Multi-year inter-laboratory exercises for the analysis of illicit drugs and metabolites in wastewater: Development of a quality control system

Thirty-seven laboratories from 25 countries present the development of an inter-laboratory testing scheme for the analysis of seven illicit drug residues in standard solutions, tap- and wastewater. Almost 10 000 concentration values were evaluated: triplicates of up to five samples and 26 laboratories per year. The setup was substantially improved with experiences gained across the six repetitions (e.g. matrix type, sample conditions, spiking levels). From this, (pre-)analytical issues (e.g. pH adjustment, filtration) were revealed for specific analytes which resulted in formulation of best-practice protocols for inter-laboratory setup and analytical procedures. The results illustrate the effectiveness of the inter-laboratory setup to assess laboratory performance in the framework of wastewater-based epidemiology. The exercise proved that measurements of laboratories were of high quality (>80% satisfactory results for six out of seven analytes) and that analytical follow-up is important to assist laboratories in improving robustness of wastewater-based epidemiology results.
This article is based upon work from COST Action ES1307 supported by COST (European Cooperation in Science and Technology). We wish to acknowledge EMCDDA and Yeonsuk Ryu for support in the organization of the scheme and assistance in the preparation of the test samples, respectively. The following funding sources are acknowledged: the Research Foundation – Flanders (FWO) (Grant number: 1285216N), the Spanish Ministry of Economy, Industry and Competitiveness, the Generalitat Valenciana, Xunta de Galicia, Stavros Niarchos Foundation, Office for Combating Narcotic Drug Abuse of the Government of the Republic of Croatia, EU FP7 project SOLUTIONS (603437), the Government of Catalonia, the Natural Sciences and Engineering Research Council of Canada (NSERC), Ministry of Education, Youth and Sports of the Czech Republic (projects CENAKVA and CENAKVA II), EU Marie Skłodowska-Curie Fellowship (APOLLO 749845) and the Swiss National Science Foundation (SNSF, P2LAP2_164892). The following persons are acknowledged for help in sample analysis: Marijan Ahel, Evroula Hapeshi, Popi Karaolia, Esther López-García, Nicola Mastroianni, Cristina Postigo, Inés Racamonde, Rosario Rodil, Isaac Rodríguez, Tania Rodríguez-Álvarez, Ivan Senta, and Senka Terzic.