Determination of sodium metabisulfite in parenteral formulations by HPIC with suppressed conductivity detection.

Sulfurous compounds: sodium sulfite Na2SO3 (E 221), sodium bisulfite NaHSO, (E 222), and sodium metabisulfite Na2S2O5 (E 223) are largely used as antioxidants in many pharmaceutical formulations. A method for determination of sodium metabisulfite in parenteral formulations containing tartrate ions was developed. High-performance ion chromatography (HPIC) method with suppressed conductivity detection was used. A satisfactory separation of SO(3)2- and SO(4)2- was achieved by the proposed HPIC method with 15 mM NaHCO3/0.6 mM Na2CO3 mobile phase and columns with various packing materials: methacrylate polymer -Allsep A-2 Anion (100 x 4.6 mm, 7 microm) and styrene-divinylbenzene copolymer - IonPac AS14A (250 x 4.0 mm, 7 microm). Use of the Allsep A-2 Anion column provides separation of SO(3)2-, SO(4)2- and C4H4O(4)2- present in the investigated products. The calibration plot was linear for 8-267.3 microg/mL sulfite (r = 0.99978, n = 6) and for 3-165.9 microg/mL sulfate (r = 0.9998, n = 6). The limit of detection for SO(3)(2-) and SO(4)2-were 3 microg/mL and 1 microg/mL, respectively.