Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry

A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N′‐bis(salicylaldehydo)4‐carboxyphenylenediamine (BSCPDA)–complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02 mol L^?1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42 μM, pH 9.6 and adsorption potential at ?50 mV versus Ag/AgCl. With an accumulation time of 20 s, the peaks current are proportional to the concentration of nickel and cadmium over the 1–180, and 0.5–200 ng mL^?1 with detection limits of 0.06 and 0.03 ng mL^?1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98 nA mL ng^?1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results.     

Simultaneous determination of copper, bismuth and lead by adsorptive stripping voltammetry in the presence of thymolphthalexone.

A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of copper, bismuth and lead is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of copper, lead and bismuth were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 4.0 microM, pH of 9.0, and accumulation potential at -800 mV vs. Ag/AgCl with an accumulation time of 80 s. The peak currents are proportional to the concentration of copper, bismuth and lead over the 0.4-300, 1-200 and 1-100 ng mL(-1) ranges with detection limits of 0.4, 0.8 and 0.7 ng mL(-1), respectively. The procedure was applied to the simultaneous determination of copper, bismuth and lead in the tap water and some synthetic samples with satisfactory results.     

Highly Selective Adsorptive Cathodic Stripping Voltammetric Determination of Uranium in the Presence of Pyromellitic Acid

A very sensitive and selective adsorptive cathodic stripping procedure for trace measurement of uranium is presented. The method is based on adsorptive accumulation of the uranium‐pyromellitic acid (benzene‐1,2,4,5‐tetracarboxylic acid) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. Influences of effective parameters such as pH, concentration of pyromellitic acid, accumulation potential and accumulation time on the sensitivity were studied. The peak current was proportional to the concentration of U(IV) up to 40 ng mL^?1 with a limit of detection of 0.136 ng mL^?1 with an accumulation time of 120 s. The range of linearity enhanced to 71.4 ng mL^?1and the detection limit improved to 0.058 ng mL^?1with accumulation times of 60 s and 300 s respectively. The relative standard deviation for 10 replicate determination of 4.76 ng mL^?1 U(IV) was equal to 2.7%. The possible interference by major cations and anions are investigated. The method was applied to the determination of uranium in some analytical grade salts, seawater and in synthetic samples corresponding to some uranium alloys with satisfactory results.     

Quantification of Sub‐Nanomolar Levels of Aluminum by Adsorptive Stripping Voltammetry Using Rubeanic Acid as a Selective Chelating Agent

A novel, sensitive and selective adsorptive stripping procedure for determination of aluminum is presented. The method is based on the adsorptive accumulation of dithiooxamide (Rubeanic acid) complex of aluminum onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the determination of aluminum were studied. The optimum analytical conditions were found to be Rubeanic acid (RA) concentration of 8.0×10^?5 M, ammonia buffer (NH₃? NH₄Cl) pH of 6.5, and accumulation potential at ?50 mV vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of aluminum over the 0.3–70 ng mL^?1 ranges with detection limit of 0.012 ng mL^?1. The procedure was applied to the determination of aluminum in the Lab. Water, HCl of Merck and potato samples with satisfactory results.     

Adsorptive Cathodic Stripping Voltammetric Determination of Uranium(VI) in Presence of N‐Phenylanthranilic Acid

N‐Phenylanthranilic acid was used as a complexing agent for determination of uranium(VI) by adsorptive cathodic stripping voltammetry. Under the optimal experimental conditions of the experimental parameters, the peak current was proportional to the concentration of U(VI) in the range 0.75–30 ng mL^?1 and the detection limit was 0.036 ng mL^?1. The influence of possible interferences was investigated. The method was applied for determination of uranium in waste water from uranium conversion facility and natural water samples. Application of the method for simultaneous determination of U(VI) and Cu(II) showed that these ions could be simultaneously determined in a single scan at relatively wide concentration range.     

Construction of Modified Carbon Paste Electrode for Highly Sensitive Simultaneous Electrochemical Determination of Trace Amounts of Copper (II) and Cadmium (II)

A chemically modified electrode was constructed for rapid, simple, accurate, selective and highly sensitive simultaneous determination of Cu(II) and Cd(II) using square wave anodic stripping voltammetry. The electrode was prepared by incorporation of SiO₂ nanoparticles, coated with a newly synthesized Schiff base, in carbon paste electrode. The limit of detection was found to be 0.28 ng mL^?1 and 0.54 ng mL^?1 for Cu(II) and Cd(II), respectively. The proposed chemically modified electrode was used for the determination of copper and cadmium in several foodstuffs and water samples.     

Stripping Voltammetry of Cerium(IIl) with a Chemically Modified Carbon Paste Electrode Containing Functionalized Nanoporous Silica Gel

This research introduces the design of an adsorptive stripping voltammetric method for the cerium(III) determination at a carbon paste electrode, chemically modified with dipyridyl‐functionalized nanoporous silica gel (DPNSG‐CPE). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at ?200 mV followed by the electrochemical detection of the Ce(III)/dipyridyl complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (1.0–28 ng mL^?1). The precision for seven determinations of 4 and 10 ng mL^?1 Ce(III) was 3.2% and 2.5% (relative standard deviation), respectively. The prepared electrode was used for the cerium determination in real samples and very good recovery results were obtained.     

Adsorptive Stripping Differential Pulse Voltammetry for Determination of Trace Amounts of Noscapine in Human Plasma

A new adsorptive anodic differential pulse stripping voltammetry method for the direct determination of noscapine at trace levels in human plasma of addicts is proposed. The procedure involves an adsorptive accumulation of noscapine on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed noscapine by voltammetry scan using differential pulse modulation. The optimum conditions for the analysis of noscapine are pH = 8.5 using Britton‐Robinson (B‐R) buffer, accumulation potential of ?100 mV (vs. Ag/AgCl), and accumulation time of 150 s. The peak current is proportional to the concentration of noscapine, and a linear calibration graph is obtained at 0.015–2.75 μg mL^?1. A relative standard deviation of 1.28% (n = 5) was obtained, and the limit of detection was 7 ng mL^?1. The capability of the method for the analysis of real samples was evaluated by determination of noscapine in spiked human plasma and addicts, human plasma with satisfactory results.     

Application of adsorptive stripping voltammetry to the simultaneous determination of bismuth and copper in the presence of nuclear fast red

A sensitive and selective method for the simultaneous determination of copper and bismuth by adsorptive stripping was developed using nuclear fast red (2-anthracenesulfonic acid, 4-amino-9,10-dihydro-1,3-dihydroxy-9,10-dioxo-, monosodium salt) as selective complexing agent onto hanging mercury drop electrode. In a single scan both metals gave peaks that were distinctly separated by 85 mV allowing their determination in the presence of each other. Optimal analytical conditions were found to be: nuclear fast red concentration of 80 μM, pH of 2.8 and adsorptive potential of −300 mV versus Ag/AgCl. With accumulation time of 180 s the peaks currents are proportional to concentration of copper and bismuth over the 1-100 and 5-60 ng mL⁻¹ range with detection limits of 0.2 and 1.2 ng mL⁻¹, respectively. The procedure was applied to simultaneous determination of copper and bismuth in some real samples.     

Simultaneous Voltammetric Determination of Lead and Tin by Adsorptive Differential Pulse Stripping Method and Orthogonal Signal Correction‐Partial Least Squares in Water Samples

An adsorptive differential pulse stripping method for the simultaneous determination of lead and tin is proposed. The procedure involves an adsorptive accumulation of lead and tin on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed lead and tin by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: 0.2 mol L^?1 HNO₃, accumulation potential of ?900 mV versus Ag/AgCl, accumulation time of 200 s, scan rate of 20 mV s^?1 and pulse height of 80 mV. Lead and tin peak currents were observed in the same potential region at about ?400 mV. The simultaneous determination of lead and tin by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of a mixture of lead and tin by the application of orthogonal signal correction‐partial least squares (OSC‐PLS) was performed. The linear dynamic ranges were 0.003‐0.35 and 0.008‐0.50 μg mL^?1 and detection limits were land 3 ng mL^?1 for lead and tin, respectively. The RMSEP for lead and tin with OSC and without OSC were 2.8737, 6.0557 and 8.0941, 9.5151, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of lead and tin in water samples with satisfactory results.     

Determination of azinphos-methyl by adsorptive stripping voltammetry

A very sensitive electrochemical stripping procedure for azinphos-methyl (Guthion) is reported. Accumulation is achieved by adsorption of the compound on a hanging mercury drop electrode. The adsorptive stripping response was evaluated with respect to accumulation time and potential, concentration dependence, electrolyte and other variables. The determination limit is 0.2 ng ml^?1 after 300 s accumulation and 0.4 ng ml^?1 after 180 s accumulation. The procedure was applied to spiked river water.     

Simultaneous Determination of Ultra Trace of Uranium and Cadmium by Adsorptive Cathodic Stripping Voltammetry Using H‐Point Standard Addition Method

A sensitive adsorptive cathodic stripping voltammetry with H‐point standard addition method for simultaneous determination of uranium and cadmium has been developed. The trace amounts of these metal ions can be simultaneously determined using the Levodpa as complexing agent. Optimal conditions were: accumulation time 50 s, accumulation potential 0.0 mV, scan rate 40 mV s^?1, supporting electrolyte 0.1 M ammonium buffer pH 9.6, and 1×10^?5 M of Levodopa. The results revealed that the cadmium and uranium could be simultaneously determined by H‐point standard addition method with different concentration ratios of uranium to cadmium. The method was successfully applied in a several of real samples.     

Determination of Trace Amounts of Copper by Adsorptive Stripping Voltammetry

ABSTRACT

A technique is presented for the determination of trace amounts of copper(II) by adsorptive cathodic stripping voltammetry. The procedure is based on adsorptive accumulation of copper(II)-Alizarin Red S (ARS) complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the reduction current of the adsorbed complex at -0.16 V (vs. Ag/AgCl). The height of the copper -ARS reduction peak is linearly dependent upon the copper(II) concentration between 0.2-15 and 15-500 ng.ml^?1. The detection limit of the technique is 0.05 ng.ml^?1 copper(II) for a collection time of 1 minute. The method is free from most interferences. The procedure has been successfully applied to the determination of trace amounts of copper(II) in some analytical grade salts.     

Determination of Trace Amount of Lead(II) in Sweet Fruit‐Flavored Powder Drinks by Differential Pulse Adsorptive Stripping Voltammetry at Carbon Paste Electrode

A new method is described for the determination of lead based on the cathodic adsorptive stripping of the lead–nuclear fast red (NFR) at a carbon paste electrode (CPE). The differential pulse voltammograms of the adsorbed complex of lead–NFR are recorded from ?0.10 to ?0.60 V (versus Ag/AgCl electrode). Optimal conditions were found to be an electrode containing 25% paraffin oil and 75% high purity graphite powder, 4.0×10^?5 mol L^?1 NFR; buffer solution (pH of 3.0), accumulation potential and time, ?0.20 V, 60 and 120 s (for high and low concentration of lead), respectively. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at ?0.34 V, corresponding to reduction of NFR in the complex at the electrode. The detection limit was found to be 0.2 ng mL^?1 with a 120s accumulation time. The linear ranges are from 0.5 to 50 (t_acc=120 s) and 50 to 200 ng mL^?1 (t_acc=60 s). Application of the procedure to the determination of lead in lake water, bottled mineral water, synthetic samples and sweet fruit‐flavored powder drinks samples gave good results.     

Simple and rapid surface-enhanced Raman Spectroscopy assay for safranine T and its application in highly sensitive determination of mercury (Ⅱ)

A simple and sensitive surface-enhanced Raman spectroscopy (SERS) method for the detection of safranine T (ST) and Hg²⁺ using silver nanoparticles (AgNPs) as substrate was developed. ST can absorb on the surface of AgNPs through electrostatic interaction, the electromagnetic effect combined with chemical adsorption effect give a notable Raman enhancement for ST. The presence of Hg²⁺ well decreased the absorbed ST molecules on AgNPs, leading to a significant decrease of SERS signals thus enabling to detect Hg²⁺. The determination conditions for SERS, including the amount of AgNPs, the concentration of NaCl, the concentration of HCl, the concentration of ST and the reaction time, were optimised. Under the optimised experimental conditions, good linear responses were obtained for ST and Hg²⁺ in the concentration ranges of 0.01–4.0 μmol L^?1 (3.5–1403.4 ng mL^?1) and 0.01–2.0 μmol L^?1 (2.0–401.2 ng mL^?1), the limit of detection were 3.0 nmol L^?1 (1.1 ng mL^?1) and 2.0 nmol L^?1 (0.4 ng mL^?1), respectively. The present method was subsequently applied to the determination of ST in tomato sauces and Hg²⁺ in environmental waters, the recoveries of ST and Hg²⁺ in spiked samples are 95.5–107.8% and 91.4–110.8 %, respectively.     

A Highly Sensitive Method for Determination of Copper (II) in Water Samples for Field Screening

Abstract

A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL^?1. The limit of detection was 0.5 ng mL^?1. This method has been used for the field screening of copper (II) with satisfactory results.     

Determination of Copper by Adsorptive Stripping Voltammetry in the Presence of Calcein Blue

An electrochemical adsorptive stripping approach is presented for the trace measurement of copper in some real samples. The method is based on the reduction of Cu²⁺ at pH 5.5 calcein blue (CB) containing solution at ?250 mV (vs. Ag/AgCl), adsorption of Cu? CB complex on hanging mercury drop electrode (HMDE) and the voltammetric determination by further reduction to Cu⁺ at HMDE. Experimental optimum conditions were determined in the fundamental studies. At the experimental optimum conditions the adsorbed complex of Cu²⁺ and calcein blue gives a well defined cathodic stripping peak current at ?0.135 V, which has been used for the determination of copper in the concentration range of 0.02 to 15 ng/mL with accumulation time of 90 s. The relative standard deviation (RSD) for the determination of 0.5 and 6.0 ng mL^?1 were 2.60 and 1.94% respectively. (n=10). The method has been applied to the analysis of copper in analytical reagent grade salts and tap water, mineral water and drug samples with satisfactory results.     

Voltammetric Determination of Mercury(II) at Poly(3‐hexylthiophene) Film Electrode. Effect of Halide Ions

The well‐known method for the determination of mercury(II), which is based on the anodic stripping voltammetry of mercury(II), has been adapted for applications at the thin film poly(3‐hexylthiophene) polymer electrode. Halide ions have been found to increase the sensitivity of the mercury response and shift it more positive potentials. This behavior is explained by formation of mercuric halide which can be easily deposited and stripped from the polymer electrode surface. The procedure was optimized for mercury determination. For 120 s accumulation time, detection limit of 5 ng mL^?1 mercury(II) has been observed. The relative standard deviation is 1.3% at 40 ng mL^?1 mercury(II). The performance of the polymer film studied in this work was evaluated in the presence of surfactants and some potential interfering metal ions such as cadmium, lead, copper and nickel.     

Simultaneous Determination of Aluminum,Cadmium and Lead in Whole Blood by Simultaneous Atomic Absorption Spectrometry with Oxygen Charring

A method for the simultaneous determination of aluminum (Al), cadmium (Cd) and lead (Pb) in whole blood has been developed by using simultaneous atomic absorption spectrometry (SIMAAS) with oxygen charring. The optimized conditions for the simultaneous determination of Al, Cd and Pb were obtained in the presence of palladium (Pd) as the chemical modifier, using 600 °C and 2400 °C as the pyrolysis and the atomization temperature, respectively. The whole blood samples were diluted 1+5 (v/v) directly with 0.1% (v/v) Triton X‐100. Oxygen was employed to eliminate the interference of carbonaceous residues in the charring step before pyrolysis. The calibration curves were carried out with aqueous standard solutions and the linear ranges were 0–40 ng mL⁻¹, 0–4 ng mL⁻¹ and 0–40 ng mL⁻¹ for Al, Cd and Pb, respectively. The detection limits were 0.96 ng mL⁻¹ (19.2 pg) for Al, 0.03 ng mL⁻¹ (0.6 pg) for Cd and 0.60 ng mL⁻¹ (12.0 pg) for Pb. The spiked recoveries of Al, Cd and Pb in whole blood were 98.0%, 100.0% and 101.7%, respectively. The accuracy of the proposed method was evaluated with the analysis of a whole blood certified reference material (Seronorm, level 2). The found concentrations were in agreement with the recommended values. The proposed method has been successfully applied to the simultaneous determination of Al, Cd and Pb in whole blood of healthy volunteers before and after eating barbecued foods.     

Analysis of Chlorpyrifos in Water,Fruit Juice,and Honeybee Extract by Chemiluminescent Elisa

Abstract

The suitability of competitive enzyme-linked immunosorbent assays (ELISAs) with chemiluminescent detection-based immobilized antigen (indirect assay) for rapid and accurate determination of chlorpyrifos in various food matrices was tested. The limit of detection (LOD) values were 1–1.75 ng mL^?1, the standard curve midpoint (IC₅₀) was 3.5 ng mL^?1, and the assay duration was 1.5 h. Assay application to the analysis of honeybee extract resulted in chlorpyrifos recoveries varying between 62 and 83% in 5–15 ng mL^?1 herbicide concentration range.