Purity assessment studies of therapeutic drugs and non-peptide hormones were selected in consultation with the CCQM-OAWG, as analyte classes for the continuation of CCQM-P20. Theophylline (1) and digoxin (2) have been identified as suitable materials for these studies. The BIPM is collaborating with the LGC (UK) to develop methodology and materials for the comparisons CCQM-P20.e (theophylline, purity determnination) and CCQM-P20.f (digoxin, purity determination).

Investigations of the extension of the comparison to include important steroid hormones such as progesterone (3), -estradiol (4) and testosterone (5) are also being undertaken. The BIPM and NMIJ (Japan) have established a collaborative programme to develop methodology and provide materials for future rounds of comparisons related to steroid hormones.