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PubMed2005

Epinephrine quantification in pharmaceutical formulations utilizing plant tissue biosensors.

A plant tissue biosensor associated with flow injection analysis is proposed to determine epinephrine in pharmaceutical samples. The polyphenol oxidase enzymes present in the fibers of a palm tree fruits (Livistona chinensis), catalyses the oxidation of epinephrine to epinephrinequinone as a primary product. This product is then electrochemically reduced (at -0.10 V versus Ag/AgClsat) on the biosensor surface and the resulting current is used for the quantification of epinephrine. The biosensor provides a linear response for epinephrine in the concentration range from 5.0 x 10(-5) to 3.5 x 10(-4) mol l(-1). The limit of detection estimated for this interval was 1.5 x 10(-5) mol l(-1) and the correlation coefficient of 0.998, working under a flow rate of 2.0 ml min(-1) and using a sample loop of 100 microl. The repeatability (R.S.D. for 10 consecutive determinations of a 3.0 x 10(-4) mol l(-1) epinephrine solution) was 3.1%. The results obtained by the method here proposed were compared with the official UV spectrophotometric procedure and also using a plant tissue reactor. The responses obtained with the proposed strategies were in good agreement with both ways of analyses, whereas the values obtained by the official spectrophotometric method was strongly affected by benzoic acid, present in the formulation of pharmaceutical product utilized for inhalation. Such favorable results obtained with the carbon paste biosensor or utilizing the bioreactor, joined with the simplicity of its preparation turns these procedures very attractive for epinephrine quantification in pharmaceutical products.

Arecaceae↗
PubMed2003

Quartz crystal biosensor for real-time monitoring of molecular recognition between protein and small molecular medicinal agents.

A quartz crystal microbalance (QCM) biosensor integrated into a flow injection analysis (FIA) system was used for the real-time investigation of molecular recognition between a protein and small molecular medicinal agents. Two sulfa-drugs, sulfamethazine (SMZ) and sulfamethoxazole (SMO), were, respectively, immobilized on the gold electrodes of the piezoelectric crystals using appropriate procedures based on self-assembly of the dithiothreitol (DTT). The binding interactions of the two immobilized drug ligands, with various proteins in solution, were followed as changes in the resonant frequency of the modified crystals. Results obtained from this rapid screen analysis clearly indicated that the two drug ligands appeared quite different in this molecular recognition procedure although their structures were similar. SMZ-immobilized sensor showed specific interaction only with IgG, while SMO-immobilized sensor showed negligible specific binding with IgG, but binding with trypsin and chymotrypsin. Further studies on the specific interaction between immobilized SMZ and three different species of IgG--human IgG, goat IgG and mouse IgG were carried out and the marked species-dependent difference was observed. The resultant sensorgrams were rapidly analyzed by using an in-house kinetic analysis software based on genetic algorithm (GA) to derive both the kinetic rate constants (kass and kdiss) and equilibrium association constants (KA) for IgG-SMZ interactions. For the interactions, KA were 5.48 x 10(5), 2.75 x 10(5) and 1.86 x 10(5) M(-1) for human IgG, goat IgG and mouse IgG, respectively. The kinetic data provided further insight into the structural/functional relationships of different IgG on a molecular level.

Adsorption↗
PubMed2001

A robust multi-syringe system for process flow analysis. Part 3. Time based injection applied to the spectrophotometric determination of nickel(II) and iron speciation.

A new software-controlled time-based system for sample or reagent introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one multi-port selection valve, the time-based injection of precise known volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Two multi-syringe time-based injection (MS-TBI) systems were implemented: first, the injection of a sample in a multiple-channel manifold where the sample would sequentially merge and react with different reagents, and second, the sequential injection of several solutions (sample and reagents) into a particular flowing stream. The first system was applied to the spectrophotometric determination of nickel(II) in diluted samples from the acidic nickel ore leaching process, by using ammonium citrate as carrier, a saturated solution of iodine as oxidizing agent and alkaline dimethylglyoxime as chromogenic reagent. The sampling frequency attained was 57 h-1. Determinations on process samples compared well at the 95% confidence level with the reference values obtained by ICP-OES. The second time-based injection system was applied to the speciation of iron. Total iron and iron(II) concentrations were separately and sequentially determined using 1,10-phenanthroline in acetic buffer medium as reagent. The developed manifold allowed the optional use of two different carrier solutions, containing or not containing ascorbic acid, for performing the separate determinations. Also, in the sequential procedure, plugs of reducing carrier were alternatively intercalated before the sample injections used for total iron determinations. Sampling frequencies of 68 injections per hour were routinely used. Accuracy was assessed by analyzing synthetic known mixtures of Fe(III) and Fe(II) standard solutions. Recoveries of 98-100.5% with a maximum relative standard deviation of 3.6% were found. Results obtained for various samples of fertilizers agreed well with those attained by the standard batch procedure.

Journal Article↗
PubMed2005

Quantitative determination of guanidinoacetate and creatine in dried blood spot by flow injection analysis-electrospray tandem mass spectrometry.

BACKGROUND: Guanidinoacetate (GAA) and creatine (Cr) are reliable biochemical markers of primary creatine disorders. The aim of this study was to develop and validate a method for the determination of GAA and Cr in dried blood spot through the use of stable isotope dilution and flow injection analysis (FIA)-ESI-MS/MS. METHODS: Dried blood spots were extracted using methanol-water solution containing D3-Cr. After evaporation and formation of butyl esters, samples were analyzed using multiple reaction monitoring mode (m/z 174.2-->101.1 for GAA, 188.3-->90.1 for Cr and 191.3-->93.1 for D3-Cr). RESULTS: The analysis was very fast (1 min). The detection limits were 0.34 micromol/l of blood and 0.30 micromol/l of blood for Cr and GAA, respectively, and the response was linear over the range 0.25-12.5 micromol/l of blood for GAA and 3.57-624.7 micromol/l of blood for Cr. Recovery range was 93-101% for Cr and 94-105% for GAA and between-run CVs were 5.3% for GAA and 4.5% for Cr. Ion suppression effect was also studied. The method was applied to spots obtained from two patients affected by GAMT deficiency, four patients affected by AGAT deficiency (including a newborn) as well as 282 healthy subjects. CONCLUSIONS: The detection of GAA in dried blood spot by FIA-ESI-MS/MS is a highly reliable and high throughput method for the diagnosis of GAMT and AGAT deficiencies and a possible tool for newborn screening of both these tractable disorders.

Amidinotransferases↗
PubMed1995

Polar organic pollutants in the Elbe river. Liquid chromatographic-mass spectrometric and flow-injection analysis-mass spectrometric analyses demonstrating changes in quality and concentration during the unification process in Germany.

During the unification process of the two German states from 1989 to 1994, water extracts from the Elbe river were analyzed by gas chromatography-mass spectrometry (GC-MS) and by high-performance liquid chromatography (HPLC) combined with ultraviolet (UV) and/or mass spectrometric detection (MS) in order to monitor the pollutants in one of the most contaminated European rivers. After column chromatography (LC) or flow-injection analysis (FIA) bypassing the analytical column, ionization was performed by a thermospray interface (TSP). Semiquantitative estimations of the pollution of the Elbe were made from the total-ion current traces (TIC) of the extracts. Determination of the total dissolved organic carbon (DOC) indicated a reduction of more than 55% of pollutants in the water phase. The pollutants were identified by tandem mass spectrometry (MS-MS), generating daughter-ion spectra by collision-induced dissociation (CID) using either column chromatography or direct mixture analysis. Compound-specific analyses indicated a reduction in the amount of pollutants as well as a change in their composition. This could be explained by reduced industrial production and by intensified construction of biological sewage treatment plants.

Chromatography, High Pressure Liquid↗
PubMed2005

Flow injection chemiluminescence analysis of some penicillins by their sensitizing effect on the potassium permanganate-glyoxal reaction.

A new chemiluminescence method using flow injection is described for the determination of four penicillins, namely: phenoxymethylpenicillin potassium, amoxicillin, ampicillin, and ampicillin sodium. The method is based on sensitizing effect of these drugs on the chemiluminescence reaction of potassium permanganate in sulfuric acid with glyoxal. The different experimental parameters affecting the chemiluminescence intensity were carefully studied and incorporated into the procedure. The method allows the determination of 0.1-1.0 microg/ml phenoxymethylpenicillin potassium, 0.1-1.0 microg/ml amoxicillin, 0.1-1.0 microg/ml ampicillin, and 0.1-1.0 microg/ml ampicillin sodium. The method was successfully applied to the determination of four penicillin antibiotics in pharmaceutical preparations.

Calibration↗
PubMed2001

[Flow injection biamperometric analysis of isoniazid].

AIM: To establish a simple, rapid, and accurate electrochemical method for on-line determination of isoniazid. METHODS: Based on the flow injection biamperometry for irreversible couple system, and using two preanodized platinum electrodes with the applied potential difference of 0 V, the biamperometric method for the determination of isoniazid has been proposed by coupling the catalytic oxidation of isoniazid and the reduction of platinum oxide. RESULTS: Common excipients, inorganic ions, amino acids, vitamins and proteins do not interfere with the determination. Linear relationship between current and the concentration of isoniazid is obtained in the range of 1.0 x 10(-6)-1.0 x 10(-4) mol.L-1 (gamma = 0.998, n = 11). The RSD of 1.8% was obtained for 8 successive determinations of 1.0 x 10(-5) mol.L-1 isoniazid. CONCLUSION: The proposed method has been shown to be sensitive, selective, rapid (120 samples.h-1), and suitable for the on-line direct determination of isoniazid.

Antitubercular Agents↗
PubMed1991

Principles of stopped-flow sequential injection analysis and its application to the kinetic determination of traces of a proteolytic enzyme.

The concept of sequential injection analysis is described, and an application of this novel technique to an assay of traces of a proteolytic enzyme is demonstrated. The automated method is based on a stopped-flow procedure with fluorescence detection. Instead of using the conventional constant flow rate, a sinusoldal flow pattern, as generated by a robust cam-driven piston pump, has been applied. The validation of the novel flow injection system using a nonreactive fluorescent compound yielded highly reproducible results over a concentration range of 3 order of magnitude. The calibration graph for the enzyme activities in the range 5-75 micron mL-1 could be fitted a second-order polynomial. The detection limit is 2.5 micron mL-1, which corresponds to 7.2 ng mL-1 pure active enzyme.

Endopeptidases↗
PubMed2000

A robust multisyringe system for process flow analysis. Part II. A multi-commuted injection system applied to the photometric determination of free acidity and iron(III) in metallurgical solutions.

A new software-controlled volume-based system for sample introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one or two additional commutation valves, the multi-commuted injection of precise sample volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Three configurations were implemented in order to achieve two different tasks: the single injection of a sample in a two- or three-channels manifold, and the dual injection into different streams. The two channel flow system using the single injection was applied to the determination of free acidity in diluted samples containing high levels of iron(III), by employing the single point titration methodology. The precipitation of ferric hydroxide was prevented using the ammonium and sodium salts of oxalate and acetate as buffer titrant. Methyl Red was employed as indicator. The procedure allows determination of acid concentration in solutions with a Fe(III)/H+ molar ratio up to 0.2. Samples with higher Fe(III)/H+ molar ratios were spiked with a known strong acid at dilution. The three-channel configuration was applied to the determination of ferric ions, using, as reagent, a merging mixture of sulfuric acid and potassium thiocyanate. The double injection system was implemented in series in a single (three-channel) manifold in such a way that a different injection volume and a changed reagent were used for each analyte. It was applied to the separated or sequential determination of free acidity and ferric ions. In this configuration, iron(III) was determined using 0.5-0.7% (w/v) sodium salicylate solution as reagent. The systems can operate at up to 100, 84 and 78 injections per hour, respectively. Determinations on synthetic and process samples compared well with the reference values and procedures. Recoveries of 95-102% with a maximum RSD value of 5.4% were found for acidity. The respective values obtained for iron determinations were 96-105% and 4.3%.

Journal Article↗
PubMed2004

Prussian blue modified amperometric FIA biosensor: one-step immunoassay for alpha-fetoprotein.

The aim of this study was to develop a rapid method to measure alpha-fetoprotein (AFP) in human serum by use of one-step sandwich enzyme-linked immunosorbent assay (ELISA)-based immunobiosensor with disposable screen-printed carbon electrode technology. Prussian blue (PB) was deposited using cyclic voltammetry (CV) on the surface of electrode to catalyze H202 from the reaction of glucose oxidase. It took only about 30 min to complete the whole experimental procedure through flow injection analysis (FIA). A detection range obtained is in the range from 5 to 500 ng/ml AFP. This detection seems to be quick, reliable and practical.

Biosensing Techniques↗
PubMedDate not supplied

Micromachined detectors for an enzyme-based FIA.

Micromachining techniques were applied to construct biosensor systems. The micromachined biosensors have small size, low production cost, and good reproducibility. We made some detection units for flow injection analysis (FIA). An electrochemical flow cell was fabricated, and both the enzyme immobilized column and electrochemical detector were integrated onto the same chip. A chemiluminescence detector was also fabricated and applied to the determination of glucose and lactic acid contained in human serum and urine.

Biosensing Techniques↗
PubMed2002

Electrochemical oxidation of chlorophenols at a boron-doped diamond electrode and their determination by high-performance liquid chromatography with amperometric detection.

Anodically pretreated diamond electrodes have been used for the detection of chlorophenols (CPs) in environmental water samples after high-performance liquid chromatographic (HPLC) separation. The anodization of as-deposited boron-doped polycrystalline diamond thin-film electrodes has enabled the stable determination of phenols over a wide concentration range. Prior to the HPLC analysis, a comparative study with ordinary glassy carbon, as-deposited diamond, and anodized diamond was made to examine the oxidative behavior of phenols by cyclic voltammety and flow injection analysis with amperometric detection. At anodized diamond electrodes, reproducible, well-defined cyclic voltammograms were obtained even at high CP concentration (5 mM), due to a low proclivity for adsorption of the oxidation products on the surface. In addition, after prolonged use, the partially deactivated diamond could be reactivated on line by applying a highly anodic potential (2.64 Vvs SCE) for 4 min, which enabled the destruction of the electrodeposited polymer deposits. Hydroxyl radicals produced by the high applied potential, in which oxygen evolution occurs, are believed to be responsible for the oxidation of the passivating layer on the surface. When coupled with flow injection analysis (FIA), anodized diamond exhibited excellent stability, with a response variability of 2.3% (n = 100), for the oxidation of a high concentration (5 mM) of chlorophenol. In contrast, glassy carbon exhibited a response variability of 39.1%. After 100 injections, the relative peak intensity, for diamond decreased by 10%, while a drastic decrease of 70% was observed for glassy carbon. The detection limit obtained in the FIA mode for 2,4-dichlorophenol was found to be 20 nM (S/N = 3), with a linear dynamic range up to 100 microM. By coupling with the column-switching technique, which enabled on-line preconcentration (50 times), the detection limit was lowered to 0.4 nM (S/N = 3). By use of this technique, anodized diamond electrodes were demonstrated for the analysis of CPs in drainwater that was condensed from the flue gas of waste incinerators.

Boron↗
PubMed1998

Chemiluminescence-based detection: principles and analytical applications in flowing streams and in immunoassays.

The present paper provides the principles of chemiluminescence (CL) and its powerful applications in analytical chemistry, mainly in the area of flow injection analysis, column liquid chromatographic and capillary electrophoretic separating systems, and its potential in immunoassays. CL is light produced by a chemical reaction. The most common advantages of chemiluminescent reactions are the relatively simple instrumentation required, the very low detection limits and wide dynamic ranges, which have contributed to the interest of CL detection in flow injection analysis, high performance liquid chromatography, including miniaturized systems, and, most recently, the exploding area of capillary electrophoresis. The latter powerful microanalytical separation technique offers high numbers of theoretical plates and relatively short analysis times requiring only small sample volumes, the migrating system comprising aqueous buffer solutions. In non-isotopic immunoassays, covering a great variety of applications in human and veterinary medicine, forensic medicine, agriculture and food industry, the radioisotope is replaced by a fluorescence or chemiluminescent label. The use of CL as a detection principle permits quantitative determination of various compounds at low concentrations. Disadvantages of the CL-based technique may include lack of sufficient selectivity and sensitivity to various physicochemical factors.

Chemistry Techniques, Analytical↗
PubMed2005

Benzene analysis in workplace air using an FIA-based bacterial biosensor.

A bacterial biosensor based on flow injection analysis (FIA) has been developed for the determination of benzene in workplace air samples. Benzene can be used by the bacteria Pseudomonas putida ML2 as a sole carbon source, and its aerobic degradation can be measured using a dissolved oxygen electrode. The bacterial cells were immobilised between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen probe, which was inserted into a custom-made flow cell. The applicability of the biosensor for the analysis of air samples containing benzene was investigated. Air samples were collected from a controlled exposure room using charcoal adsorption tubes, and benzene extracted with solvent desorption using dimethylformamide (DMF). The biosensor displayed a linear detection range between 0.025 and 0.15 mM benzene based on standard solutions containing a maximum of 2% DMF, with a response time of 6 min. This linear detection range allows the analysis of air containing between 3 and 16 ppm benzene based on a 60-min sampling period. DMF proved to be compatible for use with the biosensor, causing minimal interference with the sensor response and causing no toxic effects on the bacterial cells. The FIA system was easily transported to an in situ location, and a correlation was obtained between the biosensor and gas chromatography (GC) results for the preliminary air samples investigated. Moreover, the biosensor displayed no interference to other benzene related compounds in the BTEX range. The results from this work have shown that the biosensor has potential applications for the analysis of benzene in workplace air samples, with the added advantages over the conventional GC methods of low operation costs, ease of use, and portability for in situ measurements.

Air Pollutants, Occupational↗
PubMed2002

Determination of codeine in urine and drug formulations using a clay-modified screen-printed carbon electrode.

Both flow-injection analysis and square-wave stripping voltammetry were evaluated for the determination of codeine in pharmaceutical formulations using a nontronite clay-modified screen-printed carbon electrode. Compared with a bare screen-printed carbon electrode, the nontronite clay-modified screen-printed carbon electrode exhibited a marked enhancement of the current response of codeine. A linear calibration plot was obtained over the 2.5-45 microM range (correlation coefficient=0.999) in pH 6.0 phosphate buffer solution with a detection limit of 20 nM (S/N=3) by square-wave voltammetry (SWV). While, in flow-injection analysis, the linearity was over 5-120 ng range with a detection limit of 1 ng in 20 microl loop. The nontronite clay-modified screen-printed carbon electrode can be either disposable or reused since the renewal gave a good reproducible surface. Quantitative analysis was performed by the standard addition method for codeine content in both urine and commercially available drugs.

Adult↗
PubMed2000

Comparison study of five analytical methods for the fractionation and subsequent determination of aluminium in natural water samples.

Five methods for aluminium fractionation used in different laboratories in Norway and Finland were compared using six control, 75 soil water and 10 lake water samples. Different fractionation principles [cation exchange, formation of the Pyrocatechol Violet (PCV) or quinolin-8-ol (oxine) complex], types of cation exchanger [Amberlite (Na/H) or Bond Elut (H)], reaction time (from 2.3 s), flow systems (flow injection analysis or segmented flow) and determination principles (molecular absorption spectrometry or ICP-AES) were tested. Determination of the 'labile' fraction was strongly dependent on the method used and the largest differences were observed between the ICP-AES method with cation exchange (Bond Elut H form) and the 'quickly reacting' method (oxine, 2.3 s). Different flow systems, both using cation exchange and determination of the PCV complex but with different reaction times and an extra acidification step, resulted in large differences in the 'reactive' and 'non-labile' fractions determined. However, the determination of the labile fraction gave similar results with both these methods. The two different types of cation exchanger used (with and without pH buffering and with different counter ions) in the ICP-AES methods resulted in differences, mainly because of a smaller 'non-labile' fraction in the non-buffered system. The two flow injection systems (oxine and PCV complexation) showed common trends, which may be connected with the short reaction times used. Comparison with theoretical equilibrium calculations using the model ALCHEMI suggested that the best correlation for the determination of the 'labile' fraction were obtained with the ICP-AES method with an Amberlite column.

Aluminum↗
PubMed2000

A dual electrochemical sensor for nitrite and nitric oxide.

Nafion/lead-ruthenate pyrochlore chemically modified electrode (NPyCME) showed a remarkable dual sensing activity toward NO2- oxidation and NO reduction as demonstrated by cyclic voltammetry (CV), ac-impedance spectroscopy and flow injection analysis (FIA). The mechanistic parameters of current function, charge transfer resistance and exchange current for the NPyCME, GCE and Nafion-coated GCE were evaluated and compared. The disproportionation reaction of NIIIO2- into NIVO3- + NIIO in acidic solution was used as a model system for testing the dual sensing ability of the NPyCME. The obtained crossover peak response for NO2- oxidation and NO reduction in pH 1.65 buffer solution gave the direct proof for the applicability of the NPyCME in the dual electrocatalytic action. By flow injection analysis, under optimized conditions, the calibration curve was linear in the range of 100 nM-100 microM and 800 nM-63.3 microM and the detection limit (S/N = 3) was 4.8 nM and 15.6 nM for NO2- and NO, respectively.

Flow Injection Analysis↗
PubMed2006

FIA-fluorimetric determination of the pesticide 3-indolyl acetic acid.

The paper presents the determination of the pesticide 3-indolyl acetic acid based on its native fluorescence; the method has been optimised either in a flow injection analysis (FIA) assembly or in batch. Maximum fluorescence intensity was observed at basic pH solutions at lambda(exc) = 280 nm and lambda(em) = 364 nm. The influence of different empirical parameters as pH, surfactants presence, solvent polarity, solved oxygen amount, and temperature was studied; highest outputs only required the pH in aqueous solutions to be adjusted over the range 9.5-10.5. Different calibration ranges were obtained by working with three different sensitivity scales of the fluorimeter either in flow injection analysis or batch. With the high sensitivity scale and FIA, the linear dynamic range was from 0.005 to 0.6 mg L(-1) 3-indolyl acetic acid; with an relative standard deviation (RSD) of 4.9% inter-day reproducibility. A large series of potential interferents was studied and finally, the method was applied to several water samples.

Buffers↗