I have been trying to develop a method using IC to measure sulfite in proteins. The protein has been interfering with the measurement process. Does anyone have any ideas as to how to rid the sample of the protein and still leave the sulfite to be analyzed?

You could try centrifugal filtration devices. These come in a wide range of cut-offs. Pall Gelman is a supplier.

I haven't tried this myself, but it should work. Acidify the sample and distill over SO2. If I remember correctly this is the basis of a classical analysis for sulfite.You could probably trap in an oxidizing agent and either determine sulfate or the oxidized or reduced form of the trapping agent.

Are you getting any interferences on the front or tail end of the peak? Perhaps a different column may work (Metrosep A Supp 5) or dialysis (Metrohm 754 dialysis unit) could potentially solve this problem. Is sulfate interfering with your analysis? This is a very typical interference with sulfite. Over time sulfite will break down and the amount of sulfate will increase. On the Supp 5 column mentioned, the difference in retention time between sulfite and sulfate is about 4 minutes!

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