Synthesis of quaternised guar gum using Taguchi L₍₁₆₎ orthogonal array

Quaternised polysaccharides have diverse applications due to introduction of quaternary ammonium groups in the biopolymer. In the present study, quaternization of guar gum was carried out by adopting the Taguchi's approach of robust design of experiments for optimizing the levels of the factors to obtain quaternized guar gum with higher DS. The methodology employed far less number of experiments than the classical method which necessitates higher number of chemical reactions to achieve the required derivatisation. The application of Taguchi's L₁₆ (4⁵) orthogonal array resulted in DS of 0.49. The optimized experimental levels were 3.24 mol/AGU of NaOH and 2.04 mol/AGU of CHPTAC for 2 h at 30 °C keeping the gum: liquor ratio 1:20. The study established that Taguchi methodology provided a statistically sound and green approach for optimization of reaction conditions. The modified products were characterised by FTIR, ¹H-NMR, ¹³C-NMR, DEPT-135, HSQC and HMBC spectroscopic methods.