Sample of blood, serum, or plasma from which all proteins have been removed by chemical or physical denaturation, dialysis, ultrafiltration, or solvent extraction.
Source: PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1125 (https://doi.org/10.1515/pac-2016-1120)