Flow injection-mini-column technique with ICP-AES detection for the isolation and preconcentration of the fast reactive aluminium fraction in waters

A flow injection mini-column system based on short reaction times with 8-hydroxyquinoline (oxine) with ICP-AES detection is described for the isolation and preconcentration of the fast reactive or toxic aluminium fraction in water samples. Using a 3 s reaction time with oxine (5 × 10^–4 mol/l) at pH 5.0, the fast reactive aluminium fraction is shown not to include the non-toxic AlF²⁺ species at low F^–: Al³⁺ molar ratios (0.3 : 1). The complexed aluminium is isolated in a stable and recoverable form on mini-columns of Amberlite XAD-2 (0.3 cm × 5.0 cm, resin particle size range 0.08 mm–0.16 mm)). The retained aluminium is recovered by back-flushing the analytical column with 1 mol/l HCl for final element specific detection by ICP-AES. Detection limits (after preconcentration) of 2 g/l, a linear range of 0–500 g/l, and possible preconcentration factors of up to 18 times are demonstrated with the present system. Implications for the possible solution of sample stability problems encountered with labile aluminium species analysis and the development of a field sampling technique are discussed, where the desired Al fraction is quantitatively retained in a stable form on mini-columns.     

Anodic Stripping Voltammetric Determination of Mercury in Water Using a Chitosan‐Modified Carbon Paste Electrode

Abstract

This paper describes the preparation and electrochemical application of a modified carbon paste electrode with chitosan for the determination of Hg(II) ions in water using anodic stripping voltammetry. Experimental parameters, including the pH of the supporting electrolyte, time and potential of accumulation and scan rate were investigated. The best voltammetric response was observed for a paste composition of 60% (m/m) of graphite powder, 20% (m/m) of chitosan and 20% (m/m) of mineral oil, with 0.1 mol/l NaNO₃ solution at pH 6.3 as supporting electrolyte, a preconcentration potential of ?0.2 V, preconcentration time of 270 s and a scan rate of 25 mV/s. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 9.99×10^?7 to 3.85×10^?5 mol/l with a detection limit of 6.28×10^?7 mol/l. Three “spiked” samples of water were evaluated using the proposed sensor, and results agreed with those obtained by a reference method at the 95% confidence level.     

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.     

Enzymatic inhibition enthalpimetry: The analytical potential of the inhibitory action of a series of physiologically active alkaloids on the activity of serum cholinesterase

A kinetic method is described for the enthalpimetric determination of a series of physiologically active alkaloids based on their inhibitory effect on the cholinesterase-catalysed hydrolysis of butyrylcholine iodide. All analyses are done at pH 8.0 and at 25.0°C (short term stability ± 0.002°C). Precision (< 3.0%) data are reported for the determination of physostigmine sulphate (1.0–4.0 × 10^-8), quinine sulphate (1.0 × 10^-6–4.0 × 10^-5), procaine hydrochloride (1.0 × 10^-5–× 2.5 × 10^-4), atropine sulphate (5.0 × 10^-5–3.0 × 10^-4), morphine sulphate (1.0–8.0 × 10^-4), codeine phosphate (3.0 × 10^-4–2.4 × 10^-3), pilocarpine nitrate (5.0 × 10^-4––6.0 × 10^-3) and thiamine hydrochloride (1.0–5.0 × 10^-3); the linear response ranges in mol dm^-3 are given in parentheses. Complete inhibition curves are presented and relative “potency” is inferred. The effects of several interfering inhibitors are discussed.     

Investigations on Adsorption Potentiometry Part V Derivative Adsorption Chronopotentiometry of Beryllium(II)-4-[(4-diethylamino-2-hydroxypheanyl)-azo]-5-hydroxy-naphthalene-2,7-disurphonic Acid System

Abstract

An electroanalytical methood, based on derivative chronopotentiometry of the complex of beryllium(II) with 4-[(4-diethylamino-2-hydroxy-phenyl)-azo]-5-hydroxy-naphthalene-2,7-disurphonic acid (Beryllon II) accumulated adsorptively on the surface of a hanging mercury drop electrode, has been developed for determining trace beryllium in food. The dependences of the peak height on the dt/dE vs. E curve on the pre-concentration time, preconcentration potential and the constant reducing current are discussed. In 0.15 mol/1 NH_s+0.05 mol/1 NH₄Cl, 4×10^?7 mol/l Beryllon II, and at a preconcentration potential of -0.30 V (ve. SCE), the limit of detection and linear range are 1 × l0^?10 mol/l and 3 × 10^?10 -2 × l0^?7 mol/l, Iwpectively. The relative standard error of the method is 2.3% for 6 × 10^?8 mol/l Be(II). The method WBB applied to samples of food. The electrode procees hae been diecueeed.     

Determination of Albumin Using the Chemiluminescence of Tb3+/K2S2O8 System

A new chemiluminescence system of Tb³⁺/K₂S₂O₈ was developed for the determination of albumin. Some experimental conditions were examined and optimized. The linear ranges of the calibration curves are 5.0 × 10^?9–5.0 × 10^?6 mol/L for bovine serum albumin, 5.0 × 10^?8–1.0 × 10^?5 mol/L for human serum albumin and 2.5 × 10^?7–1.0 × 10^?5 mol/L for ovalbumin, and the corresponding detection limits are 1.9 × 10^?9 mol/L, 1.5 × 10^?8 mol/L, and 1.5 × 10^?7 mol/L, respectively. The method was applied to the determination of albumin in human serum samples, and the results were in agreement with those obtained by the bromcresol green method. The relative errors for the analytical results were from ?2.0% to 4.3%.     

Selective method for the determination of gold by anodic stripping voltammetry

A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au³⁺ reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5×10⁻⁸ to 1×10⁻⁶ mol/l. The relative standard deviation for 2×10^-7 mol/l HAuCl₄ was 4.2% (n=5). The detection limit was 4×10^-9 mol/l. The accuracy of the method was verified by the determination of gold in reference materials.     

Optimization of a sensitive method for the “switch-on” determination of mercury(II) in waters using Rhodamine B capped gold nanoparticles as a fluorescence sensor

Monodisperse and “naked” gold nanoparticles (GNPs) were modified with thioglycolic acid (TGA). The fluorescence of rhodamine B (RB) is quenched completely by the gold NPs surface with negative charge mainly as a result of fluorescence resonance energy transition (FRET) and collision. The quenching mechanism can be described by a Langmuir isotherm, which was systematically investigated by steady-state fluorescence spectrometry and absorption spectrometry. Hg(II) ion disrupts the GNPs–RB pair, producing a large “switch-on” fluorescence. A low background, highly sensitive and reproducible fluorescence assay for Hg(II) is presented. Under the optimum conditions, the restoration fluorescence intensity is proportional to the concentration of Hg(II). The calibration graphs are linear over the range of 1.0?×?10^?9 to 3.1?×?10^?8 mol L^?1 with a detection limit of 4.0?×?10^?10 mol L^?1. The relative standard deviation was 1.2% for a 5.0?×?10^?9 mol L^?1 Hg(II) solution (N?=?6). This method was applied to the analysis of Hg(II) in environmental water samples, and the results were consistent with those of atomic absorption spectroscopy (AAS).     

X-ray fluorescence analysis of trace metal ions following a preconcentration of metal-diethyldithiocarbamate complexes by homogeneous liquid-liquid extraction

A homogeneous liquid-liquid extraction method for 36 metal ions with diethyldithiocarbamate was studied. As a result, 11 metal ions were extracted as metal-chelates. Under the experimental conditions, the maximum concentration factor was 500 (i.e., 0.1?mL of sedimented liquid phase was produced from 50 mL of aqueous phase). Moreover, the proposed method was utilized as a preconcentration method for X-ray fluorescence analysis of these metals. The recovery of each metal was ca. 97–100%. All calibration curves were linear over the range of 5.0 × 10^–7 mol L^–1 to 1.0 × 10^–5 mol L^–1. The detection limits were at the ¶10^–8 mol L^–1 levels and the relative standard deviations were below 5% (5 determinations). When the proposed method was used for the determination of contaminants in a synthetic sample (Al-based alloy model) and of components in an Au-Pd alloy, the results were satisfactory.     

Use of a Carbon Paste Electrode Modified with Spinel‐Type Manganese Oxide as a Potentiometric Sensor for Lithium Ions in Flow Injection Analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel‐type manganese oxide (lambda‐MnO₂), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li⁺ against other alkali and alkaline‐earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6×10^?5–1.0×10^?2 mol L^?1 with a slope 78.9±0.3 mV dec^?1 over a wide pH range 7–10 (Tris buffer), without interference of other alkali and alkaline‐earth metals. For a flow rate of 5.0 mL min^?1 and a injection sample volume of 408.6 μL, the relative standard deviation for repeated injections of a 5.0×10^?4 mol L^?1 lithium ions was 0.3%.     

Sensitive and selective determination of mercury by differential pulse stripping voltammetry after accumulation of mercury vapour on a gold plated graphite electrode

 A selective and sensitive method is proposed for the determination of mercury by anodic stripping voltammetry after its preconcentration from the gas phase. Mercury from the sample solution is reduced to elemental Hg by SnCl₂ and volatilized by the bubbles of a carrier gas. The gas containing mercury vapour is dried and passed through a capillary onto a gold coated graphite electrode. An anodic stripping voltammogram is recorded from 0.1 mol/l HClO₄+3×10^-3 mol/l HCl solution. The calibration curve is linear from 1×10^-9 to 4×10^-8 mol/l Hg(NO₃)₂. The absolute detection limit is 0.46 ng Hg. The relative standard deviations for 4×10^-9 mol/l and 2×10^-8 mol/l Hg(NO₃)₂ are 9.8% and 6.1%, respectively (n=5). Received: 18 December 1995/Revised: 16 April 1996/Accepted: 20 April 1996     

Preconcentration of copper,lead, cadmium and zinc ions from water with 2-mercaptobenzothiazole loaded on glass beads with the aid of collodion

2-Mercaptobenzothiazole (MBT) loaded on glass beads with the aid of collodion was prepared and used for selective preconcentration of μg l^?1 levels of copper(II) and lead from aqueous solutions. Copper and lead were quantitatively retained on the loaded beads from solutions of pH 5.0–6.0 and >5.0, respectively, while cadmium(II) and zinc(II) were retained at ? pH 6.0 and 7.0, respectively. The retention capacity of the loaded beads was ca. 108 μg Cu g^?1 (1.7 μmol g^?1) at pH 5.5 for beads of 0.3–0.4 mm diameter. The mole ratios of MBT to copper(II) and lead(II) were ca. 10 and 45, respectively, regardless of the amount of MBT loaded on the beads. Copper was completely retained on the column at a high flow rate (21.7 ml min^? cm^?2) and lead(II) at up to 12.7 ml min^? cm^?2. Cadmium(II) and zinc(II) were not retained quantitatively even at low flow rates (< 1.2 ml min^?1 cm^?2). Thus, selective preconcentration of copper and lead was achieved by passing the sample through the column at high flow rate at pH 6.5. The copper and lead retained on the column were complete eluted together with the collodion with 5 ml of MIBK by batch-mode elution, and determined directly by one-drop atomic absorption spectrometry. Copper(II) and lead(II) in several kinds of water were determined.     

Vermiculite clay mineral as an effective carbon paste electrode modifier for the preconcentration and voltammetric determination of Hg(II) and Ag(I) ions

A vermiculite modified carbon paste electrode (VMCPE) was employed for the in situ preconcentration of traces of Hg(II) and Ag(I) via an ion-exchange route. Heavy metal ions were accumulated in Britton-Robinson (BR) buffer pH 7 for Hg(II) and pH 6 for Ag(I), and afterwards reduced at –0.7 V vs. Ag/AgCl in the separate measurement solution (BR buffer pH 5 + 0.05 mol/L NaNO₃) prior to the anodic stripping square-wave voltammetric (ASSWV) detection. For Hg(II) ions, at 15 min accumulation, a linear range from 1.0 × 10^–7 to 8.0 × 10^–6 mol/L was obtained, with a 5.7 × 10^–8 mol/L limit of detection. The VMCPE response was linear for Ag(I) ions in the concentration range from 2.0 × 10^–7 to 8.0 × 10^–6 mol/L, at 10 min accumulation with a corresponding limit of detection of 6.3 × 10^–8 mol/L. The relative standard deviation of the analytical procedure including accumulation from a 5 × 10^–7 mol/L solution of Hg (15 min) or Ag(I) (10 min), electrolysis, ASSWV detection, regeneration and activation of the VMCPE, was 4% (n = 6). The optimisation of the parameters for the application of the VMCPE in combination with ASSWV detection is presented and discussed.     

Spectrofluorimetric determination of hydrogen peroxide based on the catalytic effect of peroxidase-like manganese tetrakis(sulphophenyl) porphyrin on the oxidation of homovanillic acid

Traces of hydrogen peroxide (8.5 × 10^?8–2.5 × 10^?6 mol/l) and, indirectly, glucose (3–44 × 10^?6 mol/l) can be determined by the fluorescence reaction between homovanillic acid and hydrogen peroxide. Mn-TPPS₄ is found to have very similar catalytic properties to horse peroxidase.     

Solid Phase Extraction of Thallium(III) on Micro Crystalline Naphthalene Modified with N,N’-Bis(3-methylsalicylidene)- ortho-phenylenediamine and Determination by Spectrophotometry

A novel, simple, sensitive and effective method has been developed for preconcentration of thallium on N,N’-bis(3-methylsalicylidene)-ortho-phenylenediamine (MSOPD) adsorbent in a pH range 5.0—10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at λ＝520 nm. This method makes it possible to quantitize thallium in a range of 3.6×10－9 to 2.0×10－5 mol/L, with a detection limit (S/N＝3) of 1.42×10－9 mol/L. This procedure has been successfully applied to determine the ultra trace levels of thallium in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements, is better than 2.9%.     

A Novel Glucose Biosensor Based on Palladium Nanoparticles and Its Application in Detection of Glucose Level in Urine

IntroductionThelevelofglucoseinbloodorurineindicateshyper andhypoglycaemia ,bothofwhichcanresultfromavarietyofendocrinedisorders .1 4 Therapidandreliabledetermi nationofglucoselevelisaroutineprojectinclinicchem istry.Urinesamplesaresaferandmoreconvenientthanbloodones .Meanwhile ,theconcentrationofglucoseinserumiscloselyassociatedwiththatinurine .2 4 Eventhoughglucoseelectrodeshavebeensuccessfullyusedinseruminclinicalapplication ,thequestionstillremainedofhowtodetecttheglucoselevelinurine ,wh…     

Investigations on adsorption potentiometry Part I. Derivative adsorption chronopotentiometry of the iron(III)-2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol system

An electroanalytical method, based on derivative chronopotentiometry of the iron complex with 2-(5′-bromo-2′- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) accumulated adsorptively on the surface of a hanging mercury drop electrode, for determining trace iron in food has been developed. The dependences of the peak height on the dt/dE vs. E curve on the preconcentration time, preconcentration potential and electrode area are discussed. Optimum experimental conditions include 0.005 mol 1^?1 NH₃NH₄Cl, 2 × 10^?7 mol 1^?1 5-Br-PADAP and a preconcentration potential of ?0.40 V (vs. SCE). Under these conditions, the detection limit and the linear range are 2 × 10^?9 and 6.7 × 10^?9?1.7 × 10^?7 mol 1^?1, respectively. The relative standard error of the method is 1.5% for 6.7 × 10^?8 mol 1^?1 Fe(III). The method was applied to samples of microwave digested food.     

Copper(II)-selective membrane electrode based on a recently synthesized naphthol-derivative Schiff’s base

A PVC membrane electrode for copper(II) ions based on a recently synthesized naphthol-derivative Schiff’s base as membrane carrier was prepared. The sensor exhibits a Nernstian response for Cu²⁺ ions over a wide concentration range (5.0 × 10^–6–5.0 × 10^–2 mol/L) with a detection limit of 3.1 × 10^–6 mol/L (0.2 μg/mL). It has a very short response time of about 5 s and can be used for ¶3 months without any divergence in potential. The proposed electrode revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.0–7.0. It was successfully applied to the direct determination and potentiometric titration of copper ion.     

Electrocatalytic oxidation of dopamine at the polyglycine chemically modified carbon fiber bundle electrode and its voltammetric resolution with uric acid

A polyglycine chemically modified electrode shows substantial catalytic ability towards dopamine (DA). The calibration graph obtained by linear sweep voltammetry for DA is linear in the range 2.0 × 10^–8～ 4.4 × 10^–6 mol/L and the detection limit is ca. 5.0 × 10^–9 mol/L. The catalytic ability towards DA results in the voltammetric resolution of DA and uric acid (UA) in the same solution, which is impossible at the unmodified electrode. Uric acid in less than 120-fold excess does not interfere with the determination of DA.     

Polymerization of acrylamide initiated by the Ce4+/thiourea redox system

The polymerization of acrylamide (M) initiated by the Ce⁴⁺/thiourea (TU) redox system has been studied in an aqueous sulfuric acid medium at 35 ± 0.2°C under nitrogen atmosphere. The rate of polymerization is governed by the expression The activation energy is 5.9 kcal deg^?1 mol^?1 in the investigated temperature range 30–50°C. The molecular weight is directly proportional to the concentration of monomer and inversely proportional to the catalyst concentration. With increasing concentration of DMF molecular weight decreases. The range of concentrations for which these observations hold at sulfuric acid concentration of 2.5 × 10^?2 mol/L are [monomer] = 5.0 × 10^?2–3.0 × 10^?1, [catalyst] = (5.0–15.0) × 10^?4, and [activator] = (1.0–6.0) × 10^?3 mol/L.