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

10. Discussion of Type A UncertaintiesThere are two Type A uncertainties that affect the MMD. The Type Auncertainty from Q/k 0, the MMS to MMD conversion factor that was estimated in section9.1, and the Type A uncertainty from the uncertainty of the intensity of each individualoligomer in the MMS:∑β = S / S[9.1]iiiiwhere βiis the fraction of the signal for the i th oligomer with mass, m i , from the massspectrum. In the uncertainty analysis averages of each βifor approximately 500 spectraof which OctylA (the polymer that became SRM 2881) was one of the two polymersmixed, or when OctylA was used alone. None of the spectra used showed any variationwith M n or M w as a function of concentration of one or the other polymer.10.1 Type A Uncertainties in the MALDI-TOF Mass Spectrometry MeasurementThere are two sources of type A uncertainty that affect the MMD. The uncertaintyfrom Q/k 0, the mass spectrum to MMD conversion factor, that was estimated in theprevious section, and the uncertainty of the intensity of each individual oligomer in themass spectrum:∑β = S / S[5.1]iiiiwhere βiis the fraction of the signal for the i th oligomer with mass, m i . In the uncertaintyanalysis averages of each βifor approximately 500 spectra of which OctylA (thepolymer that became SRM 2881) was one of the two polymers mixed, or when OctylAwas used alone were calculated.29