Selective determination of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of nameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of arsenic(III) and differential determination of arsenic(III) and arsenic(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone or nitrobenzene, when the aqueous phase/solvent volume ratio is 5 and the injection volume in the carbon tube is 20 μl, the sensitivities for 1% absorption are 0.4 and 0.5 part per milliard of arsenic, respectively. The relative standard deviations are ca. 3%. Interference by many metal ions can be prevented by masking with EDTA. The proposed methods are applied satisfactorily for determination of As(III) and As(V) in various types of water.     

Selective separation and differential determination of antimony(III) and antimony(V) by solvent extraction with N-benzoyl-N-phenylhydroxylamine and graphite-furnace atomic-absorption spectrometry using a matrix-modification technique

If copper is used as a matrix modifier for the determination of antimony, the ashing temperature for antimony in aqueous solution and a BPHA-CHCl(3) extract can be raised to 1300 degrees and 1100 degrees , respectively. A selective procedure for separating antimony(III) from antimony(V) by extraction with BPHA in chloroform is described, along with the conditions for preserving trace antimony in water samples. The recommended method has been applied satisfactorily to the determination of antimony(III) and antimony(V) in various types of water at sub-ng/ml levels.     

Differential determination of selenium(IV) and selenium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone by atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of selenium(IV) and selenium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone in organic solvents has been investigated by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of selenium(IV) and differential determination of selenium(IV) and selenium(VI) have been developed. With sodium diethyldithiocarbamate and carbon tetrachloride, when the aqueous phase/organic solvent volume ratio is 5 and the injection volume in the carbon tube is 20 microl, the sensitivity for selenium is 0.4 ng/ml for 1% absorption. The relative standard deviations are ca. 3%. Interference by many metal ions can he prevented by masking with EDTA. The proposed methods have been applied satisfactorily to determination of Se(IV) and Se(VI) in various types of water.     

Differential determination of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone by atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of tellurium(IV) and tellurium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone in organic solvents has been investigated by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of tellurium(IV) and differential determination of tellurium(IV) and tellurium(VI) have been developed. With sodium diethyldithiocarbamate and carbon tetrachloride, when the aqueous phase/organic solvent volume-ratio is 5 and the injection volume in the carbon tube is 20 microl, the sensitivity for tellurium is 0.3 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. The proposed methods have been applied satisfactorily to determination of tellurium(IV) and tellurium(VI) in various types of water.     

Microcolumn sorption of antimony(III) chelate for antimony speciation studies

Selective sorption of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a microcolumn packed with C₁₆-bonded silica gel phase was used for the determination of Sb(III) and of total inorganic antimony after reducing Sb(V) to Sb(III) by l-cysteine. A flow injection system composed of a microcolumn connected to the tip of the autosampler was used for preconcentration. The sorbed antimony was directly eluted with ethanol into the graphite furnace and determined by AAS. The detection limit for antimony was significantly lowered to 0.007 μg l⁻¹ in comparison to 1.7 μg l⁻¹ for direct injection GFAAS. This procedure was applied for speciation determinations of inorganic antimony in tap water, snow and urine samples. For the investigation of long-term stability of antimony species a flow injection hydride generation atomic absorption spectrometry with quartz tube atomization (FI HG QT AAS) and GFAAS were used for selective determination of Sb(III) in the presence of Sb(V) and total content of antimony, respectively. Investigations on the stability of antimony in several natural samples spiked with Sb(III) and Sb(V) indicated instability of Sb(III) in tap water and satisfactory stability of inorganic Sb species in the presence of urine matrix.     

Determination of arsenic(III), arsenic(V), antimony(III), antimony(V), selenium(IV) and selenium(VI) by extraction with ammonium pyrrolidinedithiocarbamate—methyl isobutyl ketone and electrothermal atomic absorption spectrometry

The solution conditions and other parameters affecting the ammonium pyrrolidine-dithiocarbamate—methyl isobutyl ketone extraction system for graphite-furnace atomic absorption spectrometric determination of As(III), As(V), Sb(III), Sb(V), Se(IV) and Se(VI) were studied in detail. The solution conditions for the single or simultaneous extraction of As(III), Sb(III) and Se(IV) were not critical. Arsenic(V) and Se(VI) were not extracted over the entire range of pH and acidity studied. Antimony(V) was extracted only in the acidity range 0.3—1.0 M HCl. Simultaneous extraction of total arsenic and total antimony was possible after reduction of As(V) with thiosulphate. Interference studies are also reported.     

Differential determination of antimony(III) and antimony(V) by indirect spectrophotometry with chromium(VI) and diphenylcarbazide,after reduction of antimony(V)

Antimony(III) is determined indirectly through its reaction with excess of chromium(VI), the excess being quantified with diphenylcarbazide and measurement at 540 nm. Antimony(V) is reduced to antimony(III) with sodium sulfite in hydrochloric acid solution; excess of sulfite is eliminated by boiling. The subsequent determination of antimony(III) gives the concentration of total antimony, and antimony(V) is found from the difference between the results before and after reduction. Antimony in its different oxidation states can be determined in the range 0.04–0.7 mg l^?1 within an error of about 10%.     

On-line determination of antimony(III) and antimony(V) in liver tissue and whole blood by flow injection - hydride generation - atomic absorption spectrometry

A new analytical procedure for the speciation of antimony in liver tissues is presented here. For this purpose, a flow injection system has been developed for the treatment of samples and the determination of antimony by hydride generation - atomic absorption spectrometry. The method involves the sequential and the on-line extraction of antimony(III) and antimony(V) from solid lyophilized blood and hamsters liver tissues, with 1.5 mol l(-1) acetic acid and 0.5 mol l(-1) sulfuric acid for Sb(III) and Sb(V), respectively. Reduction of Sb(V) to Sb(III) for stibine generation is effected by the on-line pre-reduction with l-cysteine. The linear ranges were 2.5-20 and 1.0-25 mug l(-1) of Sb(III) and Sb(V), respectively. The detection limits (3sigma) were 1.0 mug l(-1) for Sb(III) and 0.5 mug l(-1) for Sb(V). The relative standard deviation values for fifteen independent measurements were 2.1 and 1.8% for Sb(III) and Sb(V), respectively. The recovery studies performed with samples of cattle liver provided results from 98 to 100% for Sb(III) and from 100 to 103% for Sb(V) for samples spiked with single species. For samples spiked with both Sb(III) and Sb(V), the recovery varied from 97 to 103% for Sb(III) and from 101 to 103% for Sb(V).     

Speciation of antimony by preconcentration of Sb(III) and Sb(V) in water samples onto nanometer-size titanium dioxide and selective determination by flow injection-hydride generation-atomic absorption spectrometry.

A novel method for prevention of the oxidation of Sb(III) during sample pretreatment, preconcentration of Sb(III) and Sb(V) with nanometer size titanium dioxide (rutile) and speciation analysis of antimony, has been developed. Antimony(III) could be selectively determined by flow injection-hydride generation-atomic absorption spectrometry, coexisting with Sb(V). Trace Sb(III) and Sb(V) were all adsorbed onto 50 m g TiO2 from 500 ml solution at pH 3.0 within 15 min, then eluted by 10 ml of 5 mol/l HCl solution. One eluent was directly used for the analysis of Sb(III); to the other eluent was added 0.5 g KI and 0.2 g thiourea to reduce Sb(V) to Sb(III), then the mixture was used for the determination of total antimony. The antimony(V) content is the mathematical difference of the two concentrations. Detection limits (based on 3sigma of the blank determinations, n=11) of 0.05 ng/ml for Sb(III) and 0.06 ng/ml for Sb(V), were obtained.     

Solvent extraction of antimony(v) with ethyl acetate

A method has been derived for the selective extraction of antimony(V) from hydrochloric acid solution with ethyl acetate. The method can be employed for the rapid determination of antimony in antimonates of lead, tin, mercury, nickel and chromium and in type metal. Iron(III), cobalt(II) cadmium(II), and large amounts of copper(II) and tin(II) interfere with the extraction. For the analysis of type metal, tin must be oxidized to the tetravalent state.     

Differential determination of antimony(III) and antimony(V) by solvent extraction-spectrophotometry with mandelic acid and Malachite Green, based on the difference in reaction rates

Highly sensitive and reproducible extraction-spectrophotometric methods for differential determination of antimony(III) and antimony(V) were investigated. It was found that antimony(III) reacts easily with mandelic acid to form a complex anion extractable into chlorobenzene with Malachite Green from weakly acidic media (pH 2.2-3.5) at room temperature, whereas antimony(V) reacts only slowly, and heating for 15 min at 45 degrees is needed to obtain maximum sensitivity. The significant difference between the rates of reaction of mandelic acid with antimony(III) and antimony(V) was applied to the differential determination of these two species. The calibration graph was linear over the range 0.15-6.0 mug for antimony(III), and 0.20-10 mug for antimony(V).     

Separation of antimony(III) with iodide and dithizone by sorption on polyurethane foam from sulphuric acid medium for its spectrophotometric determination in glasses

A method for quantitative separation of antimony(III) by sorption on polyether based polyurethane foam and its spectrophotometric determination has been described. The method involves formation of a pink-red complex of antimony(III) with iodide (0.045M) and dithizone (2.3 x 10(-5)M) in 0.25-0.75M H(2)SO(4) medium, sorption of the complex on polyurethane foam (within 45 min) at room temperature followed by its elution with acidified acetone (acetone containing 0.008% H(2)SO(4)) and spectrophotometric measurement at 507.2 nm ( = 2.56 x 10(4) l mol cm). The method obeys Beer's law from 0.1 to 6.0 mug antimony(III). Tolerance limits of other ions are Co (100 mug), Ni (100 mug), Fe (10 mug), Cu (0.5 mug), Sn (20 mug), Zn (100 mug), As (100 mug), Mn (200 mug), Pb (50 mug), Ti (100 mug), V (50 mug), etc. Interference by iron and copper have been eliminated by treating with KOH prior to the extraction of antimony. The method has been standardized with glass samples spiked with known amounts of antimony and applied to the determination of antimony in various glasses.     

Simultaneous determination of antimony,arsenic and copper by neutron activation analysis

A rapid procedure has been developed for the mutual separation of antimony and arsenic using tribenzylamine as the extracting agent. The extraction behaviours of Sb(III), Sb(V), As(III), As(V) and Au(III) have been studied as a function of the acidity of the aqueous phase. Various factors which affect the extraction of these complexes have been studied and optimized. The procedure was then applied to lead base alloy for the simultaneous determination of antimony, arsenic and copper. Chemical recoveries were quantitative and only about one hour is required for the chemical processing of duplicate samples.     

Indirect spectrophotometric determination of traces of antimony(III) based on its oxidation by chromium(VI) and reaction of chromium(VI) with diphenylcarbazide

An indirect method for the determination of antimony(III) is described. Antimony(III) is oxidized to antimony(V) by chromium(VI) and the excess of chromium(VI) is then determined spectrophotometrically with diphenylcarbazide. Optimal conditions were established for both the determination of antimony(III) and the elimination or reduction of interferences. Antimony(III) can be determined quickly and easily in the range 0.05–5 mg l^?1; the relative standard deviation is 2% for 1.0 mg l^?1 antimony(III). The method is applicable to marine sediments and geothermal waters.     

Selective determination of antimony(III) and antimony(V) in liver tissue by microwave-assisted mineralization and hydride generation atomic absorption spectrometry

Antimony(III) and antimony(V) species have been selectively determined in liver tissues by optimizing the acidic conditions for the evolution of stibine using the reduction with sodium borohydride. The results show that a response for Sb(III) of 0.5 to 20 microg l(-1) was selectively obtained from samples in a 1 mol l(-1) acetic acid medium. The best response for total antimony from 1 to 20 microg l(-1) is obtained after sample treatment with a 0.5 mol l(-1) sulfuric acid and 10% w/v potassium iodide. Microwave digestion has been necessary to release quantitatively antimony species from sample slurries. The amount of Sb(V) was calculated from the difference between the value for total antimony and Sb(III) concentrations. A relative standard deviation from 2.9 to 3.1% and a detection limit of 0.15 and 0.10 microg l(-1) for Sb(III) and total Sb has been obtained. The average accuracy exceeded 95% in all cases comparing the results obtained from recovery studies, electrothermal atomic absorption spectrometry and the analysis of certified reference materials.     

Separation and determination of arsenic(V) and arsenic(III) in sea-water by solvent extraction and atomic-absorption spectrophotometry by the hydride-generation technique

Arsenic(V) and arsenic(III) in sea-water have been separated by complexing the arsenic(III) with ammonium pyrrolidinedithiocarbamate (APDC) in the range 4.0-4.5 and extracting the complex with chloroform. The organic phase is then wet-ashed with a 1:1 mixture of concentrated nitric acid and perchloric acid to get rid of all organics, and the arsenic(III) is determined by hydride generation and atomic-absorption spectrophotometry. Total arsenic is determined by first reducing arsenic(V) to arsenic(III) with potassium iodide and then applying the method used for arsenic(III). The arsenic(V) content is determined by difference. The low detection limit of 0.031 ng ml and the high sensitivity and precision make the method suitable for analysis of open ocean waters.     

Speciation of antimony by differential generation of its volatile covalent hydride in aqueous and organic phase

By using the ammonium pyrrolidinedithiocarbamate (APDC) — methylisobutyl ketone (MIBK) extraction system Sb(III) is extracted into the organic phase. Sb(III) is directly determined in this organic phase by hydride generation AAS using NaBH₄/dimethylformamide solution as reducing agent. Sb(V) is determined in the aqueous phase using the same technique.     

Determination of antimony(III) with potassium hexacyanoferrate(III)

The determination of antimony(III) with potassium hexacyanoferrate(III) in 5M hydrochloric acid medium and in the presence of 40% v/v acetic acid is described. Ferroin is used as the indicator. Antimony has been determined in tartar emetic, solder and pig lead. Arsenic(III) does not interfere.     

Speciation Analysis of Antimony (III) and Antimony (V) by Flame Atomic Absorption Spectrometry After Separation/Preconcentration With Cloud Point Extraction

A sensitive and simple method for flame atomic absorption spectrometry (FAAS) determination of antimony species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the system temperature is higher than the cloud point extraction temperature, the complex of antimony (III) with N-benzoyl-N-phenyhydroxylamine (BPHA) can enter the surfactant-rich phase, whereas the antimony (V) remains in the aqueous phase. Antimony (III) in surfactant-rich phase was analyzed by FAAS and antimony (V) was calculated by subtracting of antimony (III) from the total antimony after reducing antimony (V) to antimony (III) by L-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of BPHA and Triton X-114, equilibration temperature and time, were investigated systematically. Under optimized conditions, the detection limits (3σ) were 1.82 ng mL⁻¹ for Sb(III) and 2.08 ng mL⁻¹ for Sb(total), and the relative standard deviations (RSDs) were 2.6% for Sb(III) and 2.2% for Sb(total). The proposed method was applied to the speciation of antimony species in artificial seawater and wastewater, and recoveries in the range of 95.3–106% were obtained by spiking real samples. This technique was validated by means of reference water materials and gave good agreement with certified values.     

Speciation of antimony using chromosorb 102 resin as a retention medium.

The selective retention of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a column of Chromosorb 102 resin from a buffered sample solution including Sb(V) was used for the determination of Sb(III). The retained antimony was eluted with acetone. The retention of the Sb(III)-iodide compounds with sodium iodide on the Chromosorb 102 resin column from the same solution after reducing Sb(V) to Sb(III) by iodide in acidic solution was used to preconcentrate the total antimony. The retained antimony was eluted with 0.25 mol l(-1) HNO3. The antimony in the effluent was determined by flame atomic-absorption spectrometry. Also, the total antimony was determined directly by graphite-furnace atomic absorption spectrometry. The Sb(V) concentration could be calculated by the difference. The recoveries were > or = 95%. The detection limits of a combination of the column procedure and flame AAS for antimony were 6 - 61 microg l(-1) and comparable to 4 microg l(-1) for a direct GFAAS measurement. The relative standard deviations were <6%. The procedure was applied to the determination of Sb(III) and Sb(V) in spiked tap water, waste-water samples and a certified copper metal with the satisfactory results.