UNIVERSITÀ DEGLI STUDI DI TORINO

KIT PORTATILE PER ANALISI DI SPECIAZIONE MERCURIO-METILMERCURIO

The proposed technology allows a simple and quick determination of Hgtot, Hgin and CH3Hg in fish products.

The technique provides 1) a portable procedure for the pre-treatment of samples, in order to extract the analytes quantitatively; 2) the passage of the solutions in packaged cartridges with a resin developed by us (CYXAD), in order to separate the species; 3) analysis by anode stripping voltammetry using a solid gold electrode (SGE). The technique appears to be inexpensive and accurate for on-site assessment of levels of these species toxic to human health.

Patent Status

GRANTED

Priority Number

102019000005904

Priority Date

16/04/2019

License

ITALY

Market

The kit would allow for rapid screening to monitor levels of Hg and its organic forms in different matrices such as water and/or fish products, which pose a risk to human health and the environment.

This type of analysis has the advantage of being able to be carried out also in the field very quickly compared to traditional techniques, is cheap and very simple in its application.

These characteristics make the technology interesting for companies and/or organizations.

Problem

Mercury is a highly toxic element already at the level of ultratraces. It is one of the metals most involved in phenomena of bioconcentration and biomagnification along the food chain. It is present in aquatic ecosystems and, consequently, in fish, which represent the main source of human intake of Hgin and its methylated form, the most toxic, CH3Hg. Since the 1950s, the uptake of Hg through fish has steadily increased worldwide, sometimes reaching values well above safety limits. It is clear, therefore, how important it is to constantly monitor the levels of total mercury (Hgtot) and CH3Hg in fish products placed on the market.

The proposed kit would allow a targeted, user-friendly and fast analysis that makes it very competitive on the market in order to monitor that the levels of total mercury are within the legal limits (for fish products at present 1 mg/kg in predatory fish and 0.5 mg/kg in medium-small fish and mussels, as regards total mercury). The technology could also be used by unqualified personnel allowing an increase in the number of controls of different matrices of interest.

Current Technology Limitations

Currently, the official method for the determination of mercury in fish products is the Mercury Direct Analyser (DMA). This spectroscopic technique has several advantages, such as the automatic thermal decomposition of the sample, which allows to bypass the pre-treatment step, and the possibility to automatically analyze 12 samples per hour for the determination of Hgtot. At the same time, the disadvantages are numerous: DMA requires the use of gas, qualified personnel and has very high costs when compared to electrochemical methods. It also does not allow field determination and is specific to mercury. The procedure for the determination of CH3Hg by DMA requires a long extraction procedure (2 days) using organic solvents.

Determination of Hg and its species by voltammetric analysis usually requires digestion with acidic solutions in microwave ovens. In order to make the method “portable” a system has been developed that allows to perform both the pretreatment and the analysis outside a common laboratory. Always in order to make the entire procedure portable, the analyses are conducted with a portable potentiometer powered by a field battery.

A limitation of the voltammetric analyses applied to Hg/CH3Hg speciation studies is that both forms give a signal at the same potential value. Hence the development of the adsorbent material, CYXAD, which allows the separation of the two forms before the instrumental analysis phase.

Killer Application

This kit would make it possible to better understand the distribution of the two forms of mercury in aquatic ecosystems and organisms, both for environmental monitoring and for the control of fish products to protect consumer health.

The on-site applicability makes it possible to assume direct use on board fishing boats or in port locations. In addition, there would be the opportunity to monitor culture tanks, aquifers directly on the site avoiding all the steps of sampling and transport to the laboratory, reducing the time of analysis.

Our Technology and Solutions

The system consists of two phases: 1) Hgtot determination: a sample sample is pre-treated with a 1:1 acid mixture of HNO3 and H2O2, extraction is carried out with the aid of portable thermoblocks. The sample is then filtered and analyzed by square-wave anode stripping voltammetry (SW-ASV) using the portable potentiometer, with a solid gold electrode (SGE). This first step allows, using the technique of standard additions, to determine Hgtot.

2) Determination of Hgin : for speciation the extraction process is carried out using HCl, the complex chlorine mercury species forming HgCl42- and CH3HgCl; the supernatant is passed through a column packed with anionic exchange resin patented by us, CYXAD (obtained by the chemical modification of a commercial resin with an ionic liquid): Hgin is retained by the resin while CH3Hg elutes from the column. Subsequently, Hgin is eluted using HNO3 and analyzed. The concentration of CH3Hg is then calculated as the «difference» between Hgtot and Hgin.

The whole procedure was validated by analysing a certified reference material, Tuna Fish ERM-CE 464 ([Hgtot] = 5.24 +/- 0.10 mg/kg; [CH3Hg] = 5.50 +/- 0.10 mg/kg). The procedure was then tested on real samples of fresh fish, mussels, canned fish, comparing the results obtained with the method proposed with those obtained with the official methodic DMA.

Advantages

The idea is to develop a system that, compared to the existing ones, is faster, simpler, can be automated, does not require the use of organic solvents, does not require the use of gas, does not require the aid of microwaves, works at room temperature, with lower purchase and management costs. These advantages allow to quantify both HgIN and CH3Hg in fish samples even in small laboratories and/or mobile stations. This would increase the number of product checks and help to better understand the distribution of HgIN than CH3Hg along the food chain and in the environment.

Roadmap

In order to improve the kit, investments would be needed to improve the on-site applicability of the method.

Improve the process of creating cartridges so that they can be used quickly even in environments outside the laboratory.

Implement with samples of different origins in order to further validate the method.

Possible industrial developments include:

1) Production of selective disposable cartridges for speciation studies;

2) Develop on-site test kits;

3) Develop an automated instrument for speciation analysis in conventional or extemporaneous laboratories.

Valuta la tecnologia e contattaci

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Team

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