In this article, a dataset from a collaborative non-target screening trial organized by the NORMAN Association is used to review the state-of-the-art and discuss future perspectives of non-target screening using high resolution mass spectrometry in water analysis. A total of 18 institutes from 12 European countries analysed an extract of the same water sample collected from the River Danube with either one or both of liquid and gas chromatography coupled with mass spectrometric detection. This article focuses mainly on the use of high resolution screening techniques with target, suspect and non-target workflows to identify substances in environmental samples. Specific examples are given to highlight major challenges such as isobaric and co-eluting substances, dependence on target and suspect lists, formula assignment, the use of retention information and the confidence of identification. Approaches and methods applicable to unit resolution data are also discussed. While most substances were identified using high resolution data with target and suspect screening approaches, some participants proposed tentative non-target identifications. This comprehensive dataset revealed that non-target analytical techniques are already considerably harmonized between the participants, but the data processing remains time-consuming. Although the dream of a "fully-automated identification workflow" remains elusive in the short-term, important steps in this direction have been taken, exemplified in the growing popularity of suspect screening approaches. Major recommendations to improve non-target screening include better integration and connection of desired features into software packages, the exchange of target and suspect lists and the contribution of more spectra from standard substances into (openly accessible) databases.

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Environmental analytical chemists face the challenge of investigating thousands of potential 13 organic pollutants that may be present in the aquatic environment. High resolution mass 14 spectrometry (HRMS) hyphenated to chromatography offers the possibility of detecting a 15 large number of contaminants without pre-selection of analytes due to its accurate-mass full-16 spectrum acquisition at good sensitivity. Interestingly, large screening can be made even 17 without reference standards, as the valuable information provided by HRMS allows the 18 tentative identification of the compound detected. In this work, hybrid quadrupole time-of-19 flight (QTOF) MS was combined with both liquid and gas chromatography (using a single 20 instrument) for screening of around 2,000 compounds in waters. This was feasible thanks to 21 the use of atmospheric pressure chemical ionization source in GC. The screening was 22 qualitatively validated for around 300 compounds at three levels (0.02, 0.1, 0.5 µg/L), and 23 screening detection limits were established. Surface, ground water and effluent wastewater 24 samples were analyzed, detecting and identifying a notable number of pesticides and 25 transformation products, pharmaceuticals, personal care products, and illicit drugs, among 26 others. This is one of the most universal approaches in terms of comprehensive measurement 27 for broad screening of organic contaminants within a large range of polarity and volatility in 28 waters. 29 30 KEYWORDS: liquid chromatography, gas chromatography, quadrupole time of flight 31 mass spectrometry, universal screening, water samples, organic micropollutants 32 33 3 34 INTRODUCTION 35Over the last decades, environmental pollution has become a matter of increasing concern 36 due to the high number of both regulated and unregulated organic pollutants that can be 37 present in environmental waters. The majority of these compounds, such as pesticides, 38 pharmaceuticals, drugs of abuse, surfactants, biocides, personal care products, sweeteners, 39 etc. are originated by human use. They can enter in the surface water (and even groundwater) 40 mainly via treated and untreated wastewater [1][2]. Despite the evident advances in analytical 41 chemistry, the comprehensive determination of organic contaminants in waters is still a 42 challenge at present. The main difficulty arises from the elevated number of compounds (in 43 addition to their metabolites and/or transformation products) that may be present in the 44 samples. This fact, together with the very different physico-chemical properties of analytes, 45makes the application of a single analytical methodology, appropriate for all potential 46 contaminants, unfeasible. 47 Most analytical methods developed until now have used chromatographic techniques coupled 48to mass spectrometry (MS) analyzers, as single quadrupole or ion trap, and in the last decade, 49 triple quadrupole. In these target methods, the list of analytes rarely exceeds 200-300 50 compounds, and relevant contaminants other than the ...

The potential of gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC/TOF-MS) for screening of organic pollutants in water has been explored. After optimization of the solid-phase microextraction (SPME) step, where parameters such as fiber selection and addition of salt were studied, this extraction technique was applied to the analysis of different types of water samples. Investigation of 60 target organic pollutants, including pesticides, octyl/nonyl phenols, pentachlorobenzene, and polycyclic aromatic hydrocarbons (PAHs) was carried out by evaluating the presence of up to five representative m/z ions per analyte, measured at high mass accuracy, and the attainment of their Q/q (Q, quantitative ion; q, confirmative ion) intensity ratio. This strategy led to the detection of 4-t-octylphenol, simazine, terbuthylazine, chlorpyrifos, terbumeton, and terbutryn in several water samples at low part-per-billion levels. Full spectrum acquisition data generated by the TOF-MS analyzer also allowed subsequent investigation of the presence of polybrominated diphenyl ethers and several fungicides in samples after MS data acquisition, without the need to reanalyze the water samples. In addition, nontarget analysis was also tested by application of a deconvolution software. Several organic pollutants that did not form a part of the list of contaminants investigated were identified in the water samples, thanks to the excellent sensitivity of TOF-MS in full spectrum acquisition mode and the valuable accurate mass information provided by instrument. Bisphenol A, the antioxidant 3,5-di-tert-butyl-4-hydroxy-toluene (BHT), its metabolite 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO), the polycyclic musk galaxolide, and the UV filter benzophenone were some of the compounds present in the water samples analyzed. SPME in combination with GC/TOF-MS has been proved to be an attractive and powerful approach for the rapid screening of multiclass organic pollutants in water, with very little sample manipulation and no solvent consumption. This combination provides to the analyst with information-rich MS data that facilitates the reliable identification of many different organic compounds in samples.