Dear All,

We are using a PE-SCIEX API 3000 LC/MS/MS instrument. We would like to have your opinion regarding the following,

1. Is there any possiblity or recent findings for the installation of EI probe in LCMS

2. Is there any recent finding for the use of Phospate type buffers in LCMS.

Advance thanks

1) When I was a student, I read some ancient history on LC/MS. :-) There was an ionization techique / inlet called "particle beam" for LC/MS, and it gave library searchable EI spectra. It is my understanding that the techique was mostly abandoned due to poor sensitivity. There is at least one vendor still selling particle beam sources (I received one of their ads in the mail) but I can't remember who.

2) This might not be too recent, but... A number of people have used post-column suppressors to remove nonvolatile buffers. Check the literature. I've tried it myself and found that it wasn't worth the trouble. Your mileage may vary. Also, some manufacturers claim that their source designs can handle nonvolatile buffers to a certain extent.

Dear MG,

Thanks for your useful suggestions.

We are afraid to use the post column suppressors due to the fact that it may block our isntrument and we have to spend a lot of time in cleaning...

Thanks

>We are afraid to use the post column suppressors
>due to the fact that it may block our isntrument
>and we have to spend a lot of time in
>cleaning...

That wasn't a problem when I tried it. The suppressor removed the phosphate buffer quite effectively, and there was no buildup of salt in the ion source. Of course, if you are only removing phosphate anion, the cation must be volatile (e.g. ammonium). But there are other considerations. The suppressor may change the eluent pH to something undesirable for your ionization mode. Also, I found that the suppressor would cause peak broadening or tailing for certain analytes.