I know nothing about mass spec but am currently developing a method for HPLC and need to bare in mind Mass Spec compatibility for future investigations. I am adding Sodium Bisulfite (approx 0.1%) as an antioxidant to the sample matrix, can anyone tell me if Sodium Bisulfite can go through the mass spec. If not does anyone know of an antioxidant that can.

If your analyte is well retained, then it will be separated from the salt and you won't have immediate problems with ion suppression. But, over many injections the salt will continue to crystallize in the ion source. Eventually the instrument will have to go offline for cleaning, probably sooner than if the salt were absent. One way around this is to use an automated switching valve to divert the dead volume to waste. If possible, you should use a spare pump to provide makeup flow to the ion source during the divert time. Some systems will have a switching valve built-in, either on the MS or the LC.

Thanks for your help, I will look into this further.