Chemical ionization - what to look out for

[mfiligenzi]

Hi everyone -

We're looking at getting into a project involving negative ion CI on a Waters Quattro GC. I've been doing EI GC/MS and a variety of LC/MS techniques for longer than I like to think but this is my first foray into CI work. Anyone have any caveats or any general advice? (Like maybe, "run for the hills!!!")

Thanks!

[jh1]

What types of compounds are you looking to testing for?

We have an Agilent 5975 running in CI mode, its biggest problems are water contamination from air leaks and the need to clean the source more frequently. On the plus side for the right compounds it's very sensitive.

Also obtaining high purity Methane took a bit of time, our tank had to be shipped in from Texas which took 3+ weeks.

[mfiligenzi]

Thanks for the reply. This would be work on PCBs and PBDEs. We haven't hooked the system up for CI since it was spec'd out about six months ago, but we still have the methane that they used for that, so I'm hoping it will be pure enough to work out.

That's helpful info on the air leaks. I'll try to make sure everything's tight.

[BZK]

Thanks for the reply. This would be work on PCBs and PBDEs. We haven't hooked the system up for CI since it was spec'd out about six months ago, but we still have the methane that they used for that, so I'm hoping it will be pure enough to work out.

That's helpful info on the air leaks. I'll try to make sure everything's tight.

Pay attention to NCI on PCB analysis. I have setting up a new method to measure the 12 toxic PCB dioxin like by means of low resolution HRGC-MS and NCI. Strong dechlorination occours into the ion source for the low chlorinated PCB's. Four chlorine atoms losses about of 90% of total chlorine, five around 50%, six around 30% and no significative losses for high chlorinated PCB's.

The comparison between PCI and NCI for pcb's is anyway win by NCI.
I have observed that the sensitivity with NCI is the same as PCI for 4 chlorine, two or three times more for 5 chlorine, 10 times more for 6 chlorine and up to 30 times for octa PCB's.

The cromathogram is much more clean with NCI than PCI.
I have tested methane and isobutane as reagent gas and the best result are with methane.

Have fun.

Roby

[mfiligenzi]

Pay attention to NCI on PCB analysis. I have setting up a new method to measure the 12 toxic PCB dioxin like by means of low resolution HRGC-MS and NCI. Strong dechlorination occours into the ion source for the low chlorinated PCB's. Four chlorine atoms losses about of 90% of total chlorine, five around 50%, six around 30% and no significative losses for high chlorinated PCB's.

The comparison between PCI and NCI for pcb's is anyway win by NCI.
I have observed that the sensitivity with NCI is the same as PCI for 4 chlorine, two or three times more for 5 chlorine, 10 times more for 6 chlorine and up to 30 times for octa PCB's.

The cromathogram is much more clean with NCI than PCI.
I have tested methane and isobutane as reagent gas and the best result are with methane.

Have fun.

Roby

Thanks, Roby! I appreciate the help.