Determination Of Trace Mercury Research Articles

Application of new sol–gel electrochemical sensors to the determination of trace mercury

The aim of this work was the synthesis and characterization of new modified sol–gel carbon composite electrodes and their application to the determination of trace mercury species with positive charge. Two types of modified electrodes were synthesized, sol–gel and sol–gel-PVSA carbon composite electrodes. In the last ones, poly(vinylsulfonic acid) (PVSA) was used as a functional polymer entrapped within the sol–gel material due to its cationic exchange properties. In a first stage, parameters affecting both, the sol–gel process and the electrode preparation were optimized. In a second stage, usefulness of developed electrodes applied to the determination of cationic mercury species was evaluated, optimizing the activation, preconcentration, measurement and regeneration steps. Developed electrodes showed very favourable electroanalytical properties for their use as amperometric sensors, such as small size, low cost, simple fabrication and handling, renewability and reusability. By means of an easy and low-cost methodology, satisfactory experimental results were obtained in Hg 2+ determination. In this sense, developed analytical methodology showed adequate response times, linear concentration range up to three orders of magnitude (from 5.0 × 10 −8 to 5.0 × 10 −5 M) and detection limits of 1.5 × 10 −8 M (3.0 μg L −1). These results suggest that the incorporation of different receptor molecules at the sol–gel carbon composite material in combination with a selected electrochemical reaction could improve the detection limit achieved and obtain electrochemical sensors adapted to the determination of different species of mercury and other heavy metals.

Determination of Trace Mercury by Cloud Point Extraction Preconcentration Coupled with Spectrophotometry

Determination of Trace Mercury by Cloud Point Extraction Preconcentration Coupled with Spectrophotometry

Determination of trace mercury in geological samples by direct slurry sampling cold vapor generation atomic absorption spectrometry

A new method based on ultrasonic slurry sampling atomic absorption spectrometry (AAS) was established for the determination of trace mercury in geological samples by use of recently developed mercury cold vapor generation using formic acid under ultraviolet (UV) irradiation. The generated mercury cold vapor was rapidly separated from the matrix and swept into a T-tube for the measurement of atomic absorbance. Under the optimal experimental conditions, up to 1000-fold of Cu(II), Co(II), Ni(II), Cr(VI), Mn(II), Fe(III), and Zn(II) caused no significant interference with the determination of 50 µg L−1 Hg. The limit of detection at sub-ppb level was obtained for mercury. The method was applied to the determination of mercury in geological samples with satisfactory results.

A Simple Flow-injection Spectrofluorimetric Method for the Determination of Mercury

A highly sensitive flow-injection spectrofluorimetric method is presented for the rapid and simple determination of Hg (II) in environmental and pharmaceutical samples. Murexide (ammonium purpurate) was used as the fluorescence reagent in the carrier stream. An emission peak of murexide, which is decreased linearly by addition of Hg (II), occurs at 435 nm in aqueous solution with excitation at 335 nm. A linear calibration was obtained for 5-200 ng ml(-1) Hg (II) with the relative standard deviation 2.5% (n = 5) for a 20 microl injection volume Hg (II). The limit of the detection was 1 ng ml(-1) and the sampling rate was 80 h(-1). No significant interference was found by the ions commonly found in the most environmental samples. The proposed method was successfully applied for the determination of trace mercury in real samples and the validation of the proposed methodology is provided.

Preconcentration/separation and determination of mercury using microcrystalline phenolphthalein modified by ethyl violet

Abstract A novel method was developed for enrichment and separation of trace mercury using phenolphthalein modified by ethyl violet (EV). The effects of different parameters, such as stirring time, various metal ions and salts, and the amounts of phenolphthalein, NH 4SCN, and EV on the extraction rate of mercury were studied, to select the experimental conditions. Under optimum conditions, mercury can be adsorbed on the surface of microcrystalline phenolphthalein by the intermolecular action strength. The possible reaction mechanism for the enrichment of mercury was discussed in detail. Hg(II) could be completely separated from Fe(II), Co(II), Ni(II), Mn(II), Cd(II), Cr(III), and AI(III) in the solution. The proposed method has been successfully applied to the determination of trace mercury in industrial wastewater with the recoveries above 99%. The relative standard deviation for five replicate determinations of 0.04 μg·mL −1 of Hg(II) was found to be 1.4%, 1.1%, and 1.2%, respectively. The analytical results were very satisfactory.

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn4+ to form the complex [Sn(XO)6]4+. [Sn(XO)6]4+ can interact with Fin- (fluorescein anion) to form the ion associate [Sn(XO)6]4+.[(Fin)4]-, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg2+ can catalyze H2O2 oxidizing the ion association complex [Sn(XO)6]4+.[(Fin)4]-, which causes the RTP to quench. The DeltaIp value is directly proportional to the concentration of Hg2+ in the range of 0.016-1.6 fg spot(-1) (corresponding concentration: 0.040-4.0 pg ml(-1), 0.40 microl spot(-1)), and the regression equation of working cure is DeltaIp=10.03+83.15 m Hg2+ (fg spot(-1)), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot(-1)(corresponding concentration: 9.0 x 10(-15) g ml(-1), the sample volume: 0.4 microl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H2O2 oxidizing the ion association complex ([Sn(XO)6]4+.[(Fin)4]-) SS-RTP quenching method to determine trace mercury is also discussed.

Determination of Trace Copper by Solid Substrate–Room Temperature Phosphorescence Quenching Method Based on Lead Carboxymethyl Cellulose [Pb(CMC)2] Particles Containing Luminescent Salicyl Fluorones Molecules

Luminescent particles of lead carboxymethyl cellulose [Pb(CMC)2] that contain luminescent salicyl fluorones (SAF) {[Pb(CMC)2]‐SAF} were synthesized by sol‐gel method, using sodium carboxymethyl cellulose (NaCMC) as precursor and Pb2+ as precipitator. [Pb(CMC)2]‐SAF can emit intense and stable solid substrate–room temperature phosphorescence (SS‐RTP) on filter paper. EDTA (ethylenediaminetetraacetic acid) can chelate the Pb2+ in [Pb(CMC)2]‐SAF, causing it to decompose into aqueous soluble components PbY2–, CMC–, and SAF, and these components can react with Cu2+ to form [Cu(CMC)2]‐SAF, causing decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace mercury by SS‐RTP quenching method was established. This method has been applied to the determination of trace copper in human hair and tea samples with satisfactory results.

Total reflection X-ray fluorescence trace mercury determination by trapping complexation: Application in advanced oxidation technologies

It is well known that Hg species cause high noxious effects on the health of living organisms even at very low levels (5 μg/L). Quantification of this element is an analytical challenge due to the peculiar physicochemical properties of all Hg species. The regulation of the maximal allowable Hg concentration led to search for sensitive methods for its determination. Total reflection X-ray fluorescence is a proved instrumental analytical tool for the determination of trace elements. In this work, the use of total reflection X-ray fluorescence for Hg quantification is investigated. However, experimental determination by total reflection X-ray fluorescence requires depositing a small volume of sample on the reflector and evaporation of the solvent until dryness to form a thin film. Because of volatilization of several Hg forms, a procedure to capture these volatile species in liquid samples by using complexing agents is proposed. Acetate, oxalic acid, ethylenediaminetetracetic acid and ammonium pyrrolidine–dithiocarbamate were assayed for trapping the analytes into the solution during the preparation of the sample and onto the reflector during total reflection X-ray fluorescence measurements. The proposed method was applied to evaluate Hg concentration during TiO 2-heterogeneous photocatalysis, one of the most known advanced oxidation technologies. Advanced oxidation technologies are processes for the treatment of effluents in waters and air that involve the generation of very active oxidative and reductive species. In heterogeneous photocatalysis, Hg is transformed to several species under ultraviolet illumination in the presence of titanium dioxide. Total reflection X-ray fluorescence was demonstrated to be applicable in following the extent of the heterogeneous photocatalysis reaction by determining non-transformed Hg in the remaining solution.

Hg(II)-imprinted thiol-functionalized mesoporous sorbent micro-column preconcentration of trace mercury and determination by inductively coupled plasma optical emission spectrometry

Hg(II)-imprinting thiol-functionalized mesoporous sorbent was prepared by a sol–gel method and characterized by X-ray diffraction (XRD), FT-IR spectroscopy and nitrogen gas adsorption–desorption. The static adsorption capacity of the Hg(II)-imprinted and non-imprinted sorbent was 78.5 and 26.6 mg g −1, respectively. The breakthrough capacity was 4.46 mg g −1, and the relative selectivity coefficient for Hg(II) in the presence of Cd and Pb was 3.3 and 3.9, respectively. A new method using a micro-column packed with Hg(II)-imprinting thiol-functionalized mesoporous sorbent has been developed for preconcentration of trace mercury prior to its determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The effects of pH, sample flow rate and volume, elution solution and interfering ions on the recovery of the analyte have been investigated. The limit of detection was 0.39 ng ml −1 with a concentration factor of 150 times. The developed method has been applied to the determination of trace mercury in some biological and environmental samples with satisfactory results. The accuracy was assessed through recovery experiments and analysis of certified reference material.

Selective Determination of Trace Mercury (II) after Preconcentration with 4-(2-Pyridylazo)-Resorcinol-Modified Nanometer-Sized SiO2 Particles from Sample Solutions

A rapid, selective method that utilize 4-(2-Pyridylazo)-resorcinol (PAR)-modified nanometer SiO2 (nanometer SiO2–PAR) as a new solid-phase extractant for preconcentration of trace mercury (II) has been developed. The adsorption property of nanometer SiO2–PAR for metal ions was studied by selectively extracting different metal ions from aqueous solutions. The results revealed an excellent affinity of the nanometer SiO2–PAR for mercury (II) in presence of interfering metal ions at pH 4. The main parameters of solid-phase extraction such as shaking time, elution and sample dilution effect were studied. The extractant shows rapid kinetic sorption, and the adsorption equilibrium of mercury (II) on nanometer SiO2–PAR was achieved in less than 2 min. The adsorbed mercury (II) was easily eluted by 4 mL of 6 mol L−1 HCl. The maximum preconcentration factor was 50. The maximum static adsorption capacity was 276 µmol g−1 at pH 4. The detection limit (3σ) was 0.43 µg L−1 for cold vapor atomic absorption spectrometry (CVAAS), and the relative standard deviation of the eight replicate determinations was 2.4% for the determination of 2.0 µg of Hg(II) in 100 mL water sample. The method was applied to the determination of trace mercury (II) in sample solutions with satisfactory results.

Microcolumn packed with YPA 4 chelating resin on-line separation/preconcentration combined with graphite furnace atomic absorption spectrometry using Pd as a permanent modifier for the determination of trace mercury in water samples

A new method using a microcolumn packed with YPA 4 chelating resin as solid-phase extractor has been developed for the separation and preconcentration of trace Hg prior to its measurement by GFAAS with Pd as a permanent modifier. Various parameters such as the amount of the modifier, pH, sample flow rate, the concentration and volume of eluent have been studied in order to find the best conditions for the determination of mercury. The detection limit of the method (3 σ) for Hg based on an enrichment factor of 100 was 0.2 ng ml −1. A characteristic mass of 114 pg was obtained for mercury using Pd as a permanent modifier. The relative standard deviation was 2.8% at the 10 ng ml −1 level ( n = 5). The method has been applied to the determination of trace mercury in environmental water samples and the recoveries for the spiked samples are in the range of 91–105%.

Astraphloxin Cyanine Dye as a Reagent for the Selective Extraction-Photometric Determination of Trace Mercury(II)

A procedure was developed for the extraction-photometric determination of low concentrations of mercury(II) in aqueous solutions. It is based on the reaction of the Hg Br 3 − acidocomplex with the Astraphloxin cationic dye to give an ion pair extracted with toluene. The detection limit for mercury is 0.015 mg/L. Effects of a number of heavy metal cations on determining mercury(II) were studied. It was shown that these effects appear in the presence of 500-fold molar amounts of interferents. The procedure was used for determining mercury(II) in the presence of 200-fold molar amounts of some heavy metal cations. The relative standard deviation was no worse than 5%.

The Color Reaction of Mercury(II) with the New Reagent 2-Methylthiophenyldiazoaminoazobenzene and Its Application

A new and very sensitive and selective chromogenic reagent, 2-methylthiophenyldiazoaminoa-zobenzene (MTDAA), was synthesized and studied in detail for the determination of trace mercury(II) in water samples. The method is based on the color reaction between MTDAA and mercury(II). It was found that mercury(II) reacts with MTDAA in Na2B4O7-NaOH buffer solution (pH = 10.0) to form 1 : 2 red complexes; these show maximum absorption at 520 nm. Beer’s law is obeyed in 0–15 µg of mercury(II) in 25 mL of solution. The apparent molar absorptivity of the complex is 1.33 × 105 L/(mol cm); its limit of quantification, limit of detection, and relative standard deviation are 0.75 ng/mL, 0.27 ng/mL, and 1.0%, respectively, giving better sensitivity. The influence of the reaction variables and the effect of interfering ions are reported; most of the metal ions in water samples can be tolerated in considerable amounts. Only a few ions can interfere with the determination of trace mercury(II), but these can be eliminated by prior extraction. The proposed method is sensitive, simple, and rapid. It has been applied to the determination of trace mercury(II) in water samples with satisfactory results.

Voltammetric determination of trace mercury at a sonogel–carbon electrode modified with poly-3-methylthiophene

The sonogel–carbon electrode is a new class of sol–gel electrode that exhibit favourable mechanics and electrics properties to be used as electrochemical sensor. In this paper, a modified sonogel–carbon electrode is proposed to determine mercury at trace levels. The modified electrode is obtained by electropolymerization of 3-methylthiophene on the surface of a bare sonogel–carbon electrode. This electrode shows high selectivity and sensitivity and linear response towards Hg(II), with a detection limit of 1.4 × 10 −3 mg l −1. The electrode is reusable by a simple chemical cleaning procedure. No deterioration was observed in the electrode response during at least 1 week of successive measurements.

Determination of trace mercury by solid substrate-room temperature phosphorimetry based on an ionic associate [(Rhod.6G)2]2+·[HgI4]2-

A new solid substrate-room temperature phosphorimetry (SS-RTP) method for the determination of trace mercury has been established. It is based on the fact that in the acidic medium of H2SO4, an ionic associate will be formed between [HgI4]2−and Rhodamine 6G (Rhod.6G+) ([(Rhod.6G)2]2+·[HgI4]2−). The number of Rhod.6G molecules in the associate is higher than that in Rhod.6G+·I−, and the Hg2+ will induce a heavy atom perturbation effect. Both aspects can cause sharp increase in phosphorescent intensity in a solid substrate. The linear range of this method is 0.80–160.0 fg spot−1 (corresponding concentration: 0.002–0.4 ng mL−1, sample volume: 0.4 μL spot−1) with a limit of detection of 0.15 fg spot−1 (corresponding concentration: 3.8 × 10−13 g mL−1). The regression equation for the working curve is ΔI p = 114.0 + 1.956 (fg spot−1) (r = 0.9991. n = 6). This method has been successfully applied to the determination of trace mercury(II) in human hair, cigarettes and water. The reaction mechanism for the formation of ionic associate is also discussed.

Determination of trace mercury by solid substrate room temperature phosphorescence quenching method based on lead carboxymethyl cellulose (Pb(CMC) 2) particles containing luminescent salicyl fluorones molecules

Luminescent particles of lead carboxymethyl cellulose (Pb(CMC) 2), which contains salicyl fluorones (THBF), Pb(CMC) 2-THBF, were synthesized by sol–gel method. Pb(CMC) 2-THBF can emit intense and stable solid substrate room temperature phosphorescence (SS-RTP) on filter paper. EDTA can chelate the Pb 2+ in Pb(CMC) 2-THBF, causing it decompose into aqueous soluble components PbY 2−, CMC − and THBF, and these components can react with Hg 2+ to form (CMC) 2Hg-THBF, causing decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace mercury by SS-RTP quenching method was established. The linear range of this method is 2.0–40.0 fg spot −1 (5.0–100.0 pg ml −1) of Hg 2+, with a detection limit (LD) of 0.26 fg spot −1, and the regression equation of working curve is Δ I p = 13.02 + 1.165 m H g 2 + (fg spot −1, 0.4 μl spot −1), r = 0.9994. This method has been applied to the determination of trace mercury in water sample with satisfactory results. The mechanism of SS-RTP emission is also discussed.

Development of a sequential injection system for trace mercury determination by cold vapour atomic absorption spectrometry utilizing an integrated gas–liquid separator/reactor

A simple and robust time-based on-line sequential injection system for trace mercury determination via cold vapour atomic absorption spectrometry (CVAAS), employing a new integrated gas–liquid separator (GLS), which in parallel operates as reactor, was developed. Sample and reductant are sequentially loaded into the GLS while an argon flow delivers the released mercury vapour through the atomic absorption cell. The proposed method is characterized by the ability of successfully managing variable sample volume up to 30 ml in order to achieve high sensitivity. For 20 ml sample volume, the sampling frequency is 25 h −1. The calibration curve is linear over the concentration range 0.05–5.0 μg l −1 of Hg(II), the detection limit is c L = 0.02 μg l −1, and the relative standard deviation is s r = 2.6% at 1.0 μg l −1 Hg(II) level. The performance of the proposed method was evaluated by analyzing certified reference material and applied to the analysis of natural waters and biological samples.

Simultaneous determination of trace mercury and cadmium in tobacco samples by cold vapor generation-atomic fluorescence spectrometry

A highly sensitive and simple method was developed for the simultaneous determination of trace cadmium and mercury in tobacco samples by cold vapor generation-atomic fluorescence spectrometry equipped with an intermittent flow reactor. The reaction was accomplished with potassium tetrahydroborate(III) in aqueous solutions. A newly modified atomizer was presented on the basis of the present atomic fluorescence system, which effectively improved the stability of the signals. Special accent was put on the study of the conditions for the generation of volatile cadmium and mercury species were investigated in detail. Some transition metal ions that could be used as sensitivity enhancers, including iron(III), cobalt(II), nickel(II), zinc(II) and molybdenum(VI) in the presence of thiourea. The tolerance to the interference of coexisting ions was carefully examined in this system. Under optimal conditions, the detection limits (3σ) were evaluated to be 2.8 ng l−1 for cadmium and 4.3 ng l−1 for mercury, respectively. The relative standard deviations for 10 replicate determinations of 0.8 µg l−1 mercury and 1 µg l−1 cadmium were 3.2% and 2.9%, respectively. The proposed method was successfully applied to the simultaneous determination of mercury and cadmium in tobacco leaf samples.

Determination of trace mercury by solid substrate-room temperature phosphorimetry based on catalytic effect of Hg 2+ on formation of the ion association complex [Fe(bipy) 3] 2+[rad][(FinBr 4) 2] 2−

A new solid substrate-room temperature phosphorimetry method for the determination of trace mercury has been established. It bases on the fact that in acetic acid medium, Hg 2+ ion can catalyze the substitute reaction of CN − ligand in [Fe(CN) 6] 4− by 2,2′-bipyridyl (bipy), and the resultant [Fe(bipy) 3] 2+ cation can react with FinBr 4 − anion of tetrabromofluorescein (HFinBr 4) to form ion association complex [Fe(bipy) 3] 2+ [(FinBr 4) 2] 2− which can emit phosphorescent signal on filter paper substrate. Under the optimum condition, the linear dynamic range of this method is 1.6–16 fg per spot with a detection limit (LD) of 0.18 fg per spot (0.4 μl sample solution per spot), and the regression equation of working curve is Δ I p=1.058+7.671 C Hg 2+ (fg per spot ), n=7, correlation coefficient is 0.9990. This method has been applied to the determination of trace mercury in hair and cigarette samples with satisfactory result. The reaction mechanism for formation of the ion association complex is also discussed.

Trace Mercury Determination by Differential Pulse Anodic Stripping Voltammetry Using Polythiophene-Quinoline/Glassy Carbon Modified Electrode

A Polythiophene-quinoline/glassy carbon (PTQ/GC) modified electrode was developed for the determination of trace mercury in industrial waste water, natural water. soil. and other media. The electrode was prepared by the cyclic voltammetric polymerization of thiophene and quinoline on glassy carbon (GC) electrode by the potential application from -0.6 V to +2.0 V (50 mV/sec) in a solution of 0.1 M thiophene, quinoline and tetrabutyl ammonium perchlorate (TBAP) in acetonitrile. Optimum thickness of the polymer membrane on the GC electrode was obtained with 20 repeated potential cyclings. The redox behavior of Cu(II) and Hg(II) were almost identical on this electrode. The addition of 4-(2-pyridylazo)resorcinol (PAR) to the solution containing Cu(II) and Hg(II) allowed the separation of the components due to the formation of the Cu(II)-PAR complex reduced at -0.8V, which was different from the Hg(II) reduced at -0.5 V on a saturated calomel electrode (SCE). The calibration graph of Hg(II) shows good linear relationship with the correlation factor of 0.9995 and the concentration gradient of 0. 33 μA/cm 2 /ppb down to 0.4 ppb Hg. The method developed was successfully applied to the determination of mercury in samples such as river, waste water, and sea water.