Spline wavelet in the resolution of overlapping voltammetric peaks

Spline wavelet transform is used to resolve overlapping voltammetric peaks. A suitable resolving factor is chosen to multiply the filters of spline wavelet and make it a peak resoluter. Simulated overlapping voltammetric peaks are processed by the peak resoluter and satisfactory results are obtained. Base-line separation can be achieved, the relative errors of peak position are less than 3.0%, and the relative errors of peak area are less than 5.0%. The effect of different resolving factors and spline wavelet basis are discussed. To test the procedure, two systems, cadmium (Ⅱ)-indium (Ⅲ) and lead (Ⅱ)-thallium (Ⅰ), are used.     

Development of wavelet transform voltammetric analyzer

An on-line wavelet transform algorithm and development of voltammetric analyzer with the on-line wavelet transform (WT-voltammetric analyzer) are described. Because the on-line wavelet transform decomposes the sampled signal simultaneously with the progress of sampling, the WT-voltammetric analyzer gives all the components contained in the sampled voltammogram. Applications of the WT-voltammetric analyzer in linear sweep voltammetric analysis of mixtures of Pb(II) and Tl(I) and in square wave voltammetric analysis of mixture of Cd(II) and In(III) were investigated. Results showed that the overlapping peaks of Pb(II) and Tl(I) can be separated easily, and the peak position after the on-line wavelet transform does not change. The linearity of the calibration curves for Cd(II) and In(III) in the overlapping square wave voltammetric curves were kept after the on-line wavelet transform. Quantitative determination of Cd(II) and In(III) in mixture samples were investigated. The recoveries are between 92.5 and 107.1%.     

Determination of bismuth and copper using adsorptive stripping voltammetry couple with continuous wavelet transform

A new method is proposed for the determination of bismuth and copper in the presence of each other based on adsorptive stripping voltammetry of complexes of Bi(III)-chromazorul-S and Cu(II)-chromazorul-S at a hanging mercury drop electrode (HMDE). Copper is an interfering element for the determination of Bi(III) because, the voltammograms of Bi(III) and Cu(II) overlapped with each other. Continuous wavelet transform (CWT) was applied to separate the voltammograms. In this regards, wavelet filter, resolution of the peaks and the fitness were optimized to obtain minimum detection limit for the elements. Through continuous wavelet transform Symlet4 (Sym4) wavelet filter at dilation 6, quantitative and qualitative analysis the mixture solutions of bismuth and copper was performed. It was also realized that copper imposes a matrix effect on the determination of Bi(III) and the standard addition method was able to cope with this effect. Bismuth does not have matrix effect on copper determination, therefore, the calibration curve using wavelet coefficients of CWT was used for determination of Cu(II) in the presence of Bi(III). The detection limits were 0.10 and 0.05 ng ml⁻¹ for bismuth and copper, respectively. The linear dynamic range of 0.1-30.0 and 0.1-32.0 ng ml⁻¹ were obtained for determination of bismuth in the presence of 24.0 ng ml⁻¹ of copper and copper in the presence of 24.0 ng ml⁻¹ of bismuth, respectively. The method was used for determination of these two cations in water and human hair samples. The results indicate the ability of method for the determination of these two elements in real samples.     

Antimony Film Electrode Prepared In Situ in Hydrogen Potassium Tartrate in Anodic Stripping Voltammetric Trace Detection of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II)

An antimony film electrode (SbFE) was prepared in situ on a glassy carbon support and in a new supporting electrolyte, a saturated solution of hydrogen potassium tartrate in which Sb(III) ions were complexed using tartrate. Its performance in anodic stripping voltammetric (ASV) determination of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II) traces was examined. It was found that 1.2 mg/L of Sb(III) yields the finest quality SbFE for analytical purposes. The procedure with in situ SbFE ensures well‐defined anodic stripping voltammetric curves of the investigated elements, low detection limits (0.5–3.8 µg/L), good reproducibility (1–5 %) and satisfactory sensitivity (32–184 nA/(µg/L)).     

Application of surface electrochemical passivation of lead-antimony alloy for a simple and rapid electrochemical determination of antimony content

A simple, rapid and selective electrochemical method is proposed as a novel and powerful analytical technique for the solid phase determination of less than 4% antimony in lead-antimony alloys without any separation and chemical pretreatment. The proposed method is based on the surface antimony oxidation of Pb/Sb alloy to Sb(III) at the thin oxide layer of PbSO₄/PbO that is formed by oxidation of Pb and using linear sweep voltammetric (LSV) technique. Determination was carried out in concentrate H₂SO₄ solution. The influence of reagent concentration and variable parameters was studied. Antimony of Pb/Sb alloys can be determined in the range of 0.0056–4.00% with a detection limit of 0.0045% and maximum relative standard deviation of 4.26%. This method was applied for the determination of Sb in lead/acid battery grids satisfactory.     

Simultaneous determination of antimony,arsenic and copper by neutron activation analysis

A rapid procedure has been developed for the mutual separation of antimony and arsenic using tribenzylamine as the extracting agent. The extraction behaviours of Sb(III), Sb(V), As(III), As(V) and Au(III) have been studied as a function of the acidity of the aqueous phase. Various factors which affect the extraction of these complexes have been studied and optimized. The procedure was then applied to lead base alloy for the simultaneous determination of antimony, arsenic and copper. Chemical recoveries were quantitative and only about one hour is required for the chemical processing of duplicate samples.     

Determination of major antimony species in seawater by continuous flow injection hydride generation atomic absorption spectrometry

The capabilities and limitations of the continuous flow injection hydride generation technique, coupled to atomic absorption spectrometry, for the speciation of major antimony species in seawater, were investigated. Two pre-concentration techniques were examined. After continuous flow injection hydride generation and collection onto a graphite tube coated with iridium, antimony was determined by graphite furnace atomic absorption spectrometry. The low detection limits obtained (∼5 ng l⁻¹ for Sb(III) and ∼10 ng l⁻¹ for Sb(V) for 2.5 ml seawater samples) permitted the determination of Sb(III) and total antimony in seawater with the use of selective hydride generation and on-line UV photooxidation. The number of samples that can be analyzed is about 15 per hour for Sb(III) determinations and 10 per hour for total antimony determinations. The analysis of seawater samples showed that Sb(V) was the predominant species, even in the presence of important biological activity.     

Determination of trace concentrations of antimony by the introduction of stibine into an inductively-coupled plasma for atomic emission spectrometry

A simple, rapid and sensitive method is described for the determination of trace concentrations of antimony by inductively-coupled plasma atomic emission spectrometry with hydride generation. Hydrochloric acid (1 M) is the best medium for stibine generation, but antimony(III) is also effectively reduced to stibine in 1 M malic acid or 0.5 M tartaric acid, whereas antimony(V) gives no significant signal in either of these acids. This permits the differential determination of Sb(III) and Sb(V). Most of the inter-element interference effects can be minimized by thiourea, bur standard additions are recommended for accurate determinations. Thiourea is also effective in prereducing Sb(V) to Sb(III). The detection limit is 0.19 ng Sb ml^?1 and the calibration graph is linear up to 100 μg ml^?1. The r.s.d, at 1 and 100 ng Sb ml^?1 are 3.8 and 2.1%, respectively. The method is applied to copper metal and to speciation of antimony in waste water.     

Determination of Copper(II) Through Anodic Stripping Voltammetry in Tartrate Buffer Using an Antimony Film Screen-printed Carbon Electrode

The voltammetric performance of an in situ plated antimony film screen-printed carbon electrode in hydrochloric acid, acetate buffer, and tartrate buffer was evaluated for the detection of copper(II) with differential pulse anodic stripping voltammetry. The tartrate buffer was superior, providing high sensitivity and good separation of copper and antimony stripping peaks. The analytical conditions for the determination of copper(II) were optimized. The detection limit was estimated to be 0.14?µg?L^?1 copper(II) and the relative standard deviation for 2.5?µg?L^?1 copper(II) was 3%. The applicability of the method was illustrated by the analysis of soil conditioner samples.     

Adsorptive stripping voltammetric determination of antimony

A new method is described for the determination of antimony based on the cathodic adsorptive stripping of Sb(III) complexed with 2′,3,4′,5,7-pentahydroxyflavone(morin) at a static mercury drop electrode (SMDE). The reduction current of the adsorbed antimony complex was measured by 1.5th-order derivative linear-sweep adsorption voltammetry. The peak potential is at −0.51 V (vs. SCE). The effects of various parameters on the response are discussed. The optimized analytical conditions were found to be: supporting electrolyte, chloroacetic acid (0.04 mol/l, pH 2.3); concentration of morin, 5×10⁻⁶ mol/l; accumulation potential, −0.25 V (vs. SCE); scan rate, 100 mV/s. The limit of detection and the linear range were 7×10⁻¹⁰ mol/l and 1.0×10⁻⁹3.0×10⁻⁷ mol/l Sb(III) for a 2-min accumulation time, respectively. This method has been applied to the determination of Sb(III) in steel and brass samples and satisfactory results were obtained. The adsorptive voltammetric characteristics and composition of the Sb(III)–morin complex were studied.     

Determination of arsenic and antimony in electrolytic copper by anodic stripping voltammetry at a gold film electrode

A simple procedure is described for the determination of arsenic and antimony in electrolytic copper. The copper is digested with nitric acid and copper is separated from arsenic and antimony by passing an ammoniacal solution of the sample through a column of Chelex-100 resin. After digestion with sulphuric acid and reduction to arsenic(III) and antimony(III) with sodium sulphite in 7 M sulphuric acid at 80°C, both arsenic and antimony are deposited at-0.30V and their total is determined by anodic stripping; antimony is then selectively deposited at -0.05 V for anodic stripping. The lower limits of determination are 56 ng As and 28 ng Sb per gram of copper; relative standard deviations (n = 5) are in the ranges 6.1–15.0% for 5.5—0.5 ppm arsenic in copper and 4.1–6.8% for 2.6—0.6 ppm antimony.     

Speciation of antimony by atomic absorption spectrometry. Applicability to selective determination of Sb(III) and Sb(V) in liquid samples and of bioavailable antimony in sediments and soil samples

A comparative study was made of several methods to speciale Sb(III) and Sb(V) by AAS: 1) Selective extraction of Sb(III) with lactic acid/malachite green graphite furnace-AAS, 2) Sb(III) and total antimony determination by hydride generation-AAS coupled to flow injection, batch, and continuous flow systems. These methods were applied to determine total antimony and Sb(III) in sea and surface water and total antimony in sediments and in soil. For soils different sample pretreatments were used: HNO₃-H₂SO₄-HC1O₄, HF-HNO₃-H₂SO₄-HC1O₄, cold aqua regia and slurry formation procedures in water and 4M HC1. In each case the recovery of total antimony and the ability to selective determine Sb(III) were studied. The detection limits obtained were 0.01 ng, 0.07 ng, 2.97 ng and 0.21 ppb for GF-AAS, FIA-HG-AAS, HG (Batch)-AAS, and HG (continuous flow)-AAS, respectively.     

Determination of inorganic antimony species in seawater by differential pulse anodic stripping voltammetry: stability of the trivalent state

A simple method is described for the rapid and reliable determination of ultratrace concentrations of Sb(III) and Sb(V) in seawater by differential pulse anodic stripping voltammetry. It is based on the well-known dependence of Sb(III)/Sb(V) voltammetric response on acidity conditions. Under our optimised conditions (0.5 mol l⁻¹ HCl for Sb(III) and 5 mol l⁻¹ HCl for total Sb, respectively): (i) a detection limit of 11 ng l⁻¹ is obtained for a 10 min deposition time; (ii) no prior elimination of organic matter is needed; and (iii) antimony can be determined in the presence of natural copper levels. Particular care has been taken in order to understand the chemical processes taking place in all the solutions and reactions involved in the sampling and measuring procedures. Our results revealed the need to consider (i) the effect of photooxydation of synthetic and seawater samples on Sb speciation; and (ii) the stability of Sb(III) both in seawater samples and in the analytical solutions.     

Speciation of antimony using chromosorb 102 resin as a retention medium.

The selective retention of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a column of Chromosorb 102 resin from a buffered sample solution including Sb(V) was used for the determination of Sb(III). The retained antimony was eluted with acetone. The retention of the Sb(III)-iodide compounds with sodium iodide on the Chromosorb 102 resin column from the same solution after reducing Sb(V) to Sb(III) by iodide in acidic solution was used to preconcentrate the total antimony. The retained antimony was eluted with 0.25 mol l(-1) HNO3. The antimony in the effluent was determined by flame atomic-absorption spectrometry. Also, the total antimony was determined directly by graphite-furnace atomic absorption spectrometry. The Sb(V) concentration could be calculated by the difference. The recoveries were > or = 95%. The detection limits of a combination of the column procedure and flame AAS for antimony were 6 - 61 microg l(-1) and comparable to 4 microg l(-1) for a direct GFAAS measurement. The relative standard deviations were <6%. The procedure was applied to the determination of Sb(III) and Sb(V) in spiked tap water, waste-water samples and a certified copper metal with the satisfactory results.     

Solid-phase extraction (SPE) assays to ascertain the mechanisms of retention of antimony species in several stationary phases

Liquid chromatography is the most suitable technique for antimony speciation in several types of samples. However, efficiency can be poor for some of these peaks, especially Sb(III) and Me₃SbCl₂ (TMSb). Weak and strong anion exchange stationary phases are mainly used for antimony speciation in several chromatographic conditions. The present study examines the possible contribution of the interaction between antimony species (Sb(III), Sb(V) and TMSb) and stationary phase support to the overall retention mechanism in their chromatographic separation. Several SPE cartridges, selected from those mainly used as support in anion exchange columns, were assayed. Sb (V) was quantitatively eluted from the PSDVB (polystyrene divinylbenzene) and SiO₂ phases, showing the absence of interaction. Sb (III) showed some interaction with the PSDVB phase; TMSb showed strong retention with all the cartridges studied and it was only eluted from the PSDVB phase.     

Determination of Inorganic Sb(V) and Methylantimony Species by HPLC with Hydride Generation-Atomic Fluorescence Spectrometric Detection

 An on-line method for the separation and analysis of Sb(V) and Me₃Sb in the presence of Sb(III) in liquid samples is described. Inorganic and organic antimony species were separated using anion-exchange high-performance liquid chromatography (HPLC) coupled with hydride generation-atomic fluorescence detection (HG-AFS). Optimum conditions for the separation of antimony species by HPLC and the hydride generation conditions for the determination by HG-AFS were established. Matrix interference of the chromatographic determination was studied in relation to MgSO₄ and NaCl. The method developed was applied to the separation and determination of antimony species in spiked and natural water samples. The suitability of the method for analysis in microbial growth media and physiological studies involving methylantimony species is discussed. Received December 11, 2000. Revision April 26, 2001.     

在线小波变换用于伏安分析仪的研制

将在线小波变换应用于伏安信号的在线处理,研制了具有小波变换功能的伏安分析仪。该系统利用在线小波变换对采集到所数据进行实时处理,具有控制灵活,分辨率高,数据处理方便等特点。通过对低浓度Ｃｙ＾２＋和Ｆｅ＾３＋混合样品的阶梯斜坡扫描伏安珠滤噪及定性,定量分析,结果表明可获得满意的分析结果。     

Extraction-spectrophotometric determination of traces of antimony in copper and lead metals and in lead-base alloy with pyrocatechol violet and tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of antimony in copper and lead metals and in lead-base alloy. Optimal conditions have been established for the extraction and determination of antimony. Antimony (III) is extracted from a potassium iodide—sulfuric acid or a hydrobromic—sulfuric acid medium with toluene and converted to an antimony-pyrocatechol violet (PV) complex. The complex is then extracted with tri-n-octylamine (TOA) and the absorbance of the resulting ternary Sb(III)—PV-TOA complex is measured at 555 nm. As little as 0.5 p.p.m. of antimony in copper metal and 0.2 p.p.m. of antimony in lead metal and lead-base alloy can be determined.     

Speciation of antimony by adsorptive stripping voltammetry using pyrogallol

This paper describes a new procedure for the determination of Sb (III) and Sb (V) by differential pulse adsorptive stripping voltammetry (DPAdSV) using pyrogallol as a complexing agent. The selection of the experimental conditions was made using experimental design methodology. The detection limits obtained were 1.03 × 10⁻¹⁰ and 9.48 × 10⁻⁹ mol dm⁻³ for Sb (III) and Sb (V), respectively.In order to carry out the simultaneously determination of both antimony species a partial least squares regression (PLS) is employed to resolve the voltammetric signals from mixtures of Sb (III) and Sb (V) in the presence of pyrogallol. The relative error in absolute value is less than 0.5% when concentrations of several mixtures are calculated. Moreover, the solution is analyzed for any possible effects of foreign ions. The procedure is successfully applied to the speciation of antimony in pharmaceutical preparations and water samples.     

Trace adsorptive voltammetric determination of antimony in hair

A very sensitive electrochemical procedure for trace determination of antimony is described. The complex of antimony with p-dimethyl-aminophenyl-fluorone (p-DMPF) is adsorbed on a hanging mercury drop electrode (HMDE), and the reduction current of the accumulated complex is measured by voltammetry. In linear sweep voltammetry, the reduction potential of the complex is more positive than that of the free dye. The peak height of the complex is proportional to the concentration of antimony in the range of 4.0 x 10(-9) to 4.0 x 10(-7) M, the detection limit is 1.0 x 10(-9) M Sb(III) for a 5 min preconcentration time. The relative standard error for the determination of 8.0 x 10(-8) M Sb(III) is 2.9%.