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High-resolution graphite furnace molecular absorption spectrometry combined with samples prepared as suspensions were used for the quantification of Si in geological samples and in spent catalysts used for petrochemical processing. Measurements at the main Si resonance line at 251.6110 nm were proven unfeasible due to the formation of a quasi-continuous signal, which resulted in significant memory effect. An alternative was to monitor the fine rotational spectrum of SiO, which allowed memory effect-free measurements. A SiO rotational line centered at 231.9373 nm was selected to carry out quantitative analysis of Si at high percent concentrations in a variety of solid samples. Pyrolysis and vaporization temperatures were evaluated and optimized as 800 °C and 2400 °C, respectively, without the need to use a chemical modifier. Attempts to produce SiO molecules from acidified aqueous standards containing Si were unsuccessful, as the molecule could only be produced from solid samples, likely due to the formation mechanism that involves thermal decomposition of silicates. Hence, solid samples were prepared as suspensions in 0.14 mol L−1 HNO3. Calibration was performed using a series of suspensions prepared from a gabbro rock certified reference material (CRM), resulting in a limit of detection of 0.5% (m/m). The accuracy of the method was attested by the analysis of several CRM, including rocks, soils and sediments. Solid spent petrochemical catalyst samples were also analyzed and 97–114% recovery was obtained by spiking the catalyst suspensions with a CRM. The good accuracy demonstrated that the formation of SiO is free from matrix effects and highly efficient under the adopted conditions. Overall, the method was proven accurate and consists on a simple and fast alternative to determine Si in silicate-rich samples.

This paper describes an evaluation of current test methods for total sulfur determination in biodiesel, according to international specifications requirements, which was carried out using isotope dilution and inductively coupled plasma mass spectrometry (ID-ICP-MS) as a metrological tool. Closed vessel microwave-assisted digestion was employed using nitric acid and hydrogen peroxide as the decomposition medium, followed by isotope spike with 34 S dissolved in n-propanol. In order to overcome the spectral interference due to the presence of diatomic oxygen molecules in the ion beam, a reaction cell was used. Under optimized operating conditions, the determination of sulfur could be carried out at m / z +16, i.e., monitoring SO + signal for both sulfur isotopes. The ID-ICP-MS method was able to provide reference values for a series of commercial samples, which resulted in the evaluation of an extended concentration range. Sample sets including commercial biodiesel and inorganic sulfur-enriched biodiesel were employed as a means to evaluate the accuracy of routine methods for possible different sulfur species. No statistically significant difference was observed among the values measured with the proposed method and with the standard methods by UV fluorescence spectrometry and inductively coupled plasma optical emission spectrometry.

This work presents a direct and straightforward approach for the determination of trace elements in fish muscle, oyster, and bovine liver via direct solid sample analysis (SS) using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The preliminary studies revealed the presence of spectral interferences at the analytical line of Ni at 231.096 nm, which could be corrected subtracting the spectrum of SiO and PO from the sample spectra using least-squares background correction. Moreover, all meat samples were proven homogeneous according to the homogeneity factor (H e) (all values were

Chlorine isotope ratio measurement using multi-collector ICP-mass spectrometry (MC-ICP-MS) with sample introduction using traditional pneumatic nebulization suffers from spectral interference in addition to low sensitivity. Pronounced memory effects may jeopardize the accuracy of the results and/or the sample throughput. In this work, these limitations were overcome by using (i) high mass resolution (mass resolving power of about 10 000) to resolve spectral interference, (ii) 5 mmol L−1 NH4OH as wash solution to avoid memory effects and (iii) a Cl concentration of ≥70 mg L−1. The major cation load of seawater and chloride salts (NaCl, KCl) sample solutions was efficiently removed without affecting the original isotopic composition of Cl via cation exchange chromatography with Dowex® 50WX8 resin. The method developed was demonstrated to be accurate and precise, as attested by the measurement result for the 37Cl/35Cl isotope ratio in NIST SRM 975a (experimental value of 0.319765 ± 0.000022, compared to a reference value of 0.319768 ± 0.000187 and a precision of ∼0.007% RSD, n = 3), additionally, the δ37Cl value (vs. standard mean ocean chlorine, SMOC) was determined for five different standards; the values ranged from −0.54 to +0.89‰.

A simple and accurate methodology for Br isotope ratio measurements in seawater by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with pneumatic nebulization for sample introduction was developed. The Br+ signals could be measured interference-free at high mass resolution. Memory effects for Br were counteracted using 5 mmol L-1 of NH4OH in sample, standard, and wash solutions. The major cation load of seawater was removed via cation exchange chromatography using Dowex 50WX8 resin. Subsequent Br preconcentration was accomplished via evaporation of the sample solution at 90 A degrees C, which did not induce Br losses or isotope fractionation. Mass discrimination was corrected for by external correction using a Cl-matched standard measured in a sample-standard bracketing approach, although Sr, Ge, and Se were also tested as potential internal standards for internal correction for mass discrimination. The delta Br-81 (versus standard mean ocean bromide (SMOB)) values thus obtained for the NaBr isotopic reference material NIST SRM 977 and for IRMM BCR-403 seawater certified reference material are in agreement with literature values. For NIST SRM 977, the Br-81/Br-79 ratio (0.97291) was determined with a precision a parts per thousand currency sign0.08aEuro degrees relative standard deviation (RSD).

This work describes a methodology developed to carry out Cl determination in biological materials using electrothermal vaporization inductively coupled plasma mass spectrometry and direct solid sample analysis. The solid samples were directly weighed into graphite ‘cups’ and inserted into the graphite furnace. The RF power and the carrier gas flow rate were optimized at 1300 W and 0.7 L min− 1, respectively. Calibration could be carried out using aqueous standard solutions with pre-dried modifiers (Pd + Nd or Pd + Ca) or using solid certified reference materials with the same pre-dried modifiers or without the use of modifiers. The limit of quantification was determined as 5 μg g− 1 under optimized conditions and the Cl concentration was determined in five certified reference materials with certified concentrations for Cl, in addition to three certified reference materials, for which certified values for Cl were unavailable; in the latter case, the results were compared with those obtained using high-resolution continuum source molecular absorption spectrometry. Good agreement at a 95% statistical confidence level was achieved between determined and certified or reference values.

This study describes a new approach for direct solid sample analysis using thermoplastic starch (TPS) platforms for the determination of Mo and V by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The TPS platform was prepared from a mixture of commercial corn starch (28% amylase and 72% amylopectin), with sorbitol as the plasticizer in a 70/30 mass-based ratio. Different parameters affecting the film composition, such as the proportion and plasticizer type, were evaluated taking into account the behavior in the graphite tube when the TPS platform was subjected to the heating program. The new sample introduction approach has been shown to increase the lifetime of the graphite tube significantly due to a much less pronounced tailing of the absorbance signals of elements such as Mo or V, which makes it possible to reduce atomization and cleaning times, compared to the use of a conventional graphite platform. Memory effects were significantly reduced using the starch-based platform, resulting in improved precision. The detection limit and characteristic mass were determined to be 25 pg and 7 pg for Mo, and 130 pg and 18 pg for V, respectively. The accuracy was confirmed by the analysis of a series of certified reference materials, including bovine liver, beef liver, rice flour and urban dust for Mo, and coal, urban dust, lichen and particulate matter for V.

A method has been developed for the determination of Al in commercial moisturizing body lotions using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The most sensitive absorption line at 309.271 nm has been used for all determinations. The samples were prepared via a suspension with 0.3 mol L−1 nitric acid. Comparisons were made with pyrolysis and atomization curves without a modifier and using ruthenium and zirconium as permanent modifiers, to reduce the interaction of Al with the graphite surface and to improve the atomization efficiency of Al. 400 μg Zr was finally chosen as the best permanent modifier. The limits of detection and quantification were 30 ng g−1 and 95 ng g−1 Al, respectively. The proposed method was applied for 15 commercial moisturizing body lotions with results ranging between 0.17 ± 0.05 μg g−1 and 11.8 ± 0.43 μg g−1. Analyte addition tests have been used to evaluate the accuracy of the method and the recovery ranged between 103 and 110%, indicating that there was no serious matrix effect.

A new method for the direct analysis of coal using electrothermal vaporization inductively coupled plasma mass spectrometry and direct solid sample analysis was developed, aiming at the determination of Br and Cl. The procedure does not require any significant sample pretreatment and allows simultaneous determination of both elements to be carried out, requiring small mass aliquots of sample (about 0.5 mg). All operating parameters, including carrier gas flow-rate and RF power, were optimized for maximum sensitivity. The use of modifiers/aerosol carriers (Pd, Pd+Al and Pd+Ca) was evaluated, and the mixture of Pd and Ca was chosen, allowing pyrolysis and vaporization temperatures of 700°C and 1900°C, respectively. Chlorine was accurately determined using calibration against solid standards, whereas Br could also be determined using calibration against aqueous standard solutions. The limits of quantification were 0.03 μg g(-1) for Br and 7 μg g(-1) for Cl, and no spectral interferences were observed.

A new method has been developed for the determination of chlorine in biological reference materials using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) of the strontium mono-chloride (SrCl) molecule and direct solid sample analysis. The use of the SrCl molecule for high-temperature MAS was not described up to now in the literature. Preliminary time-dependent density functional theory calculations of the SrCl structure were carried out in order to obtain reasonable estimates of the absorption spectrum of the target molecule. The calculations, which were carried out at BHandHLyp/def2-QZVP level of theory, proved a very accurate and inexpensive way to get information about the spectrum of the SrCl molecule, which enabled us to perform the Cl determination with good sensitivity and specificity. The molecular absorption of the SrCl molecule has been measured using the wavelength at 635.862 nm, and zirconium and palladium have been evaluated as the chemical modifiers in order to increase the sensitivity of the gaseous SrCl molecule generated in the graphite furnace. The pyrolysis and vaporization temperatures were 600 °C and 2300 °C, respectively. Accuracy and precision of the method have been evaluated using biological certified reference materials of both animal and plant origins, showing good agreement with the informed and certified values. Limit of detection and characteristic mass were 1.0 and 2.2 ng, respectively. The results found using HR-CS GF MAS were in agreement (95% confidence level) compared to those obtained by electrothermal vaporization-inductively coupled plasma mass spectrometry.

This work reports a simple approach for Br determination in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry. The molecular absorbance of the calcium mono-bromide (CaBr) molecule has been measured using the rotational line at 625.315 nm. Different chemical modifiers (zirconium, ruthenium, palladium and a mixture of palladium and magnesium nitrates) have been evaluated in order to increase the sensitivity of the CaBr absorption, and Zr showed the best overall performance. The pyrolysis and vaporization temperatures were 800 °C and 2200 °C, respectively. Accuracy and precision of the method have been evaluated using certified coal reference materials (BCR 181, BCR 182, NIST 1630a, and NIST 1632b) with good agreement (between 98 and 103%) with the informed values for Br. The detection limit was around 4 ng Br, which corresponds to about 1.5 μg g − 1 Br in coal, based on a sample mass of 3 mg. In addition, the results were in agreement with those obtained using electrothermal vaporization inductively coupled plasma mass spectrometry, based on a Student t -test at a 95% confidence level. A mechanism for the formation of the CaBr molecule is proposed, which might be considered for other diatomic molecules as well.

A study has been undertaken to assess the capability of high-resolution continuum source graphite furnace atomic absorption spectrometry for the determination of mercury in airborne particulate matter (APM) collected on glass fiber filters using direct solid sampling. The main Hg absorption line at 253.652 nm was used for all determinations. The certified reference material NIST SRM 1648 (Urban Particulate Matter) was used to check the accuracy of the method, and good agreement was obtained between published and determined values. The characteristic mass was 22 pg Hg. The limit of detection (3σ), based on ten atomizations of an unexposed filter, was 40 ng g− 1, corresponding to 0.12 ng m− 3 in the air for a typical air volume of 1440 m3 collected within 24 h. The limit of quantification was 150 ng g−1, equivalent to 0.41 ng m−3 in the air. The repeatability of measurements was better than 17% RSD (n = 5). Mercury concentrations found in filter samples loaded with APM collected in Buenos Aires, Argentina, were between

The simultaneous determination of Ni and V as their total and non-volatile fractions in crude oil samples using high-resolution continuum source graphite furnace atomic absorption spectrometry is p...

Cloud point extraction (CPE) is proposed as a pre-concentration procedure for the determination of Pb and Cd in undigested urine by graphite furnace atomic absorption spectrometry (GF AAS). Aliquots of 0.5 mL urine were acidified with HCl and the chelating agent ammonium O , O -diethyl dithiophosphate (DDTP) was added along with the non-ionic surfactant Triton X-114 at the optimized concentrations. Phase separation was achieved by heating the mixture to 50 °C for 15 min. The surfactant-rich phase was analyzed by GF AAS, employing the optimized pyrolysis temperatures of 900 °C for Pb and 800 °C for Cd, using a graphite tube with a platform treated with 500 μg Ru as permanent modifier. The reagent concentrations for CPE (HCl, DDTP and Triton X-114) were optimized using a Box–Behnken design. The response surfaces and the optimum values were very similar for aqueous solutions and for the urine samples, demonstrating that aqueous standards submitted to CPE could be used for calibration. Detection limits of 40 and 2 ng L − 1 for Pb and Cd, respectively, were obtained along with an enhancement factor of 16 for both analytes. Three control urine samples were analyzed using this approach, and good agreement was obtained at a 95% statistical confidence level between the certified and determined values. Five real samples have also been analyzed before and after spiking with Pb and Cd, resulting in recoveries ranging from 97 to 118%.

A method was developed for the determination of As, Cd, Pb and Tl by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) with slurry sample introduction using certified reference coal samples. The 75As, 111Cd, 208Pb and 205Tl isotopes were monitored, considering the lower probabilities of these isotopes in suffering interferences. The carrier and modifier effect of Ru added in solution was evaluated, demonstrating that sensitivity for all elements is considerably improved by the addition of 15 µg of Ru to each individual measurement. This confirms its ability to act as a physical carrier particularly for the analytes in aqueous solution. Pyrolysis and vaporization temperatures of 500 and 2500 °C, respectively, were selected after optimization for aqueous solutions and for coal slurries. Similarly, the carrier gas flow rate was optimized as 1.1 L min−1. After optimization of the operational parameters, the determination of the four elements in six certified reference coal samples was carried out by external calibration against aqueous standards in 5% v/v HNO3, resulting in good agreement between the certified or given values and the determined ones. For Tl, due to the absence of certified values, a comparison was established considering previously published data using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry. Detection limits (µg g−1) of 0.1, 0.004, 0.045 and 0.001 were achieved for As, Cd, Pb and Tl, respectively, and the precision was typically better than 10%.

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 30 pg and 43 pg, 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.

Halogens in the atmosphere play an important role in climate change and also represent a potential health hazard. However, quantification of halogens is not a trivial task, and methods that require minimum sample preparation are interesting alternatives. Hence, the aim of this work was to evaluate the feasibility of direct solid sample analysis using high-resolution continuum source molecular absorption spectrometry (HR-CS MAS) for F determination and electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for simultaneous Cl, Br, and I determination in airborne inhalable particulate matter (PM10) collected in the metropolitan area of Aracaju, Sergipe, Brazil. Analysis using HR-CS MAS was accomplished by monitoring the CaF molecule, which was generated at high temperatures in the graphite furnace after the addition of Ca. Analysis using ETV-ICP-MS was carried out using Ca as chemical modifier/aerosol carrier in order to avoid losses of Cl, Br, and I during the pyrolysis step, with concomitant use of Pd as a permanent modifier. The direct analysis approach resulted in LODs that were proven adequate for halogen determination in PM10, using either standard addition calibration or calibration against a certified reference material. The method allowed the quantification of the halogens in 14 PM10 samples collected in a northeastern coastal city in Brazil. The results demonstrated variations of halogen content according to meteorological conditions, particularly related to rainfall, humidity, and sunlight irradiation.

A method has been developed for the determination of Pb in coal using direct solid sampling (SS) and high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The certified coal reference materials used in this study were ground in an agate mortar to particle size ≤50 µm. Mass aliquots between 0.1 and 1 mg were weighed onto pyrolytic graphite platforms, and inserted directly into the graphite tube. For pyrolysis temperatures lower than 600 °C, a continuous background due to radiation scattering at solid particles preceded the atomic signal, as the coal matrix could not be sufficiently eliminated under these conditions. An optimized pyrolysis temperature of 700 °C was adopted for Pb without the use of a modifier. The optimum atomization temperature was found to be 1700 °C. Under these conditions, interference-free determination could be performed with calibration against aqueous standards in 0.5% v/v HNO3. A total of six certified reference coal samples were analyzed, and the results obtained were all in good agreement with certified and informed values, respectively, according to a Student t-test at a 95% confidence level. A detection limit of 0.008 µg g−1 for Pb was obtained at the 217.000 nm resonance line, a value comparable to those obtained by other sensitive, but much more sophisticated techniques, showing that the absence of dilution in the SS-HR-CS GF AAS method allows at least equivalent detection performance.

A method is proposed that makes possible determining total and “thermally stable” vanadium in crude oil without prior separation, and to calculate “volatile” vanadium by difference. The volatile fraction is believed to be largely vanadyl porphyrine complexes. The method is based on the unsurpassed background correction capability of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS), which allows pyrolysis temperatures as low as 300 ◦ C to be used. The samples were prepared as oil-in-water emulsions, and aqueous standards emulsified in the same way were used for calibration. Total vanadium has been determined using a pyrolysis temperature of 400 ◦ C, and “thermally stable” vanadium using a pyrolysis temperature of 800 ◦ C. The content of total vanadium in 12 Brazilian crude oil samples was found to be between less than 0.04 and about 30 mg kg −1 . The volatile fraction was between 5 and 51% of the total content, and there was no correlation between the total and the volatile vanadium content. The limits of detection and quantification were 0.04 and 0.12 mg kg −1 of V in crude oil, respectively, based on a mass of 2 g of oil in 10 mL of emulsion. The precision was better than 4% at the 3 mg kg −1 level and better than 1.5% at the 30 mg kg −1 level of V in crude oil.

Two procedures for the determination of Co in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) were compared: solid sampling (SS) and alkaline treatment with tetramethylammonium hydroxide (TMAH) using two different instruments for the investigation: a conventional line-source (LS) atomic absorption spectrometer and a prototype high-resolution continuum source atomic absorption spectrometer. For the direct introduction of the solid samples, certified reference materials (CRM) were ground to a particle size ≤50 μm. Alkaline treatment was carried out by placing about 250 mg of the sample in polypropylene flasks, adding 2 mL of 25% m/v tetramethylammonium hydroxide and de-ionized water. Due to its unique capacity of providing a 3-D spectral plot, a high-resolution continuum source (HR-CS) graphite furnace atomic absorption spectrometry was used as a tool to evaluate potential spectral interferences, including background absorption for both sample introduction procedures, revealing that a continuous background preceded the atomic signal for pyrolysis temperatures lower than 700 °C. Molecular absorption bands with pronounced rotational fine structure appeared for atomization temperatures >1800 °C probably as a consequence of the formation of PO. After optimization had been carried out using high resolution continuum source atomic absorption spectrometry, the optimized conditions were adopted also for line-source atomic absorption spectrometry. Six biological certified reference materials were analyzed, with calibration against aqueous standards, resulting in agreement with the certified values (according to the t-test for a 95% confidence level) and in detection limits as low as 5 ng g−1.

The determination of thallium by graphite furnace atomic absorption spectrometry (GFAAS) is plagued by several difficult-to-control interferences. High-resolution continuum-source GFAAS, a technique not yet commercially available, was used to investigate and eliminate spectral interferences, and to develop a reliable method for the determination of thallium in coal using direct solid sampling. The resolution of 2.1 pm per pixel, and the display of the spectral environment ±0.2 nm on both sides of the analytical line were ideally suited for that purpose. The thallium signal was preceded by excessive non-specific absorption due to the coal matrix when pyrolysis temperatures ≤600 °C were used, and a characteristic molecular absorption with pronounced fine structure was following the atomic absorption. With a pyrolysis temperature of 700 °C the non-specific absorption at the beginning of the atomization stage could be eliminated, and using an atomization temperature of 1700 °C, and no modifier, the atomic absorption could be separated in wavelength and in time from the molecular structures, making possible an interference-free determination of thallium, using Pixel 260 at 276.8085 nm for background correction. The results obtained for 11 coal samples and one coal fly ash were in agreement at a 95% confidence level without a modifier, with palladium added in solution, and with ruthenium as permanent modifier, respectively, using aqueous standards for calibration. A characteristic mass of m 0 =12 pg and 5.5 pg was obtained with the center pixel only, and the center pixel ±1, respectively. The precision, expressed as relative standard deviation was typically better than 5%, and the limit of detection, based on three times the standard deviation of the coal with the lowest analyte content, was 0.01 μg g −1 .

The present work describes the mass spectrometric detection of organometallic compounds following their atmospheric pressure ionization using a commercial direct analysis in real time (DART) ion source. Several organometallic compounds of As, Fe, Hg, Pb, Se, and Sn were examined, and their corresponding mass spectra as well as induced fragmentation patterns were recorded. Gas phase sampling of the pure organometallic compounds or their solutions prepared in toluene generated temporally stable signals. For the majority of the compounds, the molecular ion or protonated molecule was detected; noticeable exceptions are the tetra-substituted compounds for which their less-substituted species dominated. The organometallic species were used as model compounds for a systematic investigation of the impact of operating parameters of the DART source, including gas temperature and electrode voltages. In general, results have shown that powering the electrodes designed to remove ions from the DART gas stream results in a reduction in signal intensity for most of the compounds investigated, suggesting that charged species from the plasma play an important role in the ionization process of the test analytes.

Submitted by Haia Cristina Rebouças de Almeida (haia.almeida@uniceub.br) on 2015-04-17T17:28:00Z No. of bitstreams: 1 DLLME_publicado_authorreprints.pdf: 256229 bytes, checksum: 49c94a049400b8329a424caeee66ca3a (MD5) Made available in DSpace on 2015-04-17T17:28:02Z (GMT). No. of bitstreams: 1 DLLME_publicado_authorreprints.pdf: 256229 bytes, checksum: 49c94a049400b8329a424caeee66ca3a (MD5) 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 mL and 500 mL, 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 mg 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.

A simple, fast and reliable method for the determination of inorganic and total mercury in biological samples directly from slurries prepared in water has been developed using cold vapor atomic absorption spectrometry. The method does not require any standing time or heating of the slurries. Samples are simply mixed with water and measurement can be carried out immediately. For inorganic mercury determination, no additional preparation is required. For total mercury determination the samples have to be oxidized previously with a 2% m/v KMnO4 solution for 2 minutes. After that, the measurement can be carried out similarly to that for inorganic mercury determination. The methylmercury concentration can be calculated as the difference between total and inorganic mercury. The greatest advantage of this method is that only a minimum of reagents and sample handling steps are required, which stands as a prerequisite for accurate results in routine analysis, particularly for the determination of mercury. The results were in good agreement with the 95% confidence level of the certified or close to the informed value for the reference materials investigated. The relative standard deviation was better than 7% for most of the samples. The limits of detection in the sample were determined as 0.020 and 0.016 µg g−1 for inorganic and total mercury, respectively.

Direct solid sampling is an attractive alternative for the determination of lead in biological samples, since it requires almost no sample preparation and provides higher sensitivity as no dilution is employed. In addition, the time required for the analysis and the risk of analyte loss or contamination during sample pre-treatment are reduced, the latter being the main problem associated with the usual digestion and dissolution procedures. In the present work, treating the determination of Pb in biological samples at 217.001 nm with solid sampling graphite furnace atomic absorption spectrometry (GF AAS), it will be shown that high-resolution continuum source AAS (HR-CS AAS) provides a variety of new possibilities for method development that have been unavailable previously. The use of ruthenium as a permanent modifier allowed a pyrolysis temperature of 900 °C to be applied, which was sufficient to eliminate the continuous background that preceded the analyte signal due to incomplete elimination of the matrix when lower pyrolysis temperatures were used. At atomization temperatures higher than 1500 °C, background absorption with pronounced fine structure followed the atomic signal. This was due to the electron excitation spectrum of PO, as was demonstrated by applying a least-squares background correction algorithm using the spectrum obtained by vaporization of (NH4)2HPO4 as a reference. Under optimum conditions, interference-free determination could be carried out by setting integration limits adjusted to integrate only the atomic signal; calibration against aqueous standards was performed and compared with calibration against a solid certified reference material (CRM). A total of seven biological CRM were analyzed (bovine muscle, pig kidney, lobster hepatopancreas, human hair, dogfish liver, oyster tissue and bovine blood), and the determined concentration of Pb was in agreement with the certified values using both calibration procedures, according to the t-test for a 95% confidence level. The detection limit (3s, n = 10) was 0.01 μg g−1, and the precision was typically better than 10%. The method is therefore adequate because of its simplicity, high sensitivity, good accuracy and wide applicability.