Simultaneous spectrophotometric determination of cobalt,copper and nickel using 1-（2-thiazolylazo）-2-naphthol by chemometrics methods

The simultaneous determination of cobalt, copper and nickel using 1-（2-thiazolylazo）-2-naphthol （first figure of this article） by spectrophotometric method is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares （PLS） regression, it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction （OSC） is a preprocessing technique used for removing the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 550-750-nm range for 21 different mixtures of cobalt, copper and nickel. Calibration matrices were formed from samples containing 0.05-1.05, 0.05-1.30 and 0.05-0.80 μg·mL^-1 for cobalt, copper and nickel, respectively. The root mean square error of prediction （RMSEP） for cobalt, copper and nickel with OSC and without OSC were 0.007, 0.008, 0.011 and 0.031,0.037, 0.032 μg· mL^-1, respectively. This procedure allows the simultaneous determination of cobalt, copper and nickel in synthetic and real samples and good reliability of the determination was proved.     

Genetic‐Algorithm‐Based Wavelength Selection in Multicomponent Spectrophotometric Determination by PLS: Application on Ascorbic Acid and Uric Acid Mixture

Genetic algorithm (GA) is a suitable method for selecting wavelengths for partial least squares (PLS) calibration of mixtures with almost identical spectra without loss of prediction capacity using the spectrophotometric method. In this study, the concentration model is based on absorption spectra in the range of 200‐320 nm for 25 different mixtures of ascorbic acid (AA) and uric acid (UA). The calibration curve was linear over the concentration range of 1‐15 and 2‐16 μg mL^?1 for ascorbic acid and uric acid, respectively. The root mean square deviation (RMSD) for ascorbic acid and uric acid with GA and without GA were 0.3071 and 0.3006, 0.3971 and 0.7063, respectively. The proposed method was successfully applied to the simultaneous determination of both analytes in human serum and urine samples.     

Potentiometric stripping analysis for zinc,cadmium. lead and copper in sea water

Analytical procedures for the determination of zinc(II), cadmium (II), lead(II) and copper(II) in sea water by potentiometric stripping analysis are described. The results are compared with those obtained by a combined solvent extraction-atomic absorption method both in the laboratory and on-board ship. The detection limits for zinc, cadmium, lead and copper are 0.03, 0.03, 0.01 and 0.02 μg l^-1, respectively, for a total analysis time of about 75 min. A very thin mercury film is useful in the determination of lead and copper.     

Determination of cadmium, copper, lead and zinc in water samples by flame atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) has been used for the simultaneous pre-concentration of cadmium, copper, lead and zinc after the formation of a complex with 1-(2-thiazolylazo)-2-naphthol (TAN), and later analysis by flame atomic absorption spectrometry (FAAS) using octylphenoxypolyethoxyethanol (Triton X-114) as surfactant. The chemical variables affecting the separation phase and the viscosity affecting the detection process were optimized. At pH 8.6, pre-concentration of only 50 ml of sample in the presence of 0.05% Triton X-114 and 2×10⁻⁵ mol l⁻¹ TAN permitted the detection of 0.099, 0.27, 1.1 and 0.095 ng ml⁻¹ cadmium, copper, lead and zinc, respectively. The enhancement factors were 57.7, 64.3, 55.6 and 63.7 for cadmium, copper, lead and zinc, respectively. The proposed method has been applied to the determination of cadmium, copper, lead and zinc in water samples and a standard reference material (SRM).     

Pre-concentration of ultra trace amounts of copper,zinc, cobalt and nickel in environmental water samples using modified C18 extraction disks and determination by inductively coupled plasma–optical emission spectrometry

A highly sensitive and accurate method for pre-concentration and determination of ultra trace amounts of zinc, copper, cobalt and nickel ions in environmental water samples is proposed. The method is based on the solid phase extraction of these ions on C18-bonded silica extraction disks modified with a novel Schiff base 2,2′-[1,6-hexanediyl bis (nitriloethylidine)]bis-1-naphthol (HDN). The retained ions on the prepared solid phase was eluted with 10 mL 0.01 M nitric acid and measured by inductively coupled plasma–optical emission spectrometry. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of ions from the disks, pH, flow rates of sample solution and eluent, amount of HDN, effect of other ions and breakthrough volume were evaluated. The limits of detection of the method were 0.2, 0.2, 0.8 and 0.6 µg L^?1 for zinc, copper, cobalt and nickel, respectively and an enrichment factor of 100 was obtained. The proposed method was applied for determination of zinc, copper, cobalt and nickel ions in some natural and synthetic water samples with satisfactory results.     

Simultaneous determination of copper, zinc and lead by adsorptive stripping voltammetry in the presence of Morin

A sensitive and selective method for the simultaneous determination of copper, zinc and lead is presented. The method is based on the adsorptive accumulation of 2′,3,4′,5,7-pentahydroxyflavone (Morin) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. Optimal analytical conditions were found to be Morin concentration of 2.0 μM, pH of 4.0, and an adsorption potential at −500 mV versus Ag/AgCl. With an accumulation time of 60 s, the peak currents are proportional to the concentration of copper, lead and zinc over the 1 to 60, 0.3-80 and 1-70 ng ml⁻¹ range with detection limits of 0.06, 0.08 and 0.06 ng ml⁻¹, respectively. The procedure was applied to the simultaneous determination of copper, lead and zinc in some real and synthetic artificial real samples with satisfactory results.     

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).     

Determination of zinc and copper in human hair by slurry sampling employing sequential multi-element flame atomic absorption spectrometry

The present work proposes a direct method based on slurry sampling for the determination of zinc and copper in human hair samples by multi-element sequential flame atomic absorption spectrometry. The slurries were prepared by cryogenic grinding and sonication of the samples. The optimization step was performed using univariate methodology and the factors studied were: nature and concentration of the acid solution, amount sample/slurry volume, sonication time, and particle size. The established experimental conditions are the use of a sample mass of 50 mg, 2 mol L^− 1 nitric acid solution, sonication time of 20 min and slurry volume of 10 mL. Adopting the optimized conditions, this method allows the determination of zinc and copper with detection limits of 88.3 and 53.3 ng g^− 1, respectively, and precision expressed as relative standard deviation (RSD) of 1.7% and 1.6% (both, n = 10) for contents of zinc and copper of 100.0 and 33.3 μg g^− 1, respectively. The accuracy was checked and confirmed by analysis of two certified reference materials of human hair. The procedure was applied for the determination of zinc and copper in two human hair samples. The zinc and copper contents varied from 100.0 to 175.6 and from 3.2 to 32.8 μg g^− 1, respectively. These samples were also analyzed after complete digestion in a closed system and determination by FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Extraction and spectrophotometric determination of zinc in coal fly ash and pond sediments with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 10⁵ l mol^?1 cm^?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy.     

On-line solid phase extraction coupled to flame atomic absorption spectrometry for the determination of trace copper and zinc in environmental and biological samples

In this work, bamboo charcoal (BC) was used as a sorbent for on-line solid phase extraction (SPE) coupling with flame atomic absorption spectrometry (AAS) for trace copper and zinc determination in environmental and biological samples. Under the optimum pH of 5.5 (for Zn) and 7.0 (for Cu), trace copper and zinc were effectively adsorbed on the microcolumn and the retained cations were efficiently eluted with HCl or HNO₃ with an appropriate concentration and flow rate for on-line AAS determination. With a sample loading time of 60 s at a sample flow rate of 7.6 mL min^?1, the enhancement factors of 39 (for Cu) and 30 (for Zn) and detection limits (3σ) of 0.60 µg L^?1 (for Cu) and 0.36 µg L^?1 (for Zn), respectively, were achieved. The sample throughput was 45 h^?1. At the level of 20 µg L^?1of Cu(II) and Zn(II), the precision (RSD, n?=?11) were found to be 0.26% and 1.6%, respectively. The proposed method has been successfully applied to the determination of copper and zinc in environmental and biological samples.     

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.     

Comparison of slurry sampling and microwave-assisted digestion for calcium, magnesium, iron, copper and zinc determination in fish tissue samples by flame atomic absorption spectrometry

The development of a slurry sampling method for the determination of calcium, copper, iron, magnesium and zinc in fish tissue samples by flame atomic absorption spectrometry is described. In comparison with microwave-assisted digestion, the proposed method is simple, requires short time and eliminates total sample dissolution before analysis. Suspension medium was optimized for each analyte to obtain quantitative recoveries from fish tissue samples without matrix interferences. Nevertheless, iron recoveries higher than 46% were not found. Treatment of samples slurried in nitric acid by microwave irradiation for 15-30 s at 75-285 W permitted to achieve efficient recoveries for calcium, iron, magnesium and zinc. Further improvement in the matrix effects for iron determination was accomplished by the use of an additional step of short microwave-assisted suspension treatment. However, standard addition method was required for calcium and copper determination, being necessary hydrochloric acid as suspension medium for the last one. Although copper could not be determined in the certified reference material using microwave-assisted digestion, the accuracy of the slurry sampling method was verified for all the investigated analytes. Detection limits were 22.8 ± 8.0, 0.884 ± 0.092, 5.07 ± 0.76, 35.5 ± 0.7 and 1.17 ± 0.04 μg g⁻¹ for calcium, copper, iron, magnesium and zinc, respectively. The standard deviations obtained using slurry sampling method and microwave-assisted digestion were not significantly different, and the mean relative standard deviation of the over-all method (n = 3) of the slurry sampling method for different concentration levels was below 12%.     

Ion-pair extraction and determination of copper(II) and zinc(II) in environmental and pharmaceutical samples.

Copper and zinc were extracted from salicylate solution into Aliquat 336 dissolved in toluene and determined in the organic phase spectrophotometrically using 1-(2-pyridylazo)-2-naphthol. The determination of copper and zinc was also carried out titrimetrically or by atomic absorption spectrometry after stripping the metal ions from the organic phase. The method permits the determination of copper and zinc in environmental and pharmaceutical samples. The standard deviation and relative standard deviation are 0.052 micrograms and 0.69%, respectively, for copper and 0.041 micrograms and 0.60%, respectively, for zinc.     

Determination of zinc and copper in human hair by slurry sampling employing sequential multi-element flame atomic absorption spectrometry

The present work proposes a direct method based on slurry sampling for the determination of zinc and copper in human hair samples by multi-element sequential flame atomic absorption spectrometry. The slurries were prepared by cryogenic grinding and sonication of the samples. The optimization step was performed using univariate methodology and the factors studied were: nature and concentration of the acid solution, amount sample/slurry volume, sonication time, and particle size. The established experimental conditions are the use of a sample mass of 50 mg, 2 mol L^− 1 nitric acid solution, sonication time of 20 min and slurry volume of 10 mL. Adopting the optimized conditions, this method allows the determination of zinc and copper with detection limits of 88.3 and 53.3 ng g^− 1, respectively, and precision expressed as relative standard deviation (RSD) of 1.7% and 1.6% (both, n = 10) for contents of zinc and copper of 100.0 and 33.3 μg g^− 1, respectively. The accuracy was checked and confirmed by analysis of two certified reference materials of human hair. The procedure was applied for the determination of zinc and copper in two human hair samples. The zinc and copper contents varied from 100.0 to 175.6 and from 3.2 to 32.8 μg g^− 1, respectively. These samples were also analyzed after complete digestion in a closed system and determination by FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Separate determination of nickel, zinc, and cobalt 4-(2-thiazolylazo)resorcinates in a sorbent phase using chromaticity measurements

The optimum conditions for the preconcentration of nickel, zinc, cobalt, and copper on a Silochrom C-120 silica modified with 4-(2-thiazolylazo)resorcinol were found. Chromaticity characteristics of the metal chelates were determined. It was shown that nickel and zinc chelates meet the requirements of the separate determination. A method for the separate determination of 0.05-1 Μg/mL of nickel and 0.15-5 Μg/mL of zinc based on chromaticity measurements was proposed. Procedures for determining zinc, nickel, and cobalt in soils were developed.     

小波包压缩-RBF网络同时测定润滑油中铁、铜、锌

将小波包压缩-RBF网络方法用于润滑油中铁铜锌三组分分光光度同时测定该方法采用小波包函数对光谱数据进行压缩处理,用较大的小波色系数构成新的校正集和预测集代替原始的校正集和预测集,然后用RBF网络进行数据解析。研究表明,用bior2．4小波包处理原始测定数据,最佳小波基用logenerge熵标准,选择适当阈值将变量数由46个压缩成25个（压缩比为0．54）,整体预测效果最好。将此方法用于合成样预测．预测结果与实际浓度的相对误差绝对值在2．50％～9．40％之间;用于实际润滑油样品中铁、铜和锌的同时测定,解析值与原子吸收法（AAS）的测定值的相对误差绝对值作3．55％～7．86％之间。应用结果令人满意。     

Determination of copper and zinc in blood plasma by ion chromatography using a cobalt internal standard

Ion chromatography was used to detect levels of copper and zinc in blood plasma from renal dialysis patients on continuous ambulatory peritoneal dialysis (CAPD) and haemodialysis (HD). The developed method used cobalt as an internal standard and when combined with the standard additions method improved the overall precision of the results by between -0.3 and 6.0% and -0.8 and 5.7% for copper and zinc, respectively. The method was compared with inductively coupled plasma optical emission spectrometry (ICP-OES) and the results indicated no significant difference between the two methods with or without an internal standard. Without an internal standard, tcalc was 0.869 with a tcrit of 2.201 (n = 12, P = 0.05) and with an internal standard, tcalc was 0.189 compared to a tcrit of 2.201 (n = 12, P = 0.05). The copper and zinc levels in blood plasma in both dialysis groups were not significantly different to the copper and zinc levels in blood plasma of the control patients. A convenient method of analysis of trace elements in blood such as ion chromatography with UV/VIS detection is useful for determining whether inorganic elements may be disrupted in the body due to changes in the state of health.     

Substoichiometric isotope dilution analysis of copper traces in zinc by adsorptive sampling

The spontaneous deposition of Cu²⁺ from aqueous solutions on a hydrogen-saturated platinum surface as a possibility for the substoichiometric sampling of copper is shown. A sensitive isotope dilution method has been developed for the determination of traces of copper in high purity zinc making use of the spontaneous deposition of microquantities of Cu²⁺ from aqueous solutions of zinc salts on a cathodically polarized platinum surface. If the same platinum surface is used in each run, the saturation values of the deposited copper are practically independent of the concentrations and contents of copper and zinc in the solution. The copper traces were labelled with the product of the⁶⁴Zn(n,p)⁶⁴Cu nuclear reaction. A copper content of 0.18±0.03 ppm in zinc was determined by this method.     

Simultaneous determination of copper, nickel, cobalt and zinc using zincon as a metallochromic indicator with partial least squares

The partial least squares (PLS) applied to the simultaneous determination of the divalent ions of copper, nickel, cobalt and zinc based on the formation of their complexes with 2-carboxy-2′-hydroxy-5′-sulfoformazyl benzene (zincon). The absorption spectra were recorded from 515 through 750 nm. The effect of pH on sensitivity and the selectivity was studied in the range 3.0-10.0 and the pH 8.0 was choused according to net analyte signal (NAS) as a function of pH. The concentration range for Cu²⁺, Ni²⁺, Co²⁺and Zn²⁺ in solution calibration sets were 0-2.6, 0-4.6, 0-3.0 and 0-4.92 ppm, respectively. The root mean squares differences (RMSD) for copper, nickel, cobalt and zinc were 0.0181, 0.0488, 0.0309 and 0.0463, respectively.     

Determination of cadmium,copper and lead in urine by flame atomic absorption spectrometry after extraction of the iodide complexes as ion-pairs with tri-n-octylamine

A simple, rapid sensitive atomic absorption spectrometric method is described for the determination of cadmium, copper and lead in urine. The metals are extracted as their iodide complexes with tri-n-octylamine in n-butyl acetate, without elaborate pretreatment, and measured by direct nebulization of the extract into an air/ acetylene flame. Detection limits for cadmium, copper and lead in urine were 0.008, 0.05 and 0.02 × 10^?6 mol l^?1, respectively.