Fabrication of nanofiber stationary phases from chopped polyacrylonitrile co-polymer microfibers for use in ultrathin layer chromatography of amino acids

Electrospun polyacrylonitrile (PAN) copolymer nanofiber based ultrathin layer chromatographic (UTLC) plates fabricated by a facile electrospinning method have been used as the stationary phase for on-plate identification and monitoring of the migration behavior of twenty amino acids using green solvents like n-butanol, ethylene glycol, ethyl acetate and their mixtures as the mobile phase. The PAN copolymer spun nanofibers exhibited physical and chemical robustness in the mobile phases used during the present study. Nanofiber sheets were produced using three different concentrations i.e. 8, 10 and 12 wt% of PAN at variable flow rates i.e. 0.2, 0.5 and 1.0 mL h−1 for each solution of PAN. The surface morphology and diameter of the electrospun PAN nanofibers were examined using scanning electron microscopy techniques. The effect of layer thickness on chromatographic performance of UTLC plates in the separation of amino acids was also investigated. The electrospun PAN UTLC plates prepared from electrospinning 10% (w/v) PAN solution in dimethylformamide using a 0.2 mL h−1 flow rate for about 1 h were found to be most efficient for imparting differential migration among the amino acids with the use of a mixture of n-butanol–ethylene glycol–ethyl acetate (5:3:2 by volume) as the mobile phase. The chromatographic performances of PAN derived UTLC plates and commercially available precoated silica HPTLC plates were compared in respect of their use in the analysis of amino acids. In addition, PAN derived UTLC plates were also compared with silica gel TLC plates and Dowex 50 ion exchange resin (Na+-form) for amino acid sensitivity. The PAN derived UTLC plates were found to be more useful at providing better sensitivity, rapidity and lower solvent requirement for development. The developed method was successfully applied for the identification of the lysine and methionine present in commercial drug samples.