Interlaboratory studies

Paul Brereton (Queen’s University Belfast)

During the final months of the OLEUM activity all the project partners have been all very busy analysing data- lots of data. This is because we are completing one of the world’s largest interlaboratory studies. Actually a set of studies, involving 8 different analytical methods with approximately 15 laboratories for each method, analysing 10 test materials, that is over 1000 pieces of data. Additionally, some methods have two analytes and two of them have 18 (!) which takes it to over 5000 results to analyse!

The methods being studied are:  

    1. Polar phenols analysis used for assessing the olive oil health claim

    2. Free and esterified sterols analysis targeting illegal olive oil blends

    3. Improved methodology for fatty acid ethyl esters targeting illegal processing or lower quality virgin olive oil

    4. A group of methods looking at Sensory and volatiles analyses for quality and authenticity of virgin olive oil  

         a. Analysis of selected volatile compounds in virgin olive oil by gas chromatography

              i. GC-MS

              ii. GC-FID  

         b. Analysis of virgin olive oil volatile fingerprint by SPME-GC-MS and chemometrics, as screening method to support the Panel test

         c. Sensory analysis of virgin olive oils with the use of two Reference Materials  

The above methods range from slight improvements of existing methods, e.g. methods 2 & 3; to new advanced multi-analyte/profiling procedures that aim to complement the official Panel Test (sensory analysis).

Following a pre-trial study conducted in the first half of 2020, most of the main study, the “Trial Proper” took place in the Autumn of 2020. For each of the above methods each participating laboratory was sent a Standard Operating Procedure and a set samples (usually 10 test materials and one practice sample with a known value) to analyse once only. Unbeknown to the participants, the test materials actually comprised 5 sets of duplicate test materials that allow us to calculate within laboratory and between laboratory precision. Following statistics carried out to internationally recognised standards the studied methods can then be assessed for suitability as official methods.

The formalised results will be available soon once we have shared the results with participants and formally closed the study. Some of the procedures will then be proposed as official methods.

We would like to take this opportunity to thank all the laboratories that have taken part in this enormous exercise and have done so in extremely difficult (Covid-19) circumstances.