The certification of the absolute molecular mass distribution (MMD) of an n-octyl-initiated, proton-terminated, low mass, atactic polystyrene (PS) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is fully described. This polymer has been designated Standard Reference Material (SRM) 2881. The material constituting SRM 2881 was prepared commercially for the NIST Polymers Division specifically for use as a narrow-distribution polymer standard. Anticipated uses include calibration of mass spectrometers and size exclusion chromatographs (SEC) in...