Untargeted metabolomics-based approach using UHPLC-HRMS to authenticate carrots (Daucus carota L.) based on geographical origin and production mode.

Carrots produced in different agricultural regions with organic or conventional mode were analyzed by untargeted UHPLC-HRMS using reversed-phase and HILIC modes. Data were first treated separately, and further combined to possibly improve results. An in-house data processing workflow was applied to identify relevant features after peak detection. Based on these features, discrimination models were built using chemometrics. A tentative annotation of chemical markers was performed using online databases and UHPLC-HRMS/MS analyses. An independent set of samples was analyzed to assess the discrimination potential of these markers. Carrots produced in the New Aquitaine region could be successfully discriminated from carrots originating from the Normandy region by an OLPS-DA model. Arginine and 6-methoxymellein could be identified as potential markers with the C18-silica column. Additional markers (N-acetylputrescine, l-carnitine) could be identified thanks to the polar column. Discrimination based on production mode was more challenging: some trend was observed but model metrics remained unsatisfactory.

+Chlorination by-products in indoor swimming pools: Development of a pilot pool unit and impact of operating parameters.

Chlorine addition in swimming pools ensures the microbiological quality of the water and the bathers' safety. However, water chlorination is associated with disinfection byproducts (DBP) formation and adverse health effects. The impact of operating parameters and innovative water treatment systems on DBPs levels has been reported in several studies, but sampling campaign in real pools remain difficult to carry out, mainly due to unexpected attendance variations. This study presents the development of a pilot pool plant allowing to perform experiments under controlled and reproducible conditions. Bathers inputs were simulated both for the organic load and for the mechanical agitation of water. Two sampling campaigns were performed during the building of the pilot, before and after the hall was closed. Key operating parameters such as chlorine dose, water temperature and attendance were controlled and monitored. DBP levels in the pilot plant were representative of French indoor swimming pools and the impact of bathers' activity was visible on volatile DBPs. Furthermore, correlations could be stated between operating parameters and DBP levels. Stripping effectively reduced volatile DBP concentrations in water. Moreover, energy consumption data, which are usually very scarce in experimental studies, showed the influence of heat pump consumption on the global energy consumption.

Body fluid analog chlorination: Application to the determination of disinfection byproduct formation kinetics in swimming pool water.

Disinfection by-products (DBPs) are formed in swimming pools by the reactions of bather inputs with the disinfectant. Although a wide range of molecules has been identified within DBPs, only few kinetic rates have been reported. This study investigates the kinetics of chlorine consumption, chloroform formation and dichloroacetonitrile formation caused by human releases. Since the flux and main components of human inputs have been determined and formalized through Body Fluid Analogs (BFAs), it is possible to model the DBPs formation kinetics by studying a limited number of precursor molecules. For each parameter the individual contributions of BFA components have been quantified and kinetic rates have been determined, based on reaction mechanisms proposed in the literature. With a molar consumption of 4 mol Cl2/mol, urea is confirmed as the major chlorine consumer in the BFA because of its high concentration in human releases. The higher reactivity of ammonia is however highlighted. Citric acid is responsible for most of the chloroform produced during BFA chlorination. Chloroform formation is relatively slow with a limiting rate constant determined at 5.50 × 10-3 L/mol/sec. L-histidine is the only precursor for dichloroacetonitrile in the BFA. This DBP is rapidly formed and its degradation by hydrolysis and by reaction with hypochlorite shortens its lifetime in the basin. Reaction rates of dichloroacetonitrile formation by L-histidine chlorination have been established based on the latest chlorination mechanisms proposed. Moreover, this study shows that the reactivity toward chlorine differs whether L-histidine is isolated or mixed with BFA components.

Analysis of chlorination by-products in swimming pool water by membrane introduction mass spectrometry - Influence of water physicochemical parameters.

RATIONALE: Chlorine reacts in swimming pools with several compounds released by bathers to form disinfection by-products (DBPs). Epidemiological studies have shown adverse effects on health associated with the exposure to DBPs present in indoor swimming pool atmosphere. DBPs analyses require the use of multiple techniques depending on the targeted molecules. The measurement process itself is challenging due to the low stability of several compounds and the lack of specificity of certain methods. The Membrane Introduction Mass Spectrometry (MIMS) technique provides a solution to these problems by specific and sensitive in situ measurement of DBPs. This study investigates the effect of analytical conditions on quantification of DBPs and assesses the relevance of using MIMS for reliable analysis under typical swimming pool operating conditions. METHODS: MIMS is based on the simultaneous permeation of the selected compounds from the air or water samples through a polydimethylsiloxane (PDMS) membrane. DBPs are identified and quantified with a quadrupole analyzer after electron ionization. Limits of quantification (LOQs) of five DBPs are determined to assess the sensitivity of the system. Moreover, signal changes are monitored while varying physicochemical parameters such as temperature, pH and ionic strength. RESULTS: The mass spectra obtained for individual molecules show that the simultaneous measurement of trihalomethanes (THMs) and chloramines requires the monitoring of several ions and mathematical corrections of the signal. The pH and ionic strength of the solution do not significantly influence the determination of THMs. On the contrary, the temperature and hydraulics at the membrane interface must be controlled for accurate determination of DBPs. CONCLUSIONS: Results confirm that MIMS is a promising technology for the simultaneous quantification of volatile DBPs in both water and air of swimming pools. However, operating conditions such as membrane temperature should be treated with great care in order to avoid interferences.