productivity, r in biotechnology, in mass spectrometry

https://dx.doi.org/10.1351/goldbook.P04865
An economical figure denoting the mass of a product formed per unit reactor volume and unit time. Productivity is often referred to per unit of enzyme or biomass.
Source:
PAC, 1992, 64, 143 (Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)) on page 163