Development of Improved SPE-LC-HRMS/MS Methods for Identification of Emerging Contaminants, Risk Assessment and Early Warning System

It is well known that some molecules from various emerging contaminants (EC) subclasses pose difficulties in terms of abatement, remediation, and chemical analysis. For example, glyphosate and analogue herbicides, have specific chemical properties (i.e. high polarity, ionic character, high affinity towards metals) which make them recalcitrant to common water and wastewater treatment processes, and thus potentially harmful for humans, animals, and the environment due to spread contaminations. For the same reason, these molecules are also difficult to be accurately quantified in different matrices at ppb or ppt levels. Other ECs, such as algal cyanotoxins, are present as multiple congeners in very complex matrices (i.e., seawater), therefore, their determination at low concentration is very challenging, also considering the lack of commercially available reference standards for the most common congeners. In this view, the present research work presents the development and optimization of novel materials, both nano-based or molecular-selective, to be used as adsorbent phases for emerging contaminants of concern (i.e., GLY and analogue herbicides, and algal cyanotoxins), for both environmental and analytical applications. Remediation and Solid-phase extraction (SPE) materials selective for GLY were prepared by two different approaches, via magnetic and non-magnetic metal/metal oxide-based nanomaterials. The structural and chemical prepared materials were characterized by means of Fourier transform infra-red spectroscopy (FTIR), Dyanamic light scattering (DLS), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Electron dispersive X-Ray spectroscopy (EDX) and X-ray diffraction (XRD). The capacity of adsorbing GLY from the aqueous solution was tested by treating different test solutions with the sorbent phase and measuring the residual GLY concentration using ion chromatography high-resolution mass spectrometry (IC-HRMS). The developed metal-functionalized magnetic nanoparticles showed to be an efficient, fast and selective method to remove GLY and its analogues from the aqueous solutions, along with an ease of application. In particular, these nanomaterials had a greater absorption capacity than that reported in the literature for other comparable materials and were capable of entirely remediating GLY and its equivalents at concentration levels more than twice as high as normal environmental contaminations. Magnetic nanoparticles with titanium and zirconium functionalization were also able to completely remediate these contaminants in real water samples. The possibility of regenerating these magnetic nanoparticles for multiple cycles was also evaluated and a desorption protocol, based on a treatment with ammonium hydroxide, was proposed. Other materials were also prepared throough TiO2 nanocasting, based on the selective behaviour of Ti(IV) towards GLY and analogues. In particular two different ion-exchange resins, namely Lewatit® K2621 (polystyrene divinyl benzene, pS-DVB) and polyvinyl benzene (pDVB) were used as nano cast to ensure a nanometric growth of TiO2 in their free pores. As compared to conventional bulk forms of TiO2, the application of the newly synthesized nanostructured titanium oxide materials showed superior performances in extracting GLY from the aqueous phase (TiO2-anatase and TiO2-rutile). Excellent results were also obtained for these materials in this instance after testing them using a variety of parameters, including working pH, contact time, analyte concentration, and analyte/sorbent ratio. Nevertheless, further rigorous testing is required to determine whether these materials are SPE stationary phases.