Mercury speciation in thawed out and refrozen fish samples by gas chromatography coupled to inductively coupled plasma mass spectrometry and atomic fluorescence spectroscopy

Different sub-sampling procedures were applied for the determination of mercury species (as total mercury Hg, methylmercury MeHg⁺ and inorganic mercury Hg²⁺) in frozen fish meat. Analyses were carried out by two different techniques. After the sample material was pre-treated by microwave digestion, atomic fluorescence spectroscopy (AFS) was used for the determination of total Hg. Speciation analysis was performed according to the following procedure: dissolution of sample material in tetramethylammonium hydroxide (TMAH), derivatisation with sodium tetraethylborate (NaBEt₄), extraction into isooctane and measurement with gas chromatography inductively coupled plasma mass spectrometry (GC-ICPMS) for the identification and quantification of methylmercury (MeHg⁺) and inorganic mercury (Hg²⁺). The concentration range of total Hg measured in the shark fillets is between 0.9 and 3.6 g g^–1 thawed out shark fillet. Speciation analysis leads to 94% Hg present as MeHg⁺. Homogeneity, storage conditions and stability of analytical species and sample materials have great influence on analytical results. Sub-sampling of half-frozen/partly thawed out fish and analysis lead to significantly different concentrations, which are on average a factor of two lower.     

Mercury content of hair from normal and poisoned persons

Several hundred samples of human head hair were analyzed to establish the range and variation of mercury concentration in “normal” people and in persons ingesting organic mercury compounds. Instrumental neutron activation analysis was used. The 77 keV line of¹⁹⁷Hg was counted on a Ge(Li) detector. The pattern of concentration variation along hair was shown to be a more reliable criterion for hair individualization than average concentration values. The hair mercury contents of “normal” people in uncontaminated areas were 0.1–4 and 1–12 ppm, respectively. People who had ingested a mercury compound but showed no symptoms had hair mercury concentrations of from a few ppm to 300 ppm. Mild symptoms appeared with a 120–600 ppm hair mercury level, moderate with 200–800 ppm, and severe with 400–1600 ppm. There was no correlation with sex or age, except that infants showed more severe symptoms than expected, and people over 55 had mild or no symptoms with hair mercury levels of 1000 ppm and higher.     

UV irradiation controlled cold vapor generation using SnCl2 as reductant for mercury speciation.

A simple and ultrasensitive method, which was based on cold vapor generation (CVG) coupled to atomic fluorescence spectrometry (AFS), was proposed for speciation analysis of inorganic mercury (Hg2+) and methylmercury (MeHg) in water samples. In the presence of UV irradiation, all the mercury (MeHg+Hg2+) in a sample solution can be reduced to Hg0 by SnCl2; without UV irradiation, only Hg2+ species can be determined. So the concentration of MeHg can be obtained from the difference of the total mercury and Hg2+ concentration; thus, speciation analysis of Hg2+ and MeHg was simply achieved without chromatographic separation. Under the optimized experimental conditions, the limits of detection were 0.01 ng mL-1 for both Hg2+ and MeHg. The sensitivity and limit of detection were not dependent on the mercury species, and a simple Hg2+ aqueous standard series can be used for the determination of both Hg2+ and MeHg.     

Highly sensitive multiresponsive chemosensor for selective detection of Hg2+ in natural water and different monitoring environments

A new chemosensor RF1 that combines a ferrocene unit and a rhodamine block via the linkage of a carbohydrazone binding unit was designed and prepared for the highly selective detection of Hg (2+) in natural water. This chemosensor displays great brightness and fluorescence enhancement following Hg (2+) coordination within the limit of detection for Hg (2+) at 1 parts per billion (ppb). The fluorescence intensities are nearly proportional to the amount of Hg (2+) at the ppb level. It is capable of distinguishing between the safe and the toxic levels of inorganic mercury in drinking water. Hg (2+)-binding also arouses the absorption of the rhodamine moiety in RF1 significantly with the chromogenic detection limit for Hg (2+) at 50 ppb. The conventional UV-vis spectroscopic method thus has the potential to provide the critical information about the mercury hazard assessment for industrial wastewater discharging. The obvious and characteristic color change of the titration solution from colorless to pink upon the addition of Hg (2+) demonstrates that RF1 can be used for "naked-eye" detection of Hg (2+) in water. The Hg (2+) complexation also causes a significant shift of the redox potential about the ferrocene/ferrocenium couple. The electrochemical responses provide the possibility to quantitative analysis of Hg (2+) at the parts per million (ppm) level. Preliminary investigations in natural water samples including seawater and freshwater indicate that RF1 offers a direct and immediate Hg (2+) detection in complex media, pointing out its potential utility in environment monitoring and assessment. The responses of RF1 are Hg (2+) specific, and the chemosensor exhibits high selectivity toward Hg (2+) over other Group 12 metals, alkali, alkaline earth metals, and most of the divalent first-row transition metals. The RF1-Hg (2+) complex is successfully isolated and the Hg (2+)-binding is reversible. The crystal structure and spectral properties of its congener RF2 that contains one ferrocene group and two rhodamine 6G moieties were also investigated for a comparison.     

Selective Hg(II) detection in aqueous solution with thiol derivatized fluoresceins

The syntheses and photophysical properties of mercury sensors 2 and 3 (MS2 and MS3), two asymmetrically derivatized fluorescein-based dyes designed for Hg(II) detection, are described. These sensors each contain a single pyridyl-amine-thiol metal-binding moiety, form 1:1 complexes with Hg(II), and exhibit selectivity for Hg(II) over other Group 12 metals, alkali and alkaline earth metals, and most divalent first-row transition metals. Both dyes display superior brightness (Phi x epsilon) and fluorescence enhancement following Hg(II) coordination in aqueous solution. At neutral pH, the fluorescence turn-on derives from greater brightness due to increased molar absorptivity. At higher pH, photoinduced electron transfer quenching of the free dye is enhanced, and the Hg(II)-induced turn-on also benefits from alleviation of this pathway. MS2 can detect ppb levels of Hg(II) in aqueous solution, demonstrating its ability to identify environmentally relevant concentrations of Hg(II).     

Detection of mercury and phenylmercury ions using DNA-based fluorescent probe

A DNA probe labeled with a 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) quencher and a carboxyfluorescein (FAM) donor at its 5'- and 3'-termini can be used for the detection of Hg(2+) ions and phenylmercury ions (PhHg(+)). This DNA probe possesses a random coil structure that changes into a hairpin-like structure upon binding Hg(2+) and PhHg(+) ions. As a result, the fluorescence of the FAM unit decreased through quenching between the donor and the quencher. In the presence of ethylenediaminetetraacetic acid (EDTA), the DNA probe allowed the selective detection of PhHg(+) ions at concentrations as low as 70.0 nM, mainly as a result of T-Hg(2+)-T coordination and π-π stacking between the Ph unit and DNA bases. A linear correlation existed between the fluorescence intensity and the concentration of PhHg(+) ions over the range from 0.10 to 1.0 μM (R(2) = 0.99). After acid hydrolysis and neutralization of the samples, all of the mercury species are converted to Hg(2+) ions, allowing us to use the DNA-based probe to determine the concentrations of total mercury species at the nM level. The practicality of this probe has been validated by the analyses of pond water and fish samples, showing its advantages of sensitivity, selectivity, and simplicity.     

Lead and mercury sensing by calixarene-based fluoroionophores bearing two or four dansyl fluorophores

A detailed study on the photophysical and complexing properties of calixarenes bearing two and four dansyl derivatives (Calix-DANS2 and Calix-DANS4) in a CH3CN/H2O mixture (60:40 v/v) is reported. Calix-DANS2 shows a high selectivity towards Hg2+ over interfering cations (Na+, K+, Ca2+, Cu2+, Zn2+, Cd2+ and Pb2+) and a sensitivity in the 10(-7) mol L(-1) concentration range. The complexation of mercury ion induces a strong fluorescence quenching due to a well-defined electron transfer process from the fluorophore to the metal center. Calix-DANS4 exhibits an extremely high affinity for Pb2+ with a high selectivity over various competing ions. The unprecedented detection limit (4 microg L(-1)) is fully compatible with the level defined by the World Health Organisation. The affinity of Calix-DANS4 for Pb2+ can be rationalized by the activation of the inert pair of electrons on Pb2+. The number of fluorophores involved in the complexation can be determined from a careful time-resolved fluorescence characterization.     

Determination of mercurial species in fish by inductively coupled plasma mass spectrometry with anion exchange chromatographic separation

This work demonstrated the feasibility of mercury speciation analysis by anion exchange chromatographic separation with inductively coupled plasma mass spectrometry detection. For the first time, by complexing with the mobile phase containing 3-mercapto-1-propanesulfonate into negatively charged complexes, fast separation of inorganic mercury (Hg²⁺), monomethylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) was achieved within 5 min on a 12.5-mm strong anion exchange column. The detection limits for Hg²⁺, MeHg, EtHg and PhHg were 0.008, 0.024, 0.029 and 0.034 μg L⁻¹, respectively. The relative standard deviations of peak height and peak area (5.0 μg L⁻¹ for each Hg species) were all below 3%. The determined contents of Hg²⁺, MeHg and total Hg in a certified reference material of fish tissue by the proposed method were in good accordance with the certified values with satisfactory recoveries. The relative errors for determining MeHg and total mercury were −2.4% and −1.2%, respectively, with an acceptable range for spike recoveries of 94–101%. Mercury speciation in 11 fish samples were then analyzed after the pretreated procedure. The mercury contents in all fish samples analyzed were found compliant with the criteria of the National Standards of China.     

基于寡核苷酸链的汞离子荧光生物传感器

基于G-四链体结构和卟啉类化合物N-甲基卟啉二丙酸IX(NMM)结合产生强烈的荧光,利用T-Hg(Ⅱ)-T错配对汞离子(Hg2+)的特异性识别,建立了一种简单、灵敏、高效的Hg2+检测新方法.在富含鸟嘌呤(G)寡核苷酸链中,引入了大量胸腺嘧啶(T).在没有Hg2+存在时,可以自发形成G-四链体结构,与NMM结合产生强烈的荧光;在Hg2+存在时,可与另一条富含T序列的互补链通过T-Hg(Ⅱ)-T特异性结合,形成双链DNA分子,从而导致G-四链体结构不能产生.优化后最佳实验条件为:缓冲溶液的pH=6.7,20 mmol/LKCl,2.5 μmol/L NMM,反应时间为2h.在优化条件下,体系的荧光强度变化值与Hg2+浓度呈现良好的线性关系,线性范围为50～ 1000 nmol/L,检出限为22.8 nmol/L(30).此生物荧光传感器对Hg2+具有良好的选择性.实际水样中Hg2+的加标回收率为106.1％ ～ 107.8％,可以满足实际水样品中Hg2+的检测要求.     

对羟基苯甲醛缩邻氨基苯甲酸与汞的荧光猝灭反应及其应用

合成了一种新的席夫碱荧光试剂--对羟基苯甲醛缩邻氨基苯甲酸(HBAA).研究了HBAA与汞离子的络合反应及其反应条件,HBAA在390.0 nm处有一强荧光峰,汞离子存在时,可与其形成稳定的络合物并使HBAA的荧光猝灭.利用该反应建立了荧光测定痕量汞的新方法,方法的线性范围为0 ～90.0 μg/L,检出限为0.61 μg/L.考察了40种常见共存离子的干扰影响,结果表明合成的HBAA试剂具有很高的选择性.该方法简便、快速,可用于矿泉水、自来水、河水中痕量汞的测定.     

Determination of very low levels of dissolved mercury(II) and methylmercury in river waters by continuous flow with on-line UV decomposition and cold-vapor atomic fluorescence spectrometry after pre-concentration on a silica gel-2-mercaptobenzimidazol sorbent

A new, simple and sensitive method for the simultaneous determination of mercury(II) and methylmercury chloride at sub-ng l⁻¹ levels in river waters is described. Inorganic and organic mercury were preconcentrated from fresh water samples simultaneously on a laboratory-made column containing 2-mercaptobenzimidazol loaded on silica gel and then quantitatively eluted with 0.05 M KCN solution and 2.0 M HCl to desorp inorganic and methylmercury species, respectively. After irradiation with an intensive UV source, MeHg⁺ was decomposed and mercury vapours were generated from inorganic and organic mercury using an acidic SnCl₂ solution in a continuous flow system and were subsequently determined with a cold vapour atomic fluorescence (CV-AFS) spectrometer. Detection limits (3σ) were 0.07 and 0.05 ng l⁻¹ (as Hg) for mercury(II) chloride and methylmercury chloride, respectively. Relative standard deviations of method (%R.S.D.) were 8.8 and 10 for inorganic and organomercuric species in the river water, respectively. The analysis of real samples, taken from different rivers, showed that inorganic mercury levels ranged from 4.0±0.6 to 12±1 ng l⁻¹ (as Hg and 95% confidence limit) and methylmercury levels at 0.2±0.02 ng l⁻¹(as Hg).     

Lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene: synthesis, characterization, and selective recognition of Hg2+ and its sensitivity toward pyrimidine bases

The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest.     

Solution cathode glow discharge induced vapor generation of mercury and its application to mercury speciation by high performance liquid chromatography-atomic fluorescence spectrometry

A novel solution cathode glow discharge (SCGD) induced vapor generation was developed as interface to on-line couple high-performance liquid chromatography (HPLC) with atomic fluorescence spectrometry (AFS) for the speciation of inorganic mercury (Hg(2+)), methyl-mercury (MeHg) and ethyl-mercury (EtHg). The decomposition of organic mercury species and the reduction of Hg(2+) could be completed in one step with this proposed SCGD induced vapor generation system. The vapor generation is extremely rapid and therefore is easy to couple with flow injection (FI) and HPLC. Compared with the conventional HPLC-CV-AFS hyphenated systems, the proposed HPLC-SCGD-AFS system is very simple in operation and eliminates auxiliary redox reagents. Parameters influencing mercury determination were optimized, such as concentration of formic acid, discharge current and argon flow rate. The method detection limits for HPLC-SCGD-AFS system were 0.67 μg L(-1) for Hg(2+), 0.55 μg L(-1) for MeHg and 1.19 μg L(-1) for EtHg, respectively. The developed method was validated by determination of certified reference material (GBW 10029, tuna fish) and was further applied for the determination of mercury in biological samples.     

Determination of mercury in the presence of chloride by means of the ternary complex Hg(II)/xylenol orange/amberlite La-2 in non-aqueous media

The system Hg(II)/Xylenol Orange/Amberlite LA-2 dissolved in 1:1 v v 3-methylbutan-1-ol/chloroform medium has been studied. A 3:2:2 complex is formed, which is suitable for analytical measurements at temperatures <18 degrees . This complex allows the determination of mercury in the range 0.19-5.5 ppm with a molar absorptivity of 2.12 x 10(4).mole(-1).cm(-1) at 600 nm and extraction pH of 7.4 (standard deviation 0.065 ppm). The proposed method has been applied to the determination of mercury in contaminated water with a high chloride content.     

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。     

钳状杯[4]芳烃为探针的固态PVC膜汞离子选择性电极

全固膜选择性电极(All solid-state selective electrode,ASSE)综合晶体电极和膜电极的优点,具有线性范围宽、检测限低,能真实地体现膜性能等特点,ASSE主要有涂线电极(Coated wire electrode,CWE)、填充固体电解质或配合物的膜电极和电沉积型聚合物膜电极等。     

Potentiometric titration of trace amounts of mercury with dithiooxamide

Titration with dithiooxamide in potassium hydrogenphthalate medium (pH 5–6) is suitable for the determination of mercury in concentrations above 0.05 ppm. The precision in the range 0.05–1.0 ppm Hg is ? 4%. Significant amounts of sulphate, nitrate, Zn²⁺, Cd²⁺ and Pb²⁺ and small amounts of Ni²⁺, Co²⁺ and Al³⁺ can be tolerated, but Fe³⁺, Cu²⁺ and Ag⁺ interfere.     

Gold nanoparticles generated through "green route" bind Hg2+ with a concomitant blue shift in plasmon absorption peak

We discuss here a quick, simple, economic and ecofriendly method through a completely green route for the selective detection of Hg(2+) in aqueous samples. Here we exploited the ability of chitosan to generate gold nanoparticles and subsequently to act as a stabilizer for the formed nanoparticles. When chitosan stabilized gold nanoparticles (CH-Au NPs) are interacted with Hg(2+) a blue shift for its localized surface plasmon resonance absorbance (LSPR) band is observed. The blue shift is reasoned to be due to the formation of a thin layer of mercury over gold. A concentration as low as 0.01 ppm to a maximum of 100 ppm Hg(2+) can be detected based on this blue shift of the CH-Au NPs. While all other reported methods demand complex reaction steps and costly chemicals, the method we reported here is a simple, rapid and selective approach for the detection of Hg(2+). Our results also show that the CH-Au NPs have excellent selectivity to Hg(2+) over common cations namely, Pb(2+), Cd(2+), Mn(2+), Fe(2+), Ag(1+), Ce(4+), Ni(2+), and Cu(2+).     

Flow Injection Analysis of Mercury/Cold Vapor Atomic Fluorescence Spectrophotometry

Abstract

A new flow injection system for the determination of mercury by the cold vapor atomic fluorescence method is described. A sample solution (64 μ1) is injected into a stream of 0.1 M hydrochloric acid, which is mixed with a stream of 3% tin (II) chloride solution in a mixing joint. The combined stream is carried through a reaction coil for reduction of Hg (II) to Hg (0) and subsequently introduced into a specially designed gas-liquid separation vessel. Then the vaporized mercury is swept into a flow type fluorescence cell with a continuous flow of argon after removal of water in the gas phase through a condenser. Mercury is excited with an electrodeless discharge lamp as a source and the mercury fluorescence at both 184.9 and 253.7 nm is measured with a solar-blind photomultiplier. This method allows about 35 determinations of mercury in aqueous samples per hour. The calibration curve is linear over the 0–20 ppb range of mercury. The limit of detection (S/N = 3) is 0.008 ng (0.12 ppb × 64 μ1) and the coefficient of variation is below 1% for the 1–20 ppb solutions (n=10).     

A rapid,simple method for the determination of total mercury in fish and hair by cold-vapour atomic absorption spectrometry

Fuming nitric acid and acidified potassium permanganate are used to pre-digest fish or hair samples in Pyrex culture tubes. Cold-vapour atomic absorption spectrometry is used to detect the elemental mercury which is generated by reduction in a syringe. The absolute detection limit of the method is 0.66 ng Hg, and at levels of 0.14 and 0.60 parts per million (ppm) the standard deviations are ± 0.009 and ±0.008 ppm, respectively. One person can handle batches of 50–100 samples per day including standards and blanks.