Adsorptive Voltammetric Measurement of Trace Level of Iron(III) with 4–(2–Pyridylazo) Resorcin

Abstract

The polarographic behavior of the complex of iron–4– (2–pyridylazo) resorcin(PAR) was studied. In HAc– NaAc– EDTA buffer solution, the complex can be adsorped on a hanging mercury drop electrode giving a sensitive adsorptive complex reduction peak with a peak potential at -0.36V(vs. SCE). Optimum experimental conditions were found by the use of 0.08mol/L HAc, 0.06mol/L NaAc, 5.0 × 10^?3mol/L EDTA and 1.0 × 10^?5mol/L PAR. With preconcentration for 60s, the derivative peak height of the complex compound is linearly proportional to the concentration for Fe in the range from 1.0 × 10^?9mol/L to 1.0 × 10^?7mol/L. For a 2–min pre–concentration time, the detection limit found was 2.0 × 10^?10mol/L. This method has high sensitivity and selectivity. It has been applied to the determination of trace iron in food and water samples without any pre–separation step.     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Thermal Lens Spectroscopy for Quantitative Determination of a Cu(II) Complex With an 8-Aminoquinoline Derivative in Tap Water and Mining Wastewater Samples Using a Dual Beam Technique

Abstract

This article describes the quantitative determination of Cu(II) using thermal lens spectrometry. The chromogenic reaction involving Cu(II) and 5-(4-sulphophenylazo)-8-aminoquinoline in alkaline solution was studied in different experimental conditions such as pH, ligand concentration, methanol volume, and presence of interfering ions. A collinear dual beam set-up has been used for direct quantitation in water samples without a pre-concentration step. The optimized conditions provided a linear calibration in the concentration range from 3.0 to 15.0?×?10^?7?mol L^?1. The detection and quantitation limits were 6.13?×?10^?8? and 2.04?×?10^?7?mol L^?1, respectively. Resultantly, an application to Cu(II) determination in tap water (recovery 99.8–103.3%) and mining (synthetic) wastewater (95.3–98.0%) shows relative SDs ≤ 3.1%. The method is presented as a new alternative for the direct Cu(II) determination in real samples.     

Indirect Differential Pulse Voltammetric Determination of Aluminum Biological Samples in the Presence of 3, 4-Dihydroxyphenylalanine

ABSTRACT

Indirect differential pulse voltammetric (DPV) determination of aluminum in the presence of 3, 4-dihydroxyphenylalanine (L-dopa) with glass carbon electrode as working electrode has been described. The method relies on the decrease of DPV anodic peak current of L-dopa with the addition of Al^III The decreasing value of the peak current is linear with the increase of Al^III concentration. Under the optimum experimental conditions (pH 4.8, 6×10^?4 M L-dopa, 0.06M NaAc - HAc ¹buffer solution), the linear ranges are 4.0×10^?7 - 5.2×10^?6 M and 7.2×10^?6 - 4.5×10^?5 M. The relative standard deviation for 8×10^?6 M aluminum is 1.0% (n = 8) and the detection limit is 3.5×10^?7 M. A number of foreign species for interference have been studied. The method has been applied to determine aluminum in drinking water, synthetic renal dialysate and urine samples.     

6th International Conference on Flow Analysis

Abstract

The 2.5th order differential polarographic reduction behavior of malonaldehyde (MLD) was studied. A sensitive measurement method of the determination of MLD for biological samples was given by using differential voltammetry with a static mercury drop electrode at a scanning speed of 80mV/s in a solution of 0.1mol/L NH₄Cl. The linear response range of current(e″) against the concentration of MLD was 1.0×10^?6 to 1.0×10^?3 mol L and the detection limit was 1.0 × 10^?7mol/L. The contents of MLD in the sample of cardiac myocytes was determined rapidly and simply by means of the method.     

Spectrophotometric method for determination of atrazine and its application to commercial formulations and real samples

A simple sensitive spectrophotometric method has been developed for the determination of atrazine in herbicide formulations and real samples. The method was based on the reaction of atrazine with pyridine to form a quaternary halide which in the presence of alkali forms a carbinol base. The heterocyclic ring of the carbinol base breaks and forms the glutaconic dialdehyde. The glutaconic dialdehyde group was coupled with sulfanilic acid to form a yellow coloured product having λ _max 450 nm or coupled with aniline to form a orange red coloured product having λ _max 480 nm. The Beer's law was obeyed over the range from 0.1 to 25 µg mL^?1 and molar absorptivity 1.5 × 10⁴ L mol^?1 cm^?1 for sulfanilic acid, and from 0.08 to 12 µg mL^?1 and molar absorptivity 1.3 × 10⁴ L mol^?1 cm^?1 for aniline were observed. The reaction conditions and other analytical parameters were optimised. The proposed method has been successfully applied for the analysis of commercial formulations and real samples.     

Chemiluminescence Determination of Sulfite and Sulfur Dioxide Using Tris(1,10-Phenanthroline)Ruthenium-KMnO4 System

Abstract

The emission produced by sulfite after oxidation by potassium permanganate in acidic solution in the presence of Ru(phen)₃ ²⁺ is used to determine 1.0 × 10^?7 to 2.5 × 10^?5 mol/L sulfite. The limit of detection is 4.5 × 10^?9 mol/L and the relative standard deviation is 3.1% for a 1 × 10^?5 mol/L sulfite solution (n=8). The method was also applied satisfactorily to the determination of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.     

Electrochemical Behavior of 6-Mercapto-Purine at Hanging Copper Amalgam Dropping Electrode and Its Trace Determination by Differential Pulse Adsorption Cathodic Stripping Voltammetry

Abstract

The electrochemical behavior of 6-MP was studied by cyclic voltammetry at a hanging copper amalgam dropping electrode (HCADE). It was found that 6-MP could form a complex with the Cu(II) stripped from the HCADE, showing a new peak at ?0.19V in the medium of 0.1mol/L LiClO₄-0.5mol/L HClO₄ solution. The mechanism of the reaction was proposed. This new peak was sensitive and could be used for the determination of trace 6-MP by differential pulse adsorption cathodic stripping voltammetry (DPAdCSV). The linear range was from 3.6×10^?10 to 5.3×10^?6 mol/L, and the detection limit was about 1.2×10^?10 mol/L (S/N=3). The method was also successfully applied to the determination of 6-MP in pharmaceutical tablets.     

Separation and Removal of Mercury(II) from Water Samples Using (Acetylacetone)‐2‐Thiol‐Phenyleneimine Immobilized on Anion‐Exchange Resin Prior to Determination by Cold Vapor Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

(Acetylacetone)‐2‐thiol‐phenyleneimine (H₂L) immobilized on an anion‐exchange resin (Dowex) was used for separation and removal of mercury from natural water samples and for preconcentration prior to its determination by cold vapor inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 10% thiourea in 0.1 M HCl. The modified resin is higly selective with an exchange capacity of 1.60 mmol g^?1. Various parameters like pH, column flow rate, and desorbing agents are optimized. The proposed method has a linear calibration range of 15–1000 ng/ml Hg(II), with a relative standard deviation at the 15 ng/ml level of 3.5%. The precision of the method (evaluated as the relative standard deviation obtained after analyzing six series of five replicates) was ±4.2% at the 50 ng/ml level of Hg(II). The method has been used for routine determination of trace levels of mercury species in natural waters. The potential application of modified resin for the removal of mercury(II) from two natural water samples (top water and lake water) spiked with 50 ng/ml of mercury (II) was studied by ICP‐AES, and the results proved that excellent percent extraction of mercury(II) from both natural water samples was obtained by column method using modified resin.     

Determination of Lysine in Nutrition Sample by Adsorption Voltammetry

Abstract

Lysine can be determined by adsorptive voltammetry after derivatization with acetaldehyde in 1.3 x 10^?2mol/ L borax-NaOH buffer solution (containing 4 x 10^?3mol/ L of CH₃CHO at pH10). The Schiff's base product of the derivation can be adsorbed on a hanging mercury electrode and reduced with peak potential of about -1.33v (vs.SCE) after 120s pre-concentration time. The derivative peak height is linearly proportional to the concentration for lysine in the range 6.0 x 10^?7-1.0 x 10^?5mol/ L. The detection limit is 4.0 x 10^?7mol/ L. Using this method, we have directly determined lysine in nutrition samples without any pre-separation step.     

Determination of Aniline Derivatives in Water Samples by High Performance Liquid Chromatography Coupled with On-Line Flow Injection Preconcentration

An on-line SPE-HPLC method using a cigarette filter as the sorbent was developed and applied to analyze the aniline derivatives in water samples. A preconcentration column packed with cigarette filters was used to replace a conventional sample loop on the injector valve of an HPLC for on-line SPE. With the consumption of a 7.5 mL sample solution, the enhancement factors ranged from 287 to 349 in comparison with direct injections of 20 μL sample solution. The detection limits (S/N = 3) for preconcentration of 7.5 mL of sample solution ranged from 0.27 to 5.46 μg/L at a sample throughput of 6 samples per hour.     

A Neutral Carrier Membrane Calcium-Sensitive Electrode with Wide Working pH Range

Abstract

A poly(vinyl chloride) (PVC) membrane calcium-sensitive electrode based on a new type of synthetic carrier 1,7-di[2-(1-phenylazo)naphtyl]-1,4,7-trioxaheptan is introduced. This electrode exhibited Nernstian response over the concentration range 1.0×10^?1 - 3.0×10^?8 mol/L Ca²⁺ with a slope of 28.8 mV/pCa in calcium ion buffer solutions. The detection limit for calcium ion was 1.0X10^?8 mol/L. The response time varied from 10 to 30 seconds. The working pH range for the electrode was 3.5 - 12.3 when the concentration of Ca²⁺ was 10^?3 mol/L. The lifetime of the electrode was proved to exceed 8 months. It was applied successfully in the determination of calcium ion in river water, mineral water and cosmetic. A method for the determination of total calcium in urine was developed.     

Tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry for rapid determination of lead(II) and cadmium(II) ions in environmental water samples

ABSTRACT

Tandem dispersive liquid liquid microextraction coupled with micro - sampling flame atomic absorption spectrometry for rapid determination of lead2 and cadmium2 ions in environmental water samples. A simple method termed as tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry is used for determination of the lead(II) and cadmium(II) ions in different environmental water samples. According to the proposed method, the target analytes are extracted from an aqueous sample solution (10 mL) into a micro-volume of an organic solvent, and then they are selectively back-extracted into an aqueous acceptor solution (150 μL) to increase the compatibility of the extractant phase with a final analyser system and provide a suitable enrichment factor. The developed method is very fast, implemented in just about 7 min, and provides a high sample clean-up. The factors influencing the extraction efficiency including the type and volume of the organic solvent, pH and volume of the acceptor solution, and number of extractions are thoroughly examined and optimised. Under the optimal experimental conditions, the developed method provides a good linearity (in the range of 0.4–300 ng mL^?1 (R² ≥ 0.994)), and low limits of detection (in the range of 0.07–0.31 ng mL^?1). Finally, the method is successfully applied for the direct determination of the understudied analytes in the river, dam, and well water samples.     

A Fluorescence Quenching Method for the Determination of Chromium(VI) with L-Tyrosine

Abstract

A fluorescence quenching method for the determination of Cr(VI) in aqueous solution is described. The fluorescence intensity of the system is linear ever the range 5×10^?6 - 1.0×10^?4 M Cr(VI). The method has been applied to the determination of Cr(VI) In cast iron and waste water.     

Stacking and simultaneous determination of estrogens in water samples by CE with electrochemical detection

A rapid and sensitive method based on transient ITP and field enhancement in CE with electrochemical detection at copper disk electrode was developed for the simultaneous separation and determination of three estrogens: estrone, 17β‐estradiol, and estriol. The effects of several important factors that influence the separation and detection were investigated. Under the optimum conditions, the estrogens could be separated in 0.06 mol/L sodium hydroxide solution within 14 min. With transient ITP by addition of 0.5% NaCl, a good linear response was obtained for three estrogens from 0.2 to 10 μmol/L, with correlation coefficients higher than 0.9993. The detection limits were 8.9 × 10^?8, 6.7 × 10^?8, and 1.1 × 10^?7 mol/L (S/N = 3) for estriol, 17β‐estradiol, and estrone, respectively. This method was successfully employed to analyze different water samples from waterworks, tap water, fishpond, and river samples with recoveries in the range of 90.8–108.9%, and RSDs < 4.69%. The satisfied results demonstrated that this method was of convenient preparation, high sensitivity, and good repeatability, which could be applied to the rapid determination of environmental water samples.     

Flow Injection Analysis of Tannic Acid with Inhibited Electrochemiluminescent Detection

ABSTRACT

A flow injection method has been developed for the determination of tannic acid based on its inhibition of the electrochemiluminescence of luminol. The method is simple, rapid and sensitive with a detection limit of 2×10^?8 mol/l. It is effective to determine tannic acid in the range 5×10^?8 - 1×10^?5 mol/l. The variation coefficient of eleven determinations is 1.4% for 5×10^?6 mol/l. The method has been successfully applied to the determination of tannic acid in real Chinese gall and hop pellet samples.     

Development of a cloud point extraction and preconcentration method for chromium(III) and total chromium prior to flame atomic absorption spectrometry

A sensitive and selective method has been developed for the determination of chromium in water samples based on using cloud point extraction (CPE) preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Cr(III) ions with Brilliant Cresyl Blue (BCB) in the presence of non-ionic surfactant Triton X-114. Under the optimum conditions, the preconcentration of 50 mL of water sample in the presence of 0.5 g/L Triton X-114 and 1.2 × 10⁻⁵ M BCB permitted the detection of 0.42 μg/L chromium(III). The calibration graph was linear in the range of 1.5–70 μg/L, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Cr(III) in water samples and certified water samples. In addition, the developed CPE-FAAS method was also used for speciation of the inorganic chromium species after reduction of Cr(VI) to Cr(III) using a thiosulphate solution of 120 mg/L in the presence of Hg(II) ion as a stabilizer.     

Voltammetric sensing of triclosan in the presence of cetyltrimethylammonium bromide using a cathodically pretreated boron-doped diamond electrode

ABSTRACT

In the present study, a simple, cheap and sensitive electrochemical method based on a cathodically pretreated boron-doped diamond (CPT-BDD) electrode is described for the detection of triclosan with the cationic surfactant (cetyltrimethylammonium bromide, CTAB) media. The oxidation of triclosan was irreversible and exhibited an adsorption controlled process. The sensitivity of the adsorptive stripping voltammetric measurements was significantly improved with addition of CTAB. Using square-wave stripping mode, a linear response was obtained for triclosan determination in Britton-Robinson buffer solution at pH 9.0 containing 2.5 × 10^?4 M CTAB at around + 0.67 V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The method could be used in the range of 0.01–1.0 μg mL^?1 (3.5 × 10^?8–3.5 × 10^?6 M), with a detection limit of 0.0023 μg mL^?1 (7.9 × 10^?9 M). The feasibility of the proposed method for the determination of triclosan in water samples was checked in spiked tap water.     

Determination of chloride ion by electrochemiluminescence and investigation of the mechanism

The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied.Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi-tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is5.0 ×10~(-6) mol/L and the linear calibration range extends up to 1.0 ×10~(-2) mol/L; the relative standarddeviation for 1.0 ×10~(-5) mol / L chloride is 5%. The influencing factors for chloride determination arealso discussed. The possible mechanism for the electrochemiluminescence reaction may be due to theoxidation of chloride ion in the solution to ClO~-, and the latter acts on luminol and then gives outluminescence. The method has been applied to determine the total chloride in tap water with satisfactoryresults.     

Electrochemical Behavior of Hydrogen Peroxide at a Glassy Carbon Electrode Modified with Nickel Hydroxide–Decorated Multiwalled Carbon Nanotubes

Abstract

The multiwalled carbon nanotube–nickel hydroxide composite film used to modify glassy carbon electrode was prepared and confirmed by transmission electron microscopy and cyclic voltammetry. The process and mechanism of film formation were discussed in detail. The electrode modified with the composite film exhibited good catalytic activity toward electrochemical oxidation of hydrogen peroxide in 0.1 mol/L sodium hydroxide solution. Various factors affecting the electrocatalytic activity of nickel hydroxide film were investigated. The anodic peak current increased with the increased concentration of hydrogen peroxide. The linear range for the determination of hydrogen peroxide was from 1.5 × 10^?6 mol/L to 2.5 × 10^?3 mol/L with the detection limit 6.1 × 10^?7 mol/L (S/N = 3). And the proposed method was applied to the determination of hydrogen peroxide in disinfector with higher sensitivity and lower detection limit.