A French collaborative study to evaluate the impact of acquisition workflow with LC-HRMS on environmental data
Résumé
AQUAREF, the French national reference laboratory of aquatic environment monitoring, is a consortium of five French national research institutes (BRGM, IFREMER, INERIS, Irstea and LNE) joined together to reinforce the French expertise in aquatic environments monitoring. AQUAREF aims at developing and testing the operational applicability of new tools and innovative strategies for the identification of emergent contaminants in a more relevant and cost-effective way. High resolution mass spectrometry coupled with chromatography already presents great interest for non-targeted and suspected screening approaches. However, in order to integrate these new methodologies for the aquatic environment monitoring, the different laboratory practices should be well identified and harmonized. In that way a collaborative trial was made with 11 French laboratories using LC-HRMS with several different equipments.
The aim of this intercomparison exercise was to identify the impact of chromatographic methods (shift of retention time,ionization, …), specificity of equipment (detection, fragmentation, …) and source of databases (intern obtained from standard injections or extern by the use of bibliographic, constructor or on-line databases) on identification of compounds.
Two test materials were sent to the laboratories: a solution spiked with standards and a river SPE extract (unspiked). In addition, both material tests were analysed with a unique analytical method imposed by AQUAREF and with the laboratories own methods in positive and negative electrospray ionisation modes.
Raw analytical data were firstly processed (both standard mix solution and river SPE extract) with a targeted or suspected screening approaches (levels of confidence 1 or 2 from the classification of Schymanski - (Schymanski et al., 2014) based on a list of 30 compounds and target database of each laboratories.
Then, the river SPE extract was treated for suspect compound identification based on a common database of 16 compounds.
For the targeted and suspected screening approaches, the results highlighted that:
•The most relevant compounds were identified in river SPE extract by all expert laboratories. More than 100 compounds were determined between all laboratories.
•For compounds identification, the mastering level is better in the positive electrospray ionization mode than the negative one;
•A generic chromatographic method can cover a wide range of molecules but from the standard mix analysis, exclusions could be observed
•there is a need of homogenization surrounding qualification of data compliance (validation criteria) in addition to the implementation of Schymanski classification
•Need to implement QA/QC validation steps (blank, internal standards, …)
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This exercise has been helpful because it has served to share common difficulties (not distinguishable isomers, sample contaminations…) between expert laboratories. Concerning communication to the end users, there is a need to clarify the expression of results, by being clear about limitations (data compliance, false negative/positive, etc…).