REPORT ON COOPERATIVE DETERMINATION OF MO LECULAR-WEIGHT AVERAGES OF POLYMERS BY SIZE-EXCLUSION CHROMATOGRAPHY .2. A REPORT ON THE 2ND ROUND-ROBIN TEST (NO 1)

Molecular weight averages of four polystyrenes (PS) and two poly(methy lmethacrylates) (PMMA) were determined by size exclusion chromatograph y at 26 laboratories belonging to the section of special study on SEC. Polymer standards for constructing a calibration curve were delivered to the laboratories. Sample concentrations, the injection volume and the procedure for drawing the baseline were prescribed. Other experime ntal conditions were the same as in the previous report. Relative stan dard deviations (RSD) of over-all mean molecular weight averages were as follows after rejecting the suspected result in each set of data: 1 3.7 similar to 15.8% for PS number-average; 5.0 similar to 5.8% for PS weight-average; 11.9 similar to 13.3% for PMMA number-average; and 10 .9 similar to 11.3% for PMMA weight-average. Compared with the results for the former round robin test, RSD was not improved much because th e procedure for drawing the baseline was not restricted strictly.