Atomic Absorption Spectrometry Determination Research Articles

Preparation of Modified Magnetic Cobalt Nanoparticles as a New Magnetic Sorbent for the Preconcentration and Determination of Trace Amounts of Lead Ions in Environmental Water and Soil (Air-Dust) Samples

ABSTRACTIn this study, cobalt magnetic nanoparticles (MNPs) were synthesized and then modified by sodium dodecyl sulfate (SDS) and 2-(5-bromo-2-pyridylazo)-5-diethyl aminophenol ligand (5-Br-PADAP), through a chemical precipitation method. Characterization of the prepared MNP adsorbents was performed by Fourier transform infrared and transmission electron microscopy. Cobalt nanoparticles (NPs) surface modified with SDS and 5-Br-PADAP was evaluated as a nanoparticulate solid-phase extraction (SPE) absorbent for lead ions Pb(II) from water and standard samples, prior to its flame atomic absorption spectrometry determination. Effects of pH, amount of sorbent, desorption solvent, adsorption time, desorption time, and interfering ion concentration on extraction efficiency were investigated. Under optimal conditions, the calibration curve was linear in the range of 1.0–500 ng mL−1of Pb(II) with R2 = 0.998. Detection limit was 1.6 ng mL−1 in the original solution (3Sb/m), and the relative standard deviation for replicate determination of 0.5 μg mL−1 Pb(II) was ±2.7%.

Antimony speciation analysis by hydride trapping on hybrid nanoparticles packed in a needle trap device with electro-thermal atomic absorption spectrometry determination

Novel hybrid nanoparticles show faster antimony adsorption kinetics compared to single nanoparticles, becoming superior sorbents for analytical applications.

Selenium analysis by an integrated microwave digestion-needle trap device with hydride sorption on carbon nanotubes and electrothermal atomic absorption spectrometry determination

An integrated microwave assisted digestion (MW-AD) – needle trap device (NTD) for selenium determination in grape pomace samples is presented. The NTD was filled with oxidized multiwall carbon nanotubes (oxMWCNTS) where Se hydrides were preconcentrated. Determination was carried out by flow injection-electrothermal atomic absorption spectrometry (FI-ETAAS). The variables affecting the system were established by a multivariate design (Plackett Burman), indicating that the following variables significantly affect the system: sample amount, HNO3 digestion solution concentration, NaBH4 volume and elution volume. A Box-Behnken design was implemented to determine the optimized values of these variables. The system improved Se atomization in the graphite furnace, since only trapped hydrides reached the graphite furnace, and the pyrolysis stage was eliminated according to the aqueous matrix of the eluate. Under optimized conditions the system reached a limit of quantification of 0.11μgkg−1, a detection limit of 0.032μgkg−1, a relative standard deviation of 4% and a preconcentration factor (PF) of 100, reaching a throughput sample of 5samples per hour. Sample analysis show Se concentrations between 0.34±0.03μgkg−1 to 0.48±0.03μgkg−1 in grape pomace. This system provides minimal reagents and sample consumption, eliminates discontinuous stages between samples processing reaching a simpler and faster Se analysis.

Graphite Furnace Atomic Absorption Spectrometry After Dispersive Liquid–Liquid Microextraction for the Determination of Selenium in the Anodic Slime

ABSTRACTIn the present study, a method based on dispersive liquid–liquid microextraction (DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was proposed for the determination of selenium by using ammonium pyrrolidine dithiocarbamate (APDC) as the chelating reagent. The main factors influencing the DLLME were investigated systematically. Under the optimal conditions, the limit of detection for Se(IV) was 0.02 ng mL−1. The relative standard deviation was 4.1% (CSe(IV) = 0.2 ng mL−1, n = 8) with an enhancement factor of 135.8-fold from only 5 mL of the water sample. The proposed method was successfully applied to the determination of Se(IV) in anodic slime and electrolyte samples. In order to validate the proposed method, a Certified Reference Material (trace elements in water, 1643e, NIST) was analyzed, and the determined value obtained was in good agreement with the certified value.

In situ-produced CO2-assisted dispersive liquid–liquid microextraction for extraction and preconcentration of cobalt, nickel, and copper ions from aqueous samples followed by graphite furnace atomic absorption spectrometry determination

In the present work, a new microextraction technique, namely in situ-produced CO2-assisted dispersive liquid–liquid microextraction was introduced for the extraction and preconcentration of cobalt, nickel, and copper from aqueous samples followed by graphite furnace atomic absorption spectrometry detection. The proposed method relies on the CO2 gas produced due to a chemical reaction as the disperser agent instead of the disperser solvent used in the conventional dispersive liquid–liquid microextraction. Initially, a solid mixture of tartaric acid and sodium bicarbonate was placed in the bottom of a dry conical glass test tube. Then µL level of 1,1,2,2-tetrachloroethane as the extraction solvent was added into the tube. An aqueous solution of the analytes containing sodium diethyldithiocarbamate (as chelating agent) was transferred into the tube. The reaction between tartaric acid and sodium bicarbonate was immediately occurred, and the produced CO2 led to dispersion of the extraction solvent as tiny droplets into the sample which resulted in extraction of the analytes into the organic solvent. The cloudy solution was centrifuged, and the sedimented phase was analyzed by the instrumental analytical method. Under the optimum conditions, the calibration curves were linear in the ranges of 20–300, 20–200, and 15–250 ng L−1 for Co2+, Ni2+, and Cu2+, respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.3 to 4.6 and 4.5–5.6% for intra- and inter-day (n = 6, C = 50 ng L−1) precisions, respectively. Moreover, the detection limits and enrichment factors of the selected analytes were obtained in the ranges of 6.2–12 and 139–150 ng L−1, respectively. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method was successfully applied for the simultaneous analysis of the selected analytes in environmental water and fruit juice samples. The relative recoveries obtained for the analytes in the spiked samples were within in the range of 84–107%.

Separation, identification and quantification of carotenoids and chlorophylls in dietary supplements containing Chlorella vulgaris and Spirulina platensis using High Performance Thin Layer Chromatography

In this study, 14 commercial products (dietary supplements) containing alga Chlorella vulgaris and cyanobacteria Spirulina platensis, originated from China and Japan, were analysed. UV–vis spectrophotometric method was applied for rapid determination of chlorophylls, carotenoids and pheophytins; as degradation products of chlorophylls. High Performance Thin-Layer Chromatography (HPTLC) was used for effective separation of these compounds, and also Atomic Absorption Spectrometry for determination of heavy metals as indicator of environmental pollution. Based on the results obtained from UV–vis spectrophotometric determination of photosynthetic pigments (chlorophylls and carotenoids), it was confirmed that Chlorella vulgaris contains more of all these pigments compared to the cyanobacteria Spirulina platensis. The fastest mobility compound identified in Chlorella vulgaris and Spirulina platensis using HPTLC method was β-carotene. Spectral analysis and standard calibration curve method were used for identification and quantification of separated substances on Thin-Layer Chromatographic plate. Quantification of copper (Cu2+, at 324.7 nm) and zinc (Zn2+, at 213.9nm) was performed using Flame Atomic Absorption Spectrometry with air-acetylene flame atomization. Quantification of cadmium (Cd2+, at 228.8 nm), nickel (Ni2+, at 232.0nm) and lead (Pb2+, at 283.3nm) by Electrothermal Graphite Furnace Atomic Absorption Spectrometry; and quantification of mercury (Hg2+, at 254nm) by Cold Vapour Atomic Absorption Spectrometry.

Ultrasonic assisted switchable solvent based on liquid phase microextraction combined with micro sample injection flame atomic absorption spectrometry for determination of some heavy metals in water, urine and tea infusion samples

A green switchable solvent based on liquid phase microextraction (SS-LPME), has proposed to extract some heavy metal ions (Cd, Ni, Pb and Co) from various samples by micro sampling flame atomic absorption spectrometry (FAAS). Triethylamine (TEA) and protonated triethylamine carbonate (P-TEA-C) as green switchable solvents were used in two forms in the presence of CO2. Sodium hydroxide (NaOH) was performed to convert protonated triethylamine carbonate to triethylamine and as a result, the complexes of metal ions were extracted into TEA phase. Ultrasonic energy was introduced to accelerate formation of fine droplets of the extractant into the aqueous solution, and enlarge contact surface between both immiscible liquids. Several factors influencing the recovery and determination of analytes were studied. According to the results, the limits of detection were in the range of 0.24 and 0.76μgL−1 and the relative standard deviations (RSDs, n=10) in the range of 1.3 to 3.8% at 50μgL−1 for all analytes were found. Also, preconcentration factors (PFs) >100 were obtained for all analytes. The accuracy of the proposed method was verified using a certified reference material (CRM). Finally, the method was effectively utilized to the analysis of Cd, Ni, Pb and Co in water, urine and tea infusion samples.

Determination of Chromium (VI) in Airborne Particulate Matter by Electrothermal Atomic Absorption Spectrometry

ABSTRACTHexavalent chromium Cr(VI) is a well-established carcinogen associated with lung, nasal, and sinus cancer. Cr(VI) threshold limit values in workroom air have been recently lowered. Consequently, the currently available analytical methods are insufficiently sensitive or high cost. In this paper, a simple, cost-effective, sensitive, and reproducible method using solid-phase extraction with electrothermal atomic absorption spectrometry for determination of hexavalent chromium in airborne samples is reported. The method validation included selectivity, linearity, accuracy, and precision. Interferences from other ions likely to be present in airborne samples, including trivalent chromium, were tested and selectivity was demonstrated. The detection and quantification limits were, respectively, as low as 0.1 and 0.4 µg L−1. The linearity ranged from 0.5 to 50.0 µg L−1, with a regression coefficients exceeding 0.998. The extraction recovery exceeded 98%. The developed method was successfully compared with a reference spectrophotometric method. The performances achieved were similar to ion chromatography and high-performance liquid chromatography approaches. The novel method was tested on airborne samples collected from the workplace. The method’s performance suggests that it may be an alternative to high-cost techniques for monitoring occupational exposure to hexavalent chromium.

Supramolecular dispersive liquid–liquid microextraction-based solidification of floating organic drops combined with electrothermal atomic absorption spectrometry for determination of chromium species

ABSTRACTA simple, sensitive and reliable method has been developed for separation and preconcentration of chromium (VI) from aqueous samples before determination by electrothermal atomic absorption spectrometry. The method is based on the extraction of the hydrophobic complex of chromium (VI) with ammonium pyrrolidine dithiocarbamate in the coacervates made up of decanoic acid reverse micelles in the water–tetrahydrofuran mixture. Parameters affecting the extraction efficiency of the analyte were studied and optimised. Under the optimum conditions, the linear range, enhancement factor, the limit of detection and limit of quantification were found to be 0.008–0.4 µg L−1, 127, and 1.8 ng L−1 and 6.0 ng L−1, of Cr(VI), respectively. The relative standard deviation at the concentration level of 0.1 µg L−1 Cr(VI) (n = 6) was 4.2%. Total chromium was determined after the oxidation of Cr(III) to Cr(VI) with permanganate in acidic medium. The method was successfully applied to the determination of chromium species in water and human serum samples.

MICROWAVE-ASSISTED LIQUID PHASE MICROEXTRACTION FOLLOWED WITH FLAME ATOMIC ABSORPTION SPECTROMETRY FOR TRACE DETERMINATION OF ZINC IN FOOD SAMPLES

In this work, microwave-assisted liquid phase microextraction (MA-LPME) was followed by flame atomic absorption spectrometry for determination of zinc in food samples. Zinc was complexed with a chelating agent to form hydrophobic species.1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF6]) ionic liquid (IL) was used as environmentally-friendly extraction solvent. In order to disperse the extraction phase into the sample solution and improve the extraction efficiency, microwave irradiation was used as a disperser agent. The heating effect of microwave irradiation makes the ionic liquid dissolved and dispersed through the sample, which significantly improves the speed and efficiency of extraction. After extraction process, sample solution was centrifuged and the settled phase was diluted and introduced to flame atomic absorption spectrometry by conventional aspiration. Various parameters including amount of ionic liquid, microwave power, irradiation time, pH, amount of chelating agent and salt amount were studied and optimized. At optimized condition, a limit of detection (LOD) of 1.5 ng mL-1, a linear range of 5-32 ng mL-1 and a RSD of 4.3% were obtained. Finally, the developed protocol was utilized for determination of zinc in food samples.

Continuous sample drop flow-based microextraction combined with graphite furnace atomic absorption spectrometry for determination of cadmium

Continuous sample drop flow-based microextraction (CSDF-ME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this technique, a few μL of organic solvent is transferred to the bottom of a conical bottom small tube. Then a few mL of aqueous solution transforms in form fine droplets while passing through the organic solvent. At this stage, cadmium - ligand hydrophobic complex is extracted into the organic solvent. After extraction, the small conical bottom tube is transferred to the GF AAS and 15μL of extraction solvent was injected into the graphite tube by the aim of autosampler arm. Under optimum conditions, an enrichment factor of 123 was obtained for 5.0mL of water sample. The linear range and limit of detection for cadmium were 0.02–0.5 and 0.0075μgL−1, respectively. The relative standard deviation for 0.05μgL−1 of cadmium in water was 2.8 % (n=5). The relative recoveries of cadmium in tap water, mineral water and Standard Reference Material for leave apple (1515) are 94, 97 and 96%, respectively. The CSDF-ME combined with GF AAS is a very simple, rapid, and repeatable method which requires low volume of sample.

ZnO nanoparticles as an adsorbent in ultrasound-assisted dispersive micro solid-phase extraction combined with high-resolution continuum source electrothermal atomic absorption spectrometry for determination of trace germanium in food samples

An ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE) is presented for the separation and preconcentration of trace levels of germanium with the use of zinc oxide nanoparticles (nano-ZnO) as an adsorbent prior to high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ET AAS). The experimental parameters (amount of ZnO, pH of sample solution, ultrasonication and centrifugation time, ZnO slurry preparation) were studied. Effective preconcentration of trace germanium with 20mg of ZnO was achieved at pH9. After extraction, adsorbent with analyte was mixed with 200μL of H2O to prepare slurry. The concentration limit of detection was 0.003ng mL−1 for total Ge. The achieved preconcentration factor was 15. The relative standard deviations (RSDs, %) for determination of the analyte in real samples were 4–23%. The accuracy of this method was evaluated by the extraction and determination of total Ge after spiking of certified reference materials: INCT-TL-1 (Tea Leaves) and INCT-MPH-2 (Mixed Polish Herbs). The measured germanium contents were in satisfactory agreement with the added amounts (according to the t-test for a 95% confidence level). The presented method has been successfully applied for the determination of the analyte in real food samples (tea, goji berries, ginger products and aloe vera juice).

Microemulsion as Sample Preparation for Direct Flame Atomic Absorption Spectrometry (FAAS) Determination of Total Iron in Crude and Refined Vegetable Oils

This work proposed a novel, relatively low-cost and rapid analytical method using microemulsion as sample preparation to determine iron (Fe) in vegetable oils by flame atomic absorption spectrometry technique (FAAS). The vegetable oil microemulsions were obtained by mixing appropriate proportions of the crude and refined vegetable oil, Triton® X-100, 1-propanol and nitric acid 50% (v v-1). Moreover, an external calibration method was established using aqueous Fe standards instead of expensive and unstable organometallic standards. The limits of detection and quantification were 0.40 and 1.3 mg kg-1 of oil, respectively. The accuracy was checked by recovery studies (with recoveries ranging 84-105%) and by Fe determination in digested vegetable oil samples by inductively coupled plasma optical emission spectrometry (ICP OES) as comparative procedure. The proposed analytical method was efficient to determine Fe in crude and refined vegetable oils from various vegetable sources, besides being suitable for routine analyses due to its simplicity.

Nonanoic Acid-Coated Magnetite Nanoparticles for Separation and Preconcentration of Lead and Copper in Tobacco Samples prior to Flame Atomic Absorption Spectrometry Determination

A new method using nonanoic acid-coated magnetic Fe3O4 nanoparticles as adsorbent has been developed for the single-step extraction and preconcentration of lead and copper in tobacco samples. Transmission electron microscopy and X-ray diffraction spectrometry were used to characterize the adsorbent. The experimental parameters affecting extraction efficiency, including amount of nanoparticles, volume of chelating reagents, sample pH, ultrasonic time and desorption conditions were investigated. The analytes desorbed from nanoparticles were determined by flame atomic absorption spectrometry. Under the optimum conditions, good linearity was obtained in the range of 2-400 µg L-1 for copper and 5-800 µg L-1 for lead (r > 0.998, p < 0.05). The limits of detection for copper and lead were 0.2 and 0.5 µg L-1, with enrichment factors of 45 and 52, respectively. The method was successfully employed to tobacco sample analysis and got excellent recoveries between 89.2 and 100.7% with relative standard deviations (n = 6) of 4.5-5.9%.

Synthesis, characterization and theoretical investigation of magnetite nanoclay modified as a new nanocomposite for simultaneous preconcentration of lead and nickel prior to ETAAS determination

Magnetic natural montmorillonite clay nanoparticles modified by 3-[2-(2-aminoethylamino) ethylamino] propyl-trimethoxysilane (AAAPTS) were progress and used as a new adsorbent for contemporary extraction and precocentration of lead and nickel ions through magnetic solid-phase extraction (MSPE) process. Later adsorption, these ions were desorbed with nitric acid followed by electrothermal atomic absorption spectrometry determination. The processed Surface qualification of Co3O4@Clay with AAAPTS and the propagate nanoparticles were the study by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM) were used to describe the adsorbent. The MSPE requirement was optimized. The detection limits of 3.3 and 0.5ngL−1 were obtained for lead and nickel, respectively. The linear range was 0.010–0.403ngmL−1 for lead and 0.004–0.062ngmL−1 for nickel. The relative standard variation of the process for eight replicate determination of 0.10 and 0.01ngmL−1 of Pb (II) and Ni (II) were ±2.0% and ±3.3%, respectively. The method was applied for the determination of purpose ions in various samples with great recoveries. Interaction of nanoparticles of Co3O4 with clay surfaces was studied by density functional theory calculations. Nanoparticles of Co3O4 are adsorbed favorably at the Co atoms on the clay surface.

Automated Single-Phase Liquid-Liquid Extraction for Determination of Cr(VI) Using Graphite Furnace Atomic Absorption Spectrophotometry without Wet Digestion of Samples

This paper proposes a method to perform rapid and sensitive graphite furnace atomic absorption spectrometry (GFAAS) determination of Cr(VI) in vinegar samples without wet digestion. Taking into account low levels of Cr(VI) and the presence of several concomitants in the sample matrix, the proposed method uses single-phase liquid-liquid extraction (SPLLE). The method is automated, employing a flow-batch analyzer (FBA) which uses a mixing chamber designed to emulate a separation funnel promoting the formation/break of the single-phase solution, reaction and extraction. The Cr(VI) extraction procedure was performed by proportioned mixing of the vinegar sample (aqueous phase), amyl alcohol (organic phase), and ethanol (consolute) to form a single-phase solution. The chelating reagent sodium diethyldithiocarbamate (DDTC) dissolved in the consolute reacts rapidly with Cr(VI), in the single phase to produce a stable Cr-DDTC complex. The single-phase break step is performed by adding an excess of Britton-Robinson buffer, and then the organic phase enriched with Cr(VI) was analyzed by GFAAS. Factors such as extraction steps, single-phase composition, pH, chelating agent concentration, and flow-batch parameters were optimized. The FBA-SPLLE-GFAAS was evaluated in vinegar samples showing satisfactory analytical features in terms of limit of quantification (0.86 μg L −1 ), precision (RSD <12 %), characteristic mass (m0 = 0.32 pg), high sampling rate (26 h −1 ), and accuracy (recovery rate = 82–108 %). The proposed method requires one-step extraction and is eco-friendly since it consumes low amounts of non-toxic chemicals and generates little waste (about 700 μL per determination).

Chromium speciation using task specific ionic liquid/aqueous phase biphasic system combined with flame atomic absorption spectrometry

In this work, 1-alkyl-3-methylimidazolium based ionic liquids combined with salicylate or thiosalicylate anions as task specific ionic liquids were used to form a stable ionic liquids (IL)/aqueous biphasic systems for extraction of Cr(III) and Cr(VI) species prior to flame atomic absorption spectrometry (FAAS) determination. It was found that the 1-octyl-3-methylimidazolium salicylate was selective to extract Cr(III). The Cr(VI) content was calculated by subtracting Cr(III) from the total chromium with conversion of Cr(VI) to Cr(III) in the presence of ascorbic acid. Based on the preliminary experiments, the factors influencing phase behavior of the IL/aqueous biphasic system were investigated. The main factors affected the extraction of Cr(III) were modeled by using central composite design and optimized by using non-linear Nelder-Mead method. Under the defined optimum conditions, the calibration curves were linear over the concentration range of 40–470μgL−1 and 55–500μgL−1 for Cr(III) and total Cr, respectively. The limit of detection (3Sb/m) for Cr(III) was 7.7μgL−1. The relative standard deviations for six replicate determinations of 250μgL−1 of Cr(III) and total Cr were 5.5% and 7.6%, respectively. Finally, the proposed system has been successfully applied to the extraction and speciation of Cr in real water and urine samples.

Separation and preconcentration of platinum-group metals from spent autocatalysts solutions using a hetero-polymeric S, N-containing sorbent and determination by high-resolution continuum source graphite furnace atomic absorption spectrometry

This paper describes the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for determination of Pt, Pd and Rh after separation and concentration by original in-house developed heterochain polymer S, N-containing sorbent. The methods of sample preparation of spent ceramic-based autocatalysts were considered, two of which were used: autoclave decomposition in mixture of acids HCl:HNO3 (3:1) and high-temperature melting with K2S2O7. Both methods anyway limit the direct determination of analytes by HR CS GFAAS. Using the first method it is an incomplete digestion of spent autocatalysts samples, since the precipitate is Si, and the rhodium metal dissolves with difficulty and partially passes into solution. In contrast to the first method, the second method allow to completely transfer analytes into solution, however, the background signal produced by the chemical composition of the flux, overlaps the analytical zone.It was found, that Pt, Pd and Rh contained in the spent ceramic automotive catalysts could be effectively separated and concentrated by heterochain polymer S, N-containing sorbent, which has high sorption capacity, selectivity and resistant to dilute acids. The chosen HR CS GFAAS analysis conditions enable us to determine Pt, Pd and Rh with good metrological characteristics. The concentrations of Pt, Pd and Rh in two samples of automobile exhaust catalysts were found in range of 0.00015–0.00050; 0.170–0.189; 0.0180–0.0210wt%, respectively. The relative standard deviation obtained by HR CS GFAAS was not more than 5%. Limits of detection by HR CS GFAAS achieved were 6.2·10−6wt% for Pt, 1.8·10−6wt% for Pd, and 3.4·10−6wt% for Rh. Limits of determination achieved by HR CS GFAAS were 1.1·10−5wt% for Pt, 6.9·10−5wt% for Pd, and 8.3·10−5wt% for Rh.To control the accuracy of PGM in sorption concentrates by HR CS GFAAS method, it was appropriate to conduct an inter-method comparative experiment. The researches on the application of atomic-emission spectroscopy method with inductively coupled plasma as a comparative method were conducted. In addition, the trueness control of the obtained results is confirmed by added-found method.

Magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction of selenium for speciation in foods and beverages

ABSTRACTA novel, simple and rapid method based on magnetic effervescent tablet-assisted ionic liquid dispersive liquid–liquid microextraction (MEA-IL-DLLME) followed by graphite furnace atomic absorption spectrometry (GFAAS) determination was established for the speciation of selenium in various food and beverage samples. In the procedure, a special magnetic effervescent tablet containing CO2 sources (sodium carbonate and sodium dihydrogenphosphate), ionic liquids and Fe3O4 magnetic nanoparticles (MNPs) was used to combine extractant dispersion and magnetic recovery procedures into a single step. The parameters influencing the microextraction efficiency, such as pH of the sample solution, volume of ionic liquid, amount of MNPs, concentration of the chelating agent, salt effect and matrix effect were investigated and optimised. Under the optimised conditions, the limits of detection (LODs) for Se(IV) were 0.021 μg l–1 and the linear dynamic range was 0.05–5.0 μg l–1. The relative standard deviation for seven replicate measurements of 1.0 μg l–1 of Se(IV) was 2.9%. The accuracy of the developed method was evaluated by analysis of the standard reference materials (GBW10016 tea, GBW10017 milk powder, GBW10043 Liaoning rice, GBW10046 Henan wheat, GBW10048 celery). The proposed method was successfully applied to food and beverage samples including black tea, milk powder, mushroom, soybean, bamboo shoots, energy drink, bottled water, carbonated drink and mineral water for the speciation of Se(IV) and Se(VI) with satisfactory relative recoveries (92.0–108.1%).

Graphite furnace atomic absorption spectrometry for determination of thallium in blood

Colloidal palladium was used as chemical modifier in the determination of blood thallium by graphite furnace atomic absorption spectrometry. Blood samples were precipitated with 5% (V/V)nitric acid, and then determined by GFAAS with colloidal palladium used as a chemical modifier. 0.2% (W/V)sodium chloride was added in the standard series to improve the matrix matching between standard solution and sample. The detection limit was 0.2 μg/L. The correlation coefficient was 0.9991. The recoveries were between 93.9% to 101.5%.The relative standard deviations were between 1.8% to 2.7%.The certified reference material of whole blood thallium was determined and the result was within the reference range Conclusion: The method is accurate, simple and sensitive, and it can meet the needs of detection thallium in blood entirely.