gram of propionaldehyde diacetal activated 5 000 weight average molecular weight mpeg is mixed with 3 milliliters of water to produce a sample for injection 5 microliters of the sample for injection is injected into a moblile phase of 52 a and 48 b where a is 47 acetonitrile in water and b is 43 acetonitrile in water at a mobile phase flow rate of 0 75 milliliters per minute and flowed through a 5 micrometer packing diameter supelco lc 18 reverse phase column at a column temperature of 30 degrees celsius the column having an internal diameter of 4 6 millimeters and a length of 250 millimeters followed by an evaporative light scattering detector to produce the chromatogram shown in fig1 the chromatogram of fig1 shows a peak at about 3 8 minutes for mpeg a peak at about 4 8 minutes for the activated mpeg and a peak at about 5 6 minutes for the activated diol the mole percent concentration of mpeg is determined by dividing the peak area of the mpeg peak by the combined peak areas of the mpeg the activated mpeg and the activated diol peak areas and then multiplying by 100 the mole percent concentration of activated mpeg is determined by dividing the peak area of the activated mpeg peak by the combined peak areas of the mpeg the activated mpeg and the activated diol peak areas and then multiplying by 100 the mole percent concentration of activated diol is determined by dividing the peak area of the activated diol peak by the combined peak areas of the mpeg the activated mpeg and the activated diol peak areas and then multiplying by 100 evaporative light scattering detection is well.