Problems Associated with SEC Measurements of Polymers Among Laboratories: Summary on Cooperative Determination of Molecular Weight Averages of Polystyrenes by SEC in Japan

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Abstract
The results of four round-robin tests performed by the group at the Research Committee for Polymer Analysis of the Japan Society for Analytical Chemistry are reviewed. Although repeatability was under 3%, reproducibility as relative standard deviation (RSD%) among 23 laboratories was between 6% and 10% for weight-average molecular weight (M w) and 13–16% for number-average molecular weight (Mn) using individual operating conditions and by neglecting invalid values. Values of RSD% for M w were improved to 5–6% if laboratories used prescribed operational conditions and the same PS calibration standards. Standardization of baseline determination was important to obtain improved M n values. The use of the same type of detector was also important for the comparison of M n values among laboratories. The use of PS calibration standards of different manufacturers resulted in different values of calculated molecular wc:ght averages. By using prescribed operational conditions, such as PS calibration standards, concentrations of standards and samples, injection volume, baseline determination, and detector type. RSD values for M w among laboratories were less than 6% and those for M n less than 10%. If the same columns were used at different laboratories and the same person recalculated molecular weight averages, the RSD values for M w were less than 4% and that for M w less than 6%.

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