Performance of permanent iridium modifier in the presence of corrosive matrix in graphite furnace atomic absorption spectrometry

The influence of up to 16% HNO3, 28% HCl, and the mixture of both acids in aqua regia on the analytical performance of electrodeposited modifiers (Ir or Ir+Pd) was evaluated and discussed. Cadmium was used as an example of volatile elements often determined by graphite furnace atomic absorption spectrometry (GF AAS). In the presence of HCl, the maximum pyrolysis temperature that could be applied was found to be 600 degrees C. In the presence of HNO3 and aqua regia, both modifiers stabilized cadmium up to 800 degrees C. The long-term performance of electrodeposited Ir or Ir+Pd was not influenced by mineral acids; moreover the tube lifetime was significantly prolonged compared with a non-modified tube.     

Determination of palladium and platinum by electrothermal atomic absorption spectrometry after deposition on a graphite tube

The inner wall of a pyrolytically coated graphite tube served as the surface for adsorptive accumulation and/or for electrodeposition of palladium and platinum. A flow system for this preconcentration was constructed. For the electrodeposition a three-electrode arrangement was used. The flow rate for deposition, the medium and deposition potentials were optimized. After the deposition step, the graphite tube was placed into the graphite furnace and an atomization programme was applied. The procedure was applied for the determination of Pd and Pt in airborne particulates.     

Determination of noble metals in silicate rocks, ores and metallurgical samples by simultaneous multi-element graphite furnace atomic absorption spectrometry with Zeeman background correction

A new method has been developed for rapid determination of mug/g and ng/g amounts of noble metals in silicate rocks, ores and metallurgical samples by attacking with hydrofluoric acid and aqua regia, preconcentration by ion-exchange chromatography and measuring in a simultaneous multi-element graphite furnace atomic absorption spectrometer equipped with a polarized Zeeman background correction device which eliminated interferences from any incompletely separated common elements. The method was tested for Ru, Rh, Pt, Ir, Pd, Ag and Au with three Canadian certified reference materials, and then applied to the determination of ng/g amounts of these elements in four new Canadian candidate reference materials.     

Electrodeposition Sample Introduction for Ultra Trace Determinations of Platinum Group Elements (Pt,Pd, Rh,Ru) in Road Dust by Electrothermal Atomic Absorption Spectrometry

A novel method for the determination of the platinum group elements (PGEs: Pt, Pd, Rh, Ru) in environmental samples by electrothermal atomic absorption spectrometry (ET-AAS) was developed. Sample preparation involved complete microwave-assisted acid digestion of the matrix with HNO₃-HF-HClO₃/HClO₄mixtures in a high-pressure Teflon bomb. Traces of PGEs were deposited on the inner wall of a graphite tube in a flow-through cell of 1 ml volume. A flow system for this preconcentration was constructed. For the electrodeposition, a three-electrode arrangement was used. The geometry of the cell, flow rate during electrodeposition, deposition potential and electrolyte composition were optimized. After the deposition step, the graphite tube was placed into the graphite furnace and an atomization program applied. Detection limits (LOD, 3σ_{total procedure blank}, peak area) of 3.6, 0.5, 0.3 and 5.9 ng were obtained for Pt, Pd, Rh and Ru, respectively, reflecting preconcentration factors of 416, 503, 423 and 46, respectively. The detection limits were restricted by variations in the blank. Precision of replicate determination was typically 21% RSD at a concentration 25-fold above the LOD for a 100-mg sample mass. Reasonable agreement was found between results for CW7 road tunnel dust literature and for CRM NIES No. 8 Vehicle Exhaust Particulates. Calibration was achieved via the method of standard additions.     

Comparison of open digestion methods and selection of internal standards for the determination of Rh,Pd and Pt in plant samples by ICP-MS

An analytical procedure for the reliable determination of Pd, Pt and Rh in plant samples by inductively coupled plasma-mass spectrometry (ICP-MS) was developed. An ultrasonic nebulizer (USN) was used for sample introduction to improve sensitivity. Under various synthetic plant sample matrix compositions, it was established experimentally that moderate amounts (0.2–2%) of dissolved solids decreased the analyte signals significantly. Internal standardisation with In (for Pd and Rh) and Ir (for Pt) proved to be essential for obtaining correct results. Five open digestion approaches, used for converting solid plant samples to aqueous solution, were also tested for the purpose, namely dry-ashing, dry-ashing followed by HF attack, wet digestion with H₂O₂–HNO₃, wet digestion followed by HF attack and aqua regia digestion. Recovery tests in two spiked plant materials showed that only wet digestions must be used. With these ways, all PGEs could be reliably quantified by USN-ICP-MS without applying a separation or preconcentration step with a good precision (below 10% RSD). The aqua regia procedure was applied to the determination of PGEs in various plant matrices collected along a highway. Results showed that mosses were probably the best choice of samples to monitor the bioaccumulation of PGEs in time.     

Separation preconcentration method for platinum and rhodium from environmental samples using a chelating resin

A method of determining trace levels of platinum and rhodium in different samples was investigated. The method involves separation and preconcentration of the platinum and rhodium from the matrix by flow injection (FI) on-line coupled with electrothermal atomic absorption spectrometry (ETAAS) with Zeeman effect background correction. Platinum and rhodium were adsorbed on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The sorbed metals were directly eluted with nitric acid into the graphite furnace and determined by AAS.     

Determination of Ultratrace Amounts of Copper(Ⅱ) in Water Samples by Electrothermal Atomic Absorption Spectrometry After Cloud Point Extraction

A novel approach was developed for the determination of ultratrace amounts of copper in water samples by using electrothermal atomic absorption spectrometry (ETAAS) after cloud point extraction (CPE). 1-( 2-Pyridylazo)-2-naphthol was used as the chelating reagent and Triton X-114 as the micellar-forming surfactant. CPE was conducted in a pH 8.0 medium at 40 ℃ for 10 min. After the separation of the phases by centrifugation, the surfactant-rich phase was diluted with 1 mL of a methanol solution of 0. 1 mol/L HNO3. Then 20 μL of the diluted surfactant-rich phase was injected into the graphite furnace for atomization in the absence of any matrix modifier. Various experimental conditions that affect the extraction and atomization processes were optimized. A detection limit of 5 ng/L was obtained after preconcentration. The linear dynamic range of the copper mass concentration was found to be 0-2.0ng/mL, and the relative standard deviation was found to be less than 3.1% for a sample containing 1.0 ng/mL Cu(Ⅱ). This developed method was successfully applied to the determination of ultratrace amounts of Cu in drinking water, tap water, and seawater samples.     

Determination of platinum and palladium in environmental samples by graphite furnace atomic absorption spectrometry after separation on dithizone sorbent

A graphite furnace atomic absorption method of platinum and palladium determination after their separation from environmental samples has been presented. The samples were digested by aqua regia and the analyte elements were separated on the dithizone sorbent. The procedure of sorbent preparation was described and their properties were established. Two various procedures of elution by thiourea and concentrated nitric acid were described and discussed. The low limit of detection was established as 1 ng g⁻¹ for platinum and 0.2 ng g⁻¹ for palladium.There was also investigated the behaviour of platinum and palladium introduced into the soil in various chemical forms.     

Performance of electrodeposited noble metals as permanent modifiers for the determination of cadmium in the presence of mineral acids by electrothermal atomic absorption spectrometry

The analytical performance of electrodeposited noble metals (Pd, Rh or Pd+Rh) on the graphite surface for cadmium determination in the presence of inorganic acids was evaluated and discussed. The study was carried out for 16% HNO₃, 28% HCl and a mixture of both acids (aqua regia). It was demonstrated that all electrodeposited modifiers stabilized cadmium up to 800°C in the presence of HNO₃ and aqua regia. When only HCl was present in the solution the thermal stability of cadmium was less pronounced, the maximum pyrolysis temperature that could be applied was 500°C. The long-term study for Cd determination shows that permanent performance of electrodeposited modifiers is not influenced by mineral acids, moreover, the tube lifetime was doubled, compared with a non-modified tube, when Pd+Rh were electrodeposited onto the graphite surface.     

Evaluation of electrodeposited tungsten chemical modifier for direct determination of chromium in urine by ETAAS

The direct determination of chromium in urine by electrothermal atomic absorption spectrometry (ETAAS) using graphite tubes modified with tungsten is proposed. Modification of the graphite is made by tungsten electrodeposition over the whole surface atomizer followed by carbide formation by heating the tube inside its own furnace. For tungsten electrocoating, the graphite tube and a platinum electrode were connected to a power supply as cathode and anode, respectively, and immersed in a solution containing 2 mg of W in 0.1% v/v HNO₃. Then, 5 V was applied between the electrodes during 20 min for tungsten electrodeposition over the whole atomizer. A SpectrAA 220 Varian atomic absorption spectrometer equipped with a deuterium background corrector was used throughout. Undiluted urine (20 μl) was delivered over the tungsten-treated tube and the chromium-integrated absorbance was measured after applying a suitable heating program with maximum pyrolysis at 1300 °C and atomization at 2500 °C. With electrodeposited tungsten modifier, the tube lifetime increased up to four times when compared to previous published methods for Cr determination in urine by ETAAS, reaching 800 firings. Method detection limit (3 S.D.) was 0.10 μg l⁻¹, based on 10 integrated absorbance measurements of a urine sample with low Cr concentration. Two reference materials of urines (SRM 2670) from National Institute of Standards and Technology (NIST) were analyzed for method validation. For additional validation, results obtained from eight human urine samples were also analyzed in a spectrometer with Zeeman effect background correction.     

浊点萃取-热喷雾火焰炉原子吸收光谱法测定水中痕量锌(Ⅱ)

建立了以吡咯烷二硫代氨基甲酸铵(APDC)为络合剂、TritonX-100为表面活性剂的浊点萃取-热喷雾火焰原子吸收光谱法测定水样中痕量锌的方法.考查了APDC的浓度、溶液酸度、表面活性剂浓度、加热时间、水浴温度、干扰离子等实验条件对浊点萃取效率的影响.在最优化的实验条件下.方法的检出限为0.1 ng/mL,RsD为4...     

Determination of palladium in airborne particulate matter in a German city

The part of palladium in ambient urban air that is bound to particles and soluble in aqua regia was determined by means of sorbent extraction, coupled with graphite furnace atomic absorption spectrometry (GFAAS) and laser absorption fluorescence spectrometry (LAFS). Samples of about 200 m3 air were taken in a suburb of Berlin, Germany. The coupling of the selective and automated pre-concentration procedure for Pd as N,N-diethyl-N'-benzoylthiourea complex with the respective detection methods proved to be sufficiently sensitive. Severe interference with other matrix constituents, occurring mainly by direct LAFS detection, could be overcome and the detection limit was improved tremendously. The concentration of Pd in ambient air was determined to be in the range from 0.2 to 14.6 pg/m3.     

Preconcentration of gallium by coprecipitation with synthetic zeolites prior to determination by electrothermal atomic absorption spectrometry.

Synthetic zeolites were dissolved in nitric acid, and the resulting solution used as a coprecipitant for the preconcentration of trace amounts of gallium in water samples prior to determination by electrothermal atomic absorption spectrometry (ETAAS). The gallium preconcentration conditions and the ETAAS measurement conditions were optimized. Gallium was quantitatively concentrated with the zeolites coprecipitate from pH 6.0 to 8.0. The coprecipitate was easily dissolved in nitric acid, and an aliquot of the resulting solution was introduced directly into a tungsten metal furnace. The atomic absorbance of gallium in the resulting solution was measured by ETAAS. An ashing temperature of 400 degrees C and an atomizing temperature of 2600 degrees C were selected. The calibration curve was linear up to 3.0 microg of gallium and passed through the origin. The detection limit (S/N > or = 3) for gallium was 0.08 microg/100 cm3. The relative standard deviation at 1.0 microg/100 cm3 was 3.0% (n = 5). The proposed method has been successfully applied to trace gallium analysis in environmental water samples.     

Immersed single-drop microextraction interfaced with sequential injection analysis for determination of Cr(VI) in natural waters by electrothermal-atomic absorption spectrometry

Single-drop microextraction (SDME) and sequential injection analysis have been hyphenated for ultratrace metal determination by Electrothermal-Atomic Absorption Spectrometry (ETAAS). The novel method was targeted on extraction of the Cr(VI)-APDC chelate and encompasses the potential of SDME as a miniaturized and virtually solvent-free preconcentration technique, the ability of sequential injection analysis to handle samples and the versatility of furnace autosamplers for introducing microliter samples in ETAAS.     

Sequential Injection On-Line Sorption Preconcentration Using PEEK-Turnings Packed Micro-Column for Ultra-Trace Cobalt Determination by Electrothermal Atomic Absorption Spectrometry

A novel sequential injection on-line column preconcentration method for ultra-trace cobalt determination by electrothermal atomic absorption spectrometry (ETAAS) using poly(etheretherketone) (PEEK) turnings as sorbent material was developed. The method was based on the on-line chelate complex formation and retention of target analyte with ammonium pyrrolidine dithiocarbamate (APDC) on the surface of PEEK-turnings and elution with methyl isobutyl ketone (MIBK). A 40 µL fraction of MIBK containing the bulk of analyte complex introduced directly into the transversely heated graphite tube atomizer of ETAAS for quantification. Acidity of sample solution, chelating reagent concentration, and preconcentration time were investigated and optimized separately, while all other factors were optimized by full factorial design optimization methodology. The significance of the variables and their interactions was estimated by employing analysis of variance (ANOVA) and Pareto chart. Under the optimum conditions the enhancement factor for cobalt determination was 60. The detection limit was 6 ng L^?1 and the precision expressed as relative standard deviation (RSD) was 3.5% at 0.1 µg L^?1 Co(II) concentration level, respectively. The proposed method was evaluated by analyzing water certified reference materials and spiked environmental samples.     

Selective determination of ultra trace amounts of gold by graphite furnace atomic absorption spectrometry after dispersive liquid-liquid microextraction

A simple, rapid and sensitive method is proposed for selective determination of ultra trace amounts of gold from different samples. The method is based on highly efficient separation and pre-concentration of gold by dispersive liquid-liquid microextraction of gold followed by its determination with graphite furnace atomic absorption spectrometry. The pre-concentration procedure results in quantitative extraction of gold by victoria blue R from a 10-mL sample into fine droplets of chlorobenzene, with a sedimented volume of 25 microL. Then, 20 microL of 0.04% Pd(NO3)2, as chemical modifier, followed by 10 microL of the sedimented phase were consecutively pipetted into the same auto-sampler device and the content is injected into the graphite tube and the gold content is determined by graphite furnace atomic absorption spectrometry. After optimizing the extraction conditions and instrumental parameters, a pre-concentration factor of about 388 is obtained for the system. The analytical curve is linear in a concentration range of 0.03-0.5 ng mL(-1). The detection limit and relative standard deviation are 0.005 ng mL(-1) and 4.2%, respectively. The method was successfully applied to the extraction and determination of gold in tap water and silicate ore samples.     

Determination of platinum in biotic and environmental samples by graphite furnace atomic absorption spectrometry after its electrodeposition into a graphite tube packed with reticulated vitreous carbon

Summary Tobacco, beans, slag and dust samples were digested with nitric and hydrochloric acids in high-pressure PTFE bombs. Pt in the sample solutions was electrochemically deposited at –0.9 to –1.2 V in a flow system incorporating a 3-electrode flow-through cell with a graphite counter and Ag/AgCl reference electrodes. A pyrolytically coated graphite tube packed with reticulated vitreous carbon (RVC) served as the working electrode with the RVC filling axially bored to let the light beam pass through the tube during the AAS measurements. This opening was plugged with a glass rod during the preconcentration step. After the electrodeposition the tube was placed into the graphite furnace and an atomization temperature of 2700°C was applied. The geometry of the cell, flow rate for electrodeposition, deposition potential and electrolyte composition were optimized. The absolute detection limit was found to be about 0.3 ng Pt.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday On leave from: Department of Analytical Chemistry, Slovak Technical University, CS-812 37 Bratislava, Slovakia     

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

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

土壤中铅的分析方法比对

对不同的样品消解方法及电感耦合等离子体质谱、电感耦合等离子体原子发射光谱、石墨炉原子吸收光谱法测定土壤中铅的测定结果进行比对。采用电热板、微波及水浴3种加热方式,选择硝酸、氢氟酸、双氧水、王水、高氯酸、盐酸的不同组合进行土壤样品消解,通过分析测定值的精密度和准确度,考察消解体系对电感耦合等离子体质谱、电感耦合等离子体发射光谱、石墨炉原子吸收光谱法测定结果的影响。结果表明采用电感耦合等离子体质谱法测定土壤中的铅,最适宜的消解体系是硝酸-氢氟酸-高氯酸(微波加热),采用电感耦合等离子体原子发射光谱法测定最适宜的消解体系是硝酸(电热板加热),采用石墨炉原子吸收光谱法测定最适宜的消解体系是硝酸-盐酸-高氯酸(微波加热)。电感耦合等离子体质谱法的精密度和准确度优于另外两种方法。     

Preconcentration of Nickel and Cobalt Prior to Their Determination by Graphite Furnace Atomic Absorption Spectrometry Using the Water-Soluble Polymer Poly(Vinyl Pyrrolidinone)

The use of a water-soluble polymer, poly(vinyl pyrrolidinone) (PVP), for the preconcentration and separation of nickel and cobalt prior to their determination by graphite furnace atomic absorption spectrometry is described. For this purpose, the sample and the water-soluble polymer solutions were mixed, and the metal-bound polymer was precipitated by pouring the mixture into acetone. The precipitate was separated by decantation and dissolved with distilled-deionized water. The analyte elements were determined by graphite furnace atomic absorption spectrometry. The validity of the method was tested with spiked sea water and mineral water samples. The analytes added to the samples were quantitatively recovered within the range of 95% confidence limits. The proposed technique is fast, simple, precise and inexpensive. Its low blank values and high precision are other important advantages.