Quantification of ultra-trace amounts of copper by using off-line solid phase extraction-flame atomic absorption spectrometric determination through the octadecyl silica-bonded phase membrane (OSPM) C18 disks impregnated with 2,2'-[ethane-1,2-diylbis(thio)]dianiline

This study reports a very selective, easy, and precise method for rapid separation of trace amounts of copper in aqueous samples using octadecyl silica-bonded phase membrane disks modified by 2,2'-[ethane-1,2-diylbis(thio)]dianiline (EDTD) combined with flame atomic absorption spectrometric determination. In addition, the synthesis and spectral characterization of EDTD have been described in detail. All the affecting experimental variables such as pH, amount of modifier, eluent type, sample and eluent flow rate, interfering ions, and disk capacity were also investigated. The target analyte (trace copper) was quantitatively retained at pH?=?4 and eluted with 6.0 mL of 0.5 M HNO₃ at flow rates of 40 and 10 mL min^?1 for analyte passage and elution steps, respectively, through the disks modified with 17.0 mg of EDTD. The proposed method also allows an enrichment factor of about 500 and has a detection limit of 0.005 ng mL^?1. The method has been successfully applied for isolation and determination of copper in different water samples, peppers, and standard alloys.     

Flow injection online spectrophotometric determination of uranium after preconcentration on XAD-4 resin impregnated with nalidixic acid

In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min^?1. The uranium complex was removed from the resin by 0.1 mol dm^?3 HCl at flow rate of 3.2 mL min^?1 and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm^?3 HCl, 3.2 mL min^?1) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 μg L^?1, a relative standard deviation (RSD) of 0.8 % at 100 μg L^?1, enrichment factor of 30, and a sample throughput of 42 h^?1, whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 μg L^?1, a RSD of 1.32 % at 10 μg L^?1, enrichment factor of 150, and a sampling frequency of 11 h^?1 were reported.     

The use of silica gel modified with allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate for selective separation and preconcentration of lead in environmental samples

The aim of the present work is the assessment of a new sorbent, prepared using silica gel coated with a pyrimidine derivative (allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate), for extraction and preconcentration trace amount of lead from different samples prior to determination by flame atomic absorption spectrometry. Common coexisting ions did not interfere with the separation and determination of lead at pH?6, so that lead ion completely adsorbed on the column. The limit of detection based on three times the standard deviation of the blank was found to be 0.53 ng?mL^?1 in original solution. Obtained sorption capacity for 1 g sorbent was 5.0 mg Pb. The linearity was maintained in the concentration range of 0.1–30.0 ng?mL^?1 for the concentrated solution. Eight replicate determinations of 2.0 μg?mL^?1 of lead in the final solution gave relative standard deviation of ±2.6 %. The proposed method was successfully applied to the determination trace amounts of lead in the environmental samples such as carrot, rice, zardchoobe, and real water samples.     

Monitoring of trace amounts of heavy metals in different food and water samples by flame atomic absorption spectrophotometer after preconcentration by amine-functionalized graphene nanosheet

We are introducing graphene oxide modified with amine groups as a new solid phase for extraction of heavy metal ions including cadmium(II), copper(II), nickel(II), zinc(II), and lead(II). Effects of pH value, flow rates, type, concentration, and volume of the eluent, breakthrough volume, and the effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is >97 %, the limit of detections are 0.03, 0.05, 0.2, 0.1, and 1 μg L^?1 for the ions of cadmium, copper, nickel, zinc, and lead, respectively, and the adsorption capacities for these ions are 178, 142, 110, 125, and 210 mg g^?1. The amino-functionalized graphene oxide was characterized by thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The proposed method was successfully applied in the analysis of environmental water and food samples. Good spiked recoveries over the range of 95.8–100.0 % were obtained. This work not only proposes a useful method for sample preconcentration but also reveals the great potential of modified graphene as an excellent sorbent material in analytical processes.     

Solid phase extraction and determination of Cr(III) by spectrophotometry using cefaclor as a complexing reagent and FAAS

The present study reports on the application of modified groundnut shell as a new, easily prepared, and stable sorbent for the extraction of trace amount of Cr(III) in aqueous solution. 2-Hydroxybenzaldiminoglycine was immobilized on groundnut shells in alkaline medium and then used as a solid phase for the column preconcentration of Cr(III). The elution was carried out with 3 mL of 2 mol?L^?1 HCl. The amount of eluted Cr(III) was determined by spectrophotometry using cefaclor as a complexing reagent and by flame atomic absorption spectrometry (FAAS). Different experimental variables such as pH, amount of solid sorbent, volume and concentration of eluent, sample and eluent flow rate, and interference of other metal ions on the retention of Cr(III) were studied. Under the optimized conditions, the calibration curves were found to be linear over the concentration range of 13–104 and 10–75 μg?L^?1 with a detection limit of 3.64 and 1.24 μg?L^?1 for spectrophotometric method and FAAS, respectively. An enrichment factor of 200 and RSD of ±1.19–1.49 % for five successive determinations of 25 μg?L^?1 were achieved. The column preconcentration was successfully applied to the analysis of tap water and underground water samples.     

Lead isotope ratios in lichen samples evaluated by ICP-ToF-MS to assess possible atmospheric pollution sources in Havana,Cuba

Epiphytic lichens, collected from 119 sampling sites grown over “Roistonea Royal Palm” trees, were used to assess the spatial distribution pattern of lead (Pb) and identify possible pollution sources in Havana (Cuba). Lead concentrations in lichens and topsoils were determined by flame atomic absorption spectrophotometry and inductively coupled plasma (ICP) atomic emission spectrometry, respectively, while Pb in crude oils and gasoline samples were measured by ICP-time of flight mass spectrometry (ICP-ToF-MS). Lead isotopic ratios measurements for lichens, soils, and crude oils were obtained by ICP-ToF-MS. We found that enrichment factors (EF) reflected a moderate contamination for 71% of the samples (EF > 10). The ²⁰⁶Pb/²⁰⁷Pb ratio values for lichens ranged from 1.17 to 1.20 and were a mixture of natural radiogenic and industrial activities (e.g., crude oils and fire plants). The low concentration of Pb found in gasoline (<7.0 μg L^?1) confirms the official statement that leaded gasoline is no longer used in Cuba.     

Solid phase extraction of Cd,Pb, Ni,Cu, and Zn in environmental samples on multiwalled carbon nanotubes

A simple and sensitive solid phase extraction (SPE) method on multiwalled carbon nanotubes (MWCNTs) is presented for the determination of cadmium, lead, nickel, copper, and zinc at trace levels combined with flame atomic absorption spectrometry. The effects of parameters like pH, sample volume, sample and eluent flow rates, eluent concentration, and volume and type of eluent on the recovery of trace elements was examined. The metals retained on the nanotube at pH 6.5 as α-benzoin oxime complexes were eluted by 10 mL 2 M HNO₃ in acetone. The influence of matrix ions on the developed method was also evaluated. The preconcentration factor of the method was found to be 50. The detection limits for Cd(II), Pb(II), Ni(II), Cu(II), and Zn(II) were found as 1.7, 5.5, 6.0, 2.3, and 2.4 μg L^?1, respectively. To test the accuracy of the method, the method was applied to TMDA-70 fortified lake water and Spinach 1570A standard reference materials. Addition recovery studies were applied to tap water and cracked wheat samples, and determination of the analyte elements was carried out in some food samples with good results.     

Application of zirconium–iridium permanent modifier for the simultaneous determination of lead, cadmium, arsenic, and nickel in atmospheric particulate matter by multi-element electrothermal atomic absorption spectrometry

A novel and robust method for the simultaneous determination of lead, cadmium, arsenic, and nickel in atmospheric particulate matter by multi-element electrothermal atomic absorption spectrometry was developed, using zirconium–iridium coating as permanent modifier (140 μg Zr and 4 μg Ir). After 300 atomization cycles, it was necessary to add 2 μg of Ir. Due to the varying concentrations of Pb in atmospheric particulate matter, lead was monitored at two wavelengths, at the less sensitive line of 261.4 nm for high concentration samples (>20 μg?L^?1) or at 283.3 nm for the low concentration samples. Matrix-matched calibration had to be performed for quantitative recoveries (96–102 %). Following this approach, the four elements were determined in atmospheric particulate matter samples from an industrial area near the city of Athens in two different time periods (cold–warm) with limits of detection of 5.5 ng?m^?3 for Pb at 261.4 nm and 0.29 ng?m^?3 at 283.3 nm, 0.019 ng?m^?3 for Cd, 0.14 ng?m^?3 for As, and 0.22 ng?m^?3 for Ni. Lead, Cd, and As levels were very low, whereas Ni content was at comparable levels with other areas worldwide.     

Evaluation of metal contents of household detergent samples from Turkey by flame atomic absorption spectrometry

The concentrations of cadmium, copper, chromium, cobalt, iron, lead, manganese, nickel, and zinc in detergent samples from Kayseri, Turkey were determined by flame atomic absorption spectrometry. HClO₄ (10 mL)/HNO₃ (10 mL) mixture was used for the digestion of household detergent samples. The correctness of the analytical procedures was checked with standard addition–recovery tests in different detergent samples for the investigated metal ions. The concentration ranges of the elements in the detergent samples were found as 17.2–60.1, 11.1–40.1, 2.5–32.3, 8.1–10.5, 7.2–21.6, 9.8–17.9, 1.7–3.8, 12.5–22.5, and 2.0–5.8 μg/g for iron, manganese, zinc, copper, lead, cobalt, cadmium, nickel, and chromium, respectively. The values found in this work were compared with some other studies around the world conducted on detergent samples.     

Determination of some heavy metal levels in soft drinks on the Ghanaian market using atomic absorption spectrometry method

Twenty-three soft drink samples (i.e., four pineapple-based fruit drinks, eight citrus-based fruit juices, one soya-based drink, three cola carbonated drinks, one apple-based fruit drink, and six cocktail fruit drinks) were randomly purchased from retail outlets in an urban market in Accra and analyzed for the concentrations of iron, cobalt, cadmium, zinc, lead, and copper using flame atomic absorption spectrometry. The mean concentration of iron and cadmium were 0.723?±?0.448 mg/L and 0.032?±?0.012 mg/L, respectively. The mean cobalt concentration was 0.071?±?0.049 mg/L, while the mean Zn concentration in the samples was 0.060?±?0.097 mg/L. The mean concentrations of Pb and Cu in the fruit juice samples were 0.178?±?0.091 mg/L and 0.053?±?0.063 mg/L respectively. About 78 % of the samples exceeded the United States Environmental Protection Agency (USEPA) maximum contaminant level of 0.3 mg/L prescribed for iron, whereas all the samples exceeded the USEPA maximum contaminant level of 0.005 mg/L prescribed for cadmium. About 91 % of the samples exceeded the EU maximum contaminant level prescribed for lead insoft drinks.     

Solid-phase extraction of Mn(II) and slurry analysis of the sorbent by electrothermal atomic absorption spectrometry

In this study, a challenging preconcentration/separation method based on the sorption of manganese on ethylene glycol dimethacrylatemethacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrrolidine dithiocarbamate (APDC) and its slurry analysis by electrothermal atomic absorption spectrometry was described. Optimum conditions for quantitative sorption, as well as for preparing a homogeneous and stable slurry were investigated. A 100-fold enrichment factor could be reached. The analyte element in certified sea-water and bovine-liver samples were determined in the range of 95% confidence level. The proposed technique is fast, simple, and the risk of contamination is low. The limit of detection of the method for manganese in the slurry of the blank subjected to the proposed procedure was 0.07 μg L^?1 (3δ, N:10) corresponding to 0.56 μg kg^?1 slurry.     

Application of nanoclay for preconcentration of ultra trace amounts of palladium in environmental samples prior to its determination by ETAAS

In the present work, a batch preconcentration technique using nanoclay with 5-(4-dimethylaminobenzylidene)rhodanine coupled with electrothermal atomic absorption spectrometry was developed for the separation and determination of trace amounts of palladium. In this method, the sample solution was stirred with nanoclay as an adsorbent. Then, adsorbed palladium was subsequently eluted with HCl in acetone (1.5 mol L^?1) and, finally, this eluate was injected to electrothermal atomic absorption spectrometry. Under the optimum conditions, the limit of detection and linear dynamic range were found to be 2.6 and 10.0–133 ng L^?1 (in original solution), respectively. Furthermore, the enrichment factor and relative standard deviation of seven replicate determinations were 148 and ±5.1 %, respectively. This suggested method is simple, selective and sensitive and can be applied to the extraction and determination of palladium in water, tea leaves, synthetic sample and certified reference material with satisfactory results.     

Utility of cefixime as a complexing reagent for the determination of Ni(II) in synthetic mixture and water samples

A simple, sensitive, and accurate UV spectrophotometric method has been developed for the determination of nickel in synthetic mixture and water samples. The method is based on the complexation reaction of nickel ion with cefixime, thus leading to the formation of Ni–cefixime complex in ethanol-distilled water medium at room temperature. The complex showed the maximum absorption wavelength at 332 nm. Beer’s law is obeyed in the working concentration range of 0.447–4.019 μg?mL^?1 with apparent molar absorptivity of 7.314?×?10³?L?mol^?1?cm^?1 and Sandell’s sensitivity of 0.008 μg/cm²/0.001 absorbance unit. The limits of detection and quantitation for the proposed method are 0.016 and 0.054 μg?mL^?1, respectively. The factors such as cefixime concentration and solvent affecting the complexation reaction were carefully studied and optimized. The method is validated as per the International Conference on Harmonisation guideline. The method is successfully applied to the determination of Ni(II) in synthetic mixture and wadi water samples collected from Al Rustaq. The same water samples are also analyzed by atomic absorption spectrophotometry. Both methods determined the amount of Ni(II) in water sample and found to be approximately the same.     

Determination of trace amounts of zirconium in real samples after microwave digestion and ternary complex dispersive liquid–liquid microextraction

In this study, a ternary Zr(IV) system with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and fluoride was chosen on the basis of dispersive liquid–liquid microextraction method. Zirconium was extracted into the fine droplets of dichlorobenzene as extracting solvent. These drops dispersed as a cloud in the aqueous sample with the help of ultrasonic waves, and the procedure was done. Finally, atomic absorption spectrometry was applied for the determination of zirconium. The effects of different factors that influence complex formation and extraction, such as pH, amounts of complexing agents, type and volume of the extracting solvent, as well as sonication and centrifuging time, were optimized. Under optimum conditions, the calibration curve was linear in the range of 150.0–800.0 ng mL^?1 with a limit of detection of 44.0 ng mL^?1. Relative standard deviation was calculated to be 4.1 % (n?=?7, c?=?400.0 ng mL^?1). The enrichment factor was 80. The proposed method was successfully used to determine the zirconium in several water, wastewater, and soil samples.     

Ultra-sensitive quantification of copper in food and water samples by electrochemical adsorptive stripping voltammetry

A new electrochemical adsorptive stripping voltammetry method was developed for the determination of trace amounts of copper in food and water samples. The study of electrochemical behavior of Cu ion indicated that Cu(II) and Schiff base formed a complex in H₃BO₄–NaOH buffer solution (pH?=?7.25). An accumulation potential of ?100 mV (vs Ag/AgCl) was applied while the solution was stirred for 60 s. The response curve was recorded by scanning the potential, and the peak current of ?0.31 V (vs Ag/AgCl) was recorded. The peak current and concentration of copper accorded with linear relationship in the range of 0.04–120 ng mL^?1. The relative standard deviation (for 12 ng mL^?1 of copper) was 1.73 %, and the detection limit was 0.007 ng mL^?1. The possible interference of some common ions was studied. The proposed method was applied to the determination of copper in water, rice, wheat, tea, milk, and tomato with satisfactory results.     

Solid-phase extraction and separation procedure for trace aluminum in water samples and its determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS)

In the present study, a separation/preconcentration procedure for determination of aluminum in water samples has been developed by using a new atomic absorption spectrometer concept with a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution double-echelle monochromator, and a charge-coupled device array detector. Sample solution pH, sample volume, flow rate of sample solution, volume, and concentration of eluent for solid-phase extraction of Al chelates with 4-[(dicyanomethyl)diazenyl] benzoic acid on polymeric resin (Duolite XAD-761) have been investigated. The adsorbed aluminum on resin was eluted with 5 mL of 2 mol L^-1 HNO₃ and its concentration was determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Under the optimal conditions, limit of detection obtained with HR-CS FAAS and Line Source FAAS (LS-FAAS) were 0.49 μg L^?1 and 3.91 μg L^?1, respectively. The accuracy of the procedure was confirmed by analyzing certified materials (NIST SRM 1643e, Trace elements in water) and spiked real samples. The developed procedure was successfully applied to water samples.     

2-Nitroso-1-naphthol as a selective reagent for preconcentration of cobalt by vortex assisted combined with solidification of organic droplet and its determination by flame atomic absorption spectrometry

Highly rapid and selective vortex-assisted liquid–liquid microextraction based on solidification of organic drop has been used for determination of cobalt ion. 2-Nitroso-1-naphthol (2N1N) was used as a selective complexing agent to form stable cobalt–2N1N complex which can be extracted with 1-undecanol at a short time by the assistance of vortex agitator system followed by its determination using flame atomic absorption spectrometry. In vortex assisted, vigorous vortex stream as well as the vibrant effect of vortex system cause very fine droplets of extraction solvent to be produced and extraction occurred at a short time. Some parameters influencing the extraction process such as pH of samples, concentration of 2-nitroso-1-naphthol, extraction solvent volume, extraction time, ionic strength and surfactant addition, as well as interferences were evaluated in detail and optimum conditions were selected. At the optimum conditions, the calibration curve was linear in the range of 15 to 400 μg L^?1 of cobalt ions. The relative standard deviation based on ten replicate analysis of sample solution containing 50 μg L^?1 of cobalt was 3.4 %. The detection limit (calculated as the concentration equivalent to three times of the standard deviation of the blank divided by the slope of the calibration curve after preconcentration) was 5.4 μg L^?1. The accuracy of the proposed method was successfully evaluated by the analysis of certified reference materials. This selective and highly rapid method was used for determination of cobalt ions in different water samples.     

Health risk assessment of mercury and arsenic associated with consumption of fish from the Persian Gulf

Concentrations of mercury and arsenic in fish from the Persian Gulf were determined by graphite furnace atomic absorption spectrometry. Concentrations of the metals in muscle samples were 0.049–0.402 μg g^?1 for mercury and 0.168–0.479 μg g^?1 for arsenic, with means of 0.133 and 0.312 μg g^?1, respectively. The maximum daily consumption rate (grams per day) and meal consumption limit (meals per month) was calculated to estimate health risks associated with fish consumption. According to the results, the maximum allowable consumption rate varies between 8–56 and 15–96 g/day base on mercury and arsenic content, respectively. The results of this study indicate that the concentration of mercury and arsenic is well below the maximum permissible levels for mercury (0.5 μg g^?1) and arsenic (6 μg g^?1) according to international standards.     

Preconcentration of metal ions through chelation on a synthesized resin containing O, O donor atoms for quantitative analysis of environmental and biological samples

Nascent Amberlite XAD-4 has been used as the polymeric support for the synthesis of a stable extractor of metal ions, by incorporating phthalic acid through azo bridging. Elemental analyses and infra-red spectral and thermal studies were carried out for its characterization. The water regain value and hydrogen ion capacity were found to be 12.50 and 5.75 mmol g^?1, respectively. The optimum pH range for the maximum sorption of Ni(II), Mn(II), Cu(II), Zn(II), Cd(II), Cr(III), and Co(II) was observed at pH 5.5–8.0 with the corresponding half-loading time (t _1/2) of 9, 5, 9, 9, 3, 9, and 5 min, respectively. The preconcentration factor for Ni(II), Mn(II), Cu(II), Zn(II), Cd(II), Cr(III), and Co(II) are 190, 190, 190, 180, 180, 160, and 160, with the corresponding limit of preconcentration in the range of 5.25–6.25 μg L^?1. The detection limits, for flame atomic absorption spectrophotometry, were found to be 0.62, 0.60, 0.65, 0.75, 0.72, 0.84, and 0.85 μg L^?1, respectively. Method has been successfully applied to the analysis of water samples, multivitamin formulations, infant food substitutes, hydrogenated oil, and fishes.     

Fast simultaneous determination of traces of Cu(II) and Co(II) in soils and sediments with the luminol/perborate chemiluminescent system

A flow injection analysis method based on ion chromatography and luminol chemiluminescence detection was used for the simultaneous determination of copper (II) and cobalt (II) trace levels in soils and sediments following microwave-assisted acid digestion. Detection was based on chemiluminescence (CL) of the luminol–perborate system in an alkaline medium, which is catalyzed by both transition metals. The concentration and pH of the eluent (oxalic acid) was found to affect CL intensities and retention times, both of which were inversely proportional to the oxalic acid concentration. The calibration curves for both metal ions were linear and allowed a limit of detection of 0.003 μg l^?1 for cobalt (II) and 0.014 μg l^?1 for cooper (II) to be calculated. The proposed method was successfully used to determine both metal ions in certified reference materials of stream and river sediments and soil samples. Based on the results, the determination is free of interferences from the usual concomitant ions.