Development of advanced analytical methods for the determination of emerging pollutants in environmental waters

This thesis work was focused on the analytical determination of emerging pollutants in environmental water matrix, concerning preparative step and analysis using Gas Chromatography coupled with Mass Spectrometry (GCMS). The emerging pollutants are so defined because they have been recognized only recently as pollutants and regulatory and monitoring plans are not yet implemented at Italian and European level. Pharmaceuticals and Personal Care Products (PPCPs) are considered emerging contaminants, they describe a large class of chemical contaminants that can originate from human usage and excretions and veterinary applications. There are a large number of different substances used as medicines, during and after treatment, humans and animals excrete a combination of intact and metabolised pharmaceuticals, many of which are generally soluble in water and have been discharged to the aquatic environment with little evaluation of possible risks or consequences to humans and environment. In addition, the chemicals that are components of personal care products (PCPs) number in the thousands, the world’s people consume enormous quantities of skin care products, dental care products, soaps, sunscreen agents, and hair styling products. PCPs continuously enter the wastewater after their regular use during showering or bathing. Recent studies indicate the potential widespread occurrence on low-level concentrations (ng-μg/L) of PPCPs in the aquatic environment. Therefore, there’s critical need for efficient and reliable analytical methods to address the occurrence concentrations, and fate of the PPCPs in environment. GC-MS has been the basic tool for environmental analyses of various organic pollutants and it has been the approach of this study choice because of its superior separation and identification capabilities. The activity has been concentrated on the development of sample preparation procedures that could be fast, cost-effective and environmentfriendly for the analysis of PPCPs. It’s known that sample pre-treatment causes an analysis bottleneck that typically accounts for over 60% of the total analysis time. The work was focused on evaluation and optimization of different extraction techniques for treatment of water matrix. There are fundamentally two kinds of approach for parameters optimization. One Factor At Time (OFAT) method involves the testing of factors, or causes, one at a time instead of all factors are changed at once. Even more people, prominent text books and academic papers currently favour design of experiments (DOE) approach; it’s a statistically multivariate method for screening and/or optimization of different factors at the same time (multiple factors are changed at once). It shows several relevant advantages over OFAT approach: it requires less runs for the same (sometimes more) precision in effect estimation, it can estimate interactions and it provides a knowledge (and optimal settings of factors) in the whole experimental domain, where OFAT can miss them. For these reasons this approach was chosen for several published works, using in particular Central Composite Design (CCD) or Box-Behnken Design (BBD). Two different extraction procedure have been studied: Solid Phase Extraction (SPE) and Solid Phase Micro Extraction (SPME). The first technique was evaluated in order to optimize extraction step of 25 PCPs, including fragrances, PAHs, antioxidants, UV-filters, plasticizers, and pesticides, from water, using OFAT approach. The optimized parameters were different: SPE sorbent, type and volume of eluent, elution rate, and evaporation procedure. The better recovery yield considering the totality of PCPs were found extracting with a Strata-X SPE cartridge, using a volume of 15 mL of Ethyl Acetate as solvent, operating with slow flow rate, and evaporating at 40°C of temperature. Under these con ditions the procedure achieves a recovery higher than 70% for most PCPs investigated (with LOD ranged from 5 to 10 pg injected on GC), this result makes the developed method suitable for comprehensive chemical profiling of PCPs in various aqueous matrices. It is clear that higher recovery values can be achieved only for selected PCPs using specific target-compound methods. That it was done for method optimization for determination of two synthetic phenolic antioxidants and their five main metabolites in water. This is the first published method dedicated solely to the determination of this chemical class in water samples. The methodology was developed using SPE approach with derivatization before GC-MS analysis. Extraction on 10 mg Oasis HLB cartridges provides a satisfactory enrichment factor for environmental samples avoiding the need of solvent evaporation and reducing SPE costs and organic solvent wastes. After extraction, polar metabolites are derivatized with MTBSTFA to produce stable, less polar analytes that are determined by GC-MS at low levels. The usage of two surrogate internal standards results in a method providing good accuracy, with relative recoveries between 80 and 110%, and limits of detection (2-44 ng/L). The application of the method to wastewater and river samples showed BHT and BHT-Q as the compounds in higher concentrations in wastewater (up to 800 ng/L) and the metabolites BHT-CHO and BHTCOOH as the most resistant to water treatment, being at the 10-100 ng/L in sewage and river samples. In this work the optimization was done with an experimental design approach, using a Box-Behnken design (BBD). This work was developed in collaboration with University of Santiago de Compostela (E). SPME technique was investigated in order to extract a mixture of several PCPs, evaluating extraction time and temperature and desorption time and temperature. A simple SPME method has been developed for the simultaneous GC-MS determination of 23 PCPs (i.e. antioxidants, PAHs, UV-filters, pesticides, fragrances, plasticizers, that display log Kow values > 3.2) at trace levels in water. An Inscribed Central Composite (CCI) design approach was employed for investigate extraction temperature and time, and desorption temperature and time. A direct immersion mode was used for extraction from a fixed sample volume. The optimum SPME operating conditions have been defined as: extraction time of 90 min at a temperature of 80°C, desorption time of 11 min at 260°C. Under these conditions the procedure provides low detection limits (<= ppb) and satisfactory reproducibility (RSD%<=1%) for most of the PCPs investigated. The analysis was then extended to more polar compounds, for a total of 21 PPCPs that display a range of log Kow between 1.2 and 6.4 (i.e. antiseptic, antinflammatory drugs, estrogens, UV-filters) with the necessity of derivatize the compounds before GC analysis. A on-fiber after extraction approach was chosen for SPME derivatization, using silylation agent. The derivatization can be performed in only 30.5 minutes with a very small consumption of silylation reagent and without need of high temperature. Under the optimized conditions of extraction, derivatization and desorption, the procedure provides low detection limits (<= 1 ppb for the non polar analytes and <=35 ppb for the derivatized ones) and satisfactory reproducibility (RSD% <=10% or 20%) for most of the PPCPs investigated. The PhD project, in his totality, was a logic progressive work, expanding the study in term of kind of analytes studied, extraction techniques and optimization approach. A preliminary and careful study was carried out in order to properly understand the current situation and the possible research developments of interest. The study was initially focused on less polar analytes (PCPs), then extending to more polar ones (PPCPs). It was firstly took in consideration the SPE technique, going to more innovative and preferable on several points of view SPME. The expanded range (in particular polarity range) of analytes makes necessary a derivatization step before GC-MS analysis, for these reason the subsequent step was the optimization of a method that includes SPME-derivatization. Also considering the optimization approach, the work started using OFAT optimization, this approach was left after the first work for the more accurate and precise DOE. These works led to development of multiresidual analytical method suitable for the comprehensive analysis of this kind of pollutants in water matrix. These methodologies may be the basis of water monitoring for temporal and spatial changes.