Report on cooperative determination of molecular weight averages of polymers by size exclusion chromatography III. On the polymer standards for calibration

Abstract

The weight average molecular weight (Mw) of polystyrene samples determined in the first round robin test (RR-1) was compared with those in the second round robin test (RR-2) to analyse the difference in polystyrene standards for calibration. The data were divided into two groups: data determined at laboratories that used the standards obtained by the identical vendor in both RRs (case 1) and those using the standards of different vendors for RR-1 and RR-2 (case 2). The RR-1: RR-2 ratios for Mw in case 1 were 1.03-1.04 in average, but the maximum was 1.17 and the minimum 0.95. By careful adjustment of calibration conditions, the RR-1: RR-2 ratios for mw were reduced to 1.01-1.03. In case 2, as long as a calibration was constructed by passing through most data points smoothly, there was no distinct difference in calculated Mw among standards from different vendors. The relative standard deviation of these data, obtained carefully as mentioned above, were 3.9%.