EP2047233A1

EP2047233A1 - Activated mercury collector and method for the selective determination of mercury species

Info

Publication number: EP2047233A1
Application number: EP07786129A
Authority: EP
Inventors: Michael Schuster; Kerstin Leopold; Lena Harwardt
Original assignee: Analytik Jena AG; Technische Universitaet Muenchen
Current assignee: Analytik Jena AG; Technische Universitaet Muenchen
Priority date: 2006-08-02
Filing date: 2007-07-17
Publication date: 2009-04-15
Also published as: WO2008014884A1; AU2007280776A1

Abstract

A method for producing an activated mercury collector is provided, comprising the following steps: a) Application of mercury onto a substrate surface that contains a precious metal, b) Heating of the surface to 300°C - 1000°C, c) Cooling of the surface to below 100°C, d) Repetition of steps a) to c), if necessary. In addition, an activated mercury collector obtainable according to this method, and a method for the selective determination of mercury species in a liquid medium, are provided.

Description

Activated mercury collector and method for the selective determination of

mercury species

The invention relates to a method for producing an activated mercury collector, an activated mercury collector obtainable by this method and a method for the selective determination of mercury species in liquid media.

Most of the methods of mercury species analysis developed to date in the art use gas or high performance liquid chromatography (hereafter referred to as GC or HPLC, respectively) as an enrichment and / or separation process. However, the organo-mercury compounds present in environmental samples, such as the halogens of methyl and ethylmercury, show very poor chromatographic properties, e.g. strong tailing, decomposition and low separation efficiency, which is why GC recommends Grignard derivatization of the Hg species with ethyl or butyl chains to dialkyl species.

Derivatization or derivatization reaction is understood as meaning chemical reactions in which a derivative, ie a derived substance of similar structure, is formed. Derivatives are substances which, instead of an atom, have another atom or a whole atomic group or in which one or more atoms / groups of atoms have been removed. However, as recent work has shown, significant systematic errors in the determination of methylmercury may occur if derivatization with tetraethylborate as the derivatization reagent precedes. Using isotope dilution mass spectrometry analysis could be shown that in the derivatization reaction in the presence of methyl mercury halides converted to Hg ^0th The degree of conversion increases with increasing halide concentration and at 6.9 mg Cl ^' / g solution already 83% of the contained MeHg ^{+ is converted} to Hg ⁰ . This poses also the correctness of the determination of inorganic mercury and methylmercury by means of the automated speciation analyzer (ASA) in question. Although a switch to other derivatization reagents is conceivable, the search for alternative possibilities for speciation analysis seems reasonable.

In the case of HPLC, derivatization is not necessary, but the detection limits reached are usually in the μg / l range (micrograms per liter) and thus clearly too high for many environmental samples. In seawater samples e.g. The mercury contents are in the range of ng-pg / l (nano- to picogram per liter) and thus require a 3-6 orders of magnitude better detection capability.

Other prior art methods utilize coupling of GC or HPLC with ICP-MS and employ isotopic dilution analysis (IVA). The IVA is useful for detecting and eliminating systematic errors in sample preparation and for validating procedures. However, it is more expensive compared to other methods, since in addition to the actual sample preparation and standards of different species must be prepared with known isotopic composition and mixed with the sample.

Considering environmental samples from the field of hydrosphere, such as seawater, so a distinction of inorganic and organic mercury is very meaningful, since here almost exclusively methylmercury is present as the organic mercury component. Other main components are the inorganic species Hg ⁰ and Hg ²⁺ . For these determinations simpler methods are meaningful, which do without a high-performance chromatographic separation, but are more sensitive to detection. So far, few works are known in this field. Some are based on solid phase extraction / adsorption of Hg species using sulfur-containing ligands, such as 2-mercaptobenzimidazole or 1,2-bis (o-aminophenylthio) ethane, immobilized or chemically bonded to appropriate columnar materials. Advantageous are processes that work automatically in a flow injection analysis system (FIAS).

Other non-chromatographic separation methods use different variants of the cold vapor technique, which is actually considered as the classical method for the determination of total mercury in the lower concentration range. For the total mercury determination, aqueous samples are first mixed with a strong oxidizing agent to destroy organic components. Subsequently, the resulting Hg ^{2+ is} reduced to Hg ⁰ and the "cold vapor" (CoId Vapor, CV) discharged from the liquid with an inert gas stream is measured by means of atomic absorption or atomic fluorescence spectrometry A not negligible advantage of the cold vapor technique is the possibility of enrichment of mercury vapor by amalgamation on a gold or silver surface. The amalgamation proceeds at room temperature and the desorption can take place thermally.

A disadvantage of the cold vapor technique, however, is that first an equilibrium between liquid and gaseous phase must be set and by a more or less incomplete phase transfer an error in the determination of the mercury species contained in the liquid phase occurs. This error is also difficult to quantify because the completeness of the phase transfer depends on a large number of parameters, such as the size of the mercury drops in the liquid medium, the temperature, the strength and duration of the inert gas flow, etc.

For the distinction of inorganic and organic mercury, it was proposed to carry out a selective reduction of the inorganic mercury to Hg ⁰ in a part of the sample, followed by a direct, direct measurement. Subsequently, in a second part of the sample, total mercury is measured by the method described above. The chromatographic methods for the separation of all species require a great deal of work and equipment and can only achieve a determination in the ultratrace range by coupling several methods and devices.

However, previously developed, simpler methods that dispense with a precise species separation of organic and inorganic species and allow the distinction necessary for assessing the hazard potential of inorganic and organic mercury, determine organo-mercury only by difference.,. not both parameters, ie inorganic mercury in addition to organic mercury, are determined, but a parameter and the sum of total mercury are determined. Especially in environmental samples, this can cause large systematic errors, since the concentration difference between organic and inorganic mercury is usually very large. A difference, in which 99% of inorganic mercury is subtracted from 100% total mercury and thus "determined" as 1% organic mercury, is analytically extremely questionable.

Since the different types of mercury, in particular inorganic mercury species on the one hand and organic mercury species on the other hand, show different biological and toxicological properties - organomercury compounds are much more toxic and more bioaccumulated than inorganic species - a distinction between inorganic and organic mercury is useful and necessary in the analysis. It would therefore be desirable to have a method which enables a simple and rapid determination of inorganic and organic mercury species. The object of the invention is therefore to provide a mercury collector and a method for the determination of mercury species, in particular to provide a method for the selective determination of inorganic and organic mercury species, which overcome the disadvantages of the prior art.

This object is achieved by an activated mercury collector obtainable by a process comprising the steps:

a) applying mercury to a noble metal-comprising surface of a substrate, b) heating the surface to 300-1000 ^° C., c) cooling the surface to below 100 ^° C., d) optionally repeating steps a) to c).

Surprisingly, with an activated mercury collector thus obtainable, the total mercury content of a sample can be determined in a simple and rapid manner; the sum of elemental mercury, inorganic mercury ions and organic mercury species, without the need for prior derivatization or chemical transformation of the individual mercury species.

The above object is further achieved by a method for determining traces of mercury in a liquid medium, comprising the steps of:

a) contacting the liquid medium with a mercury collector comprising a substrate having a surface containing precious metal, b) washing and drying the surface of the mercury collector, c) releasing the mercury bound to the surface by eluting or heating the surface, and d) quantitative determination of the released mercury.

The above object is further achieved by a method for the selective determination of inorganic and organic mercury species in a liquid medium, wherein A) for the determination of inorganic mercury species, the above method is performed with a non-activated mercury collector and then B) in the remaining liquid medium contained in the organic mercury species can be determined quantitatively. With this method, it is possible without error-prone difference formation of measured values to determine selectively in a process sequentially inorganic and organic mercury species in a liquid sample.

For the purposes of the invention, mercury species are understood to mean elemental mercury (hereinafter also referred to as Hg ⁰ ), inorganic mercury ions (essentially Hg ₂ ²⁺ and Hg ²⁺ ) and ionic and neutral compounds of mercury in various oxidation states, all of which are either dissolved, colloidally dissolved or undissolved. Inorganic mercury species are understood to mean all of the abovementioned species which contain no Hg-C bond, ie elemental mercury and mercury ions without organic ligands. Organic mercury species are understood to mean all the species mentioned which contain at least one Hg-C bond.

Natural waters contain mercury mainly in the form of mercury (II) ions (hereinafter also referred to as Hg ²⁺ ), elemental mercury (hereinafter also referred to as Hg ⁰ ) and mono- and dimethylmercury (hereinafter also referred to as MeHg).

With the method according to the invention, the parallel determination of organic and inorganic mercury species and of the total mercury in liquid media, such as aqueous solutions, organic solutions, melts, etc. is made possible. In particular, the method of the invention is suitable for the determination of mercury species in natural aquatic samples, e.g. Drinking water, seawater, seawater, river water, rainwater,

Mineral water, industrial water, table water, purified and unpurified municipal and industrial wastewater, industrial rinsing and cooling waters, or mercury species contained in organic solvents or other organic liquids, and solutions obtained by dissolving or digesting samples (such as fish, plants, soil samples) or

Melt.

In the context of the invention it has been found that traces of various mercury species (such as Hg ⁰ , Hg ₂ ²⁺ , Hg ²⁺ , MeHg ⁺ ) can be deposited on a specially activated noble metal surface and thus enriched. The activation of the noble metal surface is carried out according to the invention by the following cycle:

a) applying mercury to a noble metal-comprising surface of a substrate, b) heating the surface to 300-1000 ^° C., c) cooling the surface to below 100 ^° C., d) optionally repeating steps a) to c). Through this activation cycle, an activated mercury collector is obtained according to the invention. Surprisingly, not only elemental mercury (Hg ⁰ ) is deposited on such activated mercury collector, but also inorganic mercury ions (especially Hg ²⁺ and Hg ₂ ^{2 *} ) contained in a liquid medium and organic mercury species such as RHg, RHg ⁺ in ionic or neutral form and R ₂ Hg, wherein R is an organic, ie carbon-containing, radical, for example an alkyl or aryl group. It is believed that impurities contained in the liquid medium and / or the organic residues of organic mercury species in the liquid medium serve as redox partners, and the activated surface of the mercury collector functions both as a catalyst and as a deposition partner.

The application of the mercury is preferably carried out by depositing elemental mercury (Hg ⁰ ) on the substrate surface. The temperature of the substrate surface is in step a) preferably less than 100 ° C, more preferably less than 50 ⁰ C, and most preferably 10-30 ° C. In the case of precious metals forming amalgams, for example gold, an at least partial amalgamation generally takes place.

In step b) the noble metal surface is heated at 300-1000 ⁰ C, preferably at 500-950 ⁰ C, more preferably at 700-900 ⁰ C. In this case, the mercury is removed from the surface (thermodesorbed). The subsequent cooling in step c) is preferably below 60 ⁰ C, particularly preferably below 30 ⁰ C, more preferably to 10-30 ⁰ C and most preferably to room temperature (16-25 ^C C).

Without being bound by the invention, it is believed that the roughness in the nanostructured area (nanorughness) of the noble metal surface is produced by the activation cycle of steps a) to c), which leads to the activation of the mercury collector.

It has also been found that a particularly good activation can be achieved if the cooling process in step c) takes place in less than 30 minutes, preferably in less than 10 minutes and particularly preferably less than 2 minutes. It is assumed that a

Restructuring in terms of a smoothing of the surface can be so particularly effectively prevented and the nanorughness is conserved, so to speak. Also the

Heating step b) is preferably carried out in less than 30 minutes, more preferably less than 10 minutes, and most preferably less than 2 minutes, so that the noble metal surface is not kept at high temperature for too long, which would favor surface restructuring. A preferred embodiment of the invention provides that the steps a) to c) are repeated in order to increase the activation of the noble metal surface. Particularly preferably, the steps a) to c) are repeated at least twice and even more preferably repeated three to five times.

The surface of the substrate preferably comprises gold or a gold alloy. With these metals, particularly active mercury collectors can be produced. Among the gold alloys, those with other noble metals are preferred, for example, ruthenium, rhodium, palladium, osmium, iridium, platinum and silver. Particularly preferred are gold-platinum alloys.

The substrate used to make the activated mercury collector may be of noble metal or may comprise a support coated with noble metal. The suitable, preferred and particularly preferred noble metals described above are also suitable for the substrate, preferred and particularly preferred. Substrate and support may be in various forms, with those forms having a high surface area per volume being preferred, for example a grid, a mesh, a wire mesh, a fiber aggregate, a particle aggregate or a powder. The substrate is preferably a grid of gold or a gold alloy or a carrier coated with gold or a gold alloy. The carrier can be, for example, a particle accumulation or a powder, which are coated with the noble metal, in particular gold or a gold alloy. In a particularly preferred embodiment of the invention, the support comprises a zeolite or graphite, which are characterized by a large active surface area.

The invention further relates to an activated mercury collector, which is obtainable by the method described above. The activated mercury collector comprises a substrate having a surface containing noble metal and having passed through the above-described activation cycle with steps a) to d). The surface of the mercury collector preferably has a roughness in the nanostructure area (nanoroughness). Further, it is preferred that the surface of the activated mercury collector consists of gold or a gold alloy, in particular a gold-platinum alloy.

Furthermore, the invention relates to the use of the activated mercury collector for the determination of traces of mercury in a liquid medium.

In the context of the invention it has also been found that traces of elemental mercury from a liquid medium, for example a dispersion or solution, can be deposited quantitatively on a precious metal surface, in particular a gold-platinum surface, which is the described activation cycle has not gone through, and can be elemental mercury so separated from other dissolved mercury species.

The invention therefore relates to a method for determining traces of mercury in a liquid medium, comprising the steps of a) contacting the liquid medium with a mercury collector comprising a substrate having a surface containing precious metal, b) washing and drying the surface of the mercury collector c) releasing the mercury bound to the surface by eluting or heating the surface, and d) quantitating the released mercury.

As a mercury collector, an activated or an unactivated mercury collector can be used. For the purposes of the invention, a non-activated mercury collector means a mercury collector comprising a substrate which has a surface which contains precious metals and has not passed through the activation cycle described above with steps a) to d).

If a non-activated mercury collector is used as the mercury collector, the elemental mercury contained in the liquid medium can be selectively determined, since only this is deposited on the non-activated mercury collector. In contrast to the above-described cold vapor technique of the prior art, no equilibrium between liquid and gaseous phase must be set so that the invention

Method has no determination error as a result of a more or less incomplete phase transfer of elemental mercury. Also the not activated

Mercury collector preferably comprises gold or a gold alloy as precious metal. Particularly preferred is gold.

Advantageously, all or individual steps of the process can be carried out in the flow stream process. For this purpose, in step a), the mercury collector is introduced into a stream of the liquid medium, which takes place within a short time, an almost complete deposition of elemental mercury. A volume flow of 1.5 to 15 ml / min is preferred. Likewise, the washing and / or elution can be carried out in the flow stream process. The flow stream process can be carried out continuously or batchwise. With particular advantage, the activated or non-activated mercury collector can be used in the fluid flow process in the form of a wound-up network, whereby a particularly effective flow of the mercury collector and thus rapid quantitative separation can be achieved. In order to determine all inorganic mercury species with the non-activated mercury collector using the method according to the invention for the determination of mercury traces in liquid media, a reducing agent can be added to the liquid medium before contacting the liquid medium with the mercury collector (step a)) have proven mild reducing agents, which are understood as reducing agents which selectively reduce inorganic mercury ions, but not organic mercury species to elemental mercury, for example tin (II) salts, hydrochloric acid, ascorbic acid, citric acid, formaldehyde, hydroxylamine and formic acid, especially in the form of aqueous Solutions. Preference is given to aqueous solutions having a concentration of 2 to 5% by weight. The reduction preferably takes place in a temperature range from 0 to 100 ^° C., in particular from 20 to 80 ^° C. This results in the reduction of the inorganic mercury ions, in particular Hg ²⁺ and Hg ₂ ²⁺ , to elemental mercury, which can then be deposited on the non-activated mercury collector in the method described above.

Dissolved inorganic mercury species (mainly Hg ²⁺ ) are quantitatively converted to elemental mercury with the mild reducing agents mentioned above (reaction equation I), with organic mercury species not undergoing a reaction (reaction equation II).

Hg ²⁺ + Sn (II) → Hg ⁰ + Sn (IV) (I)

RHg ⁺ + Sn (II) → no reaction (II)

R: alkyl, e.g. Methyl, ethyl, phenyl

To determine the total mercury content is in the process in a preferred

Embodiment of the activated mercury collector used.

For washing the mercury collector in step b), it is expediently rinsed with water, an aqueous solution or an organic solvent in order to remove any impurities. Preference is given to rinsing with ultrapure water, slightly acidified water, electrolyte-containing water, acetone, ethanol, methanol or a complexing agent-containing solution.

For subsequent drying in step b), an inert gas stream is preferably passed over the surface of the mercury collector, for example an argon or nitrogen stream. To accelerate drying, the inert gas stream and / or the Mercury collector can be heated, preferably up to 150 ° C, more preferably up to 120 ⁰ C.

The release of the mercury bound to the surface in step c) can be effected by elution or heating. For example, for the elution complexing or oxidizing solutions can be used, by which the deposited mercury is brought into solution (chemisorption). The released mercury can then be measured immediately or redeposited and then quantified. By heating the surface of the mercury collector or heating the entire mercury collector, the deposited mercury is thermodesorbed. This can be recorded by means of a gas or liquid flow and fed to a meter, eg an AFS or AAS measurement. The temperature in the heating step depends inter alia on the nature of the noble metal and is preferably 100-1000 ^° C., more preferably 300-900 ^° C.

The present invention also relates to a method for the selective determination of inorganic and organic mercury species in a liquid medium, wherein for the determination of inorganic mercury species, the method described above for the determination of mercury traces in a liquid medium is carried out and then the organic mercury contained in the remaining liquid medium - be determined quantitatively.

The method for the selective determination of inorganic and organic mercury species in a liquid medium thus comprises the steps

A) for the determination of inorganic mercury species a) contacting the liquid medium with a non-activated mercury collector, comprising a substrate having a surface containing precious metal, b) washing and drying the surface of the mercury collector, c) releasing the surface-bound Mercury by elution or heating of the surface, and d) quantitative determination of the released mercury,

subsequently

B) quantitatively determining the organic mercury species contained in the remaining liquid medium. The process is preferably carried out in the flow stream process. In a further preferred embodiment of the invention, a reducing agent is added to the liquid medium for common detection of elemental mercury and inorganic mercury ions prior to step a). Preferred are the mild reducing agents described above.

In order to distinguish between elemental mercury and other inorganic mercury species, in a first pass the process comprising steps a) to d) is carried out on an unactivated mercury collector without the addition of a reducing agent, then a reducing agent is added and the process of steps a) to d ) in a second pass with the non-activated mercury collector repeated. The organic mercury species contained in the liquid medium are not reduced to elemental mercury by the mild reducing agents described above and are then quantified.

The determination of the organic mercury species in step B) can be carried out by conventional methods, for example adding an oxidizing agent to the liquid medium, then excess oxidizing agent is optionally subsequently destroyed with a mild reducing agent, for example hydroxylamine, and the inorganic mercury species generated by oxidation, in particular Hg ²⁺ , can be quantitatively determined by known methods of the prior art, for example by atomic fluorescence spectrometry, atomic absorption spectrometry or mass spectrometry. Alternatively, after the addition of the oxidizing agent, a reducing agent may be added to reduce the inorganic mercury species produced from the organic mercury species to elemental mercury. These can then be quantified, preferably by the method described above using the non-activated or activated mercury collector.

In a preferred embodiment, the activated mercury collector of the present invention is used in step B) for the determination of the organic mercury species, whereby a particularly simple, fast and precise process control is made possible. In this embodiment, step B) of the above-described method for the selective determination of inorganic and organic mercury species in a liquid medium preferably comprises the steps

a) contacting the remaining liquid medium with an activated mercury collector, b) washing and drying the surface of the mercury collector, c) releasing the mercury bound to the surface by eluting or heating the surface, and d) quantitating the amount of mercury released.

According to the invention, the method for the selective determination of different mercury species and of total mercury is subdivided into the sub-steps, which are explained in more detail below, and which can be used in different orders or only one part for analysis as required. The mercury collector (activated or not activated) is also abbreviated to collector.

Selective reduction of inorganic mercury species to elemental mercury: By addition of suitable mild reducing agents, such as tin (II) salt solution (eg 2 wt .-% SnCl ₂ ), aqueous hydrochloric acid solution (eg 5 wt .-% HCl) or aqueous ascorbic acid (eg Wt% ascorbic acid) to the sample, all inorganic Hg species are reduced to Hg ⁰ . The reaction can be carried out in a temperature range of 0-100 ⁰ C, preferably at 20-80 ⁰ C. It can be carried out in batch mode by adding the reducing agent (usually a few μl), or integrated in a flow system in the online process by combining the sample and the reducing agent, for example, with similar volume flows. This step can be described by the following reaction equation (III):

Hg ²⁺ _aq + 2 HCl + SnCl ₂ → Hg ° _aq + 2 H ⁺ _aq + SnCl ₄ (III).

Separation and Enrichment of the Dissolved Elemental Mercury in / on a Selective Collector: According to the invention, the Hg ⁰ contained in the solution is adsorbed and / or amalgamated by contact with a suitable surface, such as a gold-platinum surface.

The separation and enrichment can in the temperature range of 0-100 ⁰ C, preferably in

Range of 20-80 ⁰ C take place. It can be batched or integrated online into a flow system by passing the sample over the surface at a volumetric flow in the range of typically 1.5-15 ml min ^-1 . The arrangement for

Separation of the inorganic mercury is referred to below as a selective or non-activated collector.

This step can be described schematically in the following way:

Hg ⁰ ^ ₊ RHg ⁺ _aq - laβ »- RHg ⁺ _{aq {| V)} Separation and Enrichment of Total Mercury in / on an Activated Collector: According to the invention, the Hg species contained in the solution are adsorbed and / or amalgamated by contact with a suitable surface, such as a pretreated, activated gold-platinum surface. The separation and enrichment may be in the temperature range of 0-100 ^C. C., preferably in the range of 20-80 ⁰ C. It may be batched or integrated into a flow system online by passing the sample over the surface at a volumetric flow in the range of typically 1.5 - 15 ml min ^-1 Mercury is referred to below as an activated collector.

Optional decomposition, optional enrichment and measurement of the organic mercury species: The organic mercury species remaining in solution can either be destroyed (eg oxidatively by addition of 1-10 wt.% BrCl solution, the excess of which is mixed with a hydroxylamine solution of 0.1 wt. % is rendered harmless) and then their concentration are determined by known methods with or without prior enrichment (eg AFS, AAS) or they are measured directly by suitable known methods (eg mass spectrometry). This step can be described with the following reaction equations (V and VI):

CH ₃ Hg ⁺ _aq + BrCl → Hg ²⁺ _aq + Cl ^' + CH ₃ Br (V)

4 BrCl + 2 NH ₂ OH → 4 Br ^" _aq + N ₂ + 2 H ₂ O + 4 HCl (VI)

Optional enrichment of the organic mercury species: According to the invention, the organic mercury species remaining in solution can be enriched on an activated surface.

Rinsing the Collector (s): The arrangement for separating the inorganic Hg is treated with a suitable liquid medium such as e.g. ultrapure water, slightly acidified water, electrolyte-containing water, acetone, ethanol, methanol, or a complexing-containing solution.

Drying of the collector (s): The arrangement for the separation of Hg is passed through with a suitable gaseous medium, such as argon or nitrogen, and dried. The gas can be used in a temperature range of 0-150 ⁰ C, preferably between 20-120 ° C.

Thermodesorption of mercury: The enriched in the collectors Hg is released by heating the collector again as Hg ⁰ and can be in a gas or Liquid flow are absorbed. The collector is heated to a temperature in the range of 100-1000 ⁰ C for this purpose.

Chemisorption of Mercury: The Hg enriched in the collectors is purified by elution with suitable solutions, e.g. releasing complexing and / or oxidizing solutions.

Measurement of the thermodesorbed mercury: The released Hg ⁰ can be fed directly by means of a gas flow to a measuring device (eg AFS or AAS measurement) or re-enriched and then measured.

Measurement of chemisorbed mercury: The released Hg can either be redeposited on an activated gold surface and measured after thermodisorption or, after reduction to Hg ⁰ by means of a gas flow, fed directly to a measuring device (eg AFS or AAS measurement) or re-enriched and then measured become.

The advantage of the method according to the invention is the selective separation of different mercury species from a solution on a noble metal surface, which is used for separation and subsequent analysis. The first part of the process, the selective reduction of inorganic mercury species to elemental mercury, may also be omitted and the method used to determine dissolved elemental mercury already present in the sample.

The device, which can be provided as an accessory for a complete analyzer (eg online device), according to an embodiment of the invention consists of a flow injection system, which includes, inter alia, a Qυarzglasrohr and a gold or a gold-platinum network and the rinsing, the Drying and heating included. According to the invention, other glass-like and / or inert materials, such as, for example, ceramic, glassy carbon, metals, plexiglass or plastics, as well as materials coated with inert materials, may also be used instead of quartz glass, depending on the temperature range and temperature resistance. Instead of the gold-platinum network / alloy, other metals and metal combinations or adsorbents, such as zeolites, as well as metal-coated or vapor-deposited materials, such as zeolites or graphite may be provided. Instead of the network, other structures, such as wool, beads and / or wire of the materials mentioned can be used. According to one embodiment of the invention, the flow system is coupled to an atomic fluorescence spectrometer (AFS), which enables the determination of mercury in very low concentrations. The invention also includes the coupling with other analytical methods, such as atomic absorption spectrometry, atomic emission spectrometry or mass spectrometry.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention.

The following examples illustrate the invention.

example 1

A methylmercury standard solution is freshly prepared by dissolving methyl mercuric chloride in ultra-pure water and diluted to a concentration of 10 ng Hg I ^-1. The content of elemental mercury is determined, as well as the inorganic and total mercury after addition of tin (II) chloride solution (2 wt .-%). For the determination of the total mercury content, in each case a part of the solution was admixed with a BrCl solution (0.5% by volume in 0.5% by volume HCl) for the oxidative decomposition of the Hg species. The excess was reacted after 12 h with hydroxylamine solution (0.06 wt .-%) and then measured by standard cold vapor technique of Hg content. The result is shown in FIG. It has been shown that methylmercury does not react with the reducing agent tin (II) chloride solution to inorganic, even if the solutions are allowed to stand for up to 10 days.

Example 2

Hg ⁰ standard solutions of different concentrations are prepared and examined for their Hg content before and after passing through the non-activated (selective) mercury collector (with gold surface). Using the selective collector, no measurement signal appears in the AFS measurement (all Hg ⁰ from the solution was separated), while without the collector, the measurement signals increase in accordance with the mercury concentration. The result is shown in FIG. The deposited mercury is released again by heating the collector and also measured. These signals also increase in accordance with the Hg concentrations of the starting solutions.

Example 3

A methylmercury standard solution is made fresh by dissolving methylmercuric chloride in ultrapure water and diluted to a concentration of 10 ng Hg I ^-1 The solution is tested for its Hg content before and after passing (passing through) the non-activated mercury collector. In this case, methylmercury is not separated from the solution at the selective collector according to Example 2, since both with and without the use of the collector give similar readings in the solution. The result is shown in FIG.

Example 4

Methylmercury standard solutions of different concentrations are prepared fresh in ultrapure water. A specific volume of each solution will be activated over the

Passed collector and this subsequently rinsed, dried and released by heating the deposited Hg again. The released Hg is measured by AFS. It turns out that methylmercury is precipitated from the solution at the activated collector and after thermodisorption a linear increase of the measuring signals can be seen. The result is shown in FIG.

Example 5

Determination of inorganic and organic mercury in seawater

FIGS. 5a and 5b show an exemplary embodiment of the mercury collector according to the invention and FIG. 6 shows an exemplary flow system. A few milliliters of a seawater sample (see Fig. 6 "Sample") contains the inorganic and organic mercury species in a concentration of 0.1-100 ng I ^"1 , in particular in the range of 1- 20 ng l ^{" 1} (volume flow 7 ml min ^"1 ), at 70 ⁰ C first in the flow system with stannous chloride solution (2 wt .-% SnCl ₂ , volume flow 2.5 ml min ^{" 1} , see Fig. 6 "selective reducing agent") are added (see. FIG. 6 "T1") and selectively reduces inorganic mercury to elemental mercury (compare FIG. 6 "RC1"). Subsequently, the elemental mercury is selectively amalgamated on a non-activated mercury collector in the form of a gold-platinum mesh, which is wound on a quartz glass capillary and is located in a quartz glass tube (see Fig. 6 "Collector").

The organic mercury species remaining in the solution are mixed with a bromine chloride solution (BrCl 4% by weight, volume flow 2.5 ml min ^-1 , cf., FIG. 6 "Oxidizing agent for decomposing the organyls") (compare FIG ") and so oxidatively destroyed (see Fig. 6" RC2 "). The excess oxidizing agent is mixed with a hydroxylamine solution (0.1% by weight, volume flow 2.5 ml min ^-1 , see Fig. 6 "Auxiliary reagent") (see Fig. 6 "T3") and harmless (See Fig. 6 "RC3".) Thereafter, the solution for measuring mercury is transported to a CV-AFS.

The collector is first rinsed with ultrapure water (volume flow 15 ml min ^'1 , rinsing solution, see Fig. 6 "T4") and then with argon (volume flow 250 ml min ^"1 , see Fig. 6" carrier gas "; Fig. 6 "T4") dried. Thereafter, the amalgamated mercury is thermally desorbed at a temperature in the range of 350-1000 ° C. The heating of the collector is achieved by applying a voltage (400 V) to a heating wire, which is mounted as a spiral around the collector. An argon gas stream (volume flow 250 ml min ^'1 , see Fig. 6 "carrier gas") transports the mercury vapor via a droplet separator made of quartz glass and a drying section (25 cm water-permeable membrane tube, see Fig. 6 "membrane for dehumidification") to the measuring cuvette AFS device in which the mercury measurement takes place.

Claims

claims

1. A process for producing an activated mercury collector, comprising the steps of a) applying mercury to a surface of a substrate comprising precious metal, b) heating the surface to 300-1000 ^° C., c) cooling the surface to below 100 ^° C., d) optionally repeating steps a) to c).

2. The method according to claim 1, characterized in that the surface in step b) to 500 - 950 ⁰ C is heated.

3. The method according to claim 1 or 2, characterized in that the surface in step c) is cooled to below 60 ⁰ C.

4. The method according to any one of claims 1 to 3, characterized in that steps a) to c) are repeated at least twice.

5. The method according to any one of claims 1 to 4, characterized in that the substrate consists of precious metal or coated with a noble metal carrier.

6. The method according to any one of claims 1 to 5, characterized in that the noble metal is gold or a gold alloy.

7. The method according to claim 6, characterized in that the gold alloy is a gold-platinum alloy.

8. Activated mercury collector, obtainable by a process according to one of claims 1 to 7.

9. Use of an activated mercury collector according to claim 8 for the determination of traces of mercury in a liquid medium.

10. A method of determining traces of mercury in a liquid medium, comprising the steps of a) contacting the liquid medium with a mercury collector comprising a substrate having a surface containing precious metal, b) washing and drying the surface of the mercury collector, c) Releasing the surface-bound mercury by eluting or heating the surface, and d) quantitating the released mercury.

11. The method according to claim 10, characterized in that the method is carried out in the flow stream method.

12. The method according to claim 10 or 11, characterized in that prior to step a) to the liquid medium, a reducing agent is added.

13. The method according to any one of claims 10 to 12, characterized in that the surface of the mercury collector comprises gold or a gold alloy.

14. The method according to any one of claims 10 to 13, characterized in that a mercury collector activated according to claim 8 is used as a mercury collector.

15. A method for the selective determination of inorganic and organic mercury species in a liquid medium, characterized in that A) for the determination of inorganic mercury species, the method according to one of

Claims 10 to 13 is performed with a non-activated mercury collector and then

B) quantitatively determining the organic mercury species contained in the remaining liquid medium.

16. The method according to claim 15, characterized in that in step B) to the remaining liquid medium, an oxidizing agent is added, then optionally a reducing agent is added and then the organic mercury species are determined quantitatively.

17. The method according to claim 15, characterized in that in step B) an activated mercury collector according to claim 8 is used.

A method according to claim 17, characterized in that step B) comprises the steps of a) contacting the remaining liquid medium with an activated mercury collector according to claim 8, b) washing and drying the surface of the mercury collector, c) releasing it to the surface bound mercury by elution or heating of the surface, and d) quantitative determination of the released mercury.