Analysing polypeptide antibiotics residues in animal muscle tissues: The crucial role of HRMS.

A confirmatory method for the determination of polypeptide antibiotics (bacitracin, colistin, and polymyxin B) in muscle samples has been developed. Extraction is performed with acidified methanol, and a clean-up step by solid-phase extraction with polymeric cartridges is applied. Separation by ultra-high performance liquid chromatography (UHPLC) is carried out using a solid core C18 column and gradient elution with water/acetonitrile containing 0.2% formic acid. High-resolution mass spectrometry (HRMS) (Q-Orbitrap) detection using different working modes has proved to be highly advantageous in eliminating interfering signals from endogenous matrix components. The analytical method has been successfully validated according to Commission Regulation 2021/808/EU and is currently used in a public health laboratory involved in veterinary medicines residue surveillance activities.

Sources of persistent organic pollutants and their physiological effects on opportunistic urban gulls.

Urbanization is associated with drastic shifts in biodiversity. While some species thrive in urban areas, the impact of inhabiting these human-altered environments on organism physiology remains understudied. We investigated how exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) affects the physiology of yellow-legged gulls (Larus michahellis) inhabiting a densely populated, industrialized city. We analyzed blood samples from 50 gulls (20 immatures and 30 adults) and assessed 27 physiological parameters and biomarkers related to xenobiotic protection, health, and feeding habits in these same individuals. We also tracked the movements of 25 gulls (15 immatures and 10 adults) to identify potential sources of persistent organic pollutants (POPs). Both adult and immature gulls primarily inhabited urban areas, followed by marine habitats. Immature gulls spent more time in freshwater, landfills, and agricultural areas. Bioaccumulated ΣPCB (median = 92.7 ng g-1 ww, 1.86-592) and ΣPBDE (median = 1.44 ng g-1 ww, 0.022-9.58) showed no significant differences between age and sex groups. Notably, immature males exhibited the highest correlations with POP concentrations, particularly with the activity of carboxylesterases (CEs), suggesting a higher sensitivity than adults. These findings highlight the potential of plasmatic CEs in immature yellow-legged gulls as effective tracers of POPs exposure and effects, offering insights into the anthropogenic impacts on urban biodiversity.

Exposure to secondhand and thirdhand smoke in private vehicles: Measurements in air and dust samples.

BACKGROUND: This study aimed to estimate airborne nicotine concentrations and nicotine, cotinine, and tobacco-specific nitrosamines (TSNAs) in settled dust from private cars in Spain and the UK. METHODS: We measured vapor-phase nicotine concentrations in a convenience sample of 45 private cars from Spain (N = 30) and the UK (N = 15) in 2017-2018. We recruited non-smoking drivers (n = 20), smoking drivers who do not smoke inside the car (n = 15), and smoking drivers who smoke inside (n = 10). Nicotine, cotinine, and three TSNAs (NNK, NNN, NNA) were also measured in settled dust in a random subsample (n = 20). We computed medians and interquartile ranges (IQR) of secondhand smoke (SHS) and thirdhand smoke (THS) compounds according to the drivers' profile. RESULTS: 24-h samples yielded median airborne nicotine concentrations below the limit of quantification (LOQ) (IQR:

Measurement of airborne nicotine, as a marker of secondhand smoke exposure, in homes with residents who smoke in 9 European countries.

OBJECTIVE: Smoke-free policies are effective in preventing secondhand smoke (SHS) exposure, but their adoption at home remains largely voluntary. This study aimed to quantify SHS exposure in homes with residents who smoke in Europe according to households' characteristics, tobacco consumption habits, and national contextual factors. METHODS: Cross-sectional study (March 2017-September 2018) based on measurements of air nicotine inside 162 homes with residents who smoke from nine European countries. We installed passive samplers for seven consecutive days to monitor nicotine concentrations. Through self-administered questionnaires, we collected sociodemographic information and the number of individuals who smoke, smoking rules, frequency, location, and quantity of tobacco use in households. Country-level factors included the overall score in the Tobacco Control Scale 2016, the smoking prevalence, and self-reported SHS exposure prevalence. Nicotine concentrations were analyzed as continuous and dichotomous variables, categorized based on the limit of quantification of 0.02 µg/m3. RESULTS: Overall, median nicotine concentration was 0.85 µg/m3 (interquartile range (IQR):0.15-4.42), and there was nicotine presence in 93% of homes. Participants reported that smoking was not permitted in approximately 20% of households, 40% had two or more residents who smoked, and in 79% residents had smoked inside during the week of sampling. We found higher nicotine concentrations in homes: with smell of tobacco smoke inside (1.45 µg/m3 IQR: 0.32-6.34), where smoking was allowed (1.60 µg/m3 IQR: 0.68-7.63), with two or more residents who smoked (2.42 µg/m3 IQR: 0.58-11.0), with more than 40 cigarettes smoked (2.92 µg/m3 IQR: 0.97-10.61), and where two or more residents smoked inside (4.02 µg/m3 IQR: 1.58-11.74). Household nicotine concentrations were significantly higher in countries with higher national smoking prevalence and self-reported SHS exposure prevalence (p < 0.05). CONCLUSIONS: SHS concentrations in homes with individuals who smoke were approximately twenty times higher in homes that allowed smoking compared to those reporting smoke-free household rules. Evidence-based interventions promoting smoke-free homes should be implemented in combination with strengthening other MPOWER measures.

Secondhand smoke exposure assessment in outdoor hospitality venues across 11 European countries.

OBJECTIVE: Due to partial or poorly enforced restrictions secondhand tobacco smoke (SHS) is still present in outdoor hospitality venues in many European countries. This study aimed to assess SHS concentrations in outdoor hospitality venues across Europe and identify contextual exposure determinants. METHODS: Cross-sectional study. We measured airborne nicotine and evidence of tobacco use in terraces of bars, cafeterias, and pubs from 11 European countries in 2017-2018. Sites were selected considering area-level socioeconomic indicators and half were visited during nighttime. We noted the smell of smoke, presence of smokers, cigarette butts, ashtrays, and number of physical covers. Contextual determinants included national smoke-free policies for the hospitality sector, the Tobacco Control Scale score (2016), and the national smoking prevalence (2017-2018). We computed medians and interquartile ranges (IQR) of nicotine concentrations and used multivariate analyses to characterize the exposure determinants. RESULTS: Nicotine was present in 93.6% of the 220 sites explored. Overall concentrations were 0.85 (IQR:0.30-3.74) µg/m3 and increased during nighttime (1.45 IQR:0.65-4.79 µg/m3), in enclosed venues (2.97 IQR:0.80-5.80 µg/m3), in venues with more than two smokers (2.79 IQR:1.03-6.30 µg/m3), in venues in countries with total indoor smoking bans (1.20 IQR:0.47-4.85 µg/m3), and in venues in countries with higher smoking prevalence (1.32 IQR:0.49-5.34 µg/m3). In multivariate analyses, nicotine concentrations were also positively associated with the observed number of cigarette butts. In venues with more than two smokers, SHS levels did not significantly vary with the venues' degree of enclosure. CONCLUSIONS: Our results suggest that current restrictions in outdoor hospitality venues across Europe have a limited protective effect and justify the adoption of total smoking bans in outdoor areas of hospitality venues.

Secondhand smoke exposure in outdoor children's playgrounds in 11 European countries.

INTRODUCTION: Tobacco presence in outdoor children's playgrounds is concerning not only because it leads to secondhand smoke (SHS) exposure, but also cigarette butt pollution and tobacco normalization. OBJECTIVES: This study aimed to assess SHS exposure in children's playgrounds, according to area-level socioeconomic status (SES), smoke-free regulations, national smoking prevalence, and SHS exposure prevalence in playgrounds (2017-2018). METHODS: We monitored vapor-phase nicotine concentration and tobacco-related variables in 20 different playgrounds in 11 European countries (n = 220 measurements) from March 2017 to April 2018. Playgrounds were selected according to area-level SES. Data on the number of people smoking, and cigarette butts inside the playground and on playground surroundings (<1 m away) were recorded. Playground smoking bans, the Tobacco Control Scale (TCS) score, national smoking prevalence and SHS exposure prevalence in playgrounds were used to group countries. To determine nicotine presence, we dichotomized concentrations using the limit of quantification as a cut-off point (0.06 µg/m3). Nicotine median concentrations were compared using non-parametric tests, and nicotine presence and tobacco-related observational variables using the Chi-squared test. RESULTS: Airborne nicotine presence was found in 40.6% of the playgrounds. Median nicotine concentration was <0.06 µg/m3 (Interquartile range: <0.06-0.125) and higher median concentrations were found in more deprived neighborhoods, non-regulated playgrounds, in countries with lower overall TCS scores, higher national smoking prevalence and higher SHS exposure prevalence in playgrounds. Overall, people were smoking in 19.6% of the playgrounds. More than half of playgrounds had cigarette butts visible inside (56.6%) and in the immediate vicinity (74.4%). Presence of butts inside playgrounds was higher in sites from a low area-level SES, in countries with low TCS scores, and greater smoking prevalence and SHS exposure prevalence (p<0.05). CONCLUSIONS: There is evidence of SHS exposure in children's playgrounds across Europe. These findings confirm the need for smoking bans in playgrounds and better enforcement in those countries with smoking bans in playgrounds.

Secondhand smoke exposure and other signs of tobacco consumption at outdoor entrances of primary schools in 11 European countries.

INTRODUCTION: Although smoking restrictions at child-related settings are progressively being adopted, school outdoor entrances are neglected in most smoke-free policies across Europe. OBJECTIVES: To describe secondhand smoke (SHS) exposure and tobacco-related signs in outdoor entrances of primary schools in Europe according to area-level socioeconomic status (SES), smoke-free policy, national smoking prevalence, and geographical region. METHODS: In this cross-sectional study we monitored vapor-phase nicotine concentrations at 220 school outdoor entrances in 11 European countries (March 2017-October 2018). To account for nicotine presence, we used the laboratory's limit of quantification of 0.06 µg/m3 as point threshold. We also recorded the presence of smell of smoke, people smoking, cigarette butts, and ashtrays. Half of the schools were in deprived areas. We grouped countries according to their Tobacco Control Scale (TCS) score, smoking prevalence (2017-2018), and United Nations M49 geographical region. RESULTS: There were detectable levels of nicotine in 45.9% of the outdoor entrances, in 29.1% smell of smoke, in 43.2% people smoking, in 75.0% discarded butts, and in 14.6% ashtrays. Median nicotine concentration was below the laboratory's limit of quantification <0.06 µg/m3 (Interquartile range:<0.06-0.119). We found higher SHS levels in countries with lower TCS scores, higher national smoking prevalence, and in the Southern and Eastern European regions. People smoking were more common in schools from lower area-level SES and in countries with lower TCS scores (p<0.05). CONCLUSIONS: Smoking at school outdoor entrances is a source of SHS exposure in Europe. These findings support the extension of smoking bans with a clear perimeter to the outdoor entrances of schools.

Validity of self-reported indicators to assess secondhand smoke exposure in the home.

INTRODUCTION: Questionnaires are widely used to assess secondhand smoke (SHS) exposure. However, the validity of self-reported SHS exposure indicators has been rarely assessed. We aimed to assess correlations, sensitivity, specificity, and predictive values between self-reported SHS exposure indicators and airborne nicotine concentrations. METHODS: We performed a cross-sectional study with a convenience sample of 175 homes in Barcelona and Santiago de Compostela, Spain. Airborne nicotine samples were collected from participants' homes and a self-administered questionnaire was completed on SHS exposure in the home. Spearman correlations coefficients and sensitivity, specificity and predictive values were assessed between self-reported SHS exposure indicators and nicotine concentrations in the home. RESULTS: All self-reported SHS exposure indicators correlated moderately strongly with airborne nicotine concentrations (Spearman correlations coefficient ranging from 0.58 to 0.65). Moreover, sensitivities and negative predictive values between self-reported indicators and the presence of nicotine in the home were below 66.4% while specificities and positive predictive values were over 78.4%. The "number of people usually smoking in the home" showed the best results (rs = 0.65, p < 0.001; sensitivity = 50.4%, specificity = 95.2%, PPV = 95.0, NPV = 51.3). CONCLUSIONS: The self-reported SHS indicators assessed in this study showed moderate and strong correlations, low sensitivities, and high specificities. Among them, the best results were obtained with the "number of people usually smoking in the home".

Second-hand smoke exposure in homes with children: assessment of airborne nicotine in the living room and children's bedroom.

BACKGROUND: The introduction of 'smoke-free laws' has reduced the population's exposure to second-hand smoke (SHS), although SHS is still an issue in homes and other public places. Children are vulnerable to its health effects, and their greatest exposure occurs at home. OBJECTIVES: To assess airborne nicotine concentration of the living room and children's bedroom of homes with children under 13 years of age, and to analyse factors associated with these levels. METHODS: We conducted a cross-sectional study in Barcelona in 2015-2016, selecting a convenience sample from families with at least one child under 13 years of age. The sample comprised 50 families with smokers and 50 without. We measured airborne nicotine concentrations in the living room and children's bedroom, and, using a questionnaire administered to the parents, collected information about smoking habits at home. RESULTS: Homes without smokers showed nicotine concentrations below the limit of detection (<0.02 µg/m3), while those with at least one smoker showed 0.16 µg/m3 in the living room and 0.12 µg/m3 in the bedroom. When smoking was allowed inside home, these values increased to 1.04 and 0.48 µg/m3, respectively. Moreover, nicotine concentrations in both rooms were strongly correlated (r=0.89), and higher nicotine levels were associated with the number of cigarettes smoked in the living room, smoking rules, the number of smokers living at home and tobacco smell. CONCLUSIONS: Homes with smokers present SHS in the living room and in the children's bedroom. Therefore, programmes focused on reducing children's SHS exposure are urgently needed.

Epicuticular Wax in Developing Olives (Olea europaea) Is Highly Dependent upon Cultivar and Fruit Ripeness.

The epicuticular wax (EW) layer is located on the surface of most plant organs. It provides the cuticle with most of its properties and is the primary barrier against biotic and abiotic stress. Despite the importance of Olea europaea cultivation, few studies have characterized the EW covering leaves and olives, which could be involved in resistance to both infection and environmental conditions. In the present study, wide-ranging screening was carried out using direct-injection electrospray ionization coupled to high-resolution mass spectrometry to analyze EW in developing olives of nine varieties. The proportions of EW fractions [wax esters (WEs), diacylglycerols, triacylglycerols (TAGs), triterpenic acids, and aldehydes] strongly depended upon the olive cultivar and, in only a few cases, were influenced by the sampling date. The specific compositions of the major fractions, WEs and TAGs, were strictly related to the cultivar, while the degree of unsaturation and chain length of the WEs evolved throughout the 4 weeks prior to the olive turning color.

Ripening and storage conditions of Chétoui and Arbequina olives: Part II. Effect on olive endogenous enzymes and virgin olive oil secoiridoid profile determined by high resolution mass spectrometry.

Several factors affect virgin olive oil (VOO) phenolic profile. The aim of this study was to monitor olive hydrolytic (ß-glucosidase) and oxidative (peroxydase, POX, and polyphenoloxydase, PPO) enzymes during olive ripening and storage and to determine their capacity to shape VOO phenolic profile. To this end, olives from the cultivars Chétoui and Arbequina were stored at 4°C or 25°C for 4weeks and their enzymatic activities and oil phenolic profiles were compared to those of ripening olives. We observed different trends in enzymes activities according to cultivar and storage temperature. Secoiridoid compounds, determined by high resolution mass spectrometry (HRMS), and their deacetoxylated, oxygenated, and deacetoxy-oxygenated derivatives were identified and their contents differed between the cultivars according to olive ripening degree and storage conditions. These differences could be due to ß-glucosidase, POX and PPO activities changes during olive ripening and storage. Results also show that oxidised phenolic compounds could be a marker of VOO ''freshness".

Direct chemical profiling of olive (Olea europaea) fruit epicuticular waxes by direct electrospray-ultrahigh resolution mass spectrometry.

In the present paper, an electrospray ionization (ESI)-Orbitrap method is proposed for the direct chemical profiling of epicuticular wax (EW) from Olea europaea fruit. It constitutes a rapid and efficient tool suitable for a wide-ranging screening of a large number of samples. In a few minutes, the method provides a comprehensive characterization of total EW extracts, based on the molecular formula of their components. Accurate mass measurements are obtained by ultrahigh resolution mass spectrometry, and compositional restrictions are set on the basis of the information available from previous studies of olive EW. By alternating positive and negative ESI modes within the same analysis, complementary results are obtained and a wide range of chemical species is covered. This provides a detailed compositional overview that otherwise would only be available by applying multiple analytical techniques.

Fragmentation studies for the structural characterization of marine dissolved organic matter.

High-resolution tandem mass spectrometry by collision-induced dissociation with a linear ion trap-Orbitrap has been performed on marine dissolved organic matter (DOM). Product ion spectra of selected precursor ions (m/z 359-375) have been acquired to obtain structural information, after method development. To evaluate the performance of the method, the Suwannee River fulvic acid (SRFA) reference standard was also analyzed. By reconstructing the individual product ion spectrum of marine DOM, several fragments were assigned to the different precursor ions indicating the presence of carboxyl, hydroxyl, lactones, quinones, esters, and structures more similar to lignin-degraded molecules. On the basis of these findings, coastal marine DOM molecules, although structurally homogeneous, might be more rich in diversity of functional groups than previously described.

Analysis of volatile thiols in alcoholic beverages by simultaneous derivatization/extraction and liquid chromatography-high resolution mass spectrometry.

A simultaneous derivatization/extraction method followed by liquid chromatography-electrospray-high resolution mass spectrometry for the determination of volatile thiols in hydroalcoholic matrixes was optimized and used to identify and quantify volatile thiols in wine and beer samples. The method was evaluated in terms of sensitivity, precision, accuracy and selectivity. The experimental LOQs of eleven thiols tested ranged between 0.01 ng/L and 10 ng/L. Intra-day relative standard deviation (RSD) was in general lower than 10% and inter-day RSD ranged between 10% and 30%. Recovery in the model and real matrixes ranged from 45% to 129%. The method was then applied for the analysis of four white wines and six beers. Five out of the eleven reference thiols were identified and quantified in the samples analyzed. The non-target approach, carried out by monitoring the diagnostic ion at m/z 275.9922 [C13H10ONSe](+) in the fragmentation spectrum, allowed detecting, in the same samples, fourteen non-target thiols.

High-field FT-ICR mass spectrometry and NMR spectroscopy to characterize DOM removal through a nanofiltration pilot plant.

Ultrahigh resolution Fourier transform ion cyclotron mass spectrometry and nuclear magnetic resonance spectroscopy were combined to evaluate the molecular changes of dissolved organic matter (DOM) through an ultrafiltration-nanofiltration (UF-NF) pilot plant, using two dissimilar NF membranes tested in parallel. The sampling was performed on seven key locations within the pilot plant: pretreated water, UF effluent, UF effluent after addition of reagents, permeate NF 1, permeate NF 2, brine NF 1 and brine NF 2, during two sampling campaigns. The study showed that there is no significant change in the nature of DOM at molecular level, when the water was treated with UF and/or with the addition of sodium metabisulfite and antiscaling agents. However, enormous decrease of DOM concentration was observed when the water was treated on the NF membranes. The NF process preferentially removed compounds with higher oxygen and nitrogen content (more hydrophilic compounds), whereas molecules with longer pure aliphatic chains and less content of oxygen were the ones capable of passing through the membranes. Moreover, slight molecular selectivity between the two NF membranes was also observed.

Determination of lipophilic marine toxins in mussels. Quantification and confirmation criteria using high resolution mass spectrometry.

A multitoxin method has been developed for quantification and confirmation of lipophilic marine biotoxins in mussels by liquid chromatography coupled to high resolution mass spectrometry (HRMS), using an Orbitrap-Exactive HCD mass spectrometer. Okadaic acid (OA), yessotoxin, azaspiracid-1, gymnodimine, 13-desmethyl spirolide C, pectenotoxin-2 and Brevetoxin B were analyzed as representative compounds of each lipophilic toxin group. HRMS identification and confirmation criteria were established. Fragment and isotope ions and ion ratios were studied and evaluated for confirmation purpose. In depth characterization of full scan and fragmentation spectrum of the main toxins were carried out. Accuracy (trueness and precision), linearity, calibration curve check, limit of quantification (LOQ) and specificity were the parameters established for the method validation. The validation was performed at 0.5 times the current European Union permitted levels. The method performed very well for the parameters investigated. The trueness, expressed as recovery, ranged from 80% to 94%, the precision, expressed as intralaboratory reproducibility, ranged from 5% to 22% and the LOQs range from 0.9 to 4.8pg on column. Uncertainty of the method was also estimated for OA, using a certified reference material. A top-down approach considering two main contributions: those arising from the trueness studies and those coming from the precision's determination, was used. An overall expanded uncertainty of 38% was obtained.

Determination of volatile thiols in virgin olive oil by derivatisation and LC-HRMS, and relation with sensory attributes.

Volatile thiols were determined by derivatisation followed by ESI-LC-HRMS in twenty-five virgin olive oils (VOOs) pertaining to different commercial classes. 4-Methoxy-2-methyl-2-butanethiol (4MMB) was quantified, and 3-methyl-2-butenethiol and methanethiol were identified for the first time in VOO by non-target analysis. In order to evaluate the influence of volatile thiols on VOO aroma, the sensory notes, defects and secondary attributes were determined in samples according to European regulation by an Official VOO Panel. A significant correlation was found between the concentration of 4MMB in VOO samples and the 'fig tree leaf' sensory attribute. To confirm these results, 4MMB odour detection threshold and odour recognition were investigated.

Determination of volatile thiols in roasted coffee by derivatization and liquid chromatography-high resolution mass spectrometric analysis.

A fast derivatization/extraction method followed by LC-ESI-HRMS was optimized for the determination of volatile thiols in roasted coffee powder, using ebselen as the derivatization agent. The analytical conditions were optimized on real coffee matrix, which was spiked with representative volatile thiols. The method sensitivity, precision, accuracy and selectivity were evaluated by using representative standard thiols. Estimated LOQs were between 0.02 and 14.8ng/kg for the thiols evaluated. Recoveries and intra-day and inter-day RSD values obtained in coffee matrix were in general around 40% and between 11 and 30%, respectively. The optimized and validated method was applied to real coffee samples. According to the established identification criteria, target thiols were identified and quantified in coffee powder samples. Among them, 4-mercapto-1-butanol and 2-methyl-3-tetrahydrofuranthiol were identified and quantified for the first time in roasted coffee. Moreover, an approach based on the formation of a diagnostic product ion was applied to detect non-target thiols, allowing the detection of nineteen thiol derivatives, fourteen of them were tentatively identified on the basis of their molecular formula. Some of them, such as methanethiol and 3-mercapto-3-methylbutyl acetate were known to be present in coffee volatile fraction, while the rest were not previously described in this product.

Determination of volatile thiols in lipid matrix by simultaneous derivatization/extraction and liquid chromatography-high resolution mass spectrometric analysis. Application to virgin olive oil.

A simple, reliable, selective and sensitive method for the determination of volatile thiols at trace levels in lipid matrices was developed. The method consisted of a single-step derivatization/extraction procedure followed by electrospray ionization-high performance liquid chromatography-high resolution mass spectrometry (ESI-HPLC-HRMS) analysis using ebselen as a derivatization agent. The analytical conditions were optimized in a lipid model system (triolein) and virgin olive oil (VOO), both spiked with seven representative volatile thiols. The method was validated and the sensitivity, precision, accuracy and selectivity were evaluated. The experimental limit of quantification (LOQ) of the tested thiols in the VOO matrix ranged from 0.05 to 0.5ng/kg. Moreover, the intra-day relative standard deviation (RSD) was in general lower than 10%, except for esters, which reached RSD values of around 13%. The inter-day RDS ranged between 9.6% and 36.6%. The recovery in VOO ranged from 79% to 20% for derivatives with the highest and lowest polarity, respectively. The methodology was applied to the analysis of some VOO samples. Within this first probe sample, some of the VOO analyzed presented concentrations of 4-methoxy-2-methyl-2-butanethiol above the LOQ, ranging between 0.2 and 1.9ng/kg. The advantage of using full-scan acquisition mode when working with HRMS is that it allows the use of a non-target approach based on the fragmentation of thiol derivatives yielding a main product ion at m/z 275.9922 [C13H10ONSe](+) and that corresponded to the ebselen moiety of the derivatives. Any positive finding satisfied the identification and confirmation criteria established during the validation: retention time drift <3-fold the standard deviation of the method, mass accuracy <2ppm with real resolution ≥20,000 (full width at half maximum) at the mass range of interest, and the presence of isotope ions containing (80)Se and (78)Se, respectively.

Molecular characterization of dissolved organic matter through a desalination process by high resolution mass spectrometry.

The effect of different water treatments such as ultrafiltration (UF) and reverse osmosis (RO) on dissolved organic matter (DOM) is still unknown. Electrospray ionization Fourier transform orbitrap mass spectrometry has been used to provide valuable information of marine DOM evolution through a desalination process on a molecular scale. In the present manuscript, the characterization of four real composite water samples from a desalination pilot plant installed in the coast of Barcelona (Spain) has been carried out. The sampling was performed on each point of the pilot plant: raw seawater (RSW), UF effluent, brine RO and permeate RO. The mass spectra of the different samples show several thousand peaks, however for the present screening study, only the mass range m/z 200-500 and the main signals in this mass range (relative intensities ≥1%) have been considered. The analysis of RSW and UF samples reveal that there is little effect on DOM by the UF pilot. However, when the water is treated on the RO an important change on DOM has been observed. The recurring periodical patterns found in RSW and UF are lost in Permeate RO sample. Compounds with more aliphatic character, with higher H/C ratio (H/Cav 1.72) are present in the Permeate and some of them have been tentatively identified as fatty acids.