Permanent Chemical Modifier Research Articles

Quantification of ytterbium in road dust applying slurry sampling and detection by high-resolution continuum source graphite furnace atomic absorption spectrometry

In this work, the determination of ytterbium in road dust samples, employing a simple and fast methodology, based on sample preparation as slurry and analysis by high resolution-continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS), is purposed. The determinations were carried out on the Yb main line, 398.799 nm, using an integration time of 5.0 s. The optimum condition for the slurry preparation of road dust samples was established through a Doehlert matrix for two variables, which employed a HNO3 concentration of 0.24 mol L−1 and homogenization time of 34 min, using ultrasonic bath. The temperatures applied to the graphite furnace were optimized, wherein the pyrolysis and atomization temperatures were 1200 °C and 2700 °C, respectively, using 250 μg of W as permanent chemical modifier. To investigate possible matrix interferences in the determination of Yb in road dust samples, external calibration and standard addition curves were compared. The comparison between slopes of the external and standard addition calibration curves showed difference of about 7.0%, an indication of absence of matrix effects for determination of Yb in road dust samples. The limit of detection (LOD) and limit of quantification (LOQ) were 22 and 72 ng g−1, respectively, with a characteristic mass of 6.0 pg. The accuracy was confirmed through analyses of three certified reference materials (CRM): Trace Elements in Soil Containing Lead From Paint (NIST 2586), Rock (NCS DC 73301) and Geochemical Soil (TILL-1), and the good agreement between the found and certified values was obtained, 99 ± 4 to 104 ± 2%, corroborating the accuracy of the analytical method. The precision was expressed as relative standard deviation (RSD) for measurements in triplicate, being lower than or equal to 10.0%. The analytical method was used for Yb determination in eight samples of dust collected in an urban area of Salvador and Jaguaquara, Bahia State, Northeast, Brazil. The concentrations obtained for Yb ranged from 172 ± 13 to 2065 ± 122 ng g−1. Thus, the proposed analytical method presents the characteristics of being fast, precise and accurate for the determination of Yb in road dust samples, employing slurry sampling and detection by HR-CS-GFAAS.

Investigation of chemical modifiers for the determination of cadmium and chromium in fish oil and lipoid matrices using HR-CS GF AAS and a simple ‘dilute-and-shoot’ approach

This work presents simple and reliable methods for the determination of Cd and Cr in fish oil and lipoid samples by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). Only a simple dilution using 1-propanol was adopted as sample preparation for the determination of Cd and Cr in order to reduce the high viscosity of the lipoid samples. Pt was employed as permanent chemical modifier and Pd was used as chemical modifier in solution, added over the sample for the determination of Cd for a better performance and sensitivity. Cr was determined without a chemical modifier. The accuracy of the proposed methods was evaluated by comparison with microwave-assisted digested samples and determination by HR-CS GF AAS, showing good agreement between 2% and 13% for both elements without statistical difference (confidence interval of 95%). The limits of detection for Cd and Cr were 0.5pg and 7pg, respectively, corresponding to 0.15ngg−1 and 2ngg−1, respectively. The developed methods can be described as clean, fast and accurate, which did not require any sample pre-treatment stages, such as digestion or matrix oxidation, and could be extended to different lipoid matrices, demonstrating their robustness.

Development of a fast screening method for the direct determination of chlorinated persistent organic pollutants in fish oil by high-resolution continuum source graphite furnace molecular absorption spectrometry

The occurrence of persistent organic pollutants (POPs), mainly organochlorine pesticides and polychlorinated biphenyls, was directly associated with several diseases and environmental endocrine disrupting. In the aquatic environment, POPs can accumulate in fish lipoid tissues due to their high hydrophobicity, and become this way one of the main sources of human exposure to POPs through the consumption of fish meat and oil as Omega-3 source. Chlorine might serve as a proxy for the presence of POPs, and a fast screening of chlorine in a complex matrix, such as fish oil, could provide substantial information about the contamination with POPs. Therefore, a method has been developed in this work for the determination of total chlorine in fish oil samples via molecular absorption of the strontium mono-chloride molecule in the gas phase using high-resolution continuum source graphite furnace molecular absorption spectrometry. The effect of zirconium as permanent chemical modifier in the pyrolysis and vaporization stages was optimized in order to avoid the need for any kind of sample preparation prior to the determination of total chlorine, using just a dilution with 1-propanol. The accuracy has been evaluated using micro-coulometric titration after sample combustion, and the values were statistically in agreement (95% confidence level) between both techniques. The method has been applied for the determination of total chlorine in five different fractions of a commercial pooled marine fish oil sample collected from the Pacific Ocean, where the majority of the fish is Peruvian anchovy (Engraulis ringens), two commercial oils from Brazil and three Omega-3 supplements acquired in Germany. The limit of detection of the procedure is 1.8 ng Cl absolute or 0.9 μg g−1 Cl in the fish oil. The time required for a single determination is less than 5 min, and less than 15 min for a triplicate determination.

Investigation of chemical modifiers for the direct determination of arsenic in fish oil using high-resolution continuum source graphite furnace atomic absorption spectrometry

High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) has been applied for the development of a method for the determination of total As in fish oil samples using direct analysis. The method does not use any sample pretreatment, besides dilution with 1-propanole, in order to decrease the oil viscosity. The stability and sensitivity of As were evaluated using ruthenium and iridium as permanent chemical modifiers and palladium added in solution over the sample. The best results were obtained with ruthenium as the permanent modifier and palladium in solution added to samples and standard solutions. Under these conditions, aqueous standard solutions could be used for calibration for the fish oil samples diluted with 1-propanole. The pyrolysis and atomization temperatures were 1400°C and 2300°C, respectively, and the limit of detection and characteristic mass were 30pg and 43pg, respectively. Accuracy and precision of the method have been evaluated using microwave-assisted acid digestion of the samples with subsequent determination by HR-CS GF AAS and ICP-MS; the results were in agreement (95% confidence level) with those of the proposed method.

A simple sample preparation procedure for the fast screening of selenium species in soil samples using alkaline extraction and hydride-generation graphite furnace atomic absorption spectrometry

This work proposes a simple procedure for the determination of selenium species in soil samples using an ultrasound-assisted alkaline extraction and hydride generation atomic absorption spectrometry (HG AAS), which is known to be specific for the determination of Se(IV) only. The hydride was trapped and atomized in a graphite tube furnace (GF) coated with iridium as a permanent chemical modifier. The limits of detection and quantification for the developed method were 6μgL−1 and 20μgL−1 Se(IV), respectively, with a linear range between 20 and 100μgL−1, and a linear coefficient of R=0.999. The total Se content in the samples was determined in the alkaline extract using high-resolution continuum source GF AAS (HR-CS GF AAS), and the content of Se(VI) was determined by difference between the total Se and the content of Se(IV). The extraction efficiency was verified by comparing the results obtained by the alkaline extraction and by direct solid sample analysis using HR-CS GF AAS. The accuracy of the method for total Se determination was ascertained using microwave-assisted acid digestion as well as direct solid sample analysis by HR-CS GF AAS of the certified reference materials MURST-ISS-A1 (Antartic marine sediment) and BCR 142R (light sandy soil), and soil samples from different regions of Brazil.

Determination of chlorine in coal via the SrCl molecule using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis

In this study, the determination of chlorine in coal is described via molecular absorption of the strontium mono-chloride (SrCl) molecule at 635.862nm using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) and direct solid sample analysis. The pyrolysis and vaporization temperatures were optimized and the measurements are accomplished with a platform coated with zirconium as a permanent chemical modifier in order to increase the sensitivity of the gaseous SrCl molecule generated in the graphite furnace. The optimum pyrolysis and vaporization temperatures were 700°C and 2100°C, respectively. Under optimized conditions, the limit of detection and characteristic mass of the method were 0.85 and 0.24ng, respectively. The accuracy of the method has been verified using four certified reference materials and one not certified reference material of coal, and the results were in good agreement with the certified or reference values.

Dispersive liquid–liquid microextraction using ammonium O,O-diethyl dithiophosphate (DDTP) as chelating agent and graphite furnace atomic absorption spectrometry for the determination of silver in biological samples

A new method for the determination of silver in biological samples is presented in this work. The method involves application of dispersive liquid–liquid microextraction (DLLME) employing ammonium O,O-diethyl dithiophosphate (DDTP) as the chelating agent for extraction and preconcentration of silver prior to quantification using graphite furnace atomic absorption spectrometry (GFAAS). Chloroform and acetone were selected as the extracting and dispersing solvent, respectively, at optimized volumes of 80 μL and 500 μL, respectively. The concentration of DDTP and the extraction time were optimized as 0.01% (m/v) and 10 min, respectively. Pyrolysis (1100 °C) and atomization (1800 °C) temperatures were optimized using a L'vov platform treated with 400 μg of tungsten as a permanent chemical modifier. The method was proven virtually free from interference from major constituents of biological samples. A detection limit of 2 ng g−1 was obtained with relative standard deviations better than 13% and an enhancement factor of 70 was achieved. The determined concentrations for Ag in certified reference biological samples were in good agreement with the certified values at a 95% statistical confidence limit. The reported method using DLLME and GFAAS presented good analytical performance for Ag determination when compared to other methods available in the literature.

Evaluation of internal standardization for the determination of semivolatile analytes in difficult matrices by simultaneous multielement atomic absorption spectrometry

The aim of the present work is to investigate the use of the internal standardization technique combined with permanent chemical modification for the determination of two semivolatile analytes, such as As and Se, in difficult matrices by electrothermal atomic absorption spectrometry. Bismuth and tellurium have been evaluated as internal standards to minimize matrix effects on the direct determination of selenium and arsenic in sediments, by simultaneous electrothermal atomic absorption spectrometry using graphite tubes with integrated platform, pre-treated with different masses of Zr and Ir as permanent modifier. A Perkin-Elmer SIMAA 6000 simultaneous multielement spectrometer was used to study the correlation between two integrated absorbance signals. Matrix effects were evaluated by calculating the slope ratio between the analytical curve obtained from reference solutions prepared in 1.0% (v/v) HNO3 and analytical curve obtained from IS additions in matrix solutions. The results showed that Te was the optimal internal standard and 200μg Zr and 20μg Ir was the optimal permanent chemical modifier for both analytes. The instrumental limits of detection for As and Se were 1.48 and 1.96μgL−1 without the use of an internal standard and 0.59 and 0.35μgL−1 when Te was used as an internal standard, respectively. Relative standard deviations for a sample with matrix effect containing 100μgL−1 As and 200μgL−1 Se were 1.3% and 2.3% (n=20) using 100μgL−1 Te, respectively, and for a standard solution sample containing 100μgL−1 As and 200μgL−1 Se were 3.0% and 1.2% (n=20) using 100μgL−1 Te, respectively. The accuracy of the proposed method was evaluated by an addition-recovery experiment and by the analysis of different certified reference materials. The recovered values were in the 95–100% range for both analytes.

Evaluation of electrothermal vaporization as a sample introduction technique for the determination of trace elements in biological samples by inductively coupled plasma mass spectrometry, following dispersive liquid–liquid microextraction

This work describes the method development process involved in the determination of Ag, Cd, Cu and Pb in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS), following dispersive liquid–liquid microextraction (DLLME). The parameters associated with DLLME such as HNO3 and diethyldithiophosphate (DDTP) concentrations, as well as the volumes of disperser (ethanol) and extracting (chloroform) solvents, were evaluated. The ICP-MS operating parameters (carrier gas flow rate and RF power) were also optimized. Several distinct approaches involving investigation on chemical modifiers (W, Ru, Pd and combinations), aerosol carriers (Na2SO4, ascorbic acid and diethyldithiophosphate – DDTP) and the effect of insertion of a L'vov platform on the transport efficiency from the ETV to the ICP and overall analytical performance were evaluated. The results suggest that the use of a platform and chemical modifiers lead to increased thermal stability, although the sensitivity is generally reduced when compared to the absence of modifiers and wall vaporization. Several calibration approaches were evaluated, including the combination of chemical modifiers and the use or absence of a L'vov platform inside the graphite tube. Accurate results were achieved for all elements upon the use of palladium as the aerosol carrier in combination with W and Ru as permanent chemical modifiers, demonstrating that the effective transportation of the analytes and equalization of the transport efficiency between samples and calibration solutions are carrier-dependent. To verify the accuracy of the proposed methodology, four certified reference biological materials were analyzed, with good agreement between certified and determined values. ‘Real’ samples were also analyzed following the optimized procedure. The proposed method resulted in detection limits between 0.001 and 0.09 μg g−1 and enhancement factors between 35 and 59, with appreciable analytical sensitivity.

Determination of Trace Elements in B5-diesel Oil by HR-CS ET AAS Using a Simple Dilute-and-Shoot Approach

This work describes a simple, fast and sensitive procedure for the determination of Al, Cd, Cu, Fe, Pb and Mn in commercial B5-diesel oil samples using high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ET AAS). The procedure consists on simple dilution of the samples using n-propanol, with further acidification with HNO3. Calibration against aqueous standards could be employed for the determination of Cu, Fe, Pb and Mn, whereas calibration solutions prepared in n-propanol were required for the determination of Al and Cd. The pyrolysis and atomization curves were investigated for the analytes prepared in aqueous solutions and for the B5-diesel oil samples. A study involving the use of modifiers was carried out. 480 µg of Zr for Al, Mn and Pb determination and 500 µg of Ir for Cd determination were employed as permanent chemical modifiers. Pyrolysis temperatures of 700 °C for Cd, 800 °C for Pb and 1000 °C for the other elements were adopted. The atomization temperatures were optimized as 1500 °C for Cd, 1900 °C for Pb, 2300 °C for Cu, Fe and Mn and 2500 °C for Al. The limits of quantification were determined as 0.001 µg g-1 for Cd and Mn, 0.002 µg g-1 for Pb, 0.006 µg g-1 for Fe and 0.01 µg g-1 for Al and Cu. Recovery tests resulted in recovery values between 89 and 120% for diesel oil samples. The method has proved to be fast, precise and accurate.

Electrochemical hydride generation of tin(II) and its determination by electrothermal atomic absorption spectrometry with in situ trapping in the graphite tube atomizer

An electrolytic hydride generation system for the determination of tin(II) by means of batch electrochemical hydride generation-electrothermal atomic absorption spectrometry (EcHG-ETAAS) with in situ trapping in a graphite tube atomizer is described. The effects of four permanent chemical modifiers – palladium, tungsten, iridium, and platinum – for graphite tube treatment on analyte absorbance and the effects of four cathode materials, i.e., Pb, Sn, Pb–Sn alloy, and glassy carbon, are checked. Three electrolytes, i.e., nitric acid, sulfuric acid, and hydrochloric acid, are examined as catholyte solutions. The influence of several parameters on EcHG is investigated using multivariate and univariate methods. Interferences of some concomitant ions are evaluated. The calibration curve is linear from 1 to 200 µg L−1, with a detection limit of 0.8 µg L−1 and a relative standard deviation of 6.2% (n = 3) for 100 µg L−1 Sn(II). The proposed method was successfully applied in the analysis of real environmental water samples and reference materials, and good spiked recoveries over the range of 93.1–115% were obtained. The proposed technique provides a means for developing hydride generation of other elements.

Determination of antimony in sediments and soils by slurry sampling graphite furnace atomic absorption spectrometry using a permanent chemical modifier

For comparison of action of mixed permanent modifiers Ir/Nb and Ir/W, the influence of the amounts of modifier components was studied and the atomic absorption pyrolysis and atomization curves were determined with different modifiers. The optimum amounts of modifier components were 30 μg Ir and 40 μg of Nb that were deposited onto the L'vov platform in advance to analytical measurements. The long-term performance of the Ir and Nb permanent modifiers was derived from the investigations by scanning electron microscopy and energy dispersive X-ray spectrometry. The soil and sediment slurries were prepared in 4% hydrofluoric acid and 6% suspension of polytetrafluoroethylene in order to remove the high concentration of silica during the pyrolysis step of 900 °C. The calibration was made by using aqueous standards. The analysis of certified reference materials confirmed the accuracy and reliability of the proposed analytical approach. The precision of Sb determination was characterized with less than 6% RSD.

A fast and accurate method for the determination of total and soluble fluorine in toothpaste using high-resolution graphite furnace molecular absorption spectrometry and its comparison with established techniques

A fast and reliable method has been developed for the determination of total and soluble fluorine in toothpaste, important quality control parameters in dentifrices. The method is based on the molecular absorption of gallium mono-fluoride, GaF, using a commercially available high-resolution continuum source atomic absorption spectrometer. Transversely heated platform tubes with zirconium as permanent chemical modifier were used throughout. Before each sample injection, a palladium and zirconium modifier solution and a gallium reagent were deposited onto the graphite platform and thermally pretreated to transform them into their active forms. The samples were only diluted and introduced directly into the graphite tube together with additional gallium reagent. Under these conditions the fluoride was stable up to a pyrolysis temperature of 550 °C, and the optimum vaporization (molecule formation) temperature was 1550 °C. The GaF molecular absorption was measured at 211.248 nm, and the limits of detection and quantification were 5.2 pg and 17 pg, respectively, corresponding to a limit of quantification of about 30 μg g −1 (ppm) F in the original toothpaste. The proposed method was used for the determination of total and soluble fluorine content in toothpaste samples from different manufactures. The samples contained different ionic fluoride species and sodium monofluorophosphate (MFP) with covalently bonded fluorine. The results for total fluorine were compared with those obtained with a modified conventional headspace gas chromatographic procedure. Accuracy and precision of the two procedures were comparable, but the proposed procedure was much less labor-intensive, and about five times faster than the latter one.

Comparison of action of mixed permanent chemical modifiers for cadmium and lead determination in sediments and soils by slurry sampling graphite furnace atomic absorption spectrometry

Slurry sampling atomic absorption spectrometry with electrothermal atomization was used to the determination of cadmium (Cd) and lead (Pb) in soils and sediments using permanent modifiers. Comparison of action of mixed permanent modifiers niobium (Nb)/iridium (Ir) and tungsten (W)/iridium (Ir) were studied in detail. The effect of amount of Ir, W and Nb on analytical signals of Cd and Pb was examined. The optimal amounts of modifiers for Cd and Pb determination were stated. Niobium carbide formation on graphite surface was studied for different pyrolysis temperatures. Finally for Cd determination in sediments and soils 200 μg of Nb mixed with 5 μg of Ir was used as permanent modifiers and 15 μg of Nb mixed with 200 μg of Ir for Pb determination. Suspensions were prepared in 5% HNO 3. The analytical procedure was optimized carefully basing on data from pyrolysis and atomization curves studies. Ammonium dihydrogen phosphate was used additionally as matrix modifier during Cd determination in samples in order to prevent interferences coming from matrix components. The analysis of CRMs confirmed the reliability of the proposed approach. The precision and accuracy of Cd and Pb determination by the described method for soils and sediments were acceptable.

Microextraction based on solidification of a floating organic drop followed by electrothermal atomic absorption spectrometry for the determination of ultratraces of lead and cadmium in waters

A procedure for the determination of ultratraces of lead and cadmium by liquid-phase microextraction based on solidification of a floating organic droplet (LPME-SFO) separation and electrothermal atomic absorption spectrometry (ETAAS) has been developed. For this purpose, 50 μL of pre-heated (50 °C) undecanoic acid (UA) are added to 25 mL of aqueous sample solution at pH 5. The mixture, maintained at 50 °C, is stirred at 1000 rpm for 10 min and then the vial is immersed in an ice-bath, which results in the solidification of the UA drop that is easily separated. Injection into the atomizer is carried out after a gentle heating. By impregnating the atomizer with tungstate as a permanent chemical modifier, the detection limits were 10 and 0.5 ng L−1 with enrichment factors of 380 and 420, for lead and cadmium, respectively. The relative standard deviation was in the 2.8–3.2% range (n = 5, 25–400 ng L−1 Pb(II) and 1–15 ng L−1 Cd(II)). The proposed method has been applied to the determination of lead and cadmium in bottled, tap and sea water samples, the reliability of the results being verified by means of recovery tests and by using ICP-MS.

Solvent bar microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic arsenic in water samples

A new method of solvent bar microextraction (SBME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the speciation of As(III) and As(V) in water samples was developed. The method is based on the chelation of As(III) and ammonium pyrrolidine dithiocarbamate (APDC) under the selected conditions, and the As(III)-PDC complex could be extracted into the organic phase, while As(V) remained in aqueous solution. The post-extraction organic phase was directly injected into ETV-ICP-MS for determination of As(III) with the use of iridium as permanent chemical modifier. As(V) was reduced to As(III) by L-cysteine and was then subjected to SBME prior to total As determination. The assay of As(V) was based on subtracting As(III) from total As. The factors affecting on the SBME, such as organic solvent, sample pH, chelating reagent concentration, stirring rate and extraction time, and chemical modification of iridium in ETV-ICP-MS have been studied. Under the optimized conditions, the enrichment factor of 220-fold could be achieved in 15 min extraction, the limit of detection (LOD) for As(III) was 0.32 pg mL − 1 , and the relative standard deviation (RSD) was 8.8% (0.1 ng mL − 1 , n = 9). Compared with hollow fiber liquid phase microextraction (HF-LPME), SBME has a higher enrichment factor and faster extraction kinetics. In order to validate the accuracy of the method, a Certified Reference Material of GSBZ50004-88 (No. 200420) water sample was analyzed and the results obtained were in good agreement with the certified values. The developed method was also applied to the speciation of inorganic As in environmental waters with satisfactory results.

Determination of ultratrace cadmium in food and environmental samples by ETAAS after vapor generation and in situ preconcentration

A method is described for the determination of ultratrace cadmium by coupling a continuous flow vapor generation system with in situ preconcentration technique and electrothermal atomic absorption spectrometry (ETAAS). A graphite tube coated with Ir as permanent chemical modifier was used for trapping cadmium vapor species. The effects of the flow rates of carrier gas and sample injection in vapor generation systems on the trapping measurement for cadmium were respectively investigated. Graphite tubes with different characteristic surfaces were comparatively studied for trapping cadmium vapor. The experimental results showed that the permanent chemical modifier of Ir is an alternative to the thermolabile modifier of Pd for simplifying the trapping measurement. The trapping efficiency of cadmium on the graphite tube coated with Ir was estimated. The trapping temperature and time were also investigated. A detection limit (3σ) of 0.005 μg·L−1 was obtained for this proposed method. The relative standard deviation (RSD) was 1.4% for 0.5 μ·L−1 of Cd (n = 11). This method can be applied to the determination of ultratrace cadmium in food and environmental samples with good agreement between the certified and found values.

Inorganic arsenic speciation analysis of water samples by trapping arsine on tungsten coil for atomic fluorescence spectrometric determination

Arsine trapping on resistively heated tungsten coil was investigated and an analytical method for ultratrace arsenic determination in environmental samples was established. Several chemical modifiers, including Re, Pt, Mo, Ta and Rh, were explored as permanent chemical modifiers for tungsten coil on-line trapping and Rh gave the best performance. Arsine was on-line trapped on Rh-coated tungsten coil at 640 °C, then released at 1930 °C and subsequently delivered to an atomic fluorescence spectrometer (AFS) by a mixture of Ar and H 2 for measurement. In the medium of 2% (v/v) HCl and 3% (m/v) KBH 4, arsine can be selectively generated from As(III). Total inorganic arsenic was determined after pre-reduction of As(V) to As(III) in 0.5% (m/v) thiourea–0.5% (m/v) ascorbic acid solution. The concentration of As(V) was calculated by difference between the total inorganic arsenic and As(III), and inorganic arsenic speciation was thus achieved. With 8 min on-line trapping, the limit of detection was 10 ng L −1 for As(III) and 9 ng L −1 for total As; and the precision was found to be <5% R.S.D. ( n = 7) for 0.2 ng mL −1 As. The proposed method was successfully applied in total arsenic determination of several standard reference materials and inorganic arsenic speciation analysis of nature water samples.

Highly sensitive and interference-free determination of bismuth in environmental samples by electrothermal vaporization atomic fluorescence spectrometry after hydride trapping on iridium-coated tungsten coil

Bismuthine was on-line trapped on tungsten coil and subsequently electrothermally vaporized for the determination by atomic fluorescence spectrometry (AFS). Several noble metals, including Pd, Rh, Pt, and Ir, were explored as permanent chemical modifier for tungsten coil on-line trapping. Investigation showed that Ir gave the best performance, in which bismuthine was on-line trapped on Ir-coated tungsten coil at 560 °C, and then released at 1550 °C for subsequent transfer to AFS by a mixture of Ar and H 2. Under optimum instrumental conditions, the trapping efficiency was found to be 73 ± 3%. With 120 s (12 mL sample volume) trapping time, a limit of detection (LOD) of 4 ng L − 1 was obtained, compared to conventional hydride generation AFS (0.09 μg L − 1 ); the LOD can be lowered down to 1 ng L − 1 by increasing the trapping time to 480 s. The LOD was found to be better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental methods such as ICP-MS and GF-AAS. A comprehensive interference study involving conventional hydride-forming elements and some transition metals was carried out, and the result showed that the gas phase interference from other hydride-forming elements was largely reduced, thanks to the use of on-line tungsten coil trapping. Finally, the proposed method was applied to the determination of bismuth in several biological and environmental standard reference materials, and a t-test shows that the analytical results by the proposed method have no significant difference from the certified values at the confidence level of 95%.

Determination of Cr and Ni in Orujo spirit samples by ETAAS using different chemical modifiers

Several analytical methods are proposed for chromium and nickel determination in Orujo spirit samples using ETAAS. Permanent chemical modifiers such as W, Ir, Ru, W–Ir and W–Ru were comparatively studied in relation to the common chemical modifier employed, Pd(NO3)2–Mg(NO3)2. Taking into account the analytical performance, the method based on the use of Ru as a permanent modifier was selected for further direct Cr determinations in Orujo samples. In the case of Ni, after comparison among the different methods developed, a method with no modifier which allows the direct interpolation in calibration graphs was chosen. Detection limits of 0.13μgL−1 and 0.30μgL−1 were obtained for Cr and Ni, respectively. For all methods developed, recoveries (ranged 98.6–102%) and precision (RSD<10%) were acceptable. The selected methods were applied for the determination of the Cr and Ni contents in 80 representative Orujo Galician samples. The Cr concentrations ranged from <LOD and 14.61μgL−1 and Ni concentrations ranged <LOD and 34.17μgL−1.