Activation analysis of mercury in high purity bismuth

A neutron activation method was developed for the determination of traces of mercury in high purity bismuth. After neutron irradiation at a flux of approx. 4.10¹¹ n/cm²/sec, mercury was separated from the matrix by displacement on metallic copper and subsequent distillation and amalgamation on silver foil. The γ-activity of the ¹⁹⁷Hg was counted in the 68–77 ke V region. The accuracy of the procedure was tested by an addition method of analysis. Bismuth samples with a mercury content in the 10 p.p.b. region were analysed.     

Determination of micromolar concentrations of iodide by electrothermal atomic absorption spectrometry

When a solution (at pH 3.4–4.8) containing iodide and mercury(II) nitrate in a graphite tube is heated by increasing the temperature at a uniform rate, two mercury absorption peaks appear because the decomposition temperature of mercury(II) iodide is higher than that of mercury(II) nitrate. Measurement of the second peak allows 1 × 10^-6–5 × 10^-5 M iodide to be determined with good reproducibility. Equimolar concentrations of cyanide, sulfide and thiosulfate interfered, but these anions could be destroyed with hydrogen peroxide. Interfering cations were removed by extraction of 8-quinolinol complexes.     

Determination of bismuth oxide in and on high-purity bismuth

Bismuth is dissolved in mercury on shaking with ammonium nitrate solution in a nitrogen atmosphere; bismuth oxide is insoluble and so can be separated by flotation and dissolved in nitric acid for spectrophotometric determination as tetraiodobismuthate(III). The method is applied to various bismuth samples containing about 0.01% Bi₂O₃, the relative standard deviation being 7–11%.     

Determination of bismuth in nickel-base alloys by atomic absorption spectrometry with introduction of solid samples into an induction furnace

Atomic absorption spectrometry with an induction furnace is applicable'to the determination of bismuth at 0.02–10 μg g^-1 levels in 1–30-mg samples of nickel-base alloys dropped into the furnace. Calibration graphs of peak absorbance versus mass of bismuth are constructed by use of standardised alloys. Samples of alloys can be added to the furnace at 2.5-min intervals. Calibration graphs, accuracy, precision and limits of detection of the method are discussed for 26 alloys. Accuracy is assessed by comparing the induction furnace results with results supplied with the alloys, and with results obtained for solutions of the alloys by atomic absorption spectrometry in association with hydride generation or a mini-Massmann furnace. With alloys containing more than 0.1 μg Bi g^-1, relative standard deviations by the induction furnace method are usually < 15%. The limit of detection for bismuth is 0.02 μg g^-1     

The Preparation and Application of Bismuth (III) Ion‐Selective Electrode Based on Nanoparticles of Bismuth Sulfide

Abstract

Nanoparticles of bismuth sulfide were prepared in the organic phase and the optimum synthesis conditions for the nanoparticles were studied in detail. Transmission electron microscope (TEM) results indicated that the size distribution of the nanoparticles was proportional with an average diameter of 46.4 nm. A novel bismuth ion‐selective electrode (ISE) was prepared by dispersing the bismuth sulfide nanoparticles in polyvinylchloride (PVC) membrane. The linear range was 1.00×10^?8～1.00×10^?4 mol L^?1 and the detection limit was 8.10×10^?9 mol L^?1. The response of the electrode was fast with quite reasonable reproducibility and stability. It was used to determine bismuth in three kinds of stomach medicines and the results were in good agreement with the flame atomic absorption spectrometry (FAAS) method.     

Highly Sensitive and Selective Measurement of Bismuth in Seawater and Drug with 1,2‐Phenylenedioxydiacetic Acid by Cathodic Adsorptive Stripping Voltammetry

A new method is presented for determination of bismuth based on cathodic adsorptive stripping of complex bismuth with 1,2‐phenylenedioxydiacetic acid (PDA) at a hanging mercury drop electrode (HMDE). The effect of various parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum conditions for determination of bismuth include nitric acid concentration 0.01 M, 8.0×10^?4 M PDA and accumulation time 120 s, accumulation potential of ?200 mV. The limits of detection are 0.25 and 0.05 nM, and responses are linear 1–1000 and 0.1–400 nM at t_acc of 60 and 120 s, respectively. Many common anions and cations do not interfere in the determination of bismuth. The method was applied to the determination of bismuth in some real samples such as sea – and spring water and drug.     

Rapid determination of total mercury in treated waste water by cold vapor atomic absorption spectrometry in alkaline medium with sodium hypochlorite solution

Addition of a sodium hypochlorite solution (9.2% (w/v)) was effective to reduce a sulfide interference in determination of organic mercury, including methylmercury and phenylmercury, as well as a previously reported determination of inorganic mercury by cold vapor atomic absorption spectrometry (CVAAS) in an alkaline medium. Total mercury ranging from 0.17 to 33 μg L⁻¹ in 15 mL of sample solutions containing up to 200 mg L⁻¹ of sulfide can be determined without any serious interference by sulfide when 1 mL of the sodium hypochlorite solution was added after dilution of the sample solution to 25 mL. The proposed method was simple and rapid because no digestion processes were required for the determination of total mercury; the time required for the determination was only about 5 min. The proposed method was applicable to the analysis of treated waste water.     

New Electrocatalytic Reactions at a Mercury Electrode in the Presence of Homocysteine or Cysteine and Cobalt or Nickel Ions

Homocysteine (Hcy) and cysteine (Cys) mercury thiolate layers were prepared by anodic polarization of a mercury electrode in amino acid containing solutions and then investigated in the cathodic regime in the presence of Ni²⁺ or Co²⁺ ions. The sulfhydryl function in the mercury thiolate undergoes a slow disintegration resulting in surface‐attached mercury sulfide. During the cathodic scan, Hg²⁺ substitution by Ni²⁺ or Co²⁺ yields minute amounts of the relevant metal sulfide. Such a species catalyzes hydrogen evolution at ?1.3 V vs. Ag|AgCl|KCl(3 M). Hcy experiences a faster decomposition and, consequently, displays a stronger catalytic effect. Each compound catalyzes the reduction of Ni²⁺ or Co²⁺, but only Cys (bound in metal complexes) induces typical catalytic hydrogen evolution processes such as the Brdi?ka reaction (with Co²⁺; pH around 9), or the catalytic hydrogen prewave (CHP) (with Ni²⁺; pH near 7). On the other hand, Hcy catalyzes the hydrogen evolution in the presence of Co²⁺ at ?1.5 V in the same way than sulfur derivatives with no amine function do. Metal sulfide formation does not interfere with CHP and Brdi?ka processes. Correlations between the physical state of the metal sulfide (adsorbed molecule or aggregate form) and its catalytic properties are discussed and possible analytical applications suggested.     

Potentiometric stripping analysis for bismuth(III) in seawater

Total bismuth(III) in seawater can be determined either directly after acidification with 0.1 M hydrochloric acid or after co-precipitation with magnesium hydroxide by means of pre-electrolysis for 8 min at —0.90 V vs. SCE at a rotated glassy carbon/mercury film electrode prior to potentiometric stripping analysis. The limits of detection (2σ) are 0.6 and 0.003 nM, respectively. Three Kattegatt surface seawater samples were found to contain bismuth(III) concentrations of 5–12 pM (l–2.5 ng l^-1).     

Determination of bismuth,lead and tellurium in copper by atomic absorption spectrometry with introduction of solid samples into an induction furnace

Atomic absorption spectrometry with an induction furnace is used for the determination of bismuth (0.015–10 μg g^-1), lead (0.2–15 μg g^-1) and tellurium (0.04–5 μg g^-1) in 2–30-mg samples of copper and low-alloy copper dropped into the furnace. Calibration graphs of peak area versus mass of element were constructed by use of standardised alloys. The accuracy, precision and limits of detection of the method are described for numerous copper samples. With alloys containing more than 0.1 μg Bi g^-1, 0.2 μg Pb g^-1 and 0.8 μg Te g^-1, average relative standard deviations are 7%, 6% and 8%, respectively. The limits of detection for bismuth, lead and tellurium are 0.01, 0.1 and 0.02 μg g^-1, respectively.     

Ex Situ Scanning Electrochemical Microscopy (SECM) Investigation of Bismuth‐ and Bismuth/Lead Alloy Film‐Modified Gold Electrodes in Alkaline Medium

Scanning electrochemical microscopy (SECM) in feedback mode was employed to characterise the reactivity and microscopic peculiarities of bismuth and bismuth/lead alloys plated onto gold disk substrates in 0.1 mol L^?1 NaOH solutions. Methyl viologen was used as redox mediator, while a platinum microelectrode was employed as the SECM tip. The metal films were electrodeposited ex situ from NaOH solutions containing either bismuth ions only or both bismuth and lead ions. Approach curves and SECM images indicated that the metal films were conductive and locally reactive with oxygen to provide Bi³⁺ and Pb²⁺ ions. The occurrence of the latter chemical reactions was verified by local anodic stripping voltammetry (ASV) at the substrate solution interface by using a mercury‐coated platinum SECM tip. The latter types of measurements allowed also verifying that lead was not uniformly distributed onto the bismuth film electrode substrate. These findings were confirmed by scanning electron microscopy images. The surface heterogeneity produced during the metal deposition process, however, did not affect the analytical performance of the bismuth coated gold electrode in anodic stripping voltammetry for the determination of lead in alkaline media, even in aerated aqueous solutions. Under the latter conditions, stripping peak currents proportional to lead concentration with a satisfactory reproducibility (within 5 % RSD) were obtained.     

Spectrophotometric determination of sulfide in the presence of sulfite and thiosulfate via the precipitation of bismuth(III) sulfide.

A photometric method has been developed for the determination of sulfide at 10(-5) mol dm(-3) levels, which is based on the reaction of sulfide with a given excess amount of bismuth(III) to form a precipitate of bismuth(III) sulfide and on the spectrophotometric measurement of the residual bismuth(III) at 335 nm after extracting with bismuthiol II reagent from an aqueous solution containing acetate buffer into benzene. The presence of sulfite and thiosulfate up to 0.002 mol dm(-3) did not cause any interference in the determination of sulfide, because both sulfite and thiosulfate do not produce any precipitate with bismuth(III). A linear calibration plot with a negative slope was obtained for sulfide over the range of 5.00 x 10(-7) - 3.00 x 10(-5) mol dm(-3) (16.0 - 960 ppb). An experimental calibration plot was in accord with the theoretical plot, taking into account the known excess of bismuth(III), showing that the reaction of sulfide with bismuth(III) proceeded to completion. The relative standard deviation of results from 10 replicate determinations of standard sulfide (2.00 x 10(-5) mol dm(-3)) was 0.44%. The proposed method was successfully applied to the determination of sulfide in hotspring water samples without any pretreatment.     

Mercury determination in sediments by CVAAS after on line preconcentration by solid phase extraction with a sol-gel sorbent containing CYANEX 471X®

The development of a preconcentration method for the measurement of trace levels of mercury in digested sediments is described. Solid phase extraction (SPE) was used for the preconcentration of mercury coupled on-line by means of a flow injection (FI) system followed by cold vapour atomic absorption spectrometry (CVAAS) detection. The SPE was carried out through a column packed with a sorbent material containing triisobutylphosphine sulfide (CYANEX 471X®) as mercury extractant and prepared by the sol-gel process. The effects of FI variables (argon, eluent, and reductant flow rates, loading and elution times) as well as the eluent concentration on the analytical performance of the method were evaluated. The proposed method was validated under the optimum conditions. The calibration graph was linear from 0.05?µg?L^?1 to 3.0 µg?L^?1 of Hg. The detection limit (DL), based on three times the standard deviation of the blank measurement criterion, was 24?ng^?L^?1. The repeatability was 1.5% and 1.8% RSD (n?=?10) at concentrations of 0.5 and 1 µg?L^?1 of Hg, respectively. Method enrichment factors of 16 with a productivity of 30 samples h^?1 or 32 with a productivity of 17 samples h^?1 were achieved under selected conditions. Certified reference materials, inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapour atomic fluorescence spectrometry (CVAFS), were used to evaluate the accuracy of the proposed method.     

Simultaneous determination of mercury and gold in bismuth by neutron activation analysis

After adding mercury as carrier, trace amounts of mercury and gold were simultaneously separated from bismuth by coprecipitating with sulfur produced by the decomposition of bismuth sulfide. The sulfur was filtered on a membrane filter, and the γ-activities were measured with a Ge(Li) detector. The recoveries were quantitative and the measurement of chemical yield was unnecessary. 123 ppm of mercury and 8 ppb of gold in a bismuth sample were determined simultaneously.     

Electroanalysis of some nitro-compounds using bulk bismuth electrode

Nitro compounds were usually determined electrochemically using the mercury drop with DPP technique. An alternate way to toxic mercury is the increasing use of the bismuth electrode as thin film electrodeposited on glassy carbon or copper for example, or as bulk bismuth disc. In the present paper several nitrocompounds were investigated: mononitrophenols, dinitrophenol, nitrobenzoic acid, nitrobenzaldehyde and a well known pesticide, parathion, which has a nitro group in para position on a phenyl cycle. Bulk bismuth electrode was a disc (cross section of a rod of 5 mm diameter embedded in Teflon®) polished with silicon carbide disc (P2400) and sonicated to remove any abrasive particle. The supporting electrolyte was the acetic buffer (pH 4.7), which was found suitable for all these compounds. Using cathodic sweep differential pulse voltammetry, it was noticed that according to the position of the nitro group on the cycle, the peak potentials might range between ?300 to ?750 mV vs. SCE. Limits of detection (LOD) and limits of quantification (LOQ) were determined for each compound whose response for increasing concentration was linear in the ～3–50 µmol L^?1 whatever the considered molecule. Adsorptive differential pulse voltammetry was found very efficient to determine parathion, because this molecule adsorbs on bismuth at ?0.2 V vs. SCE. Bulk bismuth electrode was compared to the hanging mercury drop electrode and led to an identical behaviour.     

The determination of total gaseous mercury in air at background levels

A method is described for the determination of the total gaseous mercury in air at concentrations ranging from ca. 0.1 ng m^-3 to 1μg m^-3. The method is based on the collection of mercury species on gold-coated quartz wool followed by detection with an atomic absorption detector. The collection efficiencies for mercury, dimethylmercury, methyl-mercury(II) chloride, and mercury(II) chloride are nearly quantitative at flow rates up to 10 1 min^-1 and at temperatures up to 50°C. The absolute detection limit of the method is 20 pg of mercury. Under field conditions the precision of the analytical procedure was 14.5% (n=5) for 400-l samples of air and a mercury concentration of 1.5 ng m^-3. Measurements of the mercury distribution in the atmosphere show an ambient background level in clean air masses of 1.0–4.0 ng m^-3.     

Sorption of arsenic,antimony and bismuth on glycolmethacrylate gels with bound thiol groups for direct sampling in electrothermal atomic absorption spectrometry

Batch sorption of arsenic, antimony and bismuth from solutions in 1 M sulphuric acid has distribution coefficients of 10⁴–10⁵. Quantitative sorption on the hydrophilic methacrylate gel containing thiol groups (Spheron Thiol) is possible within 60 min for bismuth or arsenic and 120 min for antimony. Conditions for the electrothermal atomization of arsenic sorbed on Spheron Thiol and injected into the graphite tube as a suspension are optimized. The sensitivities possible are 3.2 ng As ml^-1, 13 ng Sb ml^-1 and 2.8 ng Bi ml^-1; the coefficient of variation for 10 ng of As is 4%. Complete recovery of 40 ng As ml^-1 added to solutions of 5% KCI or 5% MgCl₂ and to river water was obtained.     

Preconcentration of inorganic mercury with an anion-exchange resin and direct reduction—aeration measurements by cold-vapour atomic absorption spectrometry

Inorganic mercury ions (5–50 ng l^-1) present in natural waters (500 ml) are concentrated on anion-exchange resin (0.2 g; chloride form) in a batchwise operation. The resin is filtered off and introduced into a bubbler containing tin(II) solution. The adsorbed mercury ions are reduced to the metal and vaporized with a stream of air in a closed system. Satisfactory recoveries are obtained for sea waters made 0.1 M in nitric acid, and for river and spring waters also made 0.1 M in nitric acid or 0.01 M in ammonium thiocyanate. The method preconcentrates traces of inorganic mercury ions by an order of magnitude, and is also effective in preventing mercury loss during sample storage.     

Behavior of mercury(II) salts in electrothermal atomic absorption spectrometry : Application to the Determination of Thiosulfate

Mercury(II) salts have different decomposition temperatures in a graphite tube or tantalum coil used for electrothermal atomic absorption spectrometry. The nitrate, perchlorate and acetate were spontaneously reduced to mercury vapor at room temperature, but the thiosulfate, sulfide, cyanide and bromide were reduced only on heating. Chloride and thiocyanate in a graphite furnace and iodide in a tantalum coil did not give mercury absorbance on heating. Thiosulfate (1–10 × 10^?6 M) was determined by addition to mercury(II) nitrate in acetate buffer, removing the response from the excess mercury(II) nitrate by drying below 100° C in the graphite furnace, and measuring the mercury absorbance on heating, which was proportional to the thiosulfate concentration.     

Speciation of Mercury in Terrestrial Plants Using Vapor Generation and Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

A sensitive method for mercury speciation in biological samples is reported. A simple vapor generation apparatus was coupled to liquid chromatography and inductively coupled plasma–mass spectrometry (ICP–MS) to achieve a substantial increase in sensitivity. Mercury(II) and methylmercury were separated by reversed-phase chromatography as thiolate compounds with 2-mercaptoethanol. A short reverse phase column with an octylated stationary phase (75 × 4 millimeters) was used with a mobile phase containing 0.02 mole per liter ammonium acetate, 0.2 percent (v/v) 2-mercaptoethanol, and 1 percent methanol. The effluent was mixed with hydrochloric acid (0.06 mole per liter) containing platinum (40 micrograms per liter) as the internal standard and bismuth (30 micrograms per liter) as a modifying agent followed by sodium borohydride (0.016 mole per liter). The generated volatile species were introduced into the ICP–MS by conventional solution nebulization. In addition to the sensitivity enhancement induced by vapor generation, the addition of bismuth further increased the methylmercury signal with a reduced increase in the mercury(II) signal. As a result, comparable but unequal signals were achieved: the mercury(II) signal was approximately 1.6-fold higher than the methylmercury signal. Extraction with a hydrochloric acid-2-mercaptoethanol solution was used for sample preparation. The accuracy of determination was verified using two standard reference materials and an interlaboratory reference material based on barley grown hydroponically in mercury-contaminated solution. The method was employed for mercury speciation of plant samples from a polluted region.