Pharmacosmos DEAE-Dextran
DEAE-Dextran
DEAE-Dextran is synthesised by the reaction of dextran with (2-chloroethyl) diethylammonium chloride in an alkaline solution.
DEAE-Dextran is a polycation containing three basic groups with different pKa values. There are two tertiary groups: one in the single substituted glucose unit that has a pKa value of approximately 9.2 and the tertiary group in the tandem substitution that has a pKa value of approximately 5.5.
The quaternary nitrogen cannot be protonated and cannot have a true pKa.
Titration of DEAE-Dextran
This figure shows the titration curve from the titration of DEAE-Dextran after alkylation.
The grey vertical bar shows the point at which the excess sodium hydroxide is titrated. The light blue vertical bar shows when the tertiary group with pKa of approximately 9.2 is titrated, and finally the dark blue vertical bar shows when the tertiary group with pKa near 5.5 is titrated.
The total amount of nitrogen can be calculated from the titration curve or by Kjeldahl-analysis. The nitrogen content of approximately 3.2% is equivalent to one charged group per three glucose units.
As seen in the above figure, DEAE-Dextran contains more tertiary groups than quaternary amino groups. Calculated on the amount of nitrogen in the DEAE-Dextran, approximately 2/3 of the nitrogen content belongs to the tandem substitution.
DEAE-Dextran is stable in solution at ambient temperatures and at pH values ranging from pH 4-14. The dry powder has good stability.
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