Determination of total chromium in fresh water by atomic absorption spectrometry following flotation preconcentration

A flotation method is proposed for the quantitative preconcentration and determination of total chromium by electrothermal atomic absorption spectrometry in fresh water samples, without previous reduction or oxidation of the chromium ion state. Hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate were used as precipitating collectors. The detection limit of the method is 0.01 g/L.     

Flame atomic absorption spectrometric determination of zinc after colloid precipitate flotation with hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate as collectors

Colloid flotation of zinc from fresh water with a combination of two collectors, hydrated iron(III) oxide (Fe(2)O(3).xH(2)O) and iron(III) tetramethylenedithiocarbamate (Fe(TMDTC)(3)), permits rapid separation of the precipitate before its atomic absorption spectrometric (AAS) analysis. All important parameters necessary for the successful flotation like optimal mass of collectors, pH of the medium, electrokinetic potential of the collector particle surfaces, type of tenside, induction time etc., were checked. At the optimal pH value of medium (5.5) establishing by recommended procedure, zinc was separated quantitatively (97.4-98.8%) with 5 mg Fe(III) as constitutive element of the two collectors used. The content of zinc was determined by flame atomic absorption spectrometry (FAAS). These results were compared with the results obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The FAAS detection limit for zinc is 9.4 mug 1(-1). The proposed method is simple, rapid and applicable to the zinc separation at mug 1(-1) levels from a large volume of water.     

Flow injection hydride generation electrothermal atomic absorption spectrometric determination of toxicologically relevant arsenic in urine

Analytical procedure for the determination of toxicologically relevant arsenic (the sum of arsenite, arsenate, monomethylarsonate and dimethylarsinate) in urine by flow injection hydride generation and collection of generated inorganic and methylated hydrides on an integrated platform of a transverse-heated graphite atomizer for electrothermal atomic absorption spectrometric determination (ETAAS) is elaborated. Platforms are pre-treated with 2.7 μmol of zirconium and then with 0.10 μmol of iridium which serve both as an efficient hydride sequestration medium and permanent chemical modifier. Arsine, monomethylarsine and dimethylarsine are generated from diluted urine samples (10–25-fold) in the presence of 50 mmol L⁻¹ hydrochloric acid and 70 mmol L⁻¹ l-cysteine. Collection, pyrolysis and atomization temperatures are 450, 500, 2100 and 2150 °C, respectively. The characteristic mass, characteristic concentration and limit of detection (3σ) are 39 pg, 0.078 μg L⁻¹ and 0.038 μg L⁻¹ As, respectively. The limits of detection in urine are ca. 0.4 and 1 μg L⁻¹ with 10- and 25-fold dilutions. The sample throughput rate is 25 h⁻¹. Applications to several urine CRMs are given.     

Determination of inorganic and methylmercury in fish by cold vapor atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Simple and rapid analytical procedures for the determination of Hg²⁺ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any inter-species conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L^− 1 HCl. After careful optimization of chemical parameters selective determination of Hg²⁺ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl₂ as reductant and 0.1 mol L^− 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg²⁺ is recommended for its quantification. Both Hg²⁺ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/V NaBH₄ as reductant. Quantification of the sum of Hg²⁺ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg²⁺ and methylmercury (by difference between the total Hg and Hg²⁺) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.     

Determination of major and trace elements in iron reference materials using k0-NAA

Major and trace element contents in iron ore reference materials were investigated using k ₀-instrumental neutron activation analysis (k ₀-INAA). To avoid iron interferences, radiochemical separation was developed (k ₀-RNAA). The determination of the investigated elements in the inorganic phase from hydrochloric acid solution was performed after radiochemical separation of iron by diisopropyl ether. It was found that after the Fe elimination, the limit of detection for some elements was much lower that enables their direct determination. The distribution of 39 elements (with intermediate/medium and long half-life radionuclides) after Fe removal was investigated.     

Preconcentration and separation of cadmium by use of cobalt(III) hexamethylenedithiocarbamate as a collector prior to its determination by atomic absorption spectrometry

Co(III) hexamethylenedithiocarbamate has been applied as a collector in colloid flotation preconcentration of Cd from water prior to electrothermal atomic absorption spectrometry (ETAAS). All experimental parameters necessary for successful flotation have been studied and optimized. The ETAAS results were compared with those obtained by inductive coupled plasma-atomic emission spectrometry (ICP-AES). The ETAAS detection limit was found to be 0.003 microg L(-1) Cd.     

ETAAS determination of nickel in serum and urine

Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomic absorption spectrometry (ETAAS) are described. Hydrogen peroxide was proposed as matrix modifier, assisting thermal decomposition of proteins during the ashing step. A pyrolysis temperature of 1,200 degrees C was found to be optimal while 2,100 degrees C and 2,200 degrees C were found to be optimal atomizing temperatures for Ni in serum and urine respectively. Calibration was performed by using a calibration curve prepared with aqueous standard solutions of Ni (glycine must be used as modifier for Ni in aqueous solutions). The limits of detection, defined as the blank values plus 3 times the standard deviation of the blank values, were 0.2 microg/L for both serum and urine samples. Relative standard deviations for serum samples with concentrations of Ni in the range 0.5-2 microg/L were 10-15% and for urine samples with Ni concentrations in the range 0.5-2.5 microg/L were 8-10%.     

Applicability of Hydrated Iron(III) Oxide and Dithiocarbamates as Colloid Collectors for Flotation Preconcentration of Manganese in Traces Before its ETAAS Determination

 The applicability of tetramethylenedithiocarbamate (TMDTC⁻) and hexamethylenedithiocarbamate (HMDTC⁻) for colloid flotation separation of manganese in traces from fresh (spring, well and tap) water was studied. The experimental conditions for the successful manganese separation and preconcentration before electrothermal atomic absorption spectrometric (ETAAS) determination were optimised. Higher enrichment of manganese was achieved when a larger amount of HMDTC⁻ is used. Applying iron(III) hexamethylenedithiocarbamate, Fe(HMDTC)₃, as a precipitate collector, manganese was determined at μg/L levels singly or simultaneously with lead and zinc in 1 L of water sample. The applicability of the proposed procedure have been verified by analyses of fresh water samples using the method of standard addition, as well as by comparing the results obtained by ETAAS with those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The detection limit of manganese using this method is 0.025 μg/L. Received August 30, 1999. Revision May 15, 2000     

Determination of copper in sulfide minerals by Zeeman electrothermal atomic absorption spectrometry

A method for the determination of copper in some sulfide minerals (lorandite, realgar, orpiment, marcasite, stibnite, galenite and sphalerite) by Zeeman electrothermal atomic absorption spectrometry is presented. After the dissolution of samples, copper was extracted with sodium diethyldithiocarbamate into different organic solvents (carbon tetrachloride, chloroform and methylisobutyl ketone) at pH 11.0–12.0. The procedure was verified by standard addition. The standard deviation (SD) for 0.5 ng Cu is 0.01 ng, the relative standard deviation ranges from 3.5 to 5.5% and the detection limit of the method, calculated as 3 SD of the blank, was found to be 0.05 μg · g^–1. Received: 26 May 1997 / Revised: 10 September 1997 / Accepted: 16 September 1997     

Determination of Inorganic and Total Arsenic in Wines by Hydride Generation Atomic Absorption Spectrometry

A method is described for the determination of inorganic arsenic species and total arsenic in wines by means of hydride generation atomic absorption spectrometry (HGAAS). Simple ethanol evaporation is the only pretreatment procedure proposed for wine samples prior to direct measurement of inorganic arsenic (AsIII) and As(V) species by HGAAS. The total arsenic content is determined after microwave digestion of the wine samples. The optimal parameters for the microwave digestion procedure and the next HGAAS measurement of arsenic are established. The detection limits achieved are 0.1µgL^–1 for inorganic and total arsenic determination. The relative standard deviation for both procedures and for ten independent determinations varied between 8 and 15% for arsenic species in the range of 1–30µgL^–1. The accuracy of the procedure for total arsenic determination was proved by comparative analysis using electrothermal atomic absorption spectrometry.