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Vacancy:   University of Insubria in Como (Italy9: Frontal Chromatography ICP-MS for the speciation analysis of mercury






Starting date: February 1st 2023
Salary: 1450 euro/month
Application deadline: December 15th 2022, 12:00 CET (UTC+1)


Mandatory requirements
  • MSc in chemistry or equivalent
  • PhD in chemistry, industrial chemistry, environmental science or equivalent
  • Expected skills
    • Experience in the use of ICPMS
    • Experience in clean techniques for trace elements determination
    • Experience in speciation analysis
Context
The development of novel speciation methods for trace elements and the improvement of existing ones have recently attracted much research interest (see recent reviews in [1–3]). Present speciation methods are commonly based on the hyphenation of separation techniques (e.g. High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC) or Ion Chromatography (IC)) to very sensitive spectroscopic or spectrometric detection [1,2,4,5]. Nevertheless, high resolution chromatographic separations require two separate instrumentations (HPLC or GC plus Atomic Fluorescence Spectroscopy (AFS) or Inductively Coupled Plasma – Mass Spectrometry (ICP-MS)) with associated purchase and running costs, and usually exceed the needed resolution, when a two-species problem is tackled (e.g., the separation of Cr(VI) from Cr(III)). Such shortcomings have been recently addressed in our research group by introducing an innovative Frontal Chromatography ICP-MS approach (FC-ICP-MS)[6]. A short column packed with the adequate stationary phase is positioned between the peristaltic pump and the nebulizer in the usual, commercially available ICP-MS configuration, with no need of an additional HPLC pump and injection valves. The short column (2-6 cm) is packed with relatively large diameter particles (50 micrometer): the sample may be easily run through the stationary phase by the ICP-MS peristaltic pump. The low number of theoretical plates only separates species with markedly different properties (ionic/neutral, anionic/cationic, etc.), as it is often the case in elemental speciation analysis (e.g. Cr(VI) vs. Cr(III), As(V) vs. As(III), Hg2+ vs. CH3Hg+). The FC-ICP-MS approach was demonstrated by the separation of inorganic As(III) and As(V) [6], resulting in an astonishingly simpler and faster (120 s) procedure with respect to the fastest reported HPLC-ICP-MS method [7]. We further developed the methodology and achieved the selective detection of Cr(VI) down to 0.026 µg/kg in the presence of up to 500’000-fold excess of Cr(III) with a one-minute procedure based on the complete blocking of Cr(III) by a cationic exchange column [8]. More recently, the selective determination of organomercury species was also achieved by a similar approach [9]. The developed procedure blocks inorganic mercury by an anion exchange column and selectively determines organomercury species.
The latter topic, i.e. mercury speciation analysis, attracted much attention due to the major risk posed to human health by mercury species [10–12], its species specific toxicity, toxicokinetic and environmental behavior. Accordingly, mercury species were determined in all the environments where a risk to human or ecosystem health may be foreseen: soils [13], rice paddy [14,15], seawater [16], fish farming sites [17] and fish meat [18].

Project description and activities
The present project aims at setting up and validating a FC-ICP-MS procedure for the speciation analysis of mercury, that enables the simultaneous detection of inorganic and organic mercury species. The procedure should ideally be applicable to abiotic (soil and sediments) and biological matrices (plankton, fish tissue and human hair).
The programmed research activities may be divided in five work packages:

  1. Definition of a FC-ICP-MS procedure for Hg speciation by the detection of inorganic (i-Hg) and organic (o-Hg) mercury species by an actual frontal chromatography approach (i.e. two distinct fronts for i- and o-Hg).
  2. Definition of the best extraction/dissolution method for solid samples. Extraction procedures will be preferred as they yield a simpler matrix: beside providing quantitative extraction of mercury species, the extractant solution should be compatible with the separation procedure defined in point 1. Different extractants may be also required to deal with matrix specific issues and expected mercury concentrations. As an example, when low Hg concentrations are expected, no dilution of the extractant is possible before analysis and the extractant composition should accordingly be compatible with the FC determination.
  3. Definition of the best conditions to avoid the well-known mercury memory effects [19]. This is a further constrain for mercury analysis that may be tackled by both adjusting the sample composition (provided this do not interfere with the separation) or by adding a suitable reagent after the chromatographic separation.
  4. Measurement of the figures of merit and validation of the method by Standard Reference Materials (SRMs). The customary figures of merit will be determined, like LOD, LOL, accuracy and precision, but special emphasis will be clearly given to selectivity issues aiming at defining: i) the ranges of i-Hg and o-Hg that permit the selective determination of the two species; ii) which organic species are determined: methylmercury is largely the most abundant organic species, but ethyl-Hg and phenyl-Hg are occasionally present in very low amounts.
  5. Application of the methodology to marine and freshwater food webs. The ongoing cooperation with the ecology research group of prof. Roberta Bettinetti will provide samples from the lacustrine and marine food web [20,21]. Terrestrial sample (soils) will be also investigated.

REFERENCES
1 Marcinkowska, M. et al. Talanta 161, 177–204 (2016)
2 Rekhi, H. et al. Crit. Rev. Anal. Chem. 47, 524–537 (2017)
3 Clough, R. et al. J. Anal. At. Spectrom. 35, 1236–1278 (2020)
4 Ellis, L. A. et al. J. Chromatogr. A 774, 3–19 (1997)
5 Clough, R. et al. J. Anal. At. Spectrom. 33, 1103–1149 (2018)
6 Spanu, D. et al. Anal. Chem. 91, 13810–13817 (2019)
7 Marcinkowska, M. et al. Talanta 144, 233–240 (2015)
8 Spanu, D. et al. J. Hazard. Mater. 412, 125280 (2021)
9 Spanu, D. et al. Anal. Chim. Acta 1206, 339553 (2022)
10 Kim, K.-H. et al. J. Hazard. Mater. 306, 376–385 (2016)
11 Sundseth, K. et al. Int. J. Environ. Res. Public Health 14, (2017)
12 Beckers, F. et al. Crit. Rev. Environ. Sci. Technol. 47, 693–794 (2017)
13 Fernandes, I. O. et al. Water. Air. Soil Pollut. 232, (2021)
14 Amin, S. et al. Environ. Technol. Innov. 23, (2021)
15 Zhao, L. et al. Ecotoxicol. Environ. Saf. 195, (2020)


Contact:
For more information please contact: damiano.monticelli@uninsubria.it

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