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

Appendix ANational Institute of Standards & TechnologyCertificateStandard Reference Material ® 2881PolystyreneThis Standard Reference Material (SRM) is intended primarily for use in the calibration and theperformance evaluation of instruments used to determine the molar mass and molar massdistribution of synthetic polymers. These methods include size exclusion chromatography (SEC)[1] and mass spectrometry (MS) [2]. The fractional molar mass of each oligomer from 1 % to 99% of the cumulative mass distribution were certified and are given in Table 1A unit of SRM 2881 consists of approximately 0.2 g of polystyrene powder initiated with ann-octyl group and terminated with a proton.Certified Uncertainties: The certified measurement uncertainty is expressed as a combinedexpanded uncertainty with a coverage factor k = 2, calculated in accordance with NISTprocedure [3]. Type A and Type B contributions to the expanded uncertainty of the measuredmolar mass fractions include the uncertainties in instrument and sample preparation methods.Expiration of Certification: The certification of SRM 2881 is valid, within the measurementuncertainties specified, until 1 January 2019, provided that the SRM is handled in accordancewith the storage instructions given below (see “Instructions for Use”). This certification isnullified if the SRM is modified, contaminated, or stored improperly.Maintenance of SRM Certification: NIST will monitor this SRM over the period of itscertification. If substantive technical changes occur that affect the certification before expirationof this certificate, NIST will notify the purchaser. Return of the attached registration card willfacilitate notification.Supplemental Information: M n was determined by nuclear magnetic resonance (NMR) andfound to be 9.1 x 10 +3 g/mol with an estimated uncertainty of ±0.50 x10 +3 g/mol. NMR andmatrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS)were used to analyze end groups on the polymer. Only the set of end groups (as specified above)were found.NIST Certification Method: The certified value for the oligomeric fractions in the molecularmass distribution was measured using matrix-assisted laser desorption/ionization time-of-flightmass spectrometry (MALDI-TOF MS) [4,5].55