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

An analysis of variance (ANOVA) 5 was done on each oligomeric βiassuming theywere independent of each other. There are two levels of the experimental data to look atthe ANOVA . One is from each two day period when a given pair of polymers was run toestimate slope of theGGexpTAexpTBversusGGoTAoTBplot. This has been called by us a Polymer-Pair-run. In those runs in which Octyl A was used as one of the polymers, we are able toestimate the ANOVA for each of the oligomericβiof Octyl A. None of the spectra usedin this analysis showed any variation in M n or M w as a function of concentration of one orthe other constituent polymer or as a function of the time when the spectra was taken(indicating that the sample preparation solutions did not change during the Polymer-Pairrun).As stated before, the data were checked for concentration dependence of themoments M n and M w of the MMD. The concentration was randomized for the Polymer-Pair-run collection period with 2 or 3 repeats of concentration to check for consistency.The data was analyzed as a function of time they were run in the day and/or the order ofrunning. None of these showed any significant trend in the moments. This alsosuggested the MMD was not changing significantly as a function of the overallconcentration of polymer in the matrix or of the order of the running the samples.An analysis of variance (ANOVA) 5 was done on each oligomeric βiassuming they wereindependent of each other. For these at each concentration ratio five spectra were taken of themixture on each sample preparation—making up of solution with syringes and electrosprayingthe solution of a ratio of two polymers with matrix and appropriate Ag salt. For these spectra itwas found that the sample-to-sample variance for the fraction of a given oligomeric mass ismuch greater than the within-sample variance where this case within-sample refers to the fiverepeats of one spraying and between sample refers to different sprayings and differentgravimetric mixtures. Thus, the computed F values generally ran much higher than thosegenerally expected from the F computed for the each oligomeric species in distribution forα = 0.05 with the appropriate degrees of freedom. This computed F is normally called F critical .Assuming the oligomer β are independent one would expect 5% of the computed F’s to beiabove F critical . Often as many as 50% of the F’s were above F critical suggesting that there is asignificant variation between each sample preparation.30