Determination of critical eluent composition for polyethylenglycols using on-line liquid chromatography—Fourier transform infrared spectrometry

In this work, it has been extended to methanol:water mobile phases, the use of a background correction method for on-line LC–FTIR measurements named Univariate background correction based on the use of a reference spectra matrix (UBC-RSM) and absorbance ratios. It permits to overcome the problem related to spectral changes occurring during the gradient elution, which in the past limited the on-line coupling of LC and FTIR to isocratic elutions. The combined use of the aforementioned background correction technique in on-line isocratic and gradient LC–FTIR, and partial least squares (PLS) has been applied for the search of the critical conditions for polymers. Polyethylenglycol (PEG) has been used as a model example and results found fitted well with previously published ones.