I am not sure this is the right forum to ask. I am using LC-ICP-MS for Arsenic speciation. The mobile phase is made up of two ion pairing chemicals. They are tetra-methyl ammonium hydroxide and sodium butanesuphonate with malonic acid and 0.05% methanol thrown in. I am using a c18 column. The problem is that the mobile phase is burning up in the cone of the ICP in an orange flame after 3 minutes. And when that happens the whole system stops. Has any one had experience with ion pairing LC with ICP-MS as the detector? How can this be fixed. Thank you in anticipation.

Three comments:

1). I have a difficult time understanding why one would ever choose to use such an "ion pair" system under any circumstances. The presence of the butane sulfonate will only interfere with the retention mechanism, not to mention its adverse effects on the ICP-MS.

2). If you really feel that you need to utilize such a system I would recommend that you switch to a volatile analog: trimethylamine-heptafluorobutyric acid or perhaps triethylamine-heptafluorobutyric acid.

3). Another option would be to use a suppressible eluent in combination ion exchange retention. This would allow the introduction of an eluent solution which is essentially a nonionic matrix was only sample ions to deal with. If you are interested, I can supply references for this approach.