Comparison of different chemical modifiers for the direct determination of arsenic in sea water by electrothermal atomic absorption spectrometry

A comparative study of different chemical modifiers for the direct determination of arsenic in real and in synthetic sea water samples of high (72.8 per thousand ) and low (34.2 per thousand ) salinity was carried out. The use of lanthanum chloride and magnesium nitrate (LOD=3.0 microg l(-1)) offers good recoveries for low salinities, while for high salinities an enhancement higher than 200% was obtained, rendering this method unsuitable for sea water samples. The use of silver nitrate (LOD=2.0 microg l(-1)) produces unfavourable analytical recoveries, around 150 and 300% for synthetic sea water of low and high salinity. Zirconium oxychloride (LOD=1.8 microg l(-1)) and palladium nitrate alone or combined with magnesium nitrate and reducing agents (LOD=1.1-1.3 microg l(-1)) produce analytical recoveries close to 100% for all arsenic concentration tried over all salinities; thus, a single calibration curve using aqueous standard solutions may be applied to the analysis of sea water samples over all salinities. Finally, the addition of reducing agents and magnesium nitrate to palladium does not improve the sensitivity.     

Study of chemical modifiers for direct determination of silver in sea water by ETA-AAS with deuterium background correction

Methods for the direct determination of silver in sea water samples by ETA-AAS using different chemical modifiers were studied. The effect of salinity was studied using synthetic sea water of high (72.8 per thousand) and low (34.2 per thousand) salinity, and the results were compared with aqueous standard solutions. The charring temperatures achieved were 800 and 900 degrees C for magnesium nitrate and ammonium dihydrogen phosphate respectively, being 1100 degrees C for palladium nitrate and their mixtures. The best sensitivity obtained in the peak-height measurement mode was achieved by using reduced palladium (limit of detection (LOD) between 0.5 and 1.1 mug l(-1) for an injection volume of 20 mu1) with analytical recoveries close to 100% for synthetic and real sea water samples. The use of ammonium dihydrogen phosphate (LOD of 1.3 mug l(-1) for an injection volume of 20 mu1) produced good recoveries for low salinity; at high salinity an increase of around 25% was obtained, the method being unsuitable for sea water analysis. Finally, an interference study of the major components of sea water was carried out and applied to the analysis of surface sea water from the Galicia coast.     

Determination of traces of chromium in cocaine and heroin by flameless atomic absorption spectrometry

A method for the determination of total chromium in cocaine and heroin by flameless atomic absorption spectrometry is presented. Cocaine samples were dissolved in 2 ml of HNO(3) 35.0% (v/v) and diluted to 10 ml with ultrapure water; heroin samples were dissolved in ultrapure water, adding 0.4 ml of HNO(3) 35.0% (v/v) to dissolve inert species, and also diluted to 10 ml. Mg(NO(3))(2) and HNO(3), as chemical modifiers, were compared in terms of sensitivity, precision and accuracy, a lower detection limit being obtained for the use of Mg(NO(3))(2), 5.77 mug kg(-1) (7.23 mukg(-1) for HNO(3)). Within-batch precision was found to be 6.19% and 1.48% for drug solution spiked with 0 and 10 mug l(-1) of Cr(3+), respectively, when using Mg(NO(3))(2), and 7.45 and 1.19% for the same respective concentration levels when using HNO(3). Similar results on analytical recovery were obtained for both Mg(NO(3))(2) and HNO(3). Mg(NO(3))(2) was selected as the more adequate of the two chemical modifiers. A study of the introduction of a cooling-down step of 50 degrees C was carried out and compared in terms of sensitivity to the programme without a cooling-down step, but no advantage was observed. Studies on the variation in precision and analytical recovery with the amount of sample, and interferent effects of different species on chromium determination were developed. Finally, chromium concentrations obtained in cocaine samples varied between 0.02 and 0.14 mg kg(-1), the levels in the heroin samples being in the 0.05-0.59 mg kg(-1) range.     

电感耦合等离子体原子发射光谱(ICP-AES)法测定银钯合金中银和钯

建立健全测定银钯合金中银和钯含量的检测方法,对实现银钯合金中银和钯的高精度分析以及资源化利用有着重大意义。实验建立了电感耦合等离子发射光谱法(ICP-AES)同时测定银钯合金中银钯含量的分析方法。实验采用先加入10mL硝酸,再加入50mL过量盐酸混合,采用加热套混合消解银钯合金并混合定容在酸性浓度为18%HCl为介质中,然后通过控制不同的HCl浓度来测定银钯含量。实验结果表明：银的最佳检测酸性浓度为18%、钯的最佳酸性检测浓度为4%且该方法的加标回收率在97%-100%之间,相对标准偏差(RSD, n=10)小于2%。     

Comparative study of magnesium nitrate,palladium nitrate and reduced palladium for the direct determination of mercury in sea water by electrothermal atomization atomic absorption spectrometry

A comparative study of different chemical modifiers in graphite furnace atomic absorption spectrometry for the direct determination of mercury in sea water samples, in synthetic sea water sample of high (72.8%) and low 34.2%) salinity and in aqueous solutions, was carried out. The use of reduced palladium produces better results. The mixture of palladium nitrate and ascorbic acid, gives the best limit of detection (1.9 gl^–1). The use of reduced palladium and magnesium nitrate produced excellent recoveries (close to 100%) in the whole salinity range for all mercury concentration tested. The use of palladium nitrate alone or combined with magnesium nitrate gave good recoveries with respect to a real sea water sample for low salinities. The interference from the major components of sea water were completely removed by using reduced palladium and magnesium nitrate modifiers. Thus, a single calibration curve with synthetic sea water may be applied to the analysis of sea water samples of widely differing salinities.     

Determination of manganese in brain samples by slurry sampling graphite furnace atomic absorption spectrometry

A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO₃. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml⁻¹ for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications.     

Preconcentration of silver(I), gold(III) and palladium(II) in sea water with p-dimethylaminobenzylidenerhodanine supported on silica gel

A water-insoluble chelating material, p-dimethylaminobenzylidenerhodanine on silica gel (DMABR—SG) is described for preconcentration of trace amounts of silver(I), gold(III) and palladium(II) from water samples. Radioactive tracers (^110mAg and ¹⁹⁵Au) were used to study the behavior of silver and gold; palladium was monitored spectrophotometrically as its 1-(2-pyridylazo)naphthol complex in chloroform. In batch experiments, silver was quantitatively retained on the DMABR—SG at acidities ranging from 1.7 M to pH 5, and gold from 3 M to pH 5; equilibrium was achieved within 1 min for both elements. From sea water, silver ion was completely retained at pH 1.0–6.5 and gold ion at pH 1.0–3.5. In the case of palladium, shaking for about 20 min was required for quantitative retention at pH 1.0–5.0 for aqueous solution and at pH 1.0–7.0 for sea water. The chelating capacity of the DMABR—SG was 23 μmol Ag, 11 μmol Au and 11 μmol Pd per g. Quantitative recovery of silver and gold on DMABR—SG columns from sea water was achieved at higher flow rates (1–2 l h^-1 and 2–3 l h^-1, respectively) than with other chelating resins, e.g., Chelex 100, palladium required slower flow rate (150 ml h^-1). Silver retained on the DMABR—SG column was completely eluted with 20 ml of 2.5% sodium thiosulfate solution but palladium remained on the column. Silver, gold and palladium were quantitatively eluted with 20 ml of 0.1% thiourea in 0.1 M hydrochloric acid.     

Optimization of a chemical modifier in the determination of selenium by graphite furnace atomic absorption spectrometry and its application to wheat and wheat flour analysis.

A method for the determination of total selenium in wheat and wheat flour using graphite furnace atomic absorption spectrometry (GFAAS) with palladium/ascorbic acid as a chemical modifier was studied. The effects of nickel nitrate, palladium/ascorbic acid, and palladium/magnesium nitrate as chemical modifiers on the sensitivity in the determination of selenite, selenate and selenomethionine by GFAAS were compared. The palladium/ascorbic acid modifier was used for the determination of total selenium in wheat and wheat flour, because the oxidation states of the selenium ion are not important in the determination. The detection limit was estimated to be 1 microg L(-1) (calculated as 3sigma of the blank); the calibration curve was linear for the concentration range 5 - 50 microg L(-1) and the recovery range was 96.66 - 101.80%. The optimal ashing and atomizing temperatures were 1300 degrees C and 2250 degrees C, respectively. The proposed method was successfully applied to the determination of total selenium in wheat and wheat flour.     

Silver and lanthanum as effective modifiers in trace determination of cadmium in nickel-base alloys by electrothermal atomic absorption spectrometry

Trace cadmium in nickel-base superalloys was determined by a stabilized temperature platform furnace using atomic absorption spectrometry with a deuterium arc background correction system. The volatility of cadmium limits the pyrolysis temperature. This prevents the removal of the interfering alloy matrix at the thermal pretreatment step. Hence, an enormously high background signal has been observed. Chemical modifiers including ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2pyridylazo)resorcinol, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol, Triton-X 100, EDTA, potassium nitrate, palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, lanthanum oxide, lanthanum chloride and silver nitrate have been studied. Matrix interferences were effectively reduced by silver and lanthanum. The 100–300°C increase in the pyrolysis temperature effectively reduced the non-specific absorption from the alloy matrix. Interferences from foreign ions were also investigated. The merit of the proposed method was increased by the excellent agreement between the certified and the experimental values of Cd in the standard reference material, IN100, and the recovery obtained (100–104%). The precision of six successive replicate measurements was 4.9% with Ag modifier and 2.5% with La modifier, respectively. The results of analysing Tracealloy B were also satisfactory.     

Development of a new method for direct determination of selenium associated with atmospheric particulate matter using chemical modifiers and graphite probe furnace atomic absorption spectrometry

Direct determination of selenium on or in atmospheric particulate matter (APM) has been achieved using an integrated filtration and analysis system developed in our laboratories. The filtration (sampling) and analysis system consists of a porous electrographite plate which is used initially for the purpose of collecting APM and subsequently as a probe in graphite probe furnace atomic absorption spectrometry. Selenium produced a double peak when it was atomized from such an electrographite probe. Palladium nitrate+magnesium nitrate, as a mixed chemical modifier or ascorbic acid as a chemical modifier, eliminated the double peak. The addition of the chemical modifier(s) also removed the unpredictable changes in the peak-height and the peak-area absorbance which occurred from one atomization cycle to the next if the chemical modifier was not used. Precision of 5% RSD (peak-area absorbance) was obtained for an aqueous solution of selenium standard containing 1.25 ng of selenium with palladium nitrate+magnesium nitrate mixed chemical modifier, or ascorbic acid chemical modifer. The characteristic masses and the limits of detection for the aqueous solution of selenium standard with palladium nitrate+magnesium nitrate mixed chemical modifier are 27 and 41 pg (peak-area absorbance), respectively, and with ascorbic acid chemial modifier are 29 and 36 pg, respectively (peak-area absorbance). The results of analysis of the NIST (formerly National Bureau of Standards) Standard Reference Material No. 1648, Urban Particulate Matter, for selenium with palladium nitrate+magnesium nitrate mixed chemical modifier gave a recovery of 92%, and a precision of 10% RSD, and characteristic mass and the limit of detection of 20 and 37 pg, respectively.     

Selective separation of palladium from simulated intermediate radioactive waste nitrate by IRA-410 and IRA-900 anion exchangers

Selective efficient method have been for separation of palladium by strong basic anion exchangers IRA-410 and IRA-900 from intermediate radioactive nitrate medium. The different conditions for exchange behaviour of palladium from [ILLW] solutions containing numbre of elements were investigated by batch technique. Selective recovery of palladium from the [ILLW] solution was achieved using column technique. The elution of palladium was carried out via reduction with formic acid where the rate of the reduction process was increased by decreasing the formic acid concentration till 50% followed by dissolving the separated palladium by nitric acid.     

Simultaneous determination of manganese and selenium in serum by electrothermal atomic absorption spectrometry

A method for determination of manganese and selenium in serum by simultaneous atomic absorption spectrometry (SIMAAS) is proposed. The samples (30 mul) were diluted (1+3) to 1.0% v/v HNO(3)+0.10% w/v Triton X-100 directly in the autosampler cups. A total of 20 mug Pd+10 mug Mg(NO(3))(2) was used as chemical modifier. The pyrolysis and atomization temperatures for the simultaneous heating program were 1200 and 2300 degrees C, respectively. The addition of an oxidant mixture (15% w/w H(2)O(2)+1.0% v/v HNO(3)) and the inclusion of a low temperature pyrolysis step (400 degrees C) attenuated the build-up of carbonaceous residues onto the integrated platform. An aliquot of 15 mul of the reference or sample solution was introduced into the graphite tube and heated at 80 degrees C; subsequently, 10 mul of oxidant mixture+10 mul of chemical modifier was introduced over that aliquot and the remaining heating program steps were executed. This strategy allowed at least 250 heating cycles for each THGA tube without analytical signal deterioration. The characteristic masses for manganese (6 pg) and selenium (46 pg) were estimated from the analytical curves. The detection limits were 6.5 pg (n=20, 3delta) for manganese and 50 pg (n=20, 3delta) for selenium. The reliability of the entire procedure was checked with the analysis of serum from Seronormtrade mark Trace Elements in Serum (Sero AS) and by addition and recovery tests (97+/-9% for manganese and 96+/-7% for selenium) using five serum samples.     

Determination of traces of silver in human scalp hair slurries by electrothermal atomic absorption spectrometry

A simple and rapid method for the determination of traces of silver in human hair by slurry sampling and electrothermal atomic absorption spectrometry was optimized. Hair pulverization and the particle size reduction were achieved using a vibrational zirconia mill ball for 20 min. Palladium nitrate, magnesium nitrate and palladium-magnesium nitrate were investigated as chemical modifiers to thermally stabilize silver. Glycerol was used as wetting agent to stabilize the hair slurries. A limit of detection of 21.6 g kg^–1 was obtained for the use of palladium nitrate as best chemical modifier. The repeatibility of the overall procedure (slurry preparation and atomic absorption spectrometric determination) corresponding to eleven measurements was 14.3%. Matrix effect was significant and so, the standard addition method was used to determine silver in hair samples from healthy people. The levels found varied between 0.10 and 1.62 mg kg^–1.     

Separation of palladium from simulated intermediate radioactive waste/chloroacetic acid/nitrate medium by IRA-410 and IRA-900 anion exchangers

Separation of palladium by strongly basic anion exchangers IRA-110 and IRA-900 from intermediate radioactive liquid waste in chloroacetic acid/nitrate medium containing thirteen elements have been achieved. Different conditions have been studied, the effect of NaNO₃ as salt content, chloroacetic acid and hydrogen ion concentration have been investigated. Selective recovery of palladium from the [ILLW] solution was achieved using the column technique. The selectivity increased by using chloroacetic acid/nitrate than in nitrate medium. The elution of palladium was carried out via reduction with formic acid where the rate of the reduction process was increased by decreasing the formic acid concentration till 50% followed by dissolving the separated palladium by nitric acid.     

氯化银比浊法测定镍钴锰三元素氢氧化物中氯离子

建立了氯化银比浊法测定镍钴锰三元素氢氧化物中氯离子含量的测定方法。选择了合适的测定波长,并对硝酸用量、沉淀剂用量、稳定时间对测定结果的影响进行了试验,确定了较优的分析条件。样品加标回收率在95%~103.3%,氯离子浓度在0~4μg/mL与浊度值有良好线性关系。方法为控制镍钴锰三元素氢氧化物中氯离子提供了检测依据。     

Application of silver/sulfide ion-selective electrode for the determination of aliphatic primary and secondary amines

Aliphatic primary and secondary amines were determined utilizing their reaction with carbon disulfide. A potentiometric titration of the formed dithiocarbamates (I) with silver nitrate using a silver/sulfide ion-selective electrode was carried out. The effects of solvent, base, temperature and reaction time were investigated. The optimum conditions for a quantitative formation of (I) requires a minimal amount of 1,4-dioxane, 2 drops of 0.2% sodium hydroxide solution, excess carbon disulfide to stand at room temperature for 15 min. The titration requires prior evaporation of the unreacted carbon disulfide at 46 ° C. An average recovery of 98.5% with a standard deviation of 0.69 was obtained for the analyzed amines.     

Determination of the plant growth regulator beta-naphthoxyacetic acid by micellar-stabilized room temperature phosphorescence

This paper presents a method for the determination of the plant growth regulator beta-naphthoxyacetic acid (NOA) by micellar-stabilized room temperature phosphorescence with the surfactant Triton X-100 (TX-100) as the micellar medium, thallium nitrate as the heavy atom and sodium sulphite as the oxygen scavenger. A multivariate optimization approach using the blocked cube star design of central composite was carried out. The analytical curve of NOA gives a linear dynamic range of 0.4-3.0 mug ml(-1) and a detection limit of 0.13 mug ml(-1). A recovery of 93.6% was obtained for 1 mug ml(-1) NOA in spiked apple samples.     

Determination of trace amounts of gold and silver in high-purity iron and steel by electrothermal atomic absorption spectrometry after reductive coprecipitation

Trace amounts of gold and silver in high-purity iron or steel were preconcentrated by reductive coprecipitation with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry (ET-AAS). Both gold and silver could be simultaneously separated and sensitively determined in 10 metals (aluminum, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, vanadium and zinc). Comparable values were obtained for gold and silver in reference materials (low alloy steel) by the proposed method and a non-separation method; good agreement was found between the analytical values by both methods and the certified values. The proposed method is easy, simple and not dependent on sample composition and content. Moreover, gold and silver in metal samples could be simultaneously separated together with selenium and tellurium. The detection limits for gold and silver (3 σ) are 0.003 μg g^–1 and 0.002 μg g^–1, respectively. Received: 3 February 2000 / Revised: 11 April 2000 / Accepted: 16 April 2000     

Recovery of americium from analytical solid waste containing large amounts of uranium,plutonium and silver

Trace metallic impurity analysis by spectroscopic techniques is one of the important steps of chemical quality control of nuclear fuel materials. Depending on the burn-up and the storage time of the fuel, there is an accumulation of ²⁴¹Am in plutonium based fuel materials due to β decay of ²⁴¹Pu. In this paper, attempts were made to develop a method for separation of ²⁴¹Am from 1.2 kg of analytical solid waste containing 70% U, 23% Pu, 5% Ag and 1–2% C as major constituents along with other minor constituents generated during trace metal assay of plutonium based fuel samples by d. c. arc carrier distillation atomic emission spectrometry. A combination of ion exchange, solvent extraction and precipitation methods were carried out to separate ~45 mg of ²⁴¹Am as Am(NO₃)₃ from 15 L of the analytical waste solution. Dowex 1×4 ion exchange chromatographic method was used for separation of Pu whereas 30% TBP–kerosene was utilized for separation of U. Am was separated from other impurities by fluoride precipitation followed by conversion to nitrate. The recovery of Pu from ion exchange chromatographic separation step was ~93% while the cumulative recovery of Am after separation process was found to be ~90%.     

Comparison of palladium-magnesium nitrate and ammonium dihydrogenphosphate modifiers for cadmium determination in honey samples by electrothermal atomic absorption spectrometry

The occurrence of certain trace elements, such as cadmium, in honey bee can be considered as an indication of environmental pollution. In the present work, two methods for Cd determination in honey by electrothermal atomic absorption spectrometry, using palladium-magnesium nitrate and ammonium dihydrogenphosphate as chemical modifiers, have been developed. In none of these cases honey samples required pretreatment. Honey was diluted in water (20% w/v), and hydrogen peroxide, nitric acid, and Triton X-100 were added to minimize the matrix effect. For the first method, 21.6 μg of palladium and 4.5 μg of magnesium were added as chemical modifier; for the second method, 60 μg of ammonium dihydrogenphosphate were employed. The limits of detection obtained were 0.32 ng g⁻¹ for ammonium dihydrogenphosphate method and 0.54 ng g⁻¹ for palladium-magnesium nitrate method. The characteristic mass was 0.7 and 1.0 pg for ammonium dihydrogenphosphate and palladium-magnesium nitrate methods, respectively. The relative standard deviation (<10%) and the analytical recovery (98-105%) were comparable in both methods. The optimised methods were applied to the determination of the cadmium content in unpolluted Galician honey samples. Cd has been detected the analysed samples in the range (n.d.—4.3 ng g⁻¹).