Quantification of chlorinated paraffins by chromatography coupled to high-resolution mass spectrometry - Part A: Influence of gas chromatography and ionisation source parameters.

The analysis of chlorinated paraffins (CPs) has become a major analytical challenge. GC-ECNI-HRMS coupling is often used to analyse and quantify them. However, the influence of certain GC and ECNI parameters on the responses of polychlorinated n-alkanes (PCAs), the dominant components of CPs, has hardly been studied. In this paper, we investigated not only the influence of GC column characteristics, but also oven, GC inlet and source temperatures for simultaneous analysis of PCAs with chain-length ranging from 10 up to 20 carbon atoms (PCAs-C10-20). Particular attention was paid to the absolute response and PCA homologue group pattern obtained for a CP technical mixture. The optimum conditions for a wide homologue group determination were GC inlet, final gradient and ion source temperatures set at 220-240 °C, 340 °C and 200 °C. At the same time, a higher response was obtained with the Optima 5HT column compared to Optima 1 column, and with a length and film thickness of 12.5 m and 0.25 µm, respectively. The homologue group pattern of the technical mixture studied was significantly modified as a function of the source and GC inlet temperatures, film thickness and composition of the stationary phase. Here we recommend conditions that will improve the overall PCA pattern, in order to better characterise their occurrence in future environmental monitoring and exposure assessment.

Quantification of chlorinated paraffins by chromatography coupled to high-resolution mass spectrometry - Part B: Influence of liquid chromatography separation.

The analysis of chlorinated paraffins (CPs) is today an analytical challenge. Indeed, it is still impractical to describe their real composition in terms of polychlorinated alkanes (PCAs) homologue groups, which dominate technical mixtures. The co-elution of PCA congeners generates interferences due to the competition phenomena which occur during the ionisation process as well as to the dependence of the ionisation sources on the PCA chemistry. Therefore, the aim of this study was to investigate the influence of chromatographic separation, by LC-ESI-HRMS coupling, on the PCA homologue group pattern and, eventually, on their determination in food samples from interlaboratory studies. For this, three different mobile phases and six LC chromatographic columns were studied in order to optimise the analysis of CP mixtures. The first results showed that the use of a MeOH/H2O mobile phase reveals more appropriately the higher chlorinated PCAs. However, using ACN/H2O led to less ion species, with almost exclusively [M + Cl]- adducts, formed using post-column dichloromethane addition. Regarding the choice of the stationary phases, Hypercarb column provided a completely different homologue group pattern from the other chromatographic columns, in relation with the stronger retention of PCAs. Among the other columns, the C30 column better highlighted the short-chain PCAs compared to the C18 column conventionally used. Because the regulations now concern short-chain CPs, the quantification of food samples was then carried out on the C30 column. The optimised LC-ESI-HRMS conditions using C30 column and MeOH/H2O solvent mixture led to a quantification of PCAs in samples from interlaboratory studies with satisfactory accuracy (|Z-score| ≤ 2) and precision (<15%).

First Observations of a Potential Association Between Accumulation of Per- and Polyfluoroalkyl Substances in the Central Nervous System and Markers of Alzheimer's Disease.

The entire human population is exposed to persistent organic pollutants throughout their lives. Among them, per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used in industrial and consumer products that are known to exert adverse effects on human health. As they bioaccumulate in the human brain and are known to be neurotoxic in experimental models, they are assumed to be involved in neurodegenerative processes. In this proof-of-concept study, we measured the level of 18 PFAS in cerebrospinal fluid (CSF) from 8 patients hospitalized with suspected normal pressure hydrocephalus. We then analyzed whether PFAS levels could be related to both biological and clinical markers of Alzheimer's disease. We showed that PFAS and perfluorooctanesulfonate were found in all CSF samples from a French region without fluorochemical industries. Moreover, we observed a significant difference between the levels of PFAS and perfluorooctanesulfonate in the CSF of patients with both Alzheimer's disease markers and cognitive impairment compared with those with only 1 or neither. Two previous studies have shown that PFAS levels in human CSF increase with age and are linked to impaired blood-brain barrier integrity. Our results provide the first evidence of a link between PFAS accumulation in the central nervous system and clinical and biological markers of Alzheimer's disease.

Accumulation of short-, medium-, and long- chain chlorinated paraffins in tissues of laying hens after dietary exposure.

Reliable human health risk assessment associated with chlorinated paraffins (CPs) exposure is limited by the lack of data on the fate of this complex family of contaminants. To gain knowledge on the accumulation and distribution of CPs in biota after ingestion, laying hens were dietary exposed to technical mixtures of short- (SCCPs), medium- (MCCPs), or long-chain (LCCPs) CPs of various chlorine contents during 91 days, at 200 ng/g of feed, each. Adipose tissue, liver, muscle and serum were collected at the steady-state, along with excreta. All C10-C36 CPs were detected in liver. However, differences were observed in CP distribution: LCCPs high %Cl were retained in the liver; LCCPs low %Cl circulated through the serum and were distributed in the different compartments, but were mostly excreted through the eggs; SCCPs and MCCPs were found in all tissues at similar levels. Finally, a mass balance indicated a potential for biotransformation.

Transfer of short-, medium-, and long-chain chlorinated paraffins to eggs of laying hens after dietary exposure.

Chlorinated paraffins (CPs) are a complex family of contaminants. Lack of exposure data and an understanding of the fate of these chemicals in the environment affect our ability to reliably assess the human health risk associated with CP exposure. The present study focused on the evaluation of CP transfer from feed to eggs of laying hens exposed over 91 days. Laying hens were provided feed spiked with five technical mixtures of short-, medium- or long-chain CPs and featuring low or high chlorine contents, at concentrations of 200 ng/g each. Eggs were collected daily. All mixtures except the LCCPs with high chlorine content transferred into the eggs, with accumulation ratios increasing with the chain length and chlorine content. Concentrations at the steady-state varied between 41 and 1397 ng/g lw depending on the mixture. Additionally, the homologue-dependant transfer resulted in a change of pattern compared to that from the spiked feed.

Optimized characterization of short-, medium, and long-chain chlorinated paraffins in liquid chromatography-high resolution mass spectrometry.

Chlorinated paraffins (CPs), or polychlorinated n-alkanes, form a complex family of chemicals as they exist as mixtures of several thousands of isomers. To facilitate their classification, they are subdivided into short-chains (C10C13, SCCPs), medium-chains (C14C17, MCCPs), and long-chains (C≥18, LCCPs) and further subdivided according to their chlorination degree. Until recently, the most common strategy implemented for their analysis was GC-ECNI-LRMS, with the main disadvantage being the high dependence of the response to the chlorination degree and the incapability of analysing LCCPs. In this work, we developed a method based on liquid chromatography coupled with electrospray ionisation-Orbitrap mass spectrometry (LC-ESI-HRMS) to expand the analysis capabilities of CPs. Although the different physico-chemical properties of CPs have led to compromises on the choice of analytical parameters, the addition of a mixture of DCM/ACN post-column with appropriate LC-ESI(-)-HRMS parameters enabled optimal and simultaneous detection of SCCPs, MCCPs and LCCPs from 10 to 36 carbons in one single injection. The combination of both the optimised LC-ESI parameters and the high resolution of the mass spectrometer (R = 140,000 @200 m/z) allowed separation of CPs signals of interest from unwanted halogenated ones, leading to minimum interferences in the detection. The optimised method was then successfully applied to the characterization of three types of vegetable oil, which were mostly contaminated with MCCPs. Additionally, the implementation of the LCHRMS strategy enabled the identification of highly chlorinated LCCPs in edible oil for the first time at dozens of ng g-1 lw, which demonstrates the need of such comprehensive methods to expand the knowledge about CPs occurrence in food and environmental matrices.

Measurement of phthalates diesters in food using gas chromatography-tandem mass spectrometry.

An analytical strategy dedicated to 4 major phthalate diesters (DiBP, DnBP, BBzP and DEHP) monitoring in food items has been developed and validated according to normalized guidelines. The method has been applied to a wide range of foodstuffs (n=54) to generate first-ever occurrence data at the French level. This method involves separation and detection using gas chromatography coupled to tandem mass spectrometry, in electron ionisation with highly specific selected reaction monitoring, quantification being performed according to the isotope dilution principle. A particular attention has been paid to background contamination management at any stage of the analytical process, from the sampling to the expression of the results. Limits of reporting, defined as statistically different from background contamination, were found to be 2.7, 0.53, 0.18 and 3.4 µg kg(-1), and relative combined uncertainties were finally found to be 7.6%, 12.2%, 12.0% and 14.1%, for DiBP, DnBP, BBzP and DEHP, respectively.