Coupling continuous ultrasound-assisted extraction, preconcentration and flame atomic absorption spectrometric detection for the determination of cadmium and lead in mussel samples

A new tunable dispersive liquid-liquid micro extraction method developed for the simultaneous preconcentration of lead and cadmium from lakes water: a multivariate study

A green tunable dispersive liquid-liquid micro extraction (TDLLME) technique was established for the simultaneous enrichment of lead (Pb) and cadmium (Cd) from different lakes water before analysis by flame atomic absorption spectrometry (FAAS). A solvent known as tunable polarity solvent (TPS), mixture of 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and 1-decanol, has been employed as extractant in aqueous medium. In first step this mixture can be made polar by slowly bubbling the antisolvent trigger (CO₂) through the solution, which makes a monophasic solution. During this step hydrophobic complexes of the metals with 8-hydroxy quinoline (8-HQ) were extracted by TPS. Then the mixture was switched back to hydrophobic one by heating and/or bubbling nitrogen, turning the mixture into two phases again. In second phase the metals were leached out from the complexes entrapped in TPS, by treating with a solution of nitric acid and exposing the mixture to CO₂, which switched the mixture into single phase. Then N₂ purging and/or heating again turned the mixture into two phases. The acidic aqueous phase containing the metals was introduced to FAAS for analysis, whereas TPS was recycled for next experiment. Different parameters, affecting the efficiency the technique, were optimized by multivariate approach. The method was applied to certified reference material of water and to a real sample spiked with standards of known concentration, to confirm its validity and accuracy. LOD obtained for Pb and Cd were 0.560 and 0.056μgL^-1 respectively. The developed method was applied successfully to the real water samples of two lakes of Sindh, Pakistan.

Application of dual-cloud point extraction for the trace levels of copper in serum of different viral hepatitis patients by flame atomic absorption spectrometry: a multivariate study

An efficient, innovative preconcentration method, dual-cloud point extraction (d-CPE) has been developed for the extraction and preconcentration of copper (Cu(2+)) in serum samples of different viral hepatitis patients prior to couple with flame atomic absorption spectrometry (FAAS). The d-CPE procedure was based on forming complexes of elemental ions with complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN), and subsequent entrapping the complexes in nonionic surfactant (Triton X-114). Then the surfactant rich phase containing the metal complexes was treated with aqueous nitric acid solution, and metal ions were back extracted into the aqueous phase, as second cloud point extraction stage, and finally determined by flame atomic absorption spectrometry using conventional nebulization. The multivariate strategy was applied to estimate the optimum values of experimental variables for the recovery of Cu(2+) using d-CPE. In optimum experimental conditions, the limit of detection and the enrichment factor were 0.046μgL(-1) and 78, respectively. The validity and accuracy of proposed method were checked by analysis of Cu(2+) in certified sample of serum (CRM) by d-CPE and conventional CPE procedure on same CRM. The proposed method was successfully applied to the determination of Cu(2+) in serum samples of different viral hepatitis patients and healthy controls.

Adsorption of cadmium(II) ions from aqueous solution on exfoliated graphene nanosheets and its determination by flame atomic absorption spectrometry

In this study, we investigated the enrichment ability of exfoliated graphene nanosheets for determination of trace cadmium in water and vegetable samples with flame atomic absorption spectrometry. Various experimental parameters that could affect the extraction efficiency have been investigated. Under the optimum conditions, the enrichment factor of the method for the target analyte was 100. A liner response was achieved in the concentration range of 0.3–28.8 ng mL−1. The detection limit and precision of the method were 0.2 ng mL−1 and 0.8%, respectively. The proposed method was applied to determine the cadmium in water, onion, and tomato samples and recoveries of target analyte were in the range 97.6%–98.5%. All of these experimental results indicated that this new procedure could be applied for the determination of trace cadmium in real samples.

Multivariate optimization of an ultrasound-assisted extraction procedure for Cu, Mn, Ni and Zn determination in ration to chickens

In this work, multivariate optimization techniques were used to develop a method based on the ultrasound-assisted extraction for copper, manganese, nickel and zinc determination from rations for chicken nutrition using flame atomic absorption spectrometry. The proportions of extracting components (2.0 mol.L–1 nitric, hydrochloric and acetic acid solutions) were optimized using centroid-simplex mixture design. The optimum proportions of this mixture taken as percentage of each component were respectively 20%, 37% and 43%. Variables of method (sample mass, sonication time and final acid concentration) were optimized using Doehlert design. The optimum values found for these variables were respectively 0.24 g, 18s and 3.6 mol.L–1. The developed method allows copper, manganese, nickel and zinc determination with quantification limits of 2.82; 4.52; 10.7; e 9.69 µg.g–1, and precision expressed as relative standard deviation (%RSD, 25 µg.g–1, N = 5) of 5.30; 2.13; 0.88; and 0.83%, respectively. This method was applied in the analytes determination from chicken rations collected from specialized commerce in Jequié city (Bahia State/Brazil). Application of paired t-test at the obtained results, in a confidence level of 95%, does not show significant difference between the proposed method and the microwave-assisted digestion.

Modification of Multiwalled Carbon Nanotubes by Dipyridile Amine for Potentiometric Determination of Lead(II) Ions in Environmental Samples

A carbon paste electrode was modified by dipyridile amine functionalized multiwalled carbon nanotubes for determination of trace amounts of lead(II) ions. The electrode composition was graphite powder 70%, paraffin 23%, and dipyridile amine modified MWCNTs 7% (W/W). The linear range for lead(II) was 9.5 × 10−8 to 2.5 × 10−3 mol L−1, and the limit of detection was obtained 7.0 × 10−8 mol L−1. The lifetime of the electrode was ten weeks, and a fast response time was observed. The electrode was used for determination of trace amounts of Pb(II) ions in real samples and standard reference materials of water, soil, and plant.

Cloud point extraction for determination of lead in blood samples of children, using different ligands prior to analysis by flame atomic absorption spectrometry: a multivariate study

The phase-separation phenomenon of non-ionic surfactants occurring in aqueous solution was used for the extraction of lead (Pb(2+)) from digested blood samples after simultaneous complexation with ammonium pyrrolidinedithiocarbamate (APDC) and diethyldithiocarbamate (DDTC) separately. The complexed analyte was quantitatively extracted with octylphenoxypolyethoxyethanol (Triton X-114). The multivariate strategy was applied to estimate the optimum values of experimental factors. Acidic ethanol was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometer (FAAS). The detection limit value of Pb(2+) for the preconcentration of 10 mL of acid digested blood sample was 1.14 μg L(-1). The accuracy of the proposed methods was assessed by analyzing certified reference material (whole blood). Under the optimized conditions of both CPE methods, 10 mL of Pb(2+) standards (10 μg L(-1)) complexed with APDC and DDTC, permitted the enhancement factors of 56 and 42, respectively. The proposed method was used for determination of Pb(2+) in blood samples of children with kidney disorders and healthy controls.

The determination of trace lead in drinking water by flow injection spectrophotometry

Lead is the non-essential trace element in the human body, and it has been confirmed that drinking water is one of the sources of lead in human body. In the research, based on the sensitive colour reaction of lead with I(-)-EV(+)-PVA, a simple, sensitive, accurate and portable method for the determination of trace lead in drinking waters was proposed. Chemicals and physicals had been optimized in detail. The apparent molar absorption coefficient was up to 7.4x10(5) mol L(-1) cm(-1). The developed method provided a linearity range over 5-80 microg L(-1). The regression deviation was between 0.71% and 2.33%. The 3sigma detection limit was 0.9 microg L(-1). Close to the quantitation limit for the analyte the relative standard deviation was 1.10% (n=10) at 40 microg L(-1). The method developed here for analysis of lead yielded results that were comparable with those of the GFAAS.

Hazardous impact of toxic metals on tobacco leaves grown in contaminated soil by ultrasonic assisted pseudo-digestion: multivariate study

Tobacco leaves (Nicotiana tabacum L.), agricultural soil and pollute irrigated lake water samples were collected during 2005--2006 and analyzed for Cd and Ni by electrothermal atomic absorption spectrometry (ETAAS). A simple and efficient procedure was investigated for the complete decomposition of tobacco leaves using ultrasonic assisted acid pseudo-digestion method (UPDM). A Plackett-Burman experimental design was used as a multivariate strategy for the evaluation of seven factors/variables at once, while central composite were used to found optimum values of significant variables. The accuracy of the proposed methods was assessed by analyzing certified reference (CRM); Virginia tobacco leaves (CTA-VTL-2). The results being compared with those obtained by conventional wet acid digestion method. The result obtained by optimized method showed good agreement with the certified values and sufficiently high recovery 97.8 and 98.7% for Cd and Ni, respectively. Under optimal conditions, the detection limits (3sigma) were evaluated to be 0.019 microg g(-1) for Cd and 0.37 microg g(-1) for Ni. The proposed method was successfully applied to the determination of Cd and Ni in raw, processed tobacco and different branded cigarettes samples.

On-line sorption-based systems for determination of cadmium with atomic spectrometry detectors

Determination of cadmium is often required in various environmental, biological and food samples as it is recognized worldwide as a toxic metal. However, these analysis with atomic spectrometry detectors are often difficult due to relatively low content of cadmium and complex matrices. Several preconcentration/separation procedures to determine cadmium have been devised, among them the methods based on sorbent extraction are the most popular. They can be easily implemented and controlled in flow injection (FI) or sequential injection (SI) systems to perform appropriate sample pretreatment. This work reviews the papers, published from 1990, concerning procedures based on sorption principles for on-line determination of cadmium. They were compared using experimental enhancement factor (EF) and concentration efficiency (CE) values.

Continuous Approach for Ultrasound-assisted Acid Extraction-Minicolumn Preconcentration of Chromium and Cobalt from Seafood Samples Prior to Flame Atomic Absorption Spectrometry

A rapid and sensitive method has been proposed for the determination of chromium and cobalt in seafood samples by flame atomic absorption spectrometry combined with a dynamic ultrasound-assisted acid extraction and an on-line minicolumn preconcentration. The use of diluted nitric acid as extractant in a continuous mode at a flow rate of 3.5 mL min(-1) and room temperature was sufficient for quantitative extraction of these trace metals from seafoods. A minicolumn containing a chelating resin was an excellent device for the quantitative preconcentration of chromium and cobalt prior to their detection. A flow-injection manifold was used as interface for coupling all analytical steps, which allowed the automation of the whole analytical process. A Plackett-Burman experimental design was used as a multivariate strategy for the optimization of both sample preparation and preconcentration steps. The method was successfully applied to the determination of chromium and cobalt in seafood samples.

Application of multiwalled carbon nanotubes treated by potassium permanganate for determination of trace cadmium prior to flame atomic absorption spectrometry

In this study we investigated the enrichment ability of oxidized multiwalled carbon nanotubes (MWCNTs) and established a new method for the determination of trace cadmium in environment with flame atomic absorption spectrometry. The MWCNTs were oxidized by potassium permanganate under appropriate conditions before use as preconcentration packing. Parameters influencing the recoveries of target analytes were optimized. Under optimal conditions, the target analyte exhibited a good linearity (R2=0.9992) over the concentration range 0.5-50 ng/ml. The detection limit and precision of the proposed method were 0.15 ng/ml and 2.06%, respectively. The proposed method was applied to the determination of cadmium in real-world environmental samples and the recoveries were in the range of 91.3%-108.0%. All these experimental results indicated that this new procedure could be applied to the determination of trace cadmium in environmental waters.