Study design for the evaluation of the stability on a Proficiency testing scheme: an example to the Proficiency Testing for Lipophilic marine biotoxins

The stability of the test materials selected for a Proficiency Testing (PT) is critical to  ensure the efficiency and reliability of the study. The present work is focused on the stability evaluation  during a PT using the... [ view full abstract ]

The stability of the test materials selected for a Proficiency Testing (PT) is critical to  ensure the efficiency and reliability of the study. The present work is focused on the stability evaluation  during a PT using the example of the PT for Lipophilic marine biotoxins (LPT) Transportation  conditions, in particular when samples have to be shipped to countries outside Europe or to countries with specific shipment restrictions, are critical factors that could compromise the named stability. In the proposed study, test materials were analysed shortly before their shipment being the last analysis performed shortly after the deadline for submission of results. Test materials were also analysed simulating the shipment conditions, these materials were kept in isothermal boxes, including dry ice or frozen gel-pack, depending on the transportation  requirements. These test materials were kept under ambient conditions and were analysed after the latest confirmation of reception. Test materials typically consisted in frozen whole flesh of bivalves homogenates containing LPT.  Test materials were prepared according to  the EURLMB SOP for LC-MS/MS analysis of LPT. Sample homogenates were distributed in plastic containers and then frozen and storage at -18 ºC. Samples with dry ice and frozen gel-pack remain stable below 0ºC during four days. The first analysis was performed on the frozen samples and a second analysis was carried out once the samples were completely thawed after being at  4ºC for two days. The results obtained in this study allowed to prove the reliability of the test materials used on the mentioned PT