Potentiometric titration of trace amounts of mercury after a preliminary separation by a reduction method

Isolation and concentration of mercury by reduction of mercury(II) with acidic tin(II) chloride solution and absorption of mercury vapour in acidic permanganate solution is combined with potentiometric titration with dithiooxamide. The simple procedure is applicable to 5–100 ppb mercury in 1-dm³ samples. Recoveries from organomercurials are discussed.     

The determination of total mercury in biological tissues by a modified potassium permanganate procedure.

A simple cold-tube atomic absorption method with a silver-mercury amalgam trap and potassium permanganate as oxidizing agent is described for the determination of total mercury in tissue homogenates. Results are presented for animals fed inorganic (HgCl₂) and organic (CH₃HgOH) mercury orally at a level of 1 mg Hg kg^?1. Data are presented which compare potassium permanganate oxidation of tissue homogenates with whole tissue analysed by cold-tube atomic absorption after digestion with acid, or by neutron activation. For kidney tissue there is good agreement between all three methods for animals fed inorganic and organic mercury. For liver, however, homogenization produced an average loss of about 50 % of the mercury in rats fed mercury(II) chloride. Factors such as adsorption of mercury on sample container walls, bacterial action on the tissue and inadvertent introduction of reducing agents which could reduce the mercury to its elemental state, are not significant. Despite the loss of mercury in the liver by homogenization, rank ordering of mercury values for potassium permanganate—homogenate versus direct neutron activation analyses was essentially the same.     

Breakdown of organic mercury compounds by hydrochloric acid—permanganate or bromine monochloride solution for the determination of mercury by cold-vapour atomic absorption spectrometry

Hydrochloric acid—potassium permanganate and bromine monochloride are examined for the decomposition of methylmercury(II) chloride, Ceresan, phenylmercury(II) borate and thiomersal added to waters. Both procedures give quantitative recovery of mercury. Bromine monochloride has many advantages: blanks are low, the limit of detection (3σ) is 0.06 μg Hg l^?1, routine work is simplified because only two reagents are needed and the reaction time is 5–10 min. The reagent also acts as a preservative. Common contaminants (chloride, bromide, sulphide, alcohols, benzene) do not interfere.     

Spectrofluorometric method for determination of the total mercury content in environmental samples — Waste waters

A highly selective spectrofluorometric method for the determination of total mercury (Hg) in waste waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, is the basis of this sensitive method. All forms of mercury, including organic compounds, are pre-oxidized to ionic mercury by acidic potassium permanganate. The final and complete oxidation is achieved by adding potassium persulphate and heating. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. The recoveries were done by adding 3.0 g Hg/100 ml to each sample before the digestion. It was indicated that the recoveries for determining mercury in waste waters were 98.3%–102.7%. The method gives reliable results down to a concentration of 10 ng Hg/ml waste water.     

Potentiometric stripping analysis for mercury

In potentiometric stripping analysis for mercury, elemental mercury is deposited on a glassy carbon electrode surface by means of potentiostatic reduction. It is then oxidized by potassium permanganate added to the sample prior to analysis and the “redox titration curve” thus obtained is recorded on a high-input impedance recorder. Deaeration of the sample is unnecessary. The analytical range is 5 × 10^-9–10^-3 M mercury(II), the times needed for potentiostatic accumulation ranging from 64 min at 10^-8 M to 1 min at concentrations above 10^-6 M. The chemistry of the stripping process is discussed and an automatic instrument for potentiometric stripping analysis is described.     

Determination of picomolar concentrations of bromide with a piezoelectric detector by catalysis of the permanganate/iodide reaction

The piezoelectric quartz crystal has been utilized to detect iodine produced by the bromide- catalyzed oxidation of iodine to iodate by permanganate in acidic solution. After extraction of iodine into toluene, the resulting frequency change caused by iodine adsorption on the crystal electrode is proportional to bromide concentration over the range 0.5–5 × 10^?12 M. Only silver (I), mercury(II) and large concentrations of chloride interfere significantly. The crystal detector is also used to indicate the end-point of a chloride titration with silver.     

环境样品的热解-溶液吸收预处理及其汞同位素组成的测定

利用多道接收电感耦合等离子体质谱仪(MC-ICP-MS)可实现汞同位素的高精度测定,但对样品预处理的要求很高。目前,液态、固态、气态环境样品的预处理方式不一,存在一定的系统误差。该研究旨在尽可能统一各状态样品的预处理步骤。先将各样品中的不同形态汞富集转化为固体可吸附态,令其吸附在固态载体上,包括:采用金柱富集气体样品中的气态单质汞;以吹扫-金柱捕集法富集液体样品中的溶解气态汞和总汞;用膜过滤法收集大气中的颗粒态汞。最后以管式炉热解定量固态样品,采用高氧化效率的酸性高锰酸钾混合溶液吸收热解产生的Hg~0并氧化为Hg~(2+),保存于溶液中供MC-ICP-MS测定。优化了气体流速、吸收液体积及高锰酸钾浓度等参数,考察了方法空白、回收率及精密度等指标,并将建立的方法应用于大气气态单质汞、大气颗粒态汞、溶解气态汞、雨水总汞和土壤总汞等样品中汞同位素的分析。     

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.     

Flow-injection chemiluminescence determinations for human blood lead using controlled reagent release technology

A flow-through CL method for the determination of lead combined with controlled-reagent-release technology has been developed. Chemiluminescence (CL) reagents luminol and potassium permanganate were immobilized on anion exchange resin by electrostatic interaction. Lead ion was determined by its enhancing effect on the CL reaction between luminol and potassium permanganate. Both luminol and potassium permanganate were eluted from the anion exchange resin column by sodium phosphate solution. The linear range of the system was 10 μg mL^?1, and the detection limit was 5?×?10^–9 g mL^?1 lead (3σ). A complete analysis could be performed in 1 min with a relative SD 3.2% (1.0?×?10^–7 g mL^?1, n?=?9). The column shows remarkable stability and can be reused over 350 times and 21 days. The method has been applied to determine lead in human blood samples.     

Determination of mercury in air by means of computerized flow constant-current stripping analysis with a gold fibre electrode

Mercury in air was determined after collection in potassium permanganate or sodium carbonate solution. The mercury concentration in these solutions was determined in a computerized flow potentiometric stripping analyzer with a 10-μm gold fibre working electrode, a glassy carbon reference electrode and a platinum counter electrode. After sample electrolysis for 1–10 min, stripping was done in a 1 mg l^?1 gold(III) solution in 0.01 M nitric acid/0.01 M sodium nitrate with a constant stripping current of 0.50 μA. Results obtained for flue gas samples were in good agreement with results from cold-vapor atomic absorption spectrometry.     

The determination of traces of mercury in solid fuels by high-temperature combustion and cold-vapour atomic absorption spectrometry

A high-temperature combustion technique is described for the determination of mercury in coal, coal products including ash, and other samples of environmental interest. The liberated mercury is absorbed in an acidified potassium permanganate solution and determined by cold-vapour atomic absorption spectrometry. The vapour generation assemblage is constructed of standard ground-joint glassware, and is designed to produce non-transient signals suitable for either analog or digital recording devices. Accuracy and precision for 1-g coal samples is 0.02 μg g^-1.     

Increased mercury contamination of distilled and natural water samples caused by oxidizing preservatives

The passage of mercury vapor from ambient air through the walls of conventional polyethylene (CPE), linear polyethylene (LPE), and Teflon (FEP) containers can seriously contaminate solutions of distilled and natural water stored in these containers. The rate of mercury contamination is dramatically increased when the sample solution contains oxidizing agents such as nitric acid or potassium permanganate, which are commonly used as preservatives to prevent loss of mercury(II) ion. The rate of contamination also depends on container material and decreases in the order CPE> LPE> FEP> glass. Freezing the samples in plastic containers is an effective way to prevent mercury contamination. When freezing is not practical, storage in glass containers minimizes sample contamination from ambient mercury vapor.     

Anodic stripping determination of mercury in air with a glassy carbon electrode

A technique for stripping determination of mercury traces in air employing a glassy carbon electrode is described. The sample is passed at 2 liters min^?1 for 2 hr through an absorber containing 0.2 M potassium permanganate and 10% $\text{w}\text{v}$ sulfuric acid (1:1). After reduction with hydroxylamine hydrochloride, the determination is carried out in 0.12 M potassium thiocyanate at pH 2.0 ± 0.2 in the presence of 0.2 ppm of cupric ions. Calibration curves were found to be linear in the range 20 ppb-1 ppm Hg(II) in the cell. The accuracy of the method was tested over simulated samples and it was found to be better than 95%; the relative standard deviation was 5% or less. The limit of detection of mercury in air was approximately 10 μg m^?3.     

Flow-through stripping chronopotentiometry for the monitoring of mercury in waste waters

A simple method for the determination of total mercury in waste waters is described. It makes use of a flow system incorporating a wall-jet cell equipped with a gold working electrode. The untreated sample is mixed on-line with the acidic carrier electrolyte which contains potassium permanganate and transforms the various species of mercury, especially elementary Hg, to Hg(II). The pre-treated solution enters the cell where mercury is deposited on the gold electrode. In the next step the deposit is stripped at constant current and the time corresponding to the dissolution of the deposit is obtained from the chronopotentiometric signal. The method enables it to determine and monitor Hg in the concentration range of 1 to 1000 μg/L in 5 min intervals. Received: 20 October 1997 / Revised: 23 December 1997 / Accepted: 30 December 1997     

Flow-through stripping chronopotentiometry for the monitoring of mercury in waste waters

A simple method for the determination of total mercury in waste waters is described. It makes use of a flow system incorporating a wall-jet cell equipped with a gold working electrode. The untreated sample is mixed on-line with the acidic carrier electrolyte which contains potassium permanganate and transforms the various species of mercury, especially elementary Hg, to Hg(II). The pre-treated solution enters the cell where mercury is deposited on the gold electrode. In the next step the deposit is stripped at constant current and the time corresponding to the dissolution of the deposit is obtained from the chronopotentiometric signal. The method enables it to determine and monitor Hg in the concentration range of 1 to 1000 μg/L in 5 min intervals. Received: 20 October 1997 / Revised: 23 December 1997 / Accepted: 30 December 1997     

Indirect Complexometric Determination of Mercury(II) Using Potassium Bromide as Selective Masking Agent

 A complexometric method for the determination of mercury in presence of other metal ions based on the selective masking ability of potassium bromide towards mercury is described. Mercury(II) present in a given sample solution is first complexed with a known excess of EDTA and the surplus EDTA is titrated against zinc sulfate solution at pH 5–6 using xylenol orange as the indicator. A known excess of 10% solution of potassium bromide is then added and the EDTA released from Hg-EDTA complex is titrated against standard zinc sulfate solution. Reproducible and accurate results are obtained for 8 mg to 250 mg of mercury(II) with a relative error ± 0.28% and standard deviations ≤0.5 mg. The interference of various ions is studied. This method was applied to the determination of mercury(II) in its alloys. Received April 18, 2001 Revision October 10, 2001     

Determination of heavy metals and iodide by stripping voltammetry in sodium chloride on mercury-graphite electrodes

The behavior of Cd(II), Pb(II), Cu(II), and I⁻ in the aqueous solutions of sodium chloride is studied by stripping voltammetry. A new version of using an indicator electrode from carbon glass ceramics modified with mercury for the consecutive stripping determination of Cd(II), Pb(II), Cu(II), and iodide is proposed. The mercury-graphite electrode was formed in the solution of a supporting electrolyte based on NH₄Cl, HCl, 0.05 M potassium tetraoxalate (KH₃C₄O₃ · 2H₂O), and 5 × 10⁻⁵ M mercury(II). At first, Cd(II), Pb(II), Cu(II), and then iodide were determined by anodic-cathodic stripping voltammetry after adding a sample solution (table salt, 10–100 mg/mL NaCl).     

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.     

Spectrophotometric determination of trace mercury(II) in cereals with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid

A simple and low cost method for the determination of mercury has been developed. The method was based upon the highly sensitive color reaction of mercury(II) ions with 2,4-bis(4-phenylazophenylaminodiazo)benzenesulfonic acid (BPPABSA). We found that in the presence of 2.0% Triton X-100, the reagent reacts with mercury to form a stable red complex in a borax buffer solution at pH 10.22. The formed complex shows an absorption maximum at 530 nm. The apparent molar absorptivity is 2.18 × 10⁵ L/mol cm. The content of mercury in the sample was low and some foreign ions might interfere with the determination of mercury(II), so we used sulfhydryl dextran gel (SDG) to separate and enrich trace mercury(II), which lead to a satisfactory result. Under the optimal conditions, Beer’s law is obeyed in the range of 0–15 μg/25 mL Hg²⁺, the detection limit and relative standard deviation are 0.86 ng/mL and 1.4–3.8%, respectively. The method has been applied to the determination of mercury in cereals with satisfactory results.     

Ultra-trace arsenic and mercury speciation and determination in blood samples by ionic liquid-based dispersive liquid-liquid microextraction combined with flow injection-hydride generation/cold vapor atomic absorption spectroscopy

A simple, fast, and sensitive method for speciation and determination of As (III, V) and Hg (II, R) in human blood samples based on ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) and flow injection hydride generation/cold vapor atomic absorption spectrometry (FI-HG/CV-AAS) has been developed. Tetraethylthiuram disulfide, mixed ionic liquids (hydrophobic and hydrophilic ILs) and acetone were used in the DLLME step as the chelating agent, extraction and dispersive solvents, respectively. Using a microwave assisted-UV system, organic mercury (R-Hg) was converted to Hg(II) and total mercury amount was measured in blood samples by the presented method. Total arsenic content was determined by reducing As(V) to As(III) with potassium iodide and ascorbic acid in a hydrochloric acid solution. Finally, As(V) and R-Hg were determined by mathematically subtracting the As(III) and Hg(II) content from the total arsenic and mercury, respectively. Under optimum conditions, linear range and detection limit (3σ) of 0.1–5.0 µg L^?1 and 0.02 µg L^?1 for As(III) and 0.15–8.50 µg L^?1 and 0.03 µg L^?1 for Hg(II) were achieved, respectively, at low RSD values of < 4% (N = 10). The developed method was successfully applied to determine the ultra-trace amounts of arsenic and mercury species in blood samples; the validation of the method was performed using standard reference materials.