Infrared spectroscopy of ion-exchange resins. Determination of amino acidsionic form in the resin phase

The paper shows the applicability of IR spectroscopy to investigate the ion ization of sorbates in the resin phase. Amino acids sorbed by sulphuric pol ystyrene-divinylbenzene cation-exchange resin were used as example. Charge changes in the resin phase accompanies sorption of amino acid ions. The ave rage charge of the ions in the cation-exchanger phase is more positive than in the surrounding solution. Only the sorption of the most positively char ged ions is not accompanied with recharging. The charge changing is the rea son for ion-exchange sorption of amino acids by cation-exchange resins at h igh pH. A complete interpretation of the IR spectra for systems containing different lysine and tyrosine ions was done also. The quantitative estimati on of the charge changing can be done through the comparison of the spectra l lines intensity. The ratios Lys(2+)/Lys(+) and Tyr(+)/Tyr(+/-) in the res in phase were calculated as an example. (C) 1999 Elsevier Science B.V. All rights reserved.