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PubMed1984

Screening for ochratoxin A in blood by flow injection analysis.

A micromethod for ochratoxin A detection in human sera by flow injection technique is described. The method requires 50 microliter of sera, and it is designed to distinguish samples containing less than 10 ng ochratoxin A per ml. The method is based on fluorescence measurement following a simple extraction procedure for which very small amounts of chemicals are needed. Since the method is not confirmatory, all samples showing fluorescence above a certain intensity have to be reanalysed with some other method where a confirmation step in included. Because of the small amount of serum needed and the rapid procedure (less than 15 min), a large number of samples can be analysed very quickly. The method may therefore be applicable for large screening campaigns conducted to determine the presence of ochratoxin A in blood. This conclusion is based on 1675 samples and 147 standards analysed concurrently by the flow injection technique and an earlier published enzymic method. The method is also suitable for monitoring ochratoxin A levels in the blood of experimental animals.

Chromatography, High Pressure Liquid↗
PubMed2000

Flow-injection analysis of dopamine in injections with a periodate-selective electrode.

Dopamine determination in pharmaceutical preparations based on its oxidation with periodate (IO(4)(-)) using a new IO(4)(-)-selective electrode under flow conditions is presented. An electrode with a tubular configuration, no internal reference solution, and a PVC (31. 2%) membrane, with metaperiodate bis(triphenylphosphoranylidene)ammonium (1.3%) as ion exchanger and 2-nitrophenyloctylether (67.5%) as mediator solvent, was used. Optimization procedures were directed at potentials versus dopamine readings instead of potential versus the remaining IO(4)(-). This approach was achieved by selecting a 50-cm reactor and an overall flow of 7 mL/min, and injecting 70 microL of dopamine standards in a 3.0 x 10(-4) M IO(4)(-) solution. Under these conditions, a linearity range of 8.0 x 10(-3) to 2.7 x 10(-1) g/L, with a slope of 310.1 +/- 7.4 mV L g(-1) and a reproducibility of +/-0.4 mV, were recorded (n = 8). Interference from common excipients was negligible. Under these conditions, analysis of dopamine injections (n = 12) presenting 200 mg/injection gave average and standard deviation values of 201.0 and 3.3 mg/injection, respectively. A simple and inexpensive flow-injection analysis (FIA) manifold, with a good potentiometric detector, enabled the analysis of 200 samples/h without requiring pretreatment procedures. Comparison with the dopamine injection analysis in the United States Pharmacopoeia monograph showed good accuracy, with a relative deviation of -0.2%.

Dopamine↗
PubMed2001

Determination of Henry's law constants of phenols by pervaporation-flow injection analysis.

A novel dynamic nonequilibrium technique for the determination of Henry's law constant (HLC) of phenols based on pervaporation-flow injection (PFI) is described. A linear relationship between HLC and the amount of phenol measured by a detector in the acceptor line of a PFI system was demonstrated. This relationship was constructed using five frequently encountered phenols (phenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 2-chlorophenol, and 2,3-dimethylphenol) and used for the determination of the HLC of three other phenols (2,4,6-trichlorophenol, 2-methylphenol, and 3-methylphenol). The HLC of all eight phenols were also determined by the single equilibrium static technique (SEST). Fairly good agreementwas observed between both techniques regarding the HLC of 2,4,6-trichlorophenol, 2-methylphenol, and 3-methylphenol. On the basis of the results obtained, it was concluded that the PFI technique offers considerable advantages over SEST in terms of precision, speed, labor intensity, and possibilities for automation.

Air↗
PubMed2002

Determination of picomole amounts of thiamine through flow-injection analysis based on the suppression of luminol-KIO(4) chemiluminescence system.

A continuous flow sensor for the determination of thiamine was constructed by using controlled-reagent-release technology in a FIA-CL system. The analytical reagents, luminol and KIO(4), were both immobilized on an anion-exchange column. The CL signal produced by the reaction between luminol and KIO(4), which were eluted from the column through H(2)O injection, was decreased in the presence of thiamine. The decreased CL intensity was linear with thiamine concentration in the range 3.3 pmol ml(-1)-6.7 nmol ml(-1); and the limit of detection was 1.0 pmol ml(-1) (3.). The whole process, including sampling and washing, could be completed in 0.5 min with a relative standard deviation of less than 3.0%. The flow sensor showed remarkable stability and could be easily reused over 80 h. The sensor proposed was tested in determination of thiamine in pharmaceutical preparation and human urine samples.

Calibration↗
PubMedDate not supplied

Fluorometric determination of ethanol in liquor samples by flow-injection analysis using an immobilized enzyme-reactor column with packing prepared by coupling alcohol oxidase and peroxidase onto chitosan beads.

A flow-injection system was developed for the determination of ethanol with an immobilized enzyme-reactor column. This system, which consisted of hand-made reactor columns packed with alcohol oxidase and horseradish peroxidase immobilized onto chitosan beads, and a fluorometric detector, was applied to the determination of ethanol in liquor samples. Under the recommended conditions, the ethanol, which was present in the pretreated samples, was converted to hydrogen peroxide when it was passed through the immobilized alcohol oxidase (AOD) column with 0.1 mol/dm3 phosphate buffer (pH 7.0). A sample can be analyzed with this system in <10 min. The calibration curve for ethanol was linear from 2.0 to 0.1 mg/dm3. The determination limit, which was defined by the difference between the sample peak and blank peak, was estimated to be 50 microg/dm3 for ethanol. Interferences from some substances present in actual liquor samples decreased the analytical response and activity of the immobilized AOD-reactor column, but they were removed by dilution and pretreatment with an octyldecylsilane cartridge.

Alcohol Oxidoreductases↗
PubMed2003

Determination of dipyrone in pharmaceutical products by flow injection analysis with potentiometric detection.

This work describes an FIA potentiometric procedure for the quantification of dipyrone in pharmaceutical products. For the detector, a tubular electrode comprising a polymeric membrane containing tetraoctylammonium as an electroactive material (5% w/w), dibutylphtalate as a mediator solvent (65% w/w) and PVC (30% w/w) directly applied above a graphite conductor support was used. This unit was incorporated into a monochannel FI-system with a 0.1 mol/L phosphate buffer solution (pH = 5.2) as the carrier solution. The electrode showed a linear response from 8.0 x 10(-4) to 10(-1) mol/L dipyrone, a slope of 62.1 +/- 0.2 mV/dec in pH 5.2 units, an injection volume of 500 microL and a carrier flow-rate of 6 mL/min. This procedure was applied to the analysis of pharmaceutical formulations (oral and injectable) containing dipyrone; the obtained results gave a relative error of less than 3.9% and coefficients of variation less than 1% and 5%, respectively, for the FIA and classical iodometric methods.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

[Amperometric detection in the determination of drugs by non-separating flow methods--flow injection analysis and sequential injection analysis].

The present review dealing with the use of various electrochemical detection systems in flow methods of analysis of drugs (such as FIA and SIA techniques). The review covers the period of 1988 to 1998 and involves 78 references. The drugs determined are arranged according to the functional groups undergoing electrochemical transformation; for all the analytes data on the detection conditions, detection limits and ranges of quantitation are included. Advantages and drawbacks of amperometric detection of drugs in flow systems are discussed.

Electrochemistry↗
PubMed2003

Simple and selective method for determination of iodide in pharmaceutical products by flow injection analysis using the iodine-starch reaction.

This work exploited the well-known iodine-starch reaction for development of a simple flow-injection (FI) method for determination of iodide in pharmaceutical samples. Iodide in an injected zone was oxidized to iodine. A gas diffusion unit enables selective permeation of iodine through a hydrophobic membrane. Detection was made very selective for elemental iodine by employing formation of the I(3)(-)-starch complex. The detection limit (3 S/ N) of the system was 1 mg I L(-1). For a liquid patent medicine used for asthma treatment we suggested modification of the system. Direct injection of this sample, which contains a particularly high concentration level of iodide (ca. 9000 mg I L(-1)), can be achieved by coupling a dialysis unit to the FI system. This has increased the working range to 6000-10,000 mg I L(-1) without employing complicated nanoliter injection.

Flow Injection Analysis↗
PubMedDate not supplied

Flow-injection analysis of cobalt(II) utilizing enhanced lophine chemiluminescence with hydroxylammonium chloride.

A rapid and convenient flow-injection method is described for the determination of Co(II). The method utilized the phenomenon that the lophine-Co(II)-H2O2 chemiluminescence (CL) reaction is enhanced in alkaline media by the addition of hydroxylammonium chloride. The calibration curve was linear over the range 2 x 10(-7) to 2 x 10(-5) M with a detection limit of 4.5 x 10(-8) M (0.9 pmol) at a signal-to-noise ratio of 2. The method was applied to the assay of cyanocobalamin in commercially available eye lotions.

Chromatography, Liquid↗
PubMed1994

Application of automated flow injection analysis to determine nitrite and nitrate in mouse brain.

Nitric oxide level in the mouse brain was estimated by determination of nitrite and nitrate using an automated flow injection analyser for NOx. Different experimental conditions were examined to determine which produced reproducible results. After pretreatment of tissue specimens by the ZnSO4-NaOH method for deproteinization, reproducible and constant values were obtained. The values were more accurate immediately after sectioning without freezing than after 24 h with freezing. Two sacrifice methods, decapitation and microwave irradiation of the head, were investigated, but there was no significant difference between the two. No substances in the mouse brain exerted a positive or negative influence on the results. These results show that our method is indeed applicable to the brain tissue.

Animals↗
PubMed1990

Simultaneous determination of glucose, ethanol and lactate in alcoholic beverages and serum by amperometric flow injection analysis with immobilized enzyme reactors.

Glucose, ethanol and lactate were determined simultaneously in a flow injection system by using a parallel configuration of immobilized enzyme reactors. Hydrogen peroxide produced was monitored amperometrically at the potential of +0.65 V vs. Ag/AgCl. Linear relations between sensor responses and each species were observed in the ranges of 0.02-10 mM (glucose), 5 x 10(-4)-0.1% (v/v) (ethanol) and 0.005-1 mM (lactate) with correlation coefficients larger than 0.999 for each species. The relative standard deviations for 10 successive injections were 1.4, 0.5 and 1.1% for glucose (1 mM), ethanol (5 x 10(-3)% (v/v] and lactate (0.05 mM), respectively. Analysis of serum samples was performed with urate-eliminating reactors which were set just before each immobilized enzyme reactor. Interference of ascorbate in a serum sample was completely eliminated by using an ascorbate-eliminating reactor which was set before the sample injection valve. Application of the system to alcoholic beverages and control serum was described and the results were compared with those of free enzymatic, spectrophotometric analysis (F-kit or C-test method).

Alcoholic Beverages↗
PubMed2004

Determination of choline in milk, milk powder, and soy lecithin hydrolysates by flow injection analysis and amperometric detection with a choline oxidase based biosensor.

A fast-response and interference-free amperometric biosensor based on choline oxidase immobilized onto an electropolymerized polypyrrole film for flow injection determination of choline in milk, milk powder, and soy lecithin hydrolysates is described. The sensor displayed an Imax value of 1.9 +/- 0.2 microA and an apparent Michaelis-Menten constant, k'M, equal to 1.75 +/- 0.07 mM. Detection limits of 0.12 microM could be obtained. Because even a slight deterioration of the anti-interference membrane can adversely affect measurement accuracy, a real time monitoring of the biosensor selectivity has been achieved by a dual Pt electrode flow-through cell where the enzyme modified electrode is coupled to an enzyme-free electrode in a parallel configuration. Finally, bracketing technique (alternate injections of sample and standards) allows a two-point calibration to be performed in real-time, correcting for any drift in sensor response.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Construction and performance characterization of ion-selective electrodes for potentiometric determination of pseudoephedrine hydrochloride applying batch and flow injection analysis techniques.

New pseudoephedrine selective electrodes have been constructed of the conventional polymer membrane type by incorporation of pseudoephedrine-phosphotungstate (PE-PT) or pseudoephedrine-silicotungstate (PE-SiT) ion-associates in a poly vinyl chloride (PVC) membrane plasticized with dibutyl phthalate (DBP). The electrodes were fully characterized in terms of the membrane composition, temperature, and pH. The electrodes exhibited mean slopes of calibration graphs of 57.09 and 56.10 mV concentration decade(-1) of PECl at 25 degrees C for (PE-PT) and (PE-SiT) electrodes, respectively. The electrodes showed fast, stable, and near-Nernstian response over the concentration ranges 6.31 x 10(-6)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-PT applying batch and flow injection (FI) analysis, respectively, and 1.00 x 10(-5)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-SiT for batch and FI analysis system, respectively. Detection limit was 5.01x 10(-6) M for PE-PT electrode and 6.31x10(-6) M for PE-SiT electrode. The electrodes were successfully applied for the potentiometric determination of pseudoephedrine hydrochloride (PECl) in pharmaceutical preparations with mean recovery 101.13 +/- 0.85% and 100.77+0.79% in case of PE-PT applying batch and flow injection systems, respectively, and 100.75+0.85% and 100.79 +/- 0.77% in case of PE-SiT for batch and flow injection systems, respectively. The electrodes exhibited good selectivity for PECl with respect to a large number of inorganic cations, sugars and amino acids.

Calibration↗
PubMed2003

Miniaturized tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection cell for capillary electrophoresis and flow injection analysis.

The design and performance of a miniaturized chip-type tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)3(2+)] electrochemiluminescence (ECL) detection cell suitable for both capillary electrophoresis (CE) and flow injection (FI) analysis are described. The cell was fabricated from two pieces of glass (20 x 15 x 1.7 mm), and the 0.5-mm-diameter platinum disk was used as working electrode held at +1.15 V (vs silver wire quasi-reference), the stainless steel guide tubing as counter electrode, and the silver wire as quasi-reference electrode. The performance traits of the cell in both CE and FI modes were evaluated using tripropylamine, proline, and oxalate and compared favorably to those reported for CE and FI detection cells. The advantages of versatility, sensitivity, and accuracy make the device attractive for the routine analysis of amine-containing species or oxalate by CE and FI with Ru(bpy)3(2+) ECL detection.

Journal Article↗
PubMed2000

A factorial design for optimizing a flow injection analysis system.

The use of a factorial design for the response exploration of a flow injection (FI) system is described and illustrated by FI spectrophotometric determination of paraquat. Variable response (absorbance) is explored as a function of the factors flow rate and length of the reaction coil. The present study was found to be useful to detect and estimate any interaction among the factors that may affect the optimal conditions for the maximal response in the optimization of the FI system, which is not possible with a univariate design. In addition, this study showed that factorial experiments enable economy of experimentation and yield results of high precision due to the use of the whole data for calculating the effects.

Analysis of Variance↗