Quantitative determination of cellulose dissolved in 1-ethyl-3-methylimidazolium acetate using partial least squares regression on FTIR spectra

► FTIR was investigated as a tool to measure cellulose concentration in the ionic liquid [emim][OAc]. ► Spectra were treated by partial least squares (PLS) regression to determine cellulose content. ► A model for estimating cellulose content between 0 wt.% and 4 wt.% with error of 0.53 wt.% was generated. ► The methods provide a rapid, facile technique for determination of dissolved cellulose in [emim][OAc].