Preconcentration Of Cobalt Research Articles

Pre-Concentration Procedure Based on Chitosan Combined with Ionic Liquid for the Determination of Cobalt, Nickel, and Copper in Water Samples

An environmentally friendly analytical procedure of pre-concentration of cobalt, nickel, and copper according to the rules of green chemistry has been developed. The proposed method is based on using chitosan for sorption of trace elements from water samples. The novel modification of the sorption process is the combination of an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6]) with chitosan. Ionic liquid partly decreases the crystallinity of the chitosan. The crystalline regions of the polymer are not accessible to metal ions. Although the ionic liquid cannot completely disrupt the crystalline domains of chitosan, it may gain in the reactive groups of the chitosan, even at the center of the particle. Consequently, the sorption of metal ions by chitosan is significantly improved. In this paper, adsorption characteristics of cobalt, nickel, and copper using newly developed sorption are studied. The effect of pH and time of chitosan activation, as well as sorption, salt concentration, some metals ion concentrations, and the amount of adsorbent on the extent of adsorption, are investigated. Chitosan with adsorbed metal ions was dissolved in acetic acid. After evaporation a solvent film formed and was then analyzed using X-ray fluorescence spectrometry (XRF). As it meets the criterion of thin samples for XRF analysis, the matrix effects can be neglected. With the proposed procedure we obtained detection limits of 7 ng mL(-1) for cobalt, 5 ng mL(-1) for nickel, and 4 ng mL(-1) for copper.

Potential of sawdust as a green and economical sorbent for simultaneous preconcentration of trace amounts of cadmium, cobalt, and lead from water, biological, food, and herbal samples.

Application of treated sawdust with NaOH as a green and economical sorbent for simultaneous preconcentration of trace amounts of Cd(II), Co(II), and Pb(II) ions from liver, lettuce, fish, and water as test samples with complicated matrices was investigated. Various parameters, such as effect of pH and contact time, breakthrough volume, type, and concentration of eluent and interference of ions were studied. The sorption was quantitative in the pH of 5.0 to 7.0 and desorption occurred instantaneously with 5.0mL of mixed solutions of ethanol and 2.0mol/L HNO3 -HCl and the amount of ions was measured by using flame atomic absorption spectrometry. Linearity was maintained at 3 to 500μg/L for cobalt, 5.0 to 800μg/L for lead, and 2.0 to 300μg/L for cadmium in the original solution. The relative standard deviation was less than 1.80% (n= 6, with concentration of 0.3mg/L for cadmium and 0.5mg/L for lead and cobalt). Detection limits and maximum capacity of the sorbent for Co (II), Cd (II), and Pb (II) in the original solution were 0.86, 0.50, and 1.7μg/L and 28.5, 30.6, and 47.3mg/g, respectively. The results for spiked real samples, effect of interfering ions, and adsorption capacity indicated that the applicability of this method for lead preconcentration is better than cadmium and cobalt preconcentration from complicated matrices. Practical Application: Sawdust can be applied as a green and economical sorbent for simultaneous preconcentration and solid-phase extraction of metal ions from food and environmental samples with complicated matrices.

Simultaneous Preconcentration of Cobalt, Nickel and Copper in Water Samples by Cloud Point Extraction Method and their Determination by Flame Atomic Absorption Spectrometry

Abstract A new cloud point extraction procedure was established for the simultaneous preconcentration and determination of cobalt(II), nickel(II), and copper(II) ions in water samples. After complexation with 2-(5-bromo-2-pyridylazo)-5- (diethylamino) phenol (5-Br-PADAP), the analytes could be competitively extracted in a surfactant octylphenoxy polyethoxyethanol (TritonX-114), prior to determination by flame atomic absorption spectrometry (FAAS). The effects of pH, the concentrations of chelating agent and surfactant, equilibration temperature and time, sample volume, etc on CPE were studied. The preconcentration factor obtained was 25 and the limits of detection (DL) obtained for cobalt(II), nickel(II), and copper(II) were 2.4, 1.7 and 1.5 ng·mL−1, respectively. Standard reference material of poplar leaf (GBW 07604) was analyzed by the proposed methods, giving results of cobalt(II), nickel(II), and copper(II) found contents in consistency with the standard values. The presented preconcentration procedure was successfully applied to determination cobalt(II), nickel(II), and copper(II) in water samples.

Linde Type a Zeolite and Type Y Faujasite as a Solid-Phase for Lead, Cadmium, Nickel and Cobalt Preconcentration and Determination Using a Flow Injection System Coupled to Flame Atomic Absorption Spectrometry

In this work, a flow injection analysis (FIA) method for the trace determination of lead, cadmium, nickel and cobalt in natural waters by formation of neutral chelates with ammonium pyrrolidine dithiocarbamate (APDC) was developed. The neutral chelates formed was retained in a mini-column packed with Linde type A zeolite (LTA) and type Y Faujasite zeolite (FAU) and then eluted with methyl isobutyl ketone (MIBK) to flame atomic absorption spectrometry (EAA) for its detection. Physicochemical characterization of this zeolite was carried out by Fourier Transform infrared spectroscopy and attenuated total reflectance (FTIR and IR-ATR), scanning electron microscopy and energy dispersive X-ray microanalysis (SEM-EDX) and X-ray power diffraction (XRD). Then, a FIA configuration was used with a column preconcentration system coupled to the detection system at room temperature (22?C). The detection limit and the relative standard deviation for 5 determinations of different solutions of Pb2+, Co2+, Ni2+ and Cd2+ for FAU and LTA zeolite were calculated. The sampling frequency ranged from 18-35 h-1 and preconcentration factors from 21-250 were achieved, for a sample volume of 6 mL using 20 mg of sorbents, indicating a high retention of the analytes on the zeolites material. The recoveries obtained in natural waters samples were close to 100% for all ions metal using synthetic zeolites, confirming the applicability of the method. The isotherm models of Langmuir, Scatchard, Freundlich and Dubinin-Radushkevich were used to study the equilibrium data, indicating that successfully followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms at low metal ion concentration. The Freundlich parameter n varied between 0.35-1.01, whereas D-R isotherm yields the sorption free energy E 8 kJ.mol-1 indicating psysisorption.

Graphene oxide as a solid sorbent for the preconcentration of cobalt, nickel, copper, zinc and lead prior to determination by energy-dispersive X-ray fluorescence spectrometry

A new method for sample preparation using graphene oxide (GO) as a novel sorbent was developed for the preconcentration of trace amounts of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II). The proposed preconcentration procedure is based on dispersive micro-solid phase extraction (DMSPE). It means that GO was dispersed in aqueous samples containing trace elements to be determined. During the stirring of the analyte solution containing the GO suspension, metal ions were sorbed by GO. After the sorption, the solution was filtered under vacuum and GO with the metal ions was collected onto a membrane filter. The obtained samples were analyzed directly by energy-dispersive X-ray fluorescence spectrometry (EDXRF). The parameters affecting the extraction and preconcentration process were optimized. The pH of the analyte solution, the amount of GO, the sample volume, the contact time between analytes and sorbent (stirring time), and the effects of foreign metals are discussed in detail in this paper. The proposed procedure allows us to obtain the detection limits of 0.5, 0.7, 1.5, 1.8 and 1.4 ng mL−1 for Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The linearity of the method is in the range of 5–100 ng mL−1. The proposed method was successfully applied in the analysis of water. The accuracy of the method was verified using spiked samples and inductively coupled plasma optical emission spectrometry (ICP-OES) as a comparative technique. The recoveries over the range of 94–106% were obtained. This paper shows the great potential of GO as an excellent sorbent in the preconcentration field of analytical chemistry. The proposed method meets green chemistry rules.

Функционализация поверхности целлюлозы тиосемикарбазидными группами с целью создания сорбента для концентрирования и определения тяжелых металлов в водах

A novel cellulose adsorbent bearing chemically immobilized thiosemicarbaside is synthesized. The adsorbent is used for the preconcentration of cobalt (II), mercury (II), and cadmium (II) followed by their X-ray fluorescence quantification in the concentrate. After approximation of experimental data on sorption capacity dependency on equilibrium concentration of element in the solution in coordinates of the Langmuir equation, the linear functions with correlation coefficient ≥ 0.99 were obtained. These functions we used to calculate maximum adsorption capacity (A мах ) and adsorption equilibrium constant. Using pseudo-first order kinetic equations for the approximation of experimental data on time-dependencies of sorbents capacity for Сd 2+ , Co 2+ , Hg 2+ the sorption rate constants were calculated. The possibility of determination of adsorbed Сd 2+ , Co 2+ , Hg 2 , by X-ray fluorescence in the sorbent phase was estimated for concentration phase under static conditions and pH =9 in case of the presence of all metals. Keywords : cellulose adsorbent, thiosemicarbazide, preconcentration (Russian) DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.004 Dzh.N. Konshina, Z.A. Temerdashev, V.V. Konshin, E.I. Byshkina Federal State Educational Institution of Higher Professional Education «Kuban State University» , Krasnodar, Russian Federation

Suspended nanoparticles in surfactant media as a microextraction technique for simultaneous separation and preconcentration of cobalt, nickel and copper ions for electrothermal atomic absorption spectrometry determination

The aim of this study was to describe a new method of microextraction based on the suspension of alumina nanoparticles in the surfactant media for simultaneous separation and preconcentration of the ultra-traces of cobalt, nickel and copper ions. In this technique, the alumina nanoparticles were suspended in the non-ionic surfactant solution of Triton X-114. The analytes in the sample solution were adsorbed onto the nanoparticles. After the phase separation based on the cloud point of the mixture at 40°C, the nanoparticles settled down in the surfactant rich phase. Then 120μL of nitric acid (3.0molL−1) was added to the surfactant rich phase which caused desorption of the analytes. Finally, the liquid phase was separated by centrifugation from the nanoparticles and was used for the quantification of the analytes by the electrothermal atomic absorption spectrometry (ETAAS). The parameters affecting the extraction and detection processes were optimized. Under the optimized experimental conditions (i.e. pH∼8, Triton X-114, 0.05% (v/v); temperature 40°C), a sample volume of 25mL resulted in the enhancement factors of 198, 205 and 206 and detection limits (defined as 3Sb/m) of 2.5, 2.8 and 2.6ngL−1 for Co(II), Ni(II) and Cu(II) respectively. The sorbent showed high capacity for these metal ions (30–40mgg−1 sorbent). The method was successfully applied to the determination of the analytes in natural water samples.

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.

Development of a Cloud‐Point Extraction Method for Cobalt Determination in Natural Water Samples

A new, simple, and versatile cloud‐point extraction (CPE) methodology has been developed for the separation and preconcentration of cobalt. The cobalt ions in the initial aqueous solution were complexed with 4‐Benzylpiperidinedithiocarbamate, and Triton X‐114 was added as surfactant. Dilution of the surfactant‐rich phase with acidified ethanol was performed after phase separation, and the cobalt content was measured by flame atomic absorption spectrometry. The main factors affecting CPE procedure, such as pH, concentration of ligand, amount of Triton X‐114, equilibrium temperature, and incubation time were investigated and optimized. Under the optimal conditions, the limit of detection (LOD) for cobalt was 0.5 μg L−1, with sensitivity enhancement factor (EF) of 67. Calibration curve was linear in the range of 2–150 μg L−1, and relative standard deviation was 3.2% (c = 100 μg L−1; n = 10). The proposed method was applied to the determination of trace cobalt in real water samples with satisfactory analytical results.

Sorption properties of cellulose filters with covalently immobilized thiosemicarbazide

A novel thin-layer cellulose adsorbent bearing chemically immobilized thiosemicarbaside is synthesized. The adsorbent is used for the preconcentration of cobalt(II), mercury(II), and cadmium(II) followed by their X-ray fluorescence quantification in the concentrate. The physicochemical parameters of metal sorption are determined.

Solid phase pre-concentration of cobalt(II) using pyridine–thiocyanate reagents: X-ray crystal structure of the extracted ternary cobalt(II) complex

Mixture of pyridine-2,6-dimethanol (PDM) and thiocyanate (SCN −) (1:1, mole ratio) immobilized on silica served as a very efficient sorbent for selective retention of Co(II) from other associated metal ions at trace level. The maximum sorption capacity for Co(II) was found to be 0.203 mmol g −1 at pH 9.0. Sorbed Co(II) was completely eluted by 3.5 mL of 3 mol L −1 HCl and measured using flame atomic absorption spectrometer (FAAS). The structure of the extracted Co(II) complex was confirmed by single crystal X-ray structure and Fourier transform infrared (FTIR) spectroscopy. Thermo gravimetric analysis (TGA) of the chelated Co(II) complex revealed its stability at the optimum extraction temperature (55 °C). The method was reproducible with a relative standard deviation (RSD) of 0.6% ( N = 10) with three sigma detection limit (N = 10) of 0.6 μg g −1. A pre-concentration factor, 94 was achieved. Interferences from Mn 2+ and Cu 2+ ions were eliminated by prior oxidation of Mn 2+ by KIO 4 to MnO 4 − and masking of Cu 2+ with NH 4SCN, respectively. A plausible mechanism for the selective extraction of Co(II) was attributed to the formation of a first order water insoluble inner–metallic complex as confirmed by the single crystal X-ray structure analysis. The developed method has been tested for trace level separation and estimation of cobalt in some certified reference materials. Analyses of some biological and environmental samples were performed.

Micelle-Mediated Extraction and Flame Atomic Absorption Spectrometric Method for Determination of Trace Cobalt Ions in Beverage Samples

A new method has been developed for preconcentration of cobalt at trace levels in beverage samples using calcon carboxylic acid as chelating agent and cetyl pyridinium chloride as an auxiliary ligand and entrapped into Triton X-114 prior to its determination by flame atomic absorption spectrometry (FAAS). The main parameters affecting cloud point extraction (CPE) efficiency such as pH, concentration of the complexing agent, cationic and nonionic surfactant concentration, salt effect, the equilibrium time, and temperature were investigated and optimized. After optimization of the CPE conditions, a preconcentration factor of 60, an enhancement factor of 106, and a detection limit of 0.20 μg L−1 by (R2 = 0.9978) were obtained from a calibration curve constructed in the range of 0.7–100 μg L−1. The proposed preconcentration procedure was successfully applied to the determination of cobalt ions in some real samples including natural drinking water, tap water, and beer and wine samples. The accuracy and validity of the proposed CPE/FAAS method was tested by means of five repeated analysis of reference standard materials (TM-253, a low level fortified water standard for trace elements). A good agreement between analytical results (28.8 and 28.5 μg L−1 with calibration curve and standard addition curve method, respectively) and certified value (27.9 μg L−1) for Co (p < 0.05) were obtained and verified by means of calibration curve and standard addition curve method using CPE procedure.

An online ionic liquid-based microextraction system coupled to electrothermal atomic absorption spectrometry for determination in environmental samples and pharmaceutical formulations.

In the present work, an ionic liquid (IL) lighter than water was employed as extraction solvent in a dispersive liquid-liquid microextraction (DLLME) methodology. An original flow injection system for online microextraction and preconcentration of cobalt (Co) based on the use of tetradecyl(trihexyl)phosphonium chloride (CYPHOS® IL 101) was designed. Cobalt was complexed with 4-(2-pyridylazo)-resorcinol (PAR) reagent at pH 4.8 and then, the IL-DLLME procedure was developed by dispersing CYPHOS® IL 101 with acetone in an aqueous solution containing Co-PAR complex. Different pyridylazo dyes were evaluated for Co preconcentration in terms of their molecular structure, stability and acid-base equilibrium. Online extraction of Co-PAR into the IL and separation of the dispersed IL enriched phase were accomplished with a microcolumn containing Florisil material. Cobalt was removed from the microcolumn with a 10% (v/v) HNO3 acidified-acetone solution and finally measured by electrothermal atomic absorption spectrometry (ETAAS). The detection limit achieved after preconcentration of 2 mL of sample solution was 8 ng L-1. The precision for 10 replicate determinations at the 1 µg L-1 Co level was 5.1% relative standard deviation (RSD), calculated from the peak heights obtained. The method was successfully applied to Co determination in water samples as well as ophthalmic and parenteral solutions. For the first time, an IL-based microextraction technique was applied for metal determination in these complex samples, where Co recovery varied between 97.9 and 103%.

Separation and Preconcentration of Cobalt Using a New Schiff Base Derivative on Amberlite XAD‐7

AbstractIn this study, a new solid‐phase extraction procedure has been developed for preconcentration and determination of Co ions in different water samples by flame atomic absorption spectrometry (FAAS). Cobalt was preconcentrated as N,N′‐bis(pyridine‐2‐yl‐methyl)benzene‐1,4‐diamine (Co‐BPMBDA) from sample solutions using a column containing Amberlite XAD‐7 and was determined. In order to achieve the best performance for the method, effects of several parameters such as pH, concentrations of ligand, sample flow rate, eluent, and matrix ions on the method efficiency were investigated. Under optimum conditions, the preconcentration factor was found to be 200 for 1000 mL waters samples. Detection limit based on the 3Sb criterion was calculated as 0.24 µg/L for 100 mL of sample solution and relative standard deviation was found to be 1.8%. The method was applied to determine the trace amounts of cobalt in water samples.

Ionic Liquid-Based, Single-Drop Microextraction for Preconcentration of Cobalt Before Its Determination by Electrothermal Atomic Absorption Spectrometry

An effective and environmentally friendly single-drop microextraction method was developed for the preconcentration of ultratraces of cobalt before its determination by electrothermal atomic absorption spectrometry (ETAAS). A microdrop of 1-hexyl-3-methylimidazolium hexafluorophosphate, [C6MIM][PF6], was used to extract Co(II) ions as an ammonium pyrroldinedithiocarbamate (APDC) complex. The sensitivity was improved by increasing the volume of the suspended drop. Several variables affecting microextraction efficiency and the ETAAS signal-such as pyrolysis and atomization temperature, pH, APDC concentration, extraction time, drop volume, and stirring rate-were investigated and optimized. Under the optimum experimental conditions, the detection limit (3 SD) was 0.04 microg/L, and the enrichment factor was 120. The RSD for five replicate determinations of Co(II) at 0.5 microg/L was 4.5%. The developed method was validated by analysis of a Standard Reference Material and applied to the determination of cobalt in water samples.

A procedure for determination of cobalt in water samples after dispersive liquid–liquid microextraction

In this work, a procedure for preconcentration of cobalt using dispersive liquid–liquid microextraction (DLLME) with the reagent Br-TAO as complexing reagent was developed. The procedure is based on a ternary system of solvents, where appropriate amounts of the extraction solvent, disperser solvent and the chelating agent Br-TAO are directly injected into an aqueous solution containing Co(II). A cloudy mixture is formed and the ions are extracted in the fine droplets of the extraction solvent. After extraction, the phase separation is performed with a rapid centrifugation, and cobalt is determined in the enriched phase by FAAS. Under the optimized conditions, the detection limit obtained was 0.9 µg L − 1 . The enrichment factor and the consumptive index were 16 and 0.31 mL, respectively. The accuracy of the method was tested by the determination of cobalt in certified reference material of spinach leaves, NIST 1570a. The proposed procedure was successfully applied to the determination of cobalt in water samples.

Solid phase extraction and preconcentration of cobalt in mineral waters with PAR-loaded Amberlite XAD-7 and flame atomic absorption spectrometry

A simple, sensitive, accurate, and selective method for determination of ultratrace levels of Co is modified. The method is based on preconcentration of Co on the PAR-loaded Amberlite XAD-7 at pH 2.0 ± 0.2 for contact time as low as 45 min. The adsorbed cobalt was eluted with concentrated nitric acid and measured by flame atomic absorption spectrometry. Recoveries up to 90% were achieved. The optimized preconcentration method was applied to cobalt determination in natural mineral waters. The detection limit was found to be 0.1 ng mL−1. The relative standard deviation was found to be 13% for 600 mL of 2.0 ng mL−1, for 10 replicate preconcentration procedures. Cobalt concentrations in the studied water samples were found to be in the ranges of 0.5–3.5 ng mL−1.

Cloud point extraction for cobalt preconcentration with on-line phase separation in a knotted reactor followed by ETAAS determination in drinking waters

A novel method for cobalt preconcentration by cloud point extraction with on-line phase separation in a PTFE knotted reactor and further determination by electrothermal atomic absorption spectrometry (ETAAS) is proposed. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmono- p-nonylphenylether (PONPE 7.5) and it was retained on the inner walls of a knotted reactor (KR). The surfactant rich-phase was removed from the knotted reactor with 75 μL of methanol acidified with 0.8 mol L −1 nitric acid, directly into the dosing hole of the L’Vov graphite tube. An enrichment factor of 15 was obtained with a preconcentration time of 60 s, with respect to the direct determination of cobalt by ETAAS in aqueous solutions. The value of the detection limit for the preconcentration of 5 mL of sample solution was 10 ng L −1. The precision, expressed as the relative standard deviation (R.S.D.), for 10 replicate determinations at 0.5 μg L −1 Co level was 4.5%. Verification of the accuracy was carried out by analysis of a standard reference material (NIST SRM 1640e “Trace elements in natural water”). The method was successfully applied to the determination of cobalt in drinking water samples.

Homogeneous Liquid–Liquid Extraction and Determination of Cobalt, Copper, and Nickel in Water Samples by Flame Atomic Absorption Spectrometry

A simple and effective homogeneous liquid–liquid extraction method has been used for the simultaneous extraction and preconcentration of cobalt, copper, and nickel after the formation of complex with 4‐benzylpiperidinedithiocarbamate potassium salt (K‐4‐BPDC), and later they were determined by flame atomic absorption spectrometry (FAAS) using (water/tetrabutylammonium ion (TBA+)/chloroform) as a ternary component system. The phase separation phenomenon occurred by an ion‐pair formation of TBA+ and perchlorate ion. After the optimization of complexation and extraction conditions ([K‐4‐BPDC]=2.0×10−4 mol l−1, [TBA+]=2.0×10−2 mol l−1, [CHCl3]=60.0 µl, [ClO4 −]=2.0 ×10−2 mol l −1 and pH=6.0), a preconcentration factor of 200 was obtained for only 10 ml of the sample. The analytical curves were linear in the range of 20–1500, 15–2000, 35–1600 µg l−1 and the limits of detection were 10, 5, and 15 µg l−1 for Co2+, Cu2+, and Ni2+, respectively. The proposed method was applied for the extraction and determination of Co2+, Cu2+, and Ni2+ in natural water samples with satisfactory results.

Preconcentration of cobalt using Amberlyst 36 as a solid-phase extractor and its determination in various environmental samples by flame atomic absorption spectrometry

A new and simple column-solid-phase extraction method has been developed to separate and preconcentrate trace cobalt in water and soil prior to its determination by flame atomic absorption spectrometry (FAAS). Different factors such as pH of sample solution, sample volume, amount of resin, flow rate of aqueous solution, volume and concentration of eluent, and matrix effects for preconcentration were optimized. Under optimized experimentally established conditions, an analytical detection limit of 0.44 µg L−1, precision (RSD) of 1.9%, enrichment factor of 200, and capacity of resin of 82 mg g−1 were obtained. The method was applied for cobalt determination by FAAS in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analysing standard reference material (Montana Soil, SRM 2711).