microM and 4.51 nmol/min/mg protein, respectively. The method is suitable for screening of COMT inhibitors or activators, as a large number of samples, up to 200, can be processed in one working day.

Animals↗
PubMed1987

Selective determination of lithium in biological fluids using flow injection analysis.

The use of flow injection analysis to automated extraction methods for the determination of lithium ion utilizing crown ethers or cryptands is demonstrated. The ion-pair extraction of cryptand 211, lithium, and resazurin exhibits a linear range for lithium ion of 70 ppb to 2.1 ppm. This method could tolerate up to 1000 ppm sodium ion. The chromogenic crown ether, 1-(2-hydroxy-5-nitrobenzyl)-1-aza-4,7,10-trioxacyclododecane, exhibits a linear range for lithium ion of 0.3 to 2 ppm. A sodium ion concentration of 230 ppm can be tolerated. Both extraction systems were used in the automated determination of lithium in blood serum and urine. Both methods agreed well with the known and/or atomic absorption values.

Bridged Bicyclo Compounds↗
PubMed2006

Enhanced sensitivity in flow injection analysis using a long pathlength liquid waveguide capillary flow cell for spectrophotometric detection.

Incorporation of a liquid waveguide capillary flow cell into a flow injection instrument enhances the sensitivity of flow injection analysis with spectrophotometric detection by two orders of magnitude. Nitrite determination at nM levels has been used to demonstrate the feasibility of this novel technique for trace analysis. Combining the long pathlength spectrophotometry with flow injection analysis, this technique has advantages of low detection limit, good precision and high sample throughput.

Capillary Action↗
PubMed1998

Gradient elution electrochromatography with a flow-injection analysis interface.

A flow-injection analysis-capillary electrochromatography interface is used for gradient elution capillary electrochromatography giving purely electroosmotic flow through the analytical column. Solvent gradients were generated with a micro-LC system connected to the interface. Injections were carried out on-line using an inert rotary LC valve controlled by an electric actuator. Gradient shape was measured from acetonitrile (5% acetone)-water (50:50, v/v) to (100:0) in open tubular experiments. When compared to conventional instrumentation, peak tailing and peak width increased slightly using the interface. A test mixture of nine solutes was evaluated in isocratic and gradient elution modes. Using the interface, a gradient of MeCN-water (60:40) to (90:10) provided baseline separation of all nine solutes in under 18 min with good band spacing. Reproducibility of retention times in eight replicate injections was found to be better than 2% R.S.D. for all solutes. This interface also allows use of autoinjectors and dramatically lessens movement of the packed column, improving column lifetime.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of mercury in fish by cold vapor atomic absorption spectrophotometry using a multicommuted flow injection analysis system.

A flow system was developed for the determination of total mercury concentration in fish samples by cold vapor atomic absorption spectrophotometry (CVAAS), based on the multicommuted flow injection analysis (MCFIA) approach. The system uses independently controlled solenoid valves for the introduction of reagents and samples. When not injected, solutions were recirculating to the reservoir bottles, in this way reducing the waste produced by the analytical system and also the sample consumption. Results were compared to those obtained by the reference flow injection procedure. Accuracy was also assessed by recovery studies using a certified reference material as well as spiked samples; recovery percentages in the range of 90.7% to 99.8% were found. The repeatability of the method was better than 6.0% (RSD, n = 10). A limit of detection of 4.8 microg of mercury per kg of fresh fish sample was achieved. The total waste produced was reduced to 30% of that from the reference flow injection CVAAS procedure.

Animals↗
PubMed1994

On-line monitoring of an animal cell culture with multi-channel flow injection analysis.

A multi-channel flow injection analysis system was used for on-line monitoring of a continuous animal cell culture with high cell density. With this system, the glucose, lactate and glutamine concentration were determined using immobilized dehydrogenases, ammonium using an aqueous o-phthaldialdehyde solution. Glutamine concentration was determined on the basis of the difference between a glutamine and a glutamate measurement. To prevent disturbance of the measurement and pollution of the system, the analytes in the sample were separated from high molecular compounds by on-line dialysis. On-line gas dialysis was used to avoid interference of other amino groups with the ammonium determination. In addition, dialysis was used as a dilution step. The measurement time for all four components was 42 min. This time included a final washing period after the analysis cycle. The system was calibrated once a day. Two continuous cultivations of a hybridoma cell line immobilized in open-porous glass carriers were monitored, using a fluidized bed reactor as cultivation system. The concentration of glutamine, glucose and ammonium determined with the on-line FIA system were in good agreement with the off-line data determined once a day. Only the lactate data showed some deviation. The immobilized enzyme reactors could be used for up to 3000-5000 injections. During the first cultivation, lasting 200 h, the start up period of the reactor was monitored. The on-line measurements described much better the time-course of the concentrations than the off-line data. It was possible to estimate the growth rate of the cells in the micro-carriers by the on-line data. In the course of the second cultivation, which lasted almost 1000 h, the influence of the dissolved oxygen concentration on the cell metabolism was monitored. It was noted that a sudden change of the glutamine concentration in the feed caused a fast change of the consumption and production rate of the measured metabolites.

Animals↗
PubMedDate not supplied

Sequential determination of salicylic and acetylsalicylic acids by amperometric multisite detection flow injection analysis.

An amperometric multisite detection flow injection analysis (FIA) system was developed for sequential determination of 2 analytes with a single sample injection and single detector. Tubular composite carbon electrodes with an inner diameter similar to that of the FIA manifold tubing were constructed so that measurements could be made without impairing the sample plug hydrodynamic characteristics. The electrochemical behavior of the tubular voltammetric cell in a low-dispersion FIA manifold and the behavior of the FIA system incorporating this type of voltammetric cell intended for multisite detection were evaluated by performing measurements with potassium hexacyanoferrate(II). Feasibility of the approach was demonstrated in the sequential determination of salicylic and acetylsalicylic acids in pharmaceutical products at a fixed potential of 0.98 V. The system allows sequential determination of salicylic acid concentrations ranging from 1.0 x 10(-5) to 5.0 x 10(-5) M and acetylsalicylic acid concentrations between 1.0 x 10(-3) and 5.0 x 10(-3) M with good precision on both detection sites and with relative standard deviations (RSDs) > or = 1.5% (n = 10) and 2.1% (n = 10), respectively. A comparison of these results with those of the U.S. Pharmacopeia procedure showed RSDs <5.0 and 1.0% for salicylic acid and acetylsalicylic acid, respectively. The proposed method enables 15 determinations per hour, which corresponds to the analysis of approximately 8 samples per hour. The detection limits of the methodology were approximately 3.5 x 10(-6) and 1.1 x 10(-5) M, respectively, for the first and second monitoring sites.

Aspirin↗
PubMed1999

An experimental design approach to the optimisation of a flow injection analysis method for glycine.

A flow injection analysis method for the determination of glycine, based on the reaction with ortho-phtalaldehyde and N-acetylcysteine in a basic buffer, was optimised. In the first step screening of the variables, to select the most important ones, was performed using: (i) a half-fraction factorial design and (ii) a quarter-fraction factorial design, for five factors at two levels. The effects of the factors on the peak height were calculated from both screening designs and compared. For the half-fraction factorial design (resolution IV), the significance of the factor effects on the peak height was checked by: (i) comparing them with a critical effect, calculated from two-factor interactions and based on a t-test, (ii) using a non parametric approach and (iii) drawing a normal probability plot. For the quarter-fraction factorial design (resolution III) the significance of the effects of the factors on the peak height was checked using: (i) a randomization test method, (ii) the non parametric method and (iii) a normal probability plot. In the second step, the factor found to be of importance was optimised using the uniplex method.

Acetylcysteine↗
PubMed2002

Determination of polyphenols in wines by reaction with 4-aminoantipyrine and photometric flow-injection analysis.

A new flow-injection analytical procedure is proposed for the determination of the total amount of polyphenols in wines; the method is based on the formation of a colored complex between 4-aminoantipyrine and phenols, in the presence of an oxidizing reagent. The oxidizing agents hexacyanoferrate(III), peroxodisulfate, and tetroxoiodate(VII) were tested. Batch trials were first performed to select appropriate oxidizing agents, pH, and concentration ratios of reagents, on the basis of their effect on the stability of the colored complex. Conditions selected as a result of these trials were implemented in a flow-injection analytical system in which the influence of injection volume, flow rate, and reaction-coil length, was evaluated. Under the optimum conditions the total amount of polyphenols, expressed as gallic acid, could be determined within a concentration range of 36 to 544 mg L(-1), and with a sensitivity of 344 L mol(-1) cm(-1) and an RSD <1.1%. The reproducibility of analytical readings was indicative of standard deviations <2%. Interference from sugars, tartaric acid, ascorbic acid, methanol, ammonium sulfate, and potassium chloride was negligible. The proposed system was applied to the determination of total polyphenols in red wines, and enabled analysis of approximately 55 samples h(-1). Results were usually precise and accurate; the RSD was <3.9% and relative errors, by the Folin-Ciocalteu method, <5.1%.

Ampyrone↗
PubMed1990

Fluorometric determination of urinary kynurenic acid by flow injection analysis equipped with a "bypass line".

A flow injection analysis involving a photochemical reaction and fluorometric detection has been developed for the determination of urinary kynurenic acid. Kynurenic acid was found to fluoresce on irradiation with ultraviolet light at pH 7.2 in the presence of hydrogen peroxide. This method was applied to flow injection analysis using a new procedure involving a "bypass line" for the simultaneous determination of urinary kynurenic acid and background fluorescence. The calibration graph showed linearity over the range of 0.20 to 120 pmol. For pretreatment of urinary kynurenic acid, a PRE-SEP C18 cartridge was used. The mean recovery of kynurenic acid from urine was 94.5%. The content of urinary kynurenic acid was 13.0 +/- 2.68 mumol/day. There was good correlation (r = 0.9729) between values determined by flow injection analysis and high-performance liquid chromatography.

Chemistry Techniques, Analytical↗