Multi‐Walled Carbon Nanotubes as Sorbent for Flow Injection On‐Line Microcolumn Preconcentration Coupled with Flame Atomic Absorption Spectrometry for Determination of Cadmium and Copper

Abstract

Multi‐walled carbon nanotubes (MWNTs) were used as sorbent for flow injection (FI) on‐line microcolumn preconcentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace cadmium and copper in environmental and biological samples. Effective preconcentration of trace cadmium and copper was achieved in a pH range of 4.5–6.5 and 5.0–7.5, respectively. The retained cadmium and copper were efficiently eluted with 0.5 mol L^?1 HCl for on‐line FAAS determination. The MWNTs packed microcolumn exhibited fairly fast kinetics for the adsorption of cadmium and copper, permitting the use of high sample flow rates up to at least 7.8 mL min^?1 for the FI on‐line microcolumn preconcentration system without loss of the retention efficiency. With a preconcentration time of 60 sec at a sample loading flow rate of 4.3 mL min^?1, the enhancement factor was 24 for cadmium and 25 for copper at a sample throughput of 45 h^?1. The detection limits (3σ) were 0.30 and 0.11 µg L^?1 for Cd and Cu, respectively. The precision (RSD) for 11 replicate measurements was 2.1% at the 10‐µg L^?1 Cd level and 2.4% at the 10‐µg L^?1 Cu level. The developed method was successfully applied to the determination of trace Cd and Cu in a variety of environmental and biological samples.     

Determination of Manganese(II) with Preconcentration on Almond Skin and Determination by Flame Atomic Absorption Spectrometry

Almond skin was used as a biosorbent by solid-phase extraction for the preconcentration of manganese(II) before the determination by flame atomic absorption spectrometry. Characterization of almond skin was performed by infrared spectroscopy. The functional groups of the almond skin surface were shown to be beneficial for the adsorption of manganese(II). At pH 6.0, the manganese(II) ions were retained on the almond skin and afterward quantitatively eluted using 1.5?mol?L^?1 nitric acid. The pH, flow rate and volume of sample, concentration, and flow rate of eluent and interfering ions were characterized. Using a sample size of 30?mL, a linear dynamic range of 1–120?µg?L^?1 was obtained. A detection limit of 0.24?µg?L^?1 manganese(II) and a relative standard deviation of 1.6% at 30?µg?L^?1 were achieved. The accuracy of the present procedure was evaluated by the determination of manganese(II) in a certified reference material (GSB07-1189-2000). The protocol was also used for the determination of manganese(II) in wastewater. The fortified recoveries were from 99.0 to 99.4%.     

Preconcentration of Volatile Hydrocarbons as Air Pollutants by C-18 Bonded Silica used for Solid Phase Extraction

ABSTRACT

C₁₈-Silica used for Solid-Phase Extraction exhibits the same degree of adsorption of volatile hydrocarbons as compared to conventional Tenax adsorbent. The vapor pressure of the hydrocarbons and the velocity of the air sample through the sorbent are dominants of the preconcentration. Recovery of 80% for n-hexane and 98% for p-xylene at a concentration of 10 mg.m^?3 was obtained at 10 ml.g^?.min^? velocity.

C₁₈Bond Elut cartridges have been successfully used for quantitative determination of hydrocarbons as air pollutants by gas chromatography. The detection limit for p-xylene using preconcentration from 1 L air sample and a S/N ratio of 5 was 0.1 mg.m^?3. After regeneration of C₁₈Bond Elut cartridges by washing with acetonitrile and diethyl ether and drying at 85°C/15 min, their preconcentration potential remain acceptable upon reusing at least three times.     

Separation of trace amounts palladium by SiO2/TiO2/Ce nanoparticles prior to flame atomic absorption spectrometry determination in anodic slime and wastewater samples

In the present work, a new SiO₂/TiO₂/Ce, nanoparticle was synthesed using sol-gel method and evaluated as an adsorbent for preconcentration trace amounts of Pd(II) ions. The characterization of the nanoparticles has been studied by transmission electron microscope and X-ray diffraction. The preconcentration method is based on palladium adsorption onto the surface of nanoparticle at pH 8.5. The main factors affecting Pd(II) adsorption, such as pH of sample solution, concentration and volume of eluent, sample volume, interfering of the coexisting ions and flow rate of sample and eluent were investigated and optimized. At optimum conditions, linearity was maintained between 4.0 to 1000.0 ng mL^?1. Detection limit based on 3S_b/m was 2.3 ng mL^?1. Seven replicate determinations of a solution containing of 12.5 µg palladium gave a relative standard deviation ±1.7%. According to the Langmuir linear model, the maximum adsorption capacity of palladium was found to be 34.5 mg g^?1. Finally, the feasibility of the proposed method for Pd(II) determination was assessed by analysis of certified reference materials, anodic slime and wastewater samples and satisfactory results were obtained.      

Silver modified magnetic carbon nanotubes composite as a selective solid phase extractor for preconcentration and determination of trace mercury ions in water solution

A magnetic composite of silver/iron oxides/carbon nanotubes (Ag/Fe₃O₄/CNTs) was synthesized and used as an adsorbent for the preconcentration of mercury ions in water solutions at room temperature (25°C) in this study. The silver nanoparticles were supported on the magnetic CNTs. The modification enabled the composite had not only a high adsorption capacity for mercury ions (Hg²⁺) but also the magnetic isolation properties. A fast, sensitive, and simple method was successfully developed for the preconcentration and determination of trace amount of Hg²⁺ in water using the synthesized nanocomposite as adsorbent. The mercury concentration was determined by an atomic fluorescence spectrometer (AFS). The experimental conditions such as pH value, extraction temperature, extraction time, sample volume, eluent composition and concentration, sorbent amount, and coexisting ions were investigated for the optimization. A 500 mL of sample volume resulted in a preconcentration factor of 125. When a 200 mL of sample was employed, the limit of detection for Hg²⁺ was as low as 0.03 ng mL^?1with relative standard deviation of 4.4% at 0.1 ng mL^?1 (n = 7). The ease of synthesis and separation, the good adsorption capacity, and the satisfactory recovery will possibly make the composite an attractive adsorbent for the preconcentration of ultratrace Hg²⁺ in waters.     

Simultaneous preconcentration and determination of nickel and cobalt using functionalised mesoporous silica spheres by ICP-OES

In this work functionalised mesoporous silica spheres have been utilised for the simultaneous preconcentration of nickel and cobalt. The silica spheres (SiSPs) prepared by the sol-gel method were functionalised with sodium diethyldithiocarbamate (DDTC-SiSPs). They were characterised by SEM, TEM, XRD, FTIR, CHN and nitrogen adsorption. The adsorption efficiency of DDTC-SiSPs was examined by batch equilibrium technique. The DDTC-SiSPs showed 100% adsorption for Ni (II) and Co (II). The effect of changing variables such as pH, shaking time, sample volume, preconcentration factor, eluent type and volume were investigated so as to obtain maximum recovery with high selectivity over interfering ions. The maximum adsorption capacity was found to be 15.15 mg g^?1 and 11.80 mg g^?1 for Ni (II) and Co (II) respectively using DDTC-SiSPs. 100% recovery was achieved with 5 mL of 2 M HNO₃. The maximum preconcentration factor was 400 and the 3σ limits of detection were 0.201 µg L^?1 and 0.198 µg L^?1 for Ni (II) and Co (II) respectively. Thermodynamic studies showed that adsorption of Ni (II) and Co (II) on DDTC-SiSPs is exothermic with enthalpy changes of –0.514 KJ mol^?1 and –0.854 KJ mol^?1 for Ni (II) and Co (II) respectively. The method was applied to the preconcentration and determination of Ni (II) and Co (II) from tap, river and sea water.     

β-Cyclodextrin-based polyurethane (β-CDPU) polymers as solid media for adsorption and determination of Pb(II) ions in dust and water samples

In this work, β-CD-based polyurethane copolymers (β-CDPU) have been prepared by reacting β-CD with hexamethylene diisocyanate as cross-linked agent in dry DMF. This polymer showed high selectivity for preconcentration of Pb(II) at trace level prior to its flame atomic absorption spectrometric determination. The effect of several parameters such as pH, flow rate of sample, eluent kind and volume was investigated. The adsorption behaviors and mechanisms of Pb(II) on the samples were also studied. The maximum adsorption amount of Pb(II) was 8 mg g^?1 with the preconcentration factor of 250 for Pb(II). The Langmuir isotherm was proved to describe the adsorption data better than the Freundlich isotherm and a pseudo-first-order kinetic model fits the adsorption kinetic processes well. The calibration curve was linear in the range of (3–200 ng mL^?1) with a correlation coefficient of 0.9996. The limit of detection based on three times the standard deviation of the blank was 1.15 ng mL^?1. The relative standard deviations for the determination of 10 and 100 ng mL^?1 of Pb(II) were 3.60 and 0.43 % (n = 10), respectively. The method was successfully applied to the determination of lead in some environmental samples such as Tehran and Bushehr drinking water, river water and dust samples.     

A nanocomposite made from conducting organic polymers and multi-walled carbon nanotubes for the adsorption and separation of gold(III) ions

We describe a new method for the separation and preconcentration of traces of Au(III) in environmental samples. Sorbents made from modified multiwalled carbon nanotubes and conducting polymers (PANI and PEDOT) were used for solid-phase extraction. The Au(III) ions are adsorbed as a result of the interaction with the electron pairs of =N- and -S- groups. Effects of pH value, flow rate and volume of sample, type, volume and concentration of eluent, and the adsorption capacity were investigated. The maximum adsorption capacity of MWCNTs/PANI and MWCNTs/PEDOT are 159 and 176?mg?g^?1, and the detection limits of this method are below 0.3 and 0.5?ng?mL^?1, respectively. The procedure was successfully applied to the determination of traces of Au(III) in a reference material and in environmental samples.

Online thorium determination after preconcentration in a minicolumn having XAD-4 resin impregnated with N-benzoylphenylhydroxylamine by FI-spectrophotometry

A very sensitive and selective flow injection on-line determination method of thorium (IV) after preconcentration in a minicolumn having XAD-4 resin impregnated with N-benzoylphenylhydroxylamine is described. Thorium (IV) was selectively adsorbed from aqueous solution of pH 4.5 in a minicolumn at a flow rate of 13.6 mL min^?1, eluted with 3.6 mol dm^?3 HCl (5.6 mL min^?1), mixed with arsenazo-III (0.05% in 3.6 mol dm^?3 HCl stabilized with 1% Triton X-100, 5.6 mL min^?1) at confluence point and taken to the flow through cell of spectrophotometer where its absorbance was measured at 660 nm. Peak height was used for data analyses. The preconcentration factors obtained were 32 and 162, detection limits of 0.76 and 0.150 ??g L^?1, sample throughputs of 40 and 11 h^?1 for preconcentration times of 60 and 300 s, respectively. The tolerance levels for Zr(IV) and U(VI) metal ions is increased to 50-folds higher concentration to Th(IV). The proposed method was applied on different spiked tap water, sea water and biological sample and good recovery was obtained. The method was also applied on certified reference material IAEA-SL1 (Lake Sediment) for the determination of thorium and the results were in good agreement with the reported value.     

Pulsed amperometric detection of sulfur-containing pesticides in reversed-phase liquid chromatography

Pulsed amperometric detection at a gold electrode is demonstrated for the separation of eight sulphur-containing pesticides on a C-18 reversed-phase column with 50% (v/v) acetonitrile in acetate buffer (pH 5.0) as the mobile phase. Detection was based on a two-step potential waveform with adsorption of the analyte during cathodic polarization and subsequent amperometric detection catalyzed by oxide formation following anodic polarization. The mechanism of the anodic detection involves prior adsorption of the sulfur compounds. Hence, the shape of the calibration curve is strongly influenced by the adsorption isotherm of the analyte and, therefore, deviates from linearity at high concentrations. Detection limits below 100 ng ml^?1 in 20-μl samples (e.g., 0.8 ng of dimethoate) were obtained by using preconcentration from a larger sample onto a C-18 fore column prior to injection into the separation column.     

FI-spectrophotometric determination of uranium after preconcentration on an anion exchange resin

An economical, fast, sensitive and selective method for the determination of uranium (VI) from sulfate media based on the flow injection on-line preconcentration in a minicolumn having amberlite IRA-402 (strong anion exchange) resin is described. Uranium (VI) was selectively adsorbed on the resin as uranyl trisulfate complex from aqueous solution of pH 2 in the minicolumn (2.56 mm i.d. and 7.5 cm in length) at a flow rate of 10 ml min^?1. The adsorbed uranyl trisulfate complex was eluted by HClO₄ (0.1 mol l^?1, 6.5 ml min^?1) and mixed with arsenazo-III (0.05 %, 6.5 ml min^?1), and passed through the flow through cell of spectrophotometer where its absorbance was measured at 653 nm. Various parameters affecting adsorption and elution of the uranium complex were optimized. For data analyses peak absorbance was used. For 60 and 180 s preconcentration time, enrichment factors (EF) 20 and 40, sampling frequency (SF) 45 and 18 h^?1; and detection limits (DL) (3σ) 14.2 and 8.6 μg l^?1 were obtained, respectively. To enhance the sensitivity of the system, two minicolumns (described above) were used for simultaneous preconcentration and elution purpose. For 60 and 180 s preconcentration time, EF 30 and 50, SF 42 and 17 h^?1 and DL (3σ) 4.4 and 3.44 μg l^?1 were obtained, respectively. The effect of various anions and cations was studied for single column manifold. High selectivity of this method was observed. All the anions and cations studied did not interfere up to 330 times higher mass ratio to 300 μg l^?1 U (VI) except Th(IV) which was tolerated up to 133 times by the addition of washing step in the manifold. The method based on single column manifold was applied on the spiked tap water, biological sample CRM (IAEA-V4) and synthetic leach liquor solution and good recovery was obtained. The method based on dual column manifold was validated on lake sediment SL-1 (CRM) and the results obtained were in good agreement at 95 % confidence level with the given value.     

Kinetic and Thermodynamic Investigations of Zn(II) Adsorption on Microcrystalline Anthracene Modified with 8‐Hydroxyquinoline and Its Application to the Preconcentration and Determination of Trace Zinc

A new method that utilizes microcrystalline anthracene modified with 8‐hydroxyquinoline as an adsorbent has been developed for the preconcentration of trace Zinc(II). The possible reaction mechanism is discussed in detail. The influences of different parameters, such as acidity, other metal ions, the amounts of 8‐hydroxyquinoline and anthracene, etc. on the enrichment yield of Zn(II) have been studied to optimize the experimental conditions. The experimental data were fitted well with the pseudo‐second‐order kinetic model and Langmuir model at all studied temperatures and the maximum adsorption capacity was 32.58 mg·g^?1 (300 K). The thermodynamic parameters (ΔG^θ, ΔH^θ and ΔS^θ) showed the feasibility, exothermic and spontaneous nature of the adsorption at 280～320 K. Experiments indicate that Zn(II) can be completely separated from Cu(II), Co(II), Cd(II), Mn(II), Ni(II) in the eluent. The recovery of this method is in the range of 96.0%～105.0% with preconcentration factor of 100 and the limit of detection after preconcentration is 0.068 μg·L^?1. The proposed method has been successfully applied to the determination of trace Zn(II) in effluents and synthetic water sample having a composition similar to certified water sample SLRS‐4 (NRC, Canada). Analytical results obtained by this recommended method were very satisfactory.     

Application of Ni(II)-imprinted cross-linked poly(methacrylic acid) synthesised through double-imprinting method for the on-line preconcentration of Ni(II) ions in aqueous media

The present paper describes the feasibility of on-line preconcentration of nickel ions from aqueous medium on Ni(II)-imprinted cross-linked poly(methacrylic acid) (IIP) synthesised through a double-imprinting method and their subsequent determination by FAAS. The proposed method consisted in loading the sample (20.0 mL, pH 7.25) through a mini-column packed with 50 mg of the IIP for 2 min. The elution step was performed with 1.0 mol L^?1 HNO₃ at a flow rate of 7.0 mL min^?1. The following parameters were obtained: quantification limit (QL) – 3.74 µg L^?1, preconcentration factor (PF) – 36, consumption index (CI) – 0.55 mL, concentration efficiency (CE) – 18 min^?1, and sample throughput – 25 h^?1. The precision of the procedure assessed in terms of repeatability for ten determinations was 5.6% and 2.5% for respective concentrations of 5.0 and 110.0 µg L^?1. Moreover, the analytical curve was obtained in the range of 5.0–180.0 µg L^?1 (r = 0.9973), and a 1.64-fold increase in the method sensitivity was observed when compared with the analytical curve constructed for the NIP (non-imprinted polymer), thus suggesting a synergistic effect of the Ni(II) ions and CTAB on the adsorption properties of the IIP. The practical application of the adsorbent was evaluated from an analysis of tap, mineral, lake and river water. Considering the results of addition and recovery experiments (90.2–100 %), the efficiency of this adsorbent can be ensured for the interference-free preconcentration of the Ni(II) ions.     

Modified nanoalumina sorbent for sensitive trace cobalt determination in environmental and food samples by flame atomic absorption spectrometry

1-(2-pryidylazo)-2-naphthol (PAN) immobilized on sodium dodecyl sulfate-coated nano alumina was developed for the preconcentration and determination of metal cations Co (II) from environmental and food samples. The research results displayed that adsorbent has the highest adsorption capacity for Co (II) in this system. Desorption by elution of the adsorbent with 2.0?ml of a mixture of nitric acid and ethanol was carried out. After phase separation, the enriched analyte in the final solution is determined by flame atomic absorption spectrometry (FAAS) by using a micro sample introduction system. Analytical influencing parameters including pH value, amount of sorbent, equilibrium time, sample volume, volume and concentration of eluent were examined. The effect of common matrix ions has also been investigated and it was found that they had no influence on cobalt preconcentration. Under the optimum experimental conditions, the maximum capacity of sorbent was obtained as 20?mg?g^?1. The preconcentration factor and limit of detection were found to be 250 and 0.15?µg?L^?1, respectively. This method showed good precision with the relative standard deviation (RSD) of 2.4% and 2.1% in concentrations of 20 and 50?µg?L^?1, respectively. The accuracy of the method was evaluated by comparison of results with those obtained by electrothermal atomic absorption spectrometry. This method was successfully applied for preconcentration and determination of Co (II) in environmental and food samples.     

Determination trace amounts of thallium after separation and preconcentration onto nanoclay loaded with 1-(2-pyridylazo)-2-naphthol as a new sorbent

A procedure has been proposed for the separation and preconcentration of trace amounts of thallium. It is based on the adsorption of thallium ions onto organo nanoclay loaded with 1-(2-pyridylazo)-2-naphthol (PAN). Thallium ions were quantitatively retained on the column in the pH range of 3.5–6.0, whereas quantitative desorption occurs with 5.0?mL of 5% ascorbic acid and thallium was determined by flame atomic absorption spectrometry. Linearity was maintained between 0.66?ng?mL^?1–15.0?µg?mL^?1?in initial solution. Detection limit was 0.2?ng?mL^?1?in initial solution and preconcentration factor was 150. Eight replicate determinations of 2.0?µg?mL^?1 of thallium in final solution gave a relative standard deviation of ±1.48%. Various parameters have been studied, such as the effect of pH, breakthrough volume and interference of a large number of anions and cations and the proposed method was used to determine thallium ions in water and standard samples. Determination of thallium ions in standard sample showed that the proposed method has good accuracy.     

Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb²⁺, Ni²⁺, Cd²⁺ and Cu²⁺ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L^?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L^?1, respectively. The relative SDs at 10 µg L^?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples.     

An ionic liquid-based sorbent for solid phase extraction of trace iron(Ш) from biological and natural water samples

A new ionic liquid modified silica gel sorbent was prepared from the reaction of active silica gel with N-3-(-3-triethoxysilylepropyl)-3-methylimidazolium chloride ([(TESP)MIm]Cl). This sorbent was exploited as solid phase extractant for separation and preconcentration of metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). It was found that it can selectively adsorb Fe(Ш). Identification of the surface modification was performed on the basis of FT-IR. Experimental conditions for effective adsorption of trace Fe(Ш) were optimised using both batch and column procedures. At pH 3, Fe(Ш) could be quantitatively adsorbed and completely eluted by using 2?mL of 0.1?mol?L^?1 of HCl. 150?mL of sample solution was adopted as the maximum sample volume and a high enrichment factor of 75 was obtained. Most common coexisting ions did not interfere with the separation and preconcentration of Fe(Ш) at optimal conditions. The maximum static adsorption capacity of the sorbent was 37.0?mg?g^?1. The detection limit of the present method was 0.48?µg?L^?1, and the relative standard deviation (R. S. D.) was lower than 1.7%. The method was successfully applied to the preconcentration of trace Fe(Ш) in biological and natural water samples with satisfactory results.     

The separation–preconcentration and determination of ultra-trace gold in water and solid samples by dispersive liquid–liquid microextraction using 4-ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) as chelating agent and flame atomic absorption spectrometry

A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO₃ concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L^?1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L^?1. The relative standard deviation obtained 2.1% at 50 µg L^?1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples.     

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60?s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 10³–10⁴ fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0?pg?mL^?1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1?µg?L^?1 levels.     

Solid Phase Extraction of Lead(II) by Sorption on Grinded Eucalyptus Stem and Determination with Flame Atomic Absorption Spectrometry

A sensitive and simple solid‐phase preconcentration procedure for the determination of trace amount of lead by flame atomic absorption spectrometry (FAAS) is developed. The method is based on the adsorption of Pb²⁺ on the column of fine grinded eucalyptus stem adsorbent, elution of the column by nitric acid and subsequent determination by FAAS. The effect of different variables such as pH, eluent type, flow rate and interfering ions on the recovery of the analyte was investigated and optimum conditions were established. The adsorption of lead onto fine grinded eucalyptus stem can formally be described by a Langmuir equation with a maximum adsorption capacity of 4.49 mg g^?1. A preconcentration factor of 50 was achieved using the optimum conditions. The calibration graph was linear in the range 10–125 ng mL^?1 of lead in the initial solution with r = 0.9982. The limit of detection based on 3S_b criterion was 4.5 ng mL^?1 and the relative standard deviation for eight replicate measurements of 30 and 80 ng mL^?1 of iron was 3.6 and 2.8%, respectively. The method was successfully applied to the determination of lead added to well, tap and wastewater samples.