Jr. Vega et Gr. Meira, SEC of simple polymers with molar mass detection in presence of instrumental broadening. Computer simulation study on the calculation of unbiased molecular weight distributions, J LIQ CHR R, 24(7), 2001, pp. 901-919
This theoretical work presents a correction procedure for calculating an un
biased MWD when analyzing a linear homopolymer by size exclusion chromatogr
aphy with molar mass detection. The fractionation and the measurements are
ideal, but the chromatograms are distorted by a nonuniform and skewed instr
umental broadening (IB), and are contaminated with a zero-mean random noise
. The main assumption is that the molecular weight calibration is linear in
the chromatogram range.
The following phenomenological procedure was proposed: (i) independently co
rrect the mass- and molar mass chromatograms for IB through a robust invers
e filtering technique; (ii) estimate the unbiased calibration from the rati
o of the corrected chromatograms; (iii) adjust a straight line to the mid-v
alues of that calibration; and (iv) estimate the unbiased MWD from the line
ar calibration and the corrected mass chromatogram.
For the chromatogram inversions, a minimum sized broadening matrix was sele
cted and a singular value decomposition technique was applied. The followin
g effects were evaluated: of an increased measurement noise, of uncertainti
es in the range of the measured chromatograms, and of systematic errors in
the IB function. The method fails for very narrow MWDs.