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

Concentration of total polymer to retinoic was held about at the three-quarter point in therange of linearity found by Goldschmidt and Guttman. 18 This range was re-checked inpreliminary experiments. In addition, the silver triflouroacetate concentration from the aboverecipe was found to work well for the linear range as long as there was a molar excess of silver.This was checked by making measurements at concentrations of silver triflouroacetate rangingfrom 25 % to 200 % of that value using the 10:70:20 of OctylB:ButylA:OctylC gravimetricmixture employed in the instrument optimization experiments 2 and described in section 3.4.Within the noise limits of the repeatability of the experiment there was no change of ratio ofOctylB/Butyl A or OctylC/ButylA either as a function of silver triflouroacetate concentration oras a function of the time the experiment was done.8. Data Analysis MethodsThe data for one set of linearity experiments require up to two days to collectyielding 35 sets of data to analyze. Without automated data analysis methods this canlead to a severe bottleneck in standards production. The automated data analysis programmust identify the peaks (as many as 80 or 100 for a mixture of two narrow distributionpolymers), determine the area under each peak, and for these experiments sort the peaksinto series which are identifiable by end group of polymer, sum the total area attributableto each series, determine the MMD and the MMD moments of each series and computethe apparent gravimetric mass attributable to each series. Since there are five repeats ateach point the programs must also be able to handle these and any other requiredstatistics automatically.The transformation of the data time-of-flight to mass was done using the BrukerDaltonics Xmass program (version 5.1.0). Peak picking and peak integration wereperformed using the MassSpectator FORTRAN computer code 3-5 developed at NISTfor standards production. MassSpectator makes no assumptions about peak shape andrequires no smoothing or preprocessing of the data, a process which has been shown todistort peak area. 3 The algorithm is based on a time-series segmentation routine that25