Effect of anions on atomization temperatures in furnace atomic-absorption

Atomization temperatures have been measured for silver, cadmium, chromium, copper, nickel, lead, tin and zinc. The effect of various anions on the atomization temperatures of these metals has been examined. Of the anions investigated which were added as acids, only phosphate affected the atomization temperatures. For elements which atomized at a lower temperature than tin, phosphate addition resulted in an increased atomization temperature but those which atomized at a higher temperature than tin were not affected. These observations suggested that there are two mechanisms of atom formation in the graphite furnace. The first involves reduction of the metal oxide by carbon and is applicable only to compounds which can form oxides at temperatures lower than those required for the reduction process to occur. The second mechanism is direct decomposition of the metal compound to give metal atoms and is applicable to compounds of higher thermal stability which decompose at temperatures higher than those required for the reduction process.     

镧涂层表面效应初探

本实验通过对涂镧石墨管和非涂镧石墨管的电子显微分析，证实了镧涂层并未能对石墨管壁的孔洞起到有效的填充作用，这与测定金时吸收信号未明显变化的实验现象相吻合。通过对锡原子化前后石墨表面的Ｘ光电子谱分析，尝试提出了镧在管中的催化作用及影响某些元素原子化机理、从而改变其灵敏度的观点。     

Use of Metal Carbide Coated Graphite Cuvettes Eor the Atomic Absorption Analysis of Organotins

Abstract

Organotin compounds are analyzed by graphite furnace atomic absorption (GFAA) spectrometry. The graphite cuvette furnaces which were used were treated chemically with solutions containing V, Mo, Cr, and Zr. The zirconium treatment shows the greatest reduction in atomization interferences for the analysis of tin. The tin atomic absorption signals observed for the organotin compounds can be directly compared t o the aqueous tin standard, in terms of sensitivity.     

Determination of lead and cadmium in urine by electrothermal atomization atomic absorption spectrometry

The applicability of a DETATA sorbent to the preconcentration of lead and cadmium followed by the determination of these elements in urine using atomic absorption spectrometry with electrothermal atomization was demonstrated. After preconcentration by a factor of 10, the limits of detection were 0.01 and 0.2 μg/L for cadmium and lead, respectively. The accuracy of the results was supported by the analysis of Seronorm Trace Elements Urine (Batch no. 101021).     

The determination of traces of antimony,tin and arsenic in cadmium by pulse polarography

Traces of antimony, tin and arsenic in cadmium products were determined by pulse polarography. Arsenic was distilled, while antimony and tin were precipitated as hydroxides with manganese dioxide as carrier; some lead was coprecipitated with tin, hence these elements were further separated by distillation. In all cases quantitative recoveries were obtained. Antimony(III) was determined in a hydrochloric acid-sodium hypophosphite mixture, tin(IV) in a hydrochloric-hydrobromic acid mixture and arsenic(III) in sulphuric acid as supporting electrolytes; for arsenic(III), methylene blue had to be added. A sample weight of 10 g and an end volume of 10 ml allowed the determination down to about 0.004 p.p.m. antimony, 0.006 p.p.m. tin and 0.003 p.p.m. arsenic in cadmium. Several synthetic samples and commercially available cadmium products were analysed.     

Cyclic and stripping voltammetry of tin at mercury hanging drop and film electrodes in acidic o-diphenol media in the presence of lead and cadmium

The influence of catechol, gallic acid and tiron on the voltammetric behaviour of tin(IV) in the presence of lead(II) and cadmium(II) was investigated at hanging drop and mercury film electrodes in perchloric acid, oxalic acid and formate supporting electrolytes. Under cyclic conditions, well separated peaks of tin, lead and cadmium are obtained in oxalic acid and formate solutions containing gallic acid or catechol; tiron suppresses the tin peaks significantly. The efficiency of the deposition of tin in the presence of catechol or gallic acid is less than that of lead, particularly at long deposition time. The best separation of the stripping peaks of tin, lead and cadmium is obtained in oxalic acid solution containing gallic acid or catechol. In perchloric acid solution containing gallic acid or catechol the second peak corresponding to tin oxidation is useful for determinations of tin in the presence of lead. Tin(IV) at the 10^-8 mol l^-1 level can be detemined in various salt solutions and in water samples in the presence of five-fold amounts of lead and cadmium.     

Speciation analysis of triethyl-lead and tributyl-tin compounds in human urine by liquid-liquid extraction and gas chromatography microwave-induced plasma atomic emission detection

This work describes the development of a fast method for speciation analysis of triethyl-lead and tributyl-tin species in urine samples after in situ derivatization by tetraethyl- or tetrapropyl-borate reagents. The alkylation reaction is done in the aqueous and urine medium and the less-polar derivatives are extracted in hexane by liquid-liquid extraction. The species were extracted and the extract was efficiently collected from the aqueous phase after centrifugation. Finally, the organometallic species are separated by gas chromatography and determined from the emission signals of elemental lead and tin. Atomic lead and tin are formed from the organolead and organotin compounds during atomization of the column eluate in a microwave-induced helium plasma source. The simultaneous measurement of lead (Pb) at 405.780 nm and tin (Sn) at 303.419 nm was achieved by an atomic emission detector. Finally, the analytes were determined with satisfactory precision (<5%) and detection limits of 0.05 μg Pb/L and 0.48 μg Sn/L, respectively, when 10 mL of urine is extracted with 1 mL of hexane and 1 μL of extract is injected.     

Slurry procedures for the determination of cadmium and lead in cereal-based products using electrothermal atomic absorption spectrometry

Simple and rapid methods for the determination of cadmium and lead in biscuits, bread and cereal-based products using the slurry-ETAAS approach are discussed. Suspensions were prepared in a 20% v/v ethanol medium. Phosphate was used as a chemical modifier for lead determination. For cadmium determination both palladium and a copper plus ammonia mixture were used. In both cases platform atomization was used and calibration was performed using aqueous standards. Results for two reference materials confirmed the reliability of the procedures. Relative standard deviations were in the range of 2.5–6.5% for cadmium and 4.5–14% for lead. Detection limits were, respectively, 0.5 and 8 ng/g.     

Development of a slurry atomization method for the determination of cadmium in food samples by electrothermal atomization atomic-absorption spectrometry

Matrix modifiers have been compared for the determination of cadmium in foodstuffs by ETA-AAS with the sample injected in the form of a slurry. Addition of 800 mug/ml Pd stabilized cadmium to a similar extent as did ammonium dihydrogen phosphate, but avoided the increase in background signal associated with the latter. An analytical procedure was developed, based on palladium matrix modification, platform atomization with a pre-atomization cooling step and integrated absorbance measurements. The method allowed the analysis of milk, liver and olive leaf slurries at concentrations up to at least 50 mg/ml by direct calibration with aqueous standards. The accuracy of the analytical results was within 15% and the detection limit for cadmium in analysis of a 50 mg/ml slurry was 10 ng/g.     

Determination of cadmium in indium phosphide by electrothermal atomic absorption spectrometry and ion-selective electrode potentiometry

 Two independent methods for the determination of cadmium in cadmium-doped indium phosphide have been developed. Electrothermal atomic absorption spectrometry (ETAAS) utilized both platform atomization and a chemical modifier composed of magnesium nitrate and orthophosphoric acid. As the matrix mass was found to influence the cadmium sensitivity, matrix matched calibration standards were necessary. The detection limit (3s_B) is 0.20 μg/g for a 100 mg sample. The electrochemical method employed a solid-state cadmium sulfide-silver sulfide electrode as potentiometric sensor. An excess of indium (III) influenced the electrode response. A preliminary chelation-extraction of indium with acetylacetone at pH 5.0 in acetate buffer overcame the interference. The detection limit of the ISE-potentiometric method is 10 μg/g for a 200 mg sample. Two indium phosphide single crystals grown from melts doped with cadmium sulfide or cadmium telluride were analyzed for their cadmium content. Received: 27 August 1996/Revised: 27 January 1997/Accepted: 30 January 1997     

Application of edta to direct graphite-furnace atomic absorption analysis for cadmium in sea water

A method is described for the direct determination of cadmium in undiluted sea water by graphite-furnace atomic absorption spectrometry. The addition of EDTA ( 1 mg ml^-1) reduces the temperature of atomization of cadmium to far below that of volatilization of other matrix components. The need for very careful temperature control and accurate background compensation is thus minimized. Sea water was analyzed by the method of standard additions. A detection limit of 0.01 μg l^-1, a sensitivity of 0.034 μg l^-1 and a precision of ±10% at the 0.05 μg l^-1 level were obtained for 20-μl injections.     

Simultaneous determination of four heavy metal ions in tobacco and tobacco additive by online enrichment followed by RP-HPLC and microwave digestion

A new method for the simultaneous determination of tin, lead, cadmium, and mercury in tobacco and tobacco additive by reversed-phase high-performance liquid chromatography combined with microwave digestion and an online enrichment technique is developed. The tin, lead, cadmium, and mercury ions are precolumn derivatized with tetra-(4-dimethylaminophenyl)-porphyrin (T(4)-DMAPP) to form color chelates. The Sn-T(4)-DMAPP, Hg-T(4)-DMAPP, Cd-T(4)-DMAPP, and Pb-T(4)-DMAPP chelates are absorbed onto the front of the enrichment column using a buffer solution of 0.05 mol/L pyrrolidine-acetic acid (pH = 10.0) as the mobile phase. After the concentration is finished (by switching the six-port switching valve) the retained chelates are back-flushed by the mobile phase and move to the analytical column. The chelate separation on the analytical column is satisfactory using gradient elution with methanol (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) and tetrahydrofuran (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0). The linearity range is 0.01-120 micro g/L for each metal ion. The detection limits (S/N = 3) of tin, lead, cadmium, and mercury are 0.6, 0.8, 0.5, and 0.6 ng/L, respectively. This method is applied to the determination of tin, lead, cadmium, and mercury in tobacco and it's additive with good results.     

Collection of trace heavy metals complexed with ammonium pyrrolidinedithiocarbamate on surfactant-coated alumina sorbents

Surfactant aggregates were formed on alumina surfaces by mixing 100 mg of sodium dodecyl sulfate (SDS) and 1.5 g of gamma-alumina in 50 ml of water. The SDS-coated alumina incorporated water-insoluble metal-ammonium pyrrolidinedithiocarbamate complexes over the pH range 2-8 with a recovery of > 97%. The metals were quantitatively desorbed from the alumina with 4 mol 1(-1) nitric acid, leaving > 99% of SDS on the solid phase. They were determined by inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrometry. The proposed method was successfully applied to the determination of traces of iron, cobalt, nickel, copper, cadmium and lead in high-purity alumina.     

Mechanism of interference elimination by thiourea in electrochemical atomic absorption spectrometry

The mechanism of interference elimination by thiourea in electrothermal atomization is discussed. Activation energies of atomization were measured. The experimental values for bismuth, lead, copper and cadmium were not altered in the presence of concomitants, provided that thiourea was added before atomization. These elements from complexes with thiourea which are converted to sulphides during the charring stage. Atom formation occurs from the sulphides without compound formation between analyte and concomitants.     

The atomic absorption determination of antimony,arsenic, bismuth, cadmium, lead, and tin in iron, copper,and zinc alloys with the graphite furnace

Antimony, arsenic, bismuth, cadmium, lead, and tin can be determined in metallurgical samples by flame atomic absorption spectrometry at levels of 0.005 wt%, but lower concentrations frequently necessitate preconcentration. The graphite furnace allows determination of these elements at concentrations 1–2 orders of magnitude lower than is possible with flame techniques. All six elements have detection limits at or below 1μg g⁻¹ in a variety of alloys. Calibration for antimony and load was done with standards containing the principal component of the alloy as a synthetic matrix. Bismuth, cadmium, and tin could be determined accurately only by the standard addition method. Arsenic could be determined in iron alloys with synthetic standards, but standard additions were required for copper alloys.     

Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g(-1) of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.     

直读光谱法测定析出锌中铅、铜、铁、镉、锡、铝的含量

研究了湿法冶炼产出的析出锌,经过冲床冲压脱模、马弗炉高温熔化、模具浇铸成型、车床切削等过程,于直读光谱仪上测定析出锌中铅、铜、铁、镉、锡、铝含量的方法.通过实验确认了仪器的工作条件、熔样器皿、熔样温度、析出锌取样位置,并对熔样铸锭后铅、铜、铁、镉、锡、铝的偏析情况进行了分析,铅最大偏差达到30％,经玻璃棒搅动后保温,铅...     

Effect of halogenated solvents on iron atomization in graphite-furnace atomic-absorption spectroscopy

When an iron solution in an organic solvent is examined by atomic-absorption spectroscopy, the signal decreases to below that for a comparable aqueous solution. This effect is most pronounced for halogen-containing solvents because of volatility of FeCl(2), and a change in the atomization curve with a shift towards higher temperatures for atomization. When the cuvette is pretreated with halogenated solvent a double peak is observed. The first peak corresponds to that found for aqueous solvents, the second may be correlated with the peak for iron in a halogenated solvent. The peaksplitting effect of such a solvent increases with halogen:hydrogen ratio in the solvent. The halogen penetrates the structure of the graphite cuvette and probably forms strong carbon-haloge. compounds which modify the atomization conditions for iron. When water is introduced hydrogen halide is formed, which removes the excess of halogen from the atomization region.     

Atomic absorption spectrometry of tin with electro-thermal atomization in a molybdenum microtube

The atomic absorption spectrometry of tin with atomization in a molybdenum microtube is described. The addition of hydrogen to the argon purge gas improves the efficiency of atomization of tin; measurements are best done at 224.61 nm. Phosphoric acid lowers the atomization temperature of tin, and depresses the interferences from diverse elements. Tin in canned foods (fruit juices and drinks) can be determined by direct atomization after dilution with phosphoric acid. Prior extraction is necessary for analysis of geological materials.