During the prepn. of agarose, the sulphur content of agar is reduced by agitation in a phosphate buffer and sulphate gps. contg. agar-pectin is removed by ion-exchange. Remnant charges are removed previously by redn. with norohydrides in the course of conventional suspension polymerisation. - To obtain a crosslinked prod., bead polymers are prepd. by reversed phase emulsification and crosslinked by epichlorohydrin for stabilisation. Remaining sulphate and carboxy gas are removed by sodium-borohydride redn. at 90-130 deg.C in alkaline medium. The prod. is washed with alkali contg. borohydride, neutralised with acetic-acid and rinsed to neutral by distilled water
