FIA Determination Research Articles

Simultaneous FIA Determination of Free and Combined Chlorine Based on the Difference in Decomposition Rate Under UV Light Irradiation

世界各地で水不足と水質汚染の問題が深刻となっており，衛生的な水の確保は重要な課題である．水の消毒では，遊離塩素と結合塩素の濃度を適切に管理することが重要である．遊離塩素と結合塩素の間には光分解反応速度に差が生じるため，この性質を利用することで遊離塩素と結合塩素の分別が可能であると考えた．本研究では，光照射流路と光照射のない流路への分岐を備えたフローインジェクション分析（FIA）システムを構築し，それぞれの流路を経由して得られるシグナルを時間差で検出した．その結果，それぞれのシグナルの大きさと遊離塩素及び結合塩素濃度の関係から作成した線型方程式を用いることで，一度の試料注入での同時定量が可能となった．次亜塩素酸イオンとクロラミンTの混合溶液を用いて同時定量を試みたところ，仕込み量と同等の値を得ることができた．

Coupling liquid membrane and flow-injection technique as an analytical strategy for copper analysis in saline water

A tandem system based on the coupling of a bulk liquid membrane and a flow injection analysis for the separation, preconcentration and spectrophotometric determination of copper in saline water is presented. The ligand pyridine-2-acetaldehyde benzoylhydrazone has been used as a carrier in the liquid membrane as well as a spectrophotometric reagent for UV–VIS detection. Simultaneous and sequential experimental designs were used to optimise the chosen variables of each technique, respectively. The metal was separated and preconcentrated from the sample with an efficiency of 100.5 ± 0.9% and a metal preconcentration factor of 16.1. The on-line FIA determination was accomplished after metal complexation by the reagent at pH 3. A linear response was obtained in a range from 6.9 to 984.5 µg L–1 Cu(II), providing a detection limit of 1.8 µg L–1. Saline matrix and other metal ions were not cause of interferences with relative errors below 4.6% for 50 µg L−1 of Cu(II) determination. The proposed tandem system was successfully tested using a TMDA-62 certified reference material providing a relative error of + 1.9%; it was also applied to the Cu(II) determination in coastal seawater samples with low relative errors ranging from − 3.8% to 0.0% (using DPASV as reference method).

Voltammetry and Flow Injection Analysis with Amperometric Detection for Sensitive Sodium Metamizole Determination on Glassy Carbon Electrode Modified with SWCNTs/Nafion

Novel, rapid and high sensitive voltametric methods and flow injection analysis were proposed for the determination of sodium metamizole on glassy carbon electrode modified with single-walled carbon nanotube with Nafion composite film. The results showed that SWCNT/Nafion remarkably enhanced the oxidation of metamizole which improved the anodic peak current of metamizole significantly. Under the optimized conditions peak current was proportional to sodium metamizole concentration in the range from 0.15 to 5 μM (DPV method) and from 20 to 100 μM (FIA method). The detection limit was 13 nM for DPV and 0.4 μM for FIA determination. The RSD for proposed methods were equal to 4.1% (n = 9) and 2.4% (n = 7) for voltammetry and FIA measurement respectively. Proposed methods were successfully validated by studying the recovery of metamizole in drugs and urine.

Comparison between immunoradiometric and fluorimetric brain natriuretic peptide determination in patients with congestive heart failure

This study compared two different methods, namely the immunoradiometric (IRMA) and fluorimetric (FIA), in order to determine plasma brain natriuretic peptide (BNP) in congestive heart failure (CHF) patients. CHF in-patients underwent echocardiography and plasma BNP determination using both two methods. The echocardiograms analysed left ventricular end-systolic (LVESV) and end-diastolic (LVEDV) volumes and systolic dysfunction [left ventricular ejection fraction (LVEF) <50%]. Seventy-three (71% males, age 67 ± 9.6 yr) patients were enrolled, 31.5% affected by valvular heart disease. The mean LVEF was 39.8 ± 14.1%; in 26 (35%) a hypertensive etiology emerged. The immunoradiometric assay (IRMA) BNP was found to be significantly lower than the FIA determination 116.5 ± 149 pg/ml vs 267.3 ± 285.6 pg/ml; p=0.0001) and the two methods were closely correlated (r=0.89; p=0.00001). Logistic regression demonstrated a significant correlation between BNP, LVEF, and LVESV/LVEDV (r=-0.45, p=0.0003; r=-0.48, p=0.00001; r=0.22 p=0.003; r=0.34 p=0.0001; r=0.13 p=0.02; r=0.28 p=0.001 IRMA and FIA, respectively). IRMA BNP and FIA BNP significantly increased according to the worsening functional class [from 34.3 ± 60.2 pg/ml in NYHA (New York Heart Association) I to 555.5 ± 273.1 pg/ml in NYHA IV; from 86.1 ± 162.1 pg/ml in NYHA I to 1070 ± 42.2 pg/ml in NYHA IV, respectively]. In severe systolic dysfunction (LVEF<30%), receiver operating characteristic analysis revealed a satisfactorily sensitivity and specificity using a cut-off point of 50.6 pg/ml with IRMA and 243 pg/ml with FIA. In mild systolic dysfunction (LVEF<50%), a good sensitivity and specificity using a cut-off point of 42 pg/ml with IRMA and 182 pg/ml with FIA emerged. In CHF patients both BNP methods correlated with NYHA class, LVEF, and ventricular volumes.

A biosensor based on immobilization of lactate oxidase in a PB-CTAB film for FIA determination of lactate in beer samples

An amperometric lactate biosensor with lactate oxidase immobilized into a Prussian Blue (PB) modified electrode was fabricated. The advantage of using cetyltrimethylammonium bromide (CTAB) in the electrodeposition step of PB films onto glassy carbon surfaces was confirmed taking into account both the stability and sensitivity of the measurements. The biosensor was used in the development of a FIA amperometric method for the determination of lactate. Under optimal operating conditions (pH = 6.9, E = -0.1 V), the linear response of the method was extended up to 0.28 µmol L-1 lactate with a limit of detection of 0.84 mmol L-1. The repeatability of the method for injections of a 0.28 mmol L-1 lactate solution was 2.2 % (n = 18). The usefulness of the method was demonstrated by determining lactate in beer samples and the results were in good agreement with those obtained by using a reference spectrophotometric enzyme method.

Thinly Insulated Wire Cells – A New Device for Sensitive Contactless Conductivity Detection in Flow Analyses

AbstractVery simple contactless conductivity cells have been designed, suitable for detection in flow analytical techniques (classical HPLC, FIA, SIA, continuous flow, etc.) in which this detection has so far rarely been used. The cells consist of two wire electrodes covered with a very thin layer (units of μm) of an insulating material (the dielectric) and punctured through the walls of a plastic tubing at a close mutual distance (from tenths to units of a mm) and placed either across the tube or along the tube axis, so that the detection occurs within the space limited by the two electrodes. As the thickness of the dielectric layer is substantially smaller than that in common contactless conductivity cells used in CE, the AC current flowing between the electrodes is higher and the measuring sensitivity is enhanced. The principal operational characteristics of these detectors have been tested using KCl solutions and compared with those calculated from a simple theoretical model. It has been shown that this model permits theoretical description of these cell types and reasonable prediction of their behavior. Practical application has been demonstrated on a FIA determination of inorganic carbonate.

FIA and Batch Simultaneous Determination of Sulfamethoxazole and Trimrthoprim in Pharmaceutical Formulations by Derivative Spectrophotometry

FIA and Batch Simultaneous Determination of Sulfamethoxazole and Trimrthoprim in Pharmaceutical Formulations by Derivative Spectrophotometry

Sensitivity improvement of ammonia determination based on flow-injection indophenol spectrophotometry with manganese(II) ion as a catalyst and analysis of exhaust gas of thermal power plant.

The sensitivity improvement of a flow-injection spectrophotometric method for the determination of ammonia was examined based on an indophenol blue coloration reaction with salicylate and hypochlorite in the presence of manganese(II) as a reaction promotion catalyst. The optimal conditions for achieving higher sensitivity of ammonia determination were examined using a three-line flow system. The limit of detection corresponding to a signal-to-noise ratio (S/N) of 3 was 0.005 mg l(-1) (approximately equal to 5 ppb) of NH4+. A calibration graph was linear in the range from 5 ppb to 1,000 ppb of ammonium ion. The relative standard deviations (n = 9) for 50 ppb and 100 ppb of ammonium ion were 6.4% and 2.2%, respectively. The proposed method was applied to the determination of ammonia in the exhaust gas of a thermal power plant. Prior to the FIA determination, ammonia in the exhaust gas was absorbed into a boric acid solution; the absorption solution was then analyzed by the proposed FIA.

Non-extraction batchwise and FIA determination of cationic and nonionic surfactants using Cu(II)–chromazurol S–surfactant complexes

Batchwise and FIA determinations have been developed for cationic and nonionic surfactants, based on the formation of ternary Cu(II)–chromazurol S–surfactant compounds. Optimum reaction conditions have been found (pH 8.0, λ=590 and 630 nm, respectively). For the batchwise measurement, the molar absorption coefficient values ε 590=5.1–5.7×10 4 l mol −1 cm −1 for cationic surfactants, ε 630=0.7–1.5×10 4 l mol −1 cm −1 for nonionic surfactants. A factorial design has been carried out to determine the optimum flow conditions. Calibration curves were constructed and statistically evaluated for both the batchwise and FIA determination. For example, the linear concentration ranges for batch determination of the cationic surfactant cetyltrimethylammonium bromide and nonionic surfactant Marlophen NP 10 are 0–15 μg ml −1 ( R=0.9996, R.S.D.=6.62–0.64%) and 13–53 μg ml −1 ( R=0.9993, R.S.D.=4.48–1.40%), respectively; the respective detection limits are 0.02 and 4.0 μg ml −1. For FIA determination of the same surfactants, the linear concentration ranges are 0–13 μg ml −1 ( R=0.9995, R.S.D.=4.44–0.49%) and 66–397 μg ml −1 ( R=0.9994, R.S.D.=8.92–1.12%), respectively, detection limits are 0.08 and 38 μg ml −1, respectively.

Amperometric flow-through biosensor for the determination of cholinesterase inhibitors

An amperometric flow-through biosensor based on epoxy-carbon electrode and butyrylcholinesterase immobilised on nylon, cellulose nitrate or white tracing paper has been developed and examined for the determination of reversible and irreversible inhibitors. The analytical characteristics of inhibitor determination depend on the hydrophobicity of the membrane material. Flow-through biosensor with various enzymatic membranes makes it possible to determine fluoride in the concentration range 1×10 −4–25×10 −4 mol l −1 and 3.5×10 −5–1×10 −2 mol l −1 when cholinesterase solution is used. The analytical characteristics of fluoride determination do not differ significantly from those obtained in batch conditions. For diazinon the immobilisation of cholinesterase results in the decrease of detection limits from 5×10 −9 mol l −1 (native enzyme) to 4×10 −9 mol l −1 (nylon membrane) and 1.5×10 −9 mol l −1 (cellulose nitrate membrane). The influence of membrane material on analytical characteristics of FIA determination of inhibitors is due to the non-stationary distribution of reagents (fluoride) or sorptional preconcentration of the inhibitor (diazinon) in membrane.

FIA determination of pyruvate in serum based on direct chemiluminescence oxidation

Chemiluminescence was observed by mixing acidic potassium permanganate solution with pyruvate in the presence of quinine. A new simplified method for pyruvate determination based on this phenomenon was established. The chemiluminescence intensity is a linear function of the concentration of pyruvate in the range of 2 × 10–6 to 1 × 10–3 g/mL with a detection limit of 0.8 μg/mL and a relative standard deviation of less than 2.3%. The method has been successfully used to determine pyruvate in serum.

FIA determination of Criii in tap water with chemiluminescence detection

CrIII has been determined by measuring the light emitted as a result of the CrIII-catalysed reaction between luminol and hydrogen peroxide. Increase in the sensitivity of the determination was achieved by introducing bromide into the reaction mixture while the selectivity was improved by the addition of EDTA. All the operations were performed on-line in an automated FIA system. The calibration curve for CrIII was linear in the range 0–500 µg l–1 and the limit of detection was 0.5 µg l–1. The method was applied to the determination of CrIII in tap water; the CrIII concentration varied between 10 and 20 µg l–1 with a typical coefficient of variation of 2% (n = 5).

Simultaneous FIA determination of two components with differential normal pulse voltammetric multidetection

AbstractA flow injection method for the simultaneous determination of two components based on differential normal pulse voltammetric multidetection was developed. The method entails applying two sequential potential pulses to a 3‐electrode voltammetric system (with a carbon paste working electrode) connected to a flow‐through cell. The proposed method can be applied to other complex systems comprising more than two substances provided large differences in their peak potentials.

Kinetic FIA Determination of Hg(II) Based on Its Catalytic Effect on the Reaction Between Safranin and Iodide

Abstract A sensitive kinetic spectrophotometric flow injection method has been developed for the determination of mercury(II) over the range 150–2700 ng. The method is based on the catalytic effect of this ion on the reduction reaction of safranin by iodide. Method development includes optimization of reagent concentrations, pH, reaction temperature, ionic strength and flow conditions. The optimized flow injection manifold yielded a detection limit of 90 ng Hg(II). Chemical interference studies showed that the method also has good selectivity. The method was applied to the determination of mercury in contact lense cleaning solution and human hair.

Development of Novel Redox Systems in Potentiometry and Its Application to Analytical Chemistry

The redox potential of a system involving metal ions has been modified by the complexation of metal ions with a suitable ligand. This phenomenon has a potential capacity for the development of novel redox systems which are applicable to quantitative analyses. Potentiometric titrations of vanadium(IV) with iron(III), cobalt(II) with vanadium(V) and cobalt(II) with chromium(VI) are possible in the presence of 1, 10-phenanthroline (phen) or 2, 2'bipyridine. A new spectrophotometric FIA determination of iron(II) has been presented based on the redox reaction of copper(II) with iron(II) in the presence of bathocuproinedisulfonate together with diphosphate.A new-type procedure for the spectrophotometric FIA method was developed for the simultaneous determination of redox couples of vanadium(V)/vanadium(IV) and quinone/hydroquinone based on this principle. The procedure was adapted to simultaneous determinations of iron(III) and vanadium(V) and of iron(III) and chromium(VI). It has been found that the redox reaction of cysteine with iron(III) in the presence of phen is accelerated by the addition of copper(II). A spectrophotometric FIA determination of cysteine was proposed based on the accelerating effect of copper(II) on the rate of the redox reaction. A spectrophotometric reverse FIA (rFIA) determination of complexing agents such as aminopolycarboxylic acids and polyphosphates was developed based on the redox reaction of copper(II) with iron(II) in the presence of neocuproine. By using this rFIA system, a new procedure for estimating the complexing capacity in natural water was developed.

Potentiometric flow analysis device using membrane-coated carbon rod ion-selective electrode detectors

A flow-through analysis system that utilizess a membrane-coated carbon rod ion-selective electrode was investigated. Electrodes for Cu 2+ based on a thiuram disulphide neutral carrier and for ClO 4 -, SCN -, NO 3 - and Cl - based on a bis(diphenylphosphino)propane-copper complex as ion exchanger exhibited satisfactory performance in a continous-flow system. The response of the anion electrodes in a flow-injection system was near Nernstian in the concentration range 10 −2-10 −4 or 10 −5 M. Highly reproducible measurements were obtained with sample volumes of 30-100 μl and a sample injection rate of up to 400 h −. The chloride electrode was suitable for the FIA determination of Cl - in sea water and urine.

Kinetic fluorometric FIA determination of total ascorbic acid, based on use of two serial injection valves

The kinetic determination of total ascorbic acid with a flow-injection analysis system is described. The sample is loaded into two serial sample injection valves and injected into a carrier system containing mercuric chloride and o-phenylenediamine. The formation of a fluorescent product is monitored. The single-point and double-point kinetic methods are compared by using both peak height and peak area as the analytical signal. A detection limit of 0.1 μ/ml for vitamin C was achieved with a sample throughput rate of 30 per hour.

Operator‐free flow injection analyser

A flow injection analyser has been constructed to allow an operator-free determination of up to 40 samples. Besides the usual FIA apparatus, the analyser includes a home-made sample introduction device made with three electromechanical three-way valves and an auto-sampler from Technicon which has been adapted to be commanded by an external digital signal. The analyser is controlled by a single board SDK-8085 microcomputer. The necessary interface to couple the analyser components to the microcomputer is also described. The analyser was evaluated for a Cr(VI)-FIA determination showing a very good performance with a relative standard deviation for 15 signals from the injection of 100 μl of a 1.0 mg.ml-1 standard Cr(VI) solution being equal to 0.5%.

The FIA determination of lead with 4-(2-pyridylazo)resorcinol after preconcentration on a microcolumn of a chelating sorbent

Lead can be determined conveniently by the classical or reversed FIA technique using photometric detection with 4-(2-pyridylazo)resorcinol ( cPAR = 0.1 mol l-1) in 0.1M borate buffer (λ 518 nm). For injected volumes of 50 μl, the lead concentrations can lie in the regions of 1-20 and 0.4=18 μmol l-1, respectively. The selectivity of determination can be increased one to two orders of magnitude by masking with a mixture of EDTA ( 5 μmol l-1), tartaric acid (20 μmol 1-1) and KCN (2 mmol 1-1). When combining the analysis with preconcentration on a 3 x 30 mm microcolumn of Spheron Oxin 1 000 chelating sorbent from 0.01M ammonium acetate solutions at pH 6.5 followed by elution with 0.1M-HCl, lead can be determined in concentrations of 0.1–1.2, 0.02–0.85 or 0.01–0.60 μmol 1-1 for sample volumes of 5, 10 or 20 ml, respectively. The repeatability of determination for ten independent measurements on 5, 10 and 20 ml sample volumes at cPb = 0.2, 0.05 μmol 1-1, respectively, was better than 4.7, 2.8 and 6.2%, respectively. The methodi of preconcentration on a chelating sorbent was applied to the analysis of clean industrial wastewaters. The relative deviation of the lead concentration did not exceed 6.5% in comparison with data obtained by AAS.

Chelating equilibria of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and 4-(2-pyridylazo)resorcinol with La(III) ions

2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (BrPADAP) with lanthanum(III) ions in 50% (v/v) aqueous ethanol or 30-50% (v/v) aqueous dimethylformamide (DMF) forms unprotonated chelates ML and ML2 characterized by a double absorption band with maxima at 550 and 570 nm. The ML2 species is rather unstable, hydrolyzing readily to the M(OH)L chelate, which exhibits an absorption maximum at 570 nm. The molar absorptivities of the ML, ML2, and M(OH)L species, lying in the regions of 5.3-6.5, 7.0-7.2, and 6.5-7.2 m2 mmol-1, respectively, depend on the kind and fraction of the organic component in the solvent. The conditional equilibrium constants (-log βpqr = 3.3-4.0, 12.2-12.5, and 7.8-8.2, respectively) decrease with increasing fraction of the organic solvent; in systems with high proportions of ethanol orDMF, the formation of higher species is greatly suppressed. 4-(2-Pyridylazo)resorcinol (PAR) with La(III) in acid aqueous solutions forms the MLH and ML species with absorption maxima at 490 and 506 nm, respectively ( ε = 1.2 and 2.5 m2 mmol-1, respectively) and with conditional equilibrium constants –log βpqr = -3.4 and 3.5, respectively. In alkaline solutions with excess PAR, the ML2 species with the absorption maximum at 509 mn (ε = 4.6 m2 mmol-1) and conditional equilibrium constant –log βpqr = 8.1 is formed. This chelate hydrolyses readily forming the M(OH)L species and other hydrolysis products. The ML2 species of the two reagents, forming in ammoniacal buffer at pH 9.0 – 9.5 (PAR) and 8.2 – 8.4 (BrPADAP), can be used for a sensitive (ε = 3.8 and 6.1 m2 mmol-1, respectively) post-column derivatization of lanthanoids after their separation by IEC or HPLC or for their FIA determination.