Separation and Removal of Mercury(II) from Water Samples Using (Acetylacetone)‐2‐Thiol‐Phenyleneimine Immobilized on Anion‐Exchange Resin Prior to Determination by Cold Vapor Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

(Acetylacetone)‐2‐thiol‐phenyleneimine (H₂L) immobilized on an anion‐exchange resin (Dowex) was used for separation and removal of mercury from natural water samples and for preconcentration prior to its determination by cold vapor inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 10% thiourea in 0.1 M HCl. The modified resin is higly selective with an exchange capacity of 1.60 mmol g^?1. Various parameters like pH, column flow rate, and desorbing agents are optimized. The proposed method has a linear calibration range of 15–1000 ng/ml Hg(II), with a relative standard deviation at the 15 ng/ml level of 3.5%. The precision of the method (evaluated as the relative standard deviation obtained after analyzing six series of five replicates) was ±4.2% at the 50 ng/ml level of Hg(II). The method has been used for routine determination of trace levels of mercury species in natural waters. The potential application of modified resin for the removal of mercury(II) from two natural water samples (top water and lake water) spiked with 50 ng/ml of mercury (II) was studied by ICP‐AES, and the results proved that excellent percent extraction of mercury(II) from both natural water samples was obtained by column method using modified resin.     

Preconcentration and separation of total mercury in environmental samples using chemically modified chloromethylated polystyrene-PAN (ion-exchanger) and its determination by cold vapour atomic absorption spectrometry

The use of chemically modified chloromethylated polystyrene-PAN, CMPS-PAN (ion-exchanger) for the preconcentration and separation of total mercury after digestion in preparation for determination by cold vapour atomic absorption spectrometry (CVAAS) was described. The effects on the percentage of recovered mercury by mass change of ion-exchanger, stirring time, pH of the solution samples and eluent concentration were studied. The distribution coefficient K(d) is 10(6.6) ml g(-1). The interfering effects of some foreign ions were described. The metal complex formed between CMPS-PAN ion-exchanger and mercury was characterized by IR spectroscopy, pH-metric titration and thermal analysis. The method is simple and rapidly applicable for the determination of total mercury (ng ml(-1)) in natural water, milk and urine.     

Uses of 5-Methylresorcin-bonded polyurethan foam as a new solid phase extractor for the selective separation of mercury ions from natural water samples

In this work, 5-Methylresorcin (MR) bonded to untreated polyurethane foam (PUF) was successfully employed as a sorbent (MR-PUF) for the selective separation and determination of mercury in natural water samples. Mercury can be quantitatively recovered in the pH range of 5-7. The system presented a minicolumn packed with the new sorbent, where the sample solution was passed through it for a period of time and an eluent solution stripped out the retained mercury, which was further determined with dithizone. The new matrix was characterized by using different tools (IR spectra, stability and density). The kinetics of mercury uptake by the new matrix was found to be fast, reaching equilibrium in 20 minutes. A preconcentration factor of 350 was achieved. The proposed preconcentration procedure was applied successfully to the selective separation and determination of trace mercury in natural water samples.      

Low-level mercury determination with thiamine by fluorescence optosensing

A sensitive fluorescence optosensing method for the determination of Hg(II) in water samples is described. The method, using a flow injection technique, is based on the immobilization on a non-ionic-exchanger solid support (packed in a flow cell placed in a conventional fluorimeter) of the thiochrome formed by the oxidation of thiamine with Hg(II) in a continuous flow carrier at pH 8.1. Experimental parameters such as the solid support, the carrier pH, the thiamine concentration and the flow-rate were investigated to select the optimum operating conditions. The proposed optosensor showed a relative standard deviation of + 3.0% for ten replicates analysis of 100 ng ml(-1) of mercury(II). A detection limit of 3 ng ml(-1) for mercury(II) was achieved for 4-ml sample injections. A detailed study of interferences (possible elements present in natural waters) demonstrated that this optosensing method is virtually specific for this metal, because it allows the determination of mercury in the presence of relatively large amounts of other heavy metals and compounds present in natural waters, such as Mg(II) or Ca(II). The method was successfully applied to the determination of Hg(II) in spiked samples of mineral, tap and sea water.     

The separation of mercury from sea water by adsorption colloid flotation and analysis by flameless atomic absorption

Adsorption colloid flotation has been found capable of separating ionic mercury from sea water quantitatively at levels as low as 0.02 μg l^?1 with use of a cadmium sulfide collector and octadecyltrimethylammonium chloride as the surfactant. The mercury in 25 samples can be separated in 2 h. Following the separation the mercury was analyzed by flameless atomic absorption. Recovery of mercury from 0.5 l samples spiked with 0.010 μg of inorganic mercury gave sol|0.014 ± 0.002 μg/0.5 l. Black Point, Oahu near-shore sea water was found to contain mercury in the range 0.038–0.078 μg l^?1 with no measurable organic mercury fraction. Sea-water samples collected at an open ocean station analyzed for total mercury revealed the highest mercury concentrations above 200 meters. Mercury concentrations in general showed a decreasing trend with increase in depth.     

A new fully automated on-line digestion system for ultra trace analysis of mercury in natural waters by means of FI-CV-AFS

A fully automated flow injection (FI) system utilizing the extraordinary oxidation power of bromine monochloride (BrCl) for the transformation of dissolved mercury species to Hg(2+) and oxidation of dissolved organic carbon (DOC) has been developed and coupled to cold vapor (CV) atomic fluorescence spectrometry (AFS) for highly sensitive mercury detection. The system can be applied to natural waters, sea water as well as freshwater and provides a detection limit as low as 16 pg Hg l(-1) from a sample volume of 7 ml. The relative standard deviation is about 4-10%. A 3-fold measurement of one sample is completely processed within 15 min. Dissolved organic carbon, chloride and iodide ions are tolerated in concentrations of 15 mg DOC l(-1), >21 g Cl(-)l(-1), and 10 mg I(-)l(-1). Validation of the proposed method yielded a good recovery of total mercury in a moorland water sample and in the certified reference material ORMS-3, river water. Investigation of eight real water samples with mercury concentrations in the range of 0.3-1.4 ng l(-1) also confirmed the suitability of the proposed method.     

Acid-induced cloud point extraction and preconcentration of polycyclic aromatic hydrocarbons from environmental solid samples

Liquid chromatography coupled to electrospray-mass spectrometry (LC-ES-MS) with positive ion detection was evaluated for the determination of tributyltin and triphenyltin in water samples using tripropyltin as internal standard. The separation was performed in the isocratic mode on a silica-based C18 column with a mobile phase containing 0.02% trifluoroacetic acid in acetonitrile-water (50:50, v/v). The optimum LC-ES-MS conditions were established and quantification was performed on the basis of the [M]+ ions. Limits of detection for standard solutions were 100 and 200 pg Sn injected for triphenyltin and tributyltin, respectively, and good reproducibility was observed. Solid-phase extraction was carried out on C18 cartridges to preconcentrate the analytes from natural water samples, with recoveries ranging from 80 to 110%. Limits of detection for SPE-LC-ES-MS were in the range of low ng l(-1), which demonstrates the suitability of the method for environmental samples.     

Multielemental speciation analysis of organometallic compounds of mercury, lead and tin in natural water samples by headspace-solid phase microextraction followed by gas chromatography-mass spectrometry

The development of a simple and rapid multielemental speciation method is described with the ultimate goal to simultaneously determine various organometallic compounds of mercury, lead and tin (inorganic mercury, methylmercury, trimethyllead, triethyllead, monobutyl-, dibutyl- and tributyltin) in natural water samples. The analytical method consists on the ethylation with NaBEt4, simultaneous headspace-solid phase microextraction (HS-SPME) of the derivatives and final gas chromatographic-mass spectrometric (GC-MS) analysis. After optimization of important process parameters, like SPME fiber coating, extraction time and extraction temperature, the analytical characteristics were evaluated. Detection limits in the low ng l(-1) level, linearity over three orders of magnitude and repeatability in the range of 3-20% were achieved for all compounds under study. The accuracy of the method in terms of average percentage recovery of the compounds in spiked river water and seawater samples was better than 90%. Finally, application of the proposed method to real natural aqueous samples enabled the simultaneous determination of all the compounds under study in seawater samples obtained from the marina area of Gijón (Asturias, Spain).     

Chronopotentiometric Stripping Analysis Using Gold Electrodes,an Efficient Technique for Mercury Quantification in Natural Waters

This paper proposes a simple methodology for mercury quantification in natural water by stripping chronopotentiometry at constant current, using gold (film) electrodes constructed from recordable CDs in stationary cell. The proposed method allows the direct measurement of labile mercury in natural waters. To quantify total mercury, a robust and low cost UV irradiation system was developed for the degradation of organic constituents of water. The proposed system presents such advantages as excellent sensitivity, low cost, versatility, and smaller dimensions (portability for on‐field applications) when compared with other techniques (ICP, GFAAS, fluorimetry) traditionally utilized for mercury quantification. A large linear region of responses was observed, situated over the range 0.02–200 μg L^?1. Various experimental parameters were optimized and the system allowed quantifications in natural samples, with detection limit of 8 ng L^?1 and excellent reproducibility (RSD of 1.4% for 48 repetitive measurements using a 10 μg L^?1 mercury solution). Different metal ions were evaluated, including copper, as possible interferences on stripping mercury signals. Applications of the new method were demonstrated for the analysis of certified and groundwater samples spiked with a known amount of mercury and for the quantification of methylmercury in synthetic oceanic water, originally utilized for fishes contamination experiment.     

纳米二氧化钛分离富集-原子荧光光谱法测定植物样品中的痕量汞

随着汞（Hg）污染研究的不断发展,对检测数据准确度的要求也不断提高。原子荧光光谱法（AFS）自诞生以来一直以其独特的优点作为测汞的主流方法,然而部分植物样品中含量极低的汞难以被准确检测,适宜的分离富集方法很少。本文采用纳米二氧化钛（TiO2）动态分离富集-原子荧光光谱法测定植物样品中的痕量汞,对分离富集条件进行了系统研究,最优条件为:粒径25nm、过柱溶液pH中性、硝酸为洗脱液用酸、硝酸体积分数5%、洗脱液体积30mL。在此基础上建立了汞的检测方法,方法检出限0.27ng·g-1,精密度（RSD/%）7.2%,并对国家一级标准物质GBW10014a（圆白菜）、GBW10015a（菠菜）进行检测,测定值均符合参考范围。     

Sulfhydryl-functionalised magnetic nanoparticles as sorbent in dispersive solid-phase extraction for the rapid enrichment of mercury species from natural water samples

The sulfhydryl-functionalised core-shell Fe₃O₄@SiO₂ magnetic nanoparticles (Fe₃O₄@SiO₂–RSH MNPs)-based dispersive solid-phase extraction method was developed. The goal of this method is the extraction of mercury species from natural water samples. An interesting aspect of the method is that, thanks to the spontaneously aggregate, the MNPs with a sub-30-nm-size range could be fast and efficiently extracted by 0.45 μm pore size mixed cellulose esters membrane filter. Thus, the elution step can be conducted by passing small amounts eluent through the MNPs on the membrane. It is also found that addition of Ag⁺ to water sample could improve the elution efficiency, and furthermore, minimises the matrix effects during the extraction of mercury species from natural water samples. The feasibility of the method was studied, and extraction efficiency was evaluated. The results showed that, calculated at 5 ng/L spiked concentration levels, absolute recoveries were 89.4%, 91.9% and 64.2%, and enrichment factors (EFs) were 596, 613 and 428, for inorganic mercury, methylmercury and ethylmercury, respectively. The high EFs were achieved in 5 min of overall extraction time. The method was applied to groundwater and river water samples. The results showed that its suitability for use in fast extracting trace levels of mercury species from natural water samples.     

On-line separation for the speciation of mercury in natural waters by flow injection-cold vapour-atomic absorption spectrometry

Inorganic mercury and methylmercury are determined in natural waters by injecting the filtered samples onto a low cost commercial flow injection system in which an anion exchange microcolumn is inserted after the injection loop (FIA-IE). If hydrochloric acid is used as the carrier solution, the HgCl4(2-) species (inorganic mercury) will be retained by the anion exchanger while the CH3HgCI species (methylmercury) will flow through the resin with negligible retention. Four anion exchangers and seven elution agents were checked, in a batch mode, to search for the best conditions for optimal separation and elution of both species. Dowex M-41 and L-cysteine were finally selected. Mercury detection was performed by cold vapour-electrothermal atomic adsorption spectrometry (HG-ETAAS). Both systems were coupled to perform the continuous on-line separation/detection of both inorganic mercury and methylmercury species. Separation and detection conditions were optimized by two chemometric approaches: full factorial design and central composite design. A limit of detection of 0.4 microg L(-1) was obtained for both mercury species (RSD < 3.0% for 20 microg L(-1) inorganic and methylmercury solutions). The method was applied to mercury speciation in natural waters of the Nerbioi-lbaizabal estuary (Bilbao, North of Spain) and recoveries of more than 95% were obtained.     

Mercury removal from aqueous and organo-aqueous solutions by natural Mexican erionite

The sorption of Hg(II) from aqueous and organo aqueous solutions was investigated by Mexican natural erionite. The mercury chemical species (anionic, cationic or neutral) were determined by high voltage electrophoresis, and the mercury chemical species present in the aqueous media were simulated by a program MEDUSA. The mercury sorption process was monitored during 48 hours. The mercury content was determined by neutron activation analysis. Mixtures of benzene/water[Hg(II)], toluene/water[Hg(II)] and ethanol/water[Hg(II)] were chosen as organo-aqueous media. It was found that both the mercury chemical species and the dielectric constant of solvents play an important role in the mercury sorption by erionite.     

Determination of Hg from Cu concentrates by X-ray fluorescence through preconcentration on polyurethane foam

A methodology was developed for the separation and determination of microamounts of mercury from copper concentrate samples by wavelength dispersive X-ray fluorescence (WDXRF) after solid-phase extraction of mercury from iodide medium using polyurethane foam (PUF). The best sorption conditions for the Hg-KI-PUF system were settled using X-ray fluorescence technique after collection of ground PUF on a filter paper by vacuum filtration and direct measurement of the intensity signal of the sorbed mercury on PUF. The main parameters of sorption such as iodide concentration, pH, shaking time and sample dilution effect were studied. The system shows rapid kinetic sorption and maximum X-ray intensity signal was achieved after shaking for 2 min a 0.01 mol l⁻¹ iodide solution containing microamounts of mercury in the pH range from 1.0 to 9.0. Effective sorption up to a volume of 0.9 l allows preconcentration of mercury. A linear fit up to 50 μg mercury was obtained by the plot of the initial mercury mass in the bulk solution (0.5 l) vs. its respective XRF intensity signal measurement on ground PUF after the sorption process. The calibration sensitivity, quantification and detection limits found were 9.09 CPS μg⁻¹, 9.0 and 2.7 μg, respectively. The sorption of many elements was also evaluated under the best conditions. High concentrations of Cu(II) and Fe(III) interfere seriously. Mercury-selective separation could be achieved using citrate or EDTA as masking agent; no interference due to copper matrix samples was observed in citrate medium. This methodology was evaluated by recovery for mercury determination in copper concentrate ore samples supplied by a mining industry and copper sulfate salts; the results were between 98% and 106%.     

Flotation-spectrophotometric determination of mercury in water samples using iodide and ferroin.

This paper describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of trace amounts of mercury. The method is based on the flotation of an ion-associate of HgI4(2-) and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and dissolved in acetonitrile to measure its absorbance. Quantitative flotation of the ion-associate was achieved when the volume of the water sample containing Hg(II) was varied over 50 - 800 ml. Beer's law was obeyed over the concentration range of 3.2 x 10(-8) - 9.5 x 10(-7) mol l(-1) with an apparent molar absorptivity of 1 x 10(6) l mol(-1) cm(-1) for a 500 ml aliquot of the water sample. The detection limit (n = 25) was 6.2 x 10(-9) mol l(-1), and the RSD (n = 5) for 3.19 x 10(-7) mol l(-1) of Hg(II) was 1.9%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of the almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic waste, and seawater samples was carried out by the present method and a well-established method of extraction with dithizone. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed in encountering with real samples.     

Simultaneous determination of inorganic mercury and methylmercury compounds in natural waters

The purpose of the present work was to develop a simple, rapid, sensitive and accurate method for the simultaneous determination of inorganic mercury (Hg(2+)) and monomethylmercury compounds (MeHg) in natural water samples at the pg L(-1) level. The method is based on the simultaneous extraction of MeHg and Hg(2+)dithizonates into an organic solvent (toluene) after acidification of about 300 mL of a water sample, followed by back extraction into an aqueous solution of Na(2)S, removal of H(2)S by purging with N(2), subsequent ethylation with sodium tetraethylborate, room temperature precollection on Tenax, isothermal gas chromatographic separation (GC), pyrolysis and cold vapour atomic fluorescence spectrometric detection (CV AFS) of mercury. The limit of detection calculated on the basis of three times the standard deviation of the blank was about 0.006 ng L(-1) for MeHg and 0.06 ng L(-1) for Hg(2+)when 300 mL of water was analysed. The repeatability of the results was about 5% for MeHg and 10% for Hg(2+). Recoveries were 90-110% for both species.     

Solid-phase microextraction for the analysis of short-chain chlorinated paraffins in water samples

A novel solid-phase microextraction (SPME) method coupled to gas chromatography with electron capture detection (GC-ECD) was developed as an alternative to liquid-liquid and solid-phase extraction for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples. The extraction efficiency of five different commercially available fibres was evaluated and the 100-microm polydimethylsiloxane coating was the most suitable for the absorption of the SCCPs. Optimisation of several SPME parameters, such as extraction time and temperature, ionic strength and desorption time, was performed. Quality parameters were established using Milli-Q, tap water and river water. Linearity ranged between 0.06 and 6 microg l(-1) for spiked Milli-Q water and between 0.6 and 6 microg l(-1) for natural waters. The precision of the SPME-GC-ECD method for the three aqueous matrices was similar and gave relative standard deviations (RSD) between 12 and 14%. The limit of detection (LOD) was 0.02 microg l(-1) for Milli-Q water and 0.3 microg l(-1) for both tap water and river water. The optimised SPME-GC-ECD method was successfully applied to the determination of SCCPs in river water samples.     

Determination of haloacetic acids in aqueous environments by solid-phase extraction followed by ion-pair liquid chromatography-electrospray ionization mass spectrometric detection.

Haloacetic acids (HAAs) were determined in different water samples by a new, fast and simple analysis method based on enrichment of 50-ml water samples at pH 1.8 by solid-phase extraction (SPE) followed by liquid chromatography (LC) separation and electrospray ionization mass spectrometric detection in the negative ionization mode. Deprotonated (M-H)-haloacetates and decarboxylated (M-COOH)- ions were detected. Different polymeric SPE sorbents were tested, and LiChrolut EN was found to be the best material for the extraction. Complete LC separation of all compounds could only be achieved by ion-pair chromatography using triethylamine as volatile ion-pairing reagent. The detection limits were in the low microg/l range. High microg/l concentration levels for the chlorinated and brominated haloacetates were found in drinking water from a drinking water treatment plant in Barcelona, and the corresponding tap water. In swimming pool water samples from Catalonia mg/l levels and in surface river water from Portugal microg/l values were detected. These results confirm other recent reports on the ubiquitous occurrence of HAAs in aqueous environments.     

Determination of trace lead, cadmium and mercury by on-line column enrichment followed by RP-HPLC as metal-tetra-(4-bromophenyl)-porphyrin chelates

This paper reports the utilization of tetra-(4-bromophenyl)-porphyrin (T(4)BPP) as a chelating reagent using Waters Xterratrade mark RP(18) column for the on-line column enrichment and the separation of trace lead, cadmium and mercury ions by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detector. When the Hg-T(4)BPP, Pb-T(4)BPP and Cd-T(4)BPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol l(-1) of pH 10.0 pyrrolidine-phosphoric acid buffer solution (containing 10% of tetrahydrofuran (THF)) as mobile phase. The chelates were retained on the top of the enrichment column. After the enrichment is finished, by switching the valve of six-ports switching valve, the retained metal-T(4)BPP chelates will be eluted by mobile phase in reverse direction and will travel towards analytical column. With THF (containing 0.05 mol l(-1), pH 10.0 pyrrolidine-phosphoric acid buffer salt) and 0.05 mol l(-1), pH 10.0 pyrrolidine-phosphoric acid buffer solution (containinging 10% THF) gradient elution as mobile phase, the chelates separation on the analytical column was satisfactory. The linearity ranges are 0.01-120 mug l(-1) for each metal ion. The detection limits (S/N=3) of lead, cadmium and mercury are 1.0, 0.5 and 1.0 ng l(-1), respectively. This method can be applied to the determination (mug l(-1)) level of lead, cadmium and mercury in drinking water with satisfactory results.     

微波萃取高效液相色谱-冷原子荧光光谱法测定沉积物中甲基汞和无机汞

建立了微波萃取高效液相色谱-冷原子荧光光谱法(MAE-HPLC-CVAFS)测定沉积物中甲基汞(MeHg+)和无机汞(Hg2+)的方法。以0.1%(V/V)2-巯基乙醇为萃取剂,用于沉积物样品中汞形态的萃取,在80℃下萃取8 min,萃取液直接注入HPLC-CVAFS系统分析。在优化条件下,MeHg+和Hg2+的检出限分别为0.58和0.48 ng/g;加标回收率分别为96.2%和95.8%;RSD(n=6)分别为5.7%和4.1%。对标准参考物质(IAEA-405和ERM-CC580)的分析结果与推荐值一致。本方法简单、快速、准确、检出限低,抗干扰能力强,具有很好的实用性和推广价值。