A ring trial of the Part-Filter Method, under the auspices of the CORESTA Smoking Behaviour Sub-Group, involving laboratories from the tobacco industry and the contract sector was concluded and the results presented to the Sub-Group in October 2013. A total of eight laboratories returned valid data and the results could be related tentatively to an earlier ring trial reported in 2012, although some details in the standardised method and participating laboratories differed. The aim of the ring trial was to assess the standardised method agreed by the Sub-Group to produce a measure of the repeatability and reproducibility of estimated nicotine and tar yields across the participating laboratories.

The repeatability and reproducibility (as coefficient of variation) for estimated nicotine were 4.8 and 9.6%, respectively, averaged across four test product levels. The repeatability and reproducibility (as coefficient of variation) for estimated tar were 5.1 and 26.2%, respectively, averaged across the four test product levels. A general rule for the variation introduced by the measurement system is that the methodology is acceptable if the error is below 10%. According to this criterion the method for estimating nicotine yields from nicotine extracted from part filters is under control, while that for estimating tar from the UV absorbance from part-filters requires further attention.

It is the opinion of the Sub-Group that the methodology used in the 2013 ring trial for estimated nicotine yield should be progressed towards becoming a CORESTA Recommended Method.