PURPOSE: To enable GPC chromatograph measurement of a high polymer electrolyte which is considered to be immeasurable thus far by using a soln. which contains a specific compd. and of which the pH value is adjusted by dissolving an inorg. acid therein.

CONSTITUTION: A soln. which contains the compd. (I) expressed by the formula I and of which the pH value is adjusted to 2W6 by dissolving an inorg. acid therein is used. The ratio of the compd. (I) in a solvent mixture is made preferably to ≤90vol% and ≥40vol%. The purpose of using the compd. (I) is to dissolve the sample which does not dissolve with generally used THF and CHCl3 and to perform the GPC measurement thereof. The pH value of the eluate is more particularly preferably adjusted to 3.0W4.0pH. When the pH value exceeds 6.0, the reproducibility for the GPC chromatogram is lost if the sample is a high polymer electrolyte. If the pH value is below 2.0, corrosion of the device by the effect of the acid and the deterioration of the packing material for a column are liable to arise.