Standard Reference Material 2881 - National Institute of Standards ...

ABSTRACTThe certification of an absolute molecular mass distribution polymer Standard ReferenceMaterial, SRM 2881, is described. SRM 2881 is an n-octyl-initiated, proton-terminated, narrowpolydispersity, low mass, atactic polystyrene. The absolute molecular mass distribution (MMD)was obtained by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF MS). The certification includes estimates of uncertainties, both Type A (random)and Type B (systematic), for each oligomer in the sample having a concentration of at least0.18 % of the total of all oligomers on the low mass tail of the MMD and 0.02 % on the highmass tail. The bottle-to-bottle variation of the packaged SRM was checked by size exclusionchromatography and found to be negligible.DISCLAIMERSCertain commercial materials and equipment are identified in this paper in order to specifyadequately the experimental procedure. In no case does such identification implyrecommendation or endorsement by the National Institute of Standards and Technology, nordoes it imply necessarily the best available for the purpose.According to ISO 31-8, the term “molecular mass” has been replaced by “relative molecularmass,” symbol M r . Thus, if that nomenclature and notation were followed in this publication, oneshould write M r,w instead of the historically conventional M w for the weight-average molecularmass with similar changes for M n , and M z . M w would be called the “mass-average relativemolecular mass.” The conventional notation, rather than the ISO notation, has been used in thispublication.2