Fast determination of lead in lake sediment samples using electrothermal atomic absorption spectrometry with slurry samples introduction

An analytical method for the determination of glutamic acid by the sequential perturbation caused by different amounts of glutamic acid on the oscillating chemical system involving the Cu(II)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium is proposed. The method relies on the linear relationship between the changes in the oscillation amplitude of the chemical system and the concentration of glutamic acid. The reaction is implemented in a continuous-flow stirred-tank reactor, and changes in the oscillation amplitude on each perturbation are proportional to the glutamic acid concentration. The use of the analyte pulse perturbation (APP) technique permits sequential determinations on the same oscillating system owing to the expeditiousness with which the steady state is regained after each perturbation. The dynamic range lies between 2.5x10(-6) and 3.2x10(-4) M of glutamic acid, with the regression coefficient is 0.9987. The precision is excellent (less than 0.68% as relative standard deviation (R.S.D.)). Some aspects of the potential mechanism of action of glutamic acid on the oscillating system are discussed.     

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.     

Kinetic determination of ascorbic acid by the BZ oscillating chemical system

A new analytical method for the determination of ascorbic acid by the perturbation caused by different amounts of ascorbic acid on the BZ oscillating chemical system involving the Ce(IV)-catalyzed reaction between potassium bromate and malonic acid in a acidic medium is proposed. The method relies on the linear relationship between the change in the oscillation amplitude of the chemical system and the concentration of ascorbic acid, which is in this work exposed for the first time. The calibration curve is linearly proportional to the concentration of ascorbic acid over the range 3.5x10(-6)-4.7x10(-4) M, with the regression coefficient is 0.9975. Two different methodologies were used to address the determination. Some aspects of the potential mechanism of action of ascorbic acid on the BZ oscillating chemical system are discussed in detail.     

Rapid determination of vitamin B12 concentration with a chemiluminescence lab on a chip

This paper reports a novel method for the rapid determination of vitamin B(12) concentration in a continuous-flow lab-on-a-chip system. This new method is based on luminol-peroxide chemiluminescence (CL) assays for the detection of cobalt(II) ions in vitamin B(12) molecules. The lab-on-a-chip device consisted of two passive micromixers acting as microreactors and a double spiral microchannel network serving as an optical detection region. This system could operate in two modes. In the first mode, samples are acidified and evaluated directly in the microchip. In the second mode, samples are treated externally by acidification prior to detection in the microchip. In the first mode, the linear range obtained was between 1.00 ng ml(-1) to 10 μg ml(-1), R(2) = 0.996, with a relative standard deviation (RSD) of 1.23 to 2.31% (n = 5) and a limit of detection (lod) of 0.368 pg ml(-1). The minimum sample volume required and the analytical time were 30 μl and 3.6 s, respectively. In the second mode, the linear range obtained was between 0.10 ng ml(-1) to 10 μg ml(-1), R(2) = 0.994, with the RSD of 0.90 to 2.32% (n = 6) and a lod of 0.576 pg ml(-1). The minimum sample and the analytical time required were 50 μl and 6 s, respectively. The lab on a chip working in mode II was successfully used for the determination of vitamin B(12) concentrations in nutritional supplemental tablets and hen egg yolks.     

Use of pruned computational neural networks for processing the response of oscillating chemical reactions with a view to analyzing nonlinear multicomponent mixtures

The suitability of pruned computational neural networks (CNNs) for resolving nonlinear multicomponent systems involving synergistic effects by use of oscillating chemical reaction-based methods implemented using the analyte pulse perturbation technique is demonstrated. The CNN input data used for this purpose are estimates provided by the Levenberg-Marquardt method in the form of a three-parameter Gaussian curve associated with the singular profile obtained when the oscillating system is perturbed by an analyte mixture. The performance of the proposed method was assessed by applying it to the resolution of mixtures of pyrogallol and gallic acid based on their perturbating effect on a classical oscillating chemical system, viz. the Belousov-Zhabotinskyi reaction. A straightforward network topology (3:3:2, with 18 connections after pruning) allowed the resolution of mixtures of the two analytes in concentration ratios from 1:7 to 6:2 with a standard error of prediction for the testing set of 4.01 and 8.98% for pyrogallol and gallic acid, respectively. The reduced dimensions of the selected CNN architecture allowed a mathematical transformation of the input vector into the output one that can be easily implemented via software. Finally, the suitability of response surface analysis as an alternative to CNNs was also tested. The results were poor (relative errors were high), which confirms that properly selected pruned CNNs are effective tools for solving the analytical problem addressed in this work.     

Determination of <Emphasis Type="Italic">p</Emphasis>-nitrobenzene-azo-naphthol by an oscillating chemical reaction using the analyte pulse perturbation technique

A simple analytical method for the determination of p-nitrobenzene-azo-naphthol was proposed by a sequential perturbation with different amounts of p-nitrobenzene-azo-naphthol on an oscillating chemical system. The method involves a Cu(II)-catalysed oscillating reaction between hydrogen peroxide and sodium thiocyanate in alkaline medium with the aid of continuous-flow stirred tank reactor (CSTR). A good linear relationship between the changes, oscillation amplitude or/and period, and the concentration of p-nitrobenzene-azo-naphthol was obtained. The use of analyte pulse perturbation technique provides a possibility of sequential determination in a same oscillating system, due to a new steady state that reappeared rapidly after each perturbation. The calibration curve fits a linear equation very well when the concentration of p-nitrobenzene-azo-naphthol ranging from 5.2×10⁻⁷ to 3.3×10⁻³M. Influence of temperature, injection point, flow rate and reactants variables on this system were investigated in detail.     

A new analytical procedure for assay of lysozyme in human tear and saliva with immobilized reagents in flow injection chemiluminescence system.

A novel analytical procedure based on chemiluminescence (CL) detection was described for the determination of lysozyme at ng ml(-1) level by using controlled-reagent-release technology in a flow injection system. The analytical reagents involved in the CL reaction, including luminol and periodate, were both immobilized on the anion-exchange resins in the flow injection system. Through water injection, luminol and periodate were eluted from the anion-exchange column to generate the chemiluminescence, which was inhibited in the presence of lysozyme. By measuring the decrease of CL intensity, one could analyze the lysozyme quantitatively. The decrement of CL emission was linear over the logarithm of lysozyme concentration in the range of 30-1000 ng ml(-1). A typical analytical procedure, including sampling and washing, could be performed in 0.5 min at a flow rate of 2.0 ml min(-1), giving a throughput of 120 h(-1), with a relative standard deviation of less than 3.0%. The proposed method was applied successfully to the determination of lysozyme in human tear and saliva samples, and the recovery was from 92.0% to 105.7%.     

Kinetic Determination of GA by the BZ Oscillating Chemical System

A new analytic method for the determination of gibberellic acid (GA) by perturbation causing different amounts of GA on the BZ oscillating chemical system involving the Mn(II)‐catalyzed reaction between L‐alanine, potassium bromate, and malonic acid in the acidic medium is proposed. The method relies on the linear relationship between the change in the oscillating period of the chemical system and the concentration of GA, which is in this work exposed for the first time. The calibration curve is linearly proportional to the concentration of GA over the range 1.0 × 10⁸ ?1.0 × 10^?6M, where the regression coefficient is 0.9998, and the detection limit is 5.0 × 10^?9 M of GA. Some aspects of the potential mechanism of action of GA on the BZ oscillating chemical system are discussed in detail.     

Studies on oscillating chemical reaction in Cu(II)‐catalyzed thiocyanate–hydrogen peroxide–NaOH system using pulsating sensor

We present a novel measurement technique to study an oscillating chemical reaction using a new class of sensor, viz. a pulsating sensor developed in‐house. A halogen‐free oscillating chemical reaction in the Cu(II)‐catalyzed H₂O₂‐KSCN–NaOH system reported by Orban was chosen to examine the performance of this technique. Shift in potential during the oscillating reaction was captured online with high precision and excellent resolution using this simple but high‐performance pulsating potentiometric measurement technique. In this work, the influence of bath temperature and flow rate of reagents on the Cu(II)‐catalyzed H₂O₂–KSCN–NaOH oscillating chemical reaction is investigated to optimize the conditions for rapid oscillations. This, in turn, helps to evolve analyte pulse perturbation techniques for rapid assay of hydrazine, uranium(VI), and sodium thiosulfate in aqueous solutions using the above oscillating reaction. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 19–29, 2013     

Determination of Heroin Based on Analyte Pulse Perturbation to an Oscillating Chemical Reaction

IntroductionOscillating chemical reaction is a complexphysico- chemical system,which deals with manyintermediate processes and intermediate species.Basically,in an oscillating chemical reaction sys-tem,the concentrations of the catalyst and/or in-termediate species undergo oscillations with time.Under specific reaction conditions,the oscillationsare reflected in color change[1] ( the oscillatingspecies exhibit different colors) ,p H change[2 ]( variations in H+ or OH-concentration in themedi…     

Hollow fiber-based liquid-phase microextraction (HF-LPME) of ibuprofen followed by FIA-chemiluminescence determination using the acidic permanganate-sulfite system

Hollow fiber-based liquid-phase microextraction (HF-LPME) is a relatively new technique employed in analytical chemistry for sample pretreatment which offers more selectivity and sensitivity than any traditional extraction technique. This paper describes a three-phase HF-LPME method for ibuprofen using a polypropylene membrane supporting dihexyl ether followed by a chemiluminescence (CL) determination using the CL enhancement on the acidic permanganate-sulfite system in a FIA configuration which is the first time that both techniques have been combined for analytical purposes. The CL intensity (peak area) was proportional to the log of ibuprofen concentration in the donor phase over the range 0.1-20 μg mL⁻¹. The detection limit was 0.03 μg mL⁻¹ of ibuprofen in the donor phase. The method was satisfactory reproducible and has been applied to the ibuprofen determination in pharmaceuticals and in real human urine samples.     

超痕量H_2O_2对MnSO_4-KBrO_3-乙酰丙酮化学振荡体系的扰动

化学振荡波和生物体内的生物振荡及生物形态现象的相似性促使人们认识到生命现象和非生命现象之间遵循着某些相同的规律 ,因而化学振荡反应非线性动力学一直是物理化学研究的热点 [1,2 ] .近年来它在分析化学中的应用使其研究扩展到了一个新的领域 ,但仍停留在 1 0 - 7mol/L的水平上 [3] .显然 ,以这个量去研究包含众多基元反应和反应中间体的振荡反应 ,得到的是数目庞大的反应物种群体行为 ,而这种行为并不足以说明生命现象的猝发病变、代谢功能衰竭及运动寿命终止的原因 .　　我们在研究 H2 O2 对 Mn SO4 - KBr O3-乙酰丙酮宏观振荡规…     

Studies of oscillating chemical in the H<Subscript>2</Subscript>O<Subscript>2</Subscript>–KSCN–CuSO<Subscript>4</Subscript>–NaOH system using a conductometry method

This paper reports a new methodological approach for investigating oscillating chemical reactions using simple and fast analytical information by measuring the conductivity of the solution. Although this technique is very common, and one of the simplest methods among the analytical techniques, however no work has been reported so far using this method for studying an oscillating system. For measuring conductivity, we use the oscillating system of H₂O₂–KSCN–CuSO₄–NaOH. Results indicate that the conductivity of the system fluctuates during the oscillating reaction. The oscillating conduction of this system was studied by changing the concentration of species involved in the oscillating reaction. Results indicate that the oscillating behaviour is varied by changing the concentration of the species.     

A novel chemiluminescence technique for quantitative measurement of low concentration human serum albumin.

An efficient and highly sensitive chemiluminescence (CL) technique is proposed in the current study for detection of low levels of human serum albumin (HSA). Chemiluminescence (CL) produced during interaction between fluoresceinyl cypridina luciferin analog (FCLA)-1O2 can be modified with the presence of HSA. The conventional CL technique uses a quenching effect of HSA for its quantitative measurement. We are reporting here that the CL intensity can be enhanced, rather than quenched, by the addition of HSA. The CL signal can be linearly correlated with the HSA concentration over a clinically interesting range of 5 x 10(-9) - 8 x 10(-8) mol L(-1), with a detection limit of 2.5 x 10(-9) mol L(-1). The determination result was consistent with that obtained from conventional methods. One possible mechanism of HSA detection technique using CL enhancement approach is discussed. Intermolecular energy transfer in chemiluminescence systems and changes of microenvironment are likely to be contributors of the CL enhancement with HSA.     

Determination of Butylated Hydroxyanisole by Briggs‐Rauscher Oscillating Reaction Catalyzed by a Macrocyclic Nickel (II) Complex

A novel analytical approach for quantitative measurement of butylated hydroxyanisole (BHA) is dis‐ cussed in this paper. Such a method depends on the inhibitory effect of BHA on a Briggs‐Rauscher (B‐R) oscillating reaction. Unlike the classical B‐R system which involves Mn²⁺ as the catalyst, such a B‐R sys‐ tem is catalyzed by a macrocyclic nickel (II) complex [NiL](ClO₄)₂, where L in the complex is an unsatu‐ rated ligand 5,7,7,12,14,14‐hexemethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene. By perturbation of BHA on the system, the oscillation was inhibited in the presence trace amounts of BHA and the inhibition time was found to be proportional to the concentration of BHA over the range 1.00×10^?7–1.20×10^?4 mol/L. Two calibration curves were obtained: the first linear regression is over the range of 1.00×10^?7–2.00×10^?6 mol/L, and the second linear regression is over the range between 2.00×10^?6 and 1.20×10^?4 mol/L, with a lowest limit of detection of 4.00×10^?8 mol/L. UV spectra measurements were employed to clarify the possible perturbation mechanism caused by BHA on the B‐R oscillating reaction.     

Determination of vitamin B<Subscript>12</Subscript> using a chemiluminescence flow system

A method to determine vitamin B₁₂ by measuring the chemiluminescence (CL) intensities using a flow injection (FI) system has been proposed. It is based on the catalytic effect of cobalt(II) in vitamin B₁₂ on the CL reaction between luminol and hydrogen peroxide in a basic medium. The increment of the CL intensity is proportional to the concentration of vitamin B₁₂ in the range 8.68–86.9 ng/mL (r ² = 0.9984) with a detection limit (3σ) of 0.89 ng/mL. The CL response is obtained in 10 s at a flow rate of 3.0 mL/min with a relative standard deviation (RSD) of less than 2.5% (n = 6). The method has been successfully applied to the determination of vitamin B₁₂ in pharmaceutical injections. The text was submitted by the authors in English.     

Determination of Ascorbic Acid Using a New Oscillating chemical System of Lactic Acid—Acetone—BrO3^— —Mn^2 —H2SO4

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Determination of ascorbic acid in pharmaceutical dosage forms and urine by means of an oscillatory reaction system using the pulse perturbation technique

A simple and reliable method for the determination of ascorbic acid (AA) is proposed and validated. It is based on potentiometric monitoring of the concentration perturbations of an oscillatory reaction system in a stable nonequilibrium stationary state close to the bifurcation point. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix, to the perturbation by different concentrations of AA, is followed by a Pt electrode. The linear relationship between maximal potential shift and the logarithm of the amount of AA is obtained between 0.01 and 1.0 μmol. The sensitivity of the proposed method (as the limit of detection) is 0.009 μmol and the method has excellent sample throughput (30 samples per hour). The procedure was used for AA determination in pharmaceutical formulations and urine. The results are in agreement with those obtained using the official method. Some aspects of the possible mechanism of AA action on the BL oscillating chemical system are discussed.     

The study of a chemiluminescence immunoassay using the peroxyoxalate chemiluminescent reaction and its application

The paper presented a novel chemiluminescence (CL) immunoassay method, which combines the advantages of traditional enzyme-linked immunosorbent assays (ELISA) and bis (2,4,6-trichlorophenyl) oxalate (TCPO)-hydrogen peroxide CL detection system. A fluorescent product 2,3-diaminophenazine (DAPN) was produced by reaction between o-phenylenediamine (OPDA, 1,2-diaminobenzene) and H₂O₂ catalyzed by horseradish peroxidase (HRP). DAPN was excited by the reactive intermediate of TCPO-H₂O₂ chemiluminescent reaction, and led to CL. The dependence of the CL intensity on the concentrations of antigen was studied. As analytical application, the proposed method was used for determination of recombinant human interleukin 6 (rHu IL-6) and β-human chorionic gonadotropin (β-HCG). Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentration of rHu IL-6 in the range of 4.0-625.0 pg/ml, and β-HCG in the range of 12.5-400.0 mIU/ml. The detection limits were 0.5 pg/ml for rHu IL-6 and 3 mIU/ml for β-HCG with relative standard deviation of 2.3 for 78.0 pg/ml rHu IL-6, and 3.9 for 50.0 mIU/ml β-HCG. This method has been applied to the determination of rHu IL-6 in human serum and β-HCG in urine with satisfactory results.     

Xanthene Dye Chemiluminescence for Determination of Free Chlorine in Water

Abstract

Preliminary investigations by a batch method are described for aiming at the flow determination of free chlorine in water with novel chemiluminescence (CL) detection. The CL originates from the reaction of xanthene dyes with free chlorine, Cl₂, HOCl, and OCl^?. Through the measurements of CL decay curves, fundamental CL characteristics were explored from the analytical point of view. Among xanthene dyes tested, eosin Y. eosin B. pyronin B. and rhodamine 6G were found to be promising CL reagents with such sensitivity and selectivity that free chlorine can be readily determined in tap water. In particular. these CL systems have the special advantage of being insensitive to oxo acids of chlorine and chloramine. Recommended flow systems are proposed.