How to upgrade MS source to Extractor 350?

EhsanKhedive  What is the model number listed along with the serial number label on your system?  For example, this one is a G7077C, a 5977C system with a turbomolecular high vaccum pump and an extractor ion source.

Hi paulsalverda ,

Thank you for your attention! The model numberd is G7080B with a diffusion oil pump.

I mean 99.999%

The lower the injection port pressure, the less realistic is the vapor volume calculator. It's not perfection in there and 82% is too much.  With Chloroform you'd want the initial oven temperature to be 40° C or even lower. You say your compounds are very light, so reducing it to even 35° C might help chromatographic peak shapes.

Pulsed splitless.30×250×.25 at 1 ml/min is your normal column flow with the inlet at 7.2892 psi at 45°C.  The diffusion pump in your system has a maximum allowable flow of 2 ml/min and the gas calculator says 16.497 psi to get that, so a pulse of 16 psi until 0.5 minutes and then purge flow 50 to split vent at 1.00 minutes would be a good starting point.  Then have gas saver on 25 ml/min at 2.00 minutes. 2 µL of chloroform at 16 psi and 260° C inlet gives 52% expansion, much better, much more realistic/safe/usable.

The split splitless and multimode inlets require a minimum of at least 15 ml/min of total flow to function properly.  That 15 ml/min is not really enough to eliminate the possibility of air diffusion into the system, so I recommend 25 ml/min at all times.    If you need to save helium, Agilent sells a Helium Conservation Module that will let you switch to nitrogen whenever the system is not being used.

You can scan from 10 m/z if you'd like as long as you understand that the TIC baseline will include 18, 28, and 32. 

ANY 32 - oxygen -- in your system degrades the column and oxidizes the ion source requiring more cleaning. 

Thank you for your time and valuable information Paul! I really appreciate it! I am aware of water (18), N2 (28), and O2(32) and constantly check their presence.

Best!

Ehsan

Hi paulsalverda 

Just wanted to ask a question out of curiosity. We are located in Fort Collins, 5,000 ft above sea level. So, the atmospheric pressure would be ~12.2 psi here. Is it possible to put inlet pressure at 12.5 psi along with a low septum purge (e.g. 3 ml/min) to prevent air from diffusing to GC when GC is in standby instead of having septum purge of 50ml/min? In this case column flow would be 1.48 ml/min for my setup.

Thanks!

Ehsan

For standby method I'd recommend inlet pressure ~5 psi.  This is gauge pressure so it'll work to prevent air diffusing into the inlet if there are any small leaks.  Keep in splitless mode, set purge flow to 20 mL/min, septum purge to 3 mL/min.

Keep constant flow 1.2 ml/min into the MS and do a Pulsed Splitless injection, tips in the help section of the Operating manual.  Your system's diffusion high vacuum pump can only handle 2.0 ml/min maximum so do not exceed that ever.

If you have a 30m × 0.25mmid column installed, try these parameters.

Oven initial temp 45° C for 1 minute at least.

Pulsed splitless, 18.6 psi pulse for 0.5 minutes, then purge flow to split vent 50 ml/min at 1 minute. Gas Saver ON, 20 ml/min at 2 minutes.

What is your injection solvent?  You can use the vapor volume calculator in the acquisition software to see if more sample will fit into the liner.

Keep constant flow 1.2 ml/min into the MS and do a Pulsed Splitless injection, tips in the help section of the Operating manual.  Your system's diffusion high vacuum pump can only handle 2.0 ml/min maximum so do not exceed that ever.

If you have a 30m × 0.25mmid column installed, try these parameters.

Oven initial temp 45° C for 1 minute at least.

Pulsed splitless, 18.6 psi pulse for 0.5 minutes, then purge flow to split vent 50 ml/min at 1 minute. Gas Saver ON, 20 ml/min at 2 minutes.

What is your injection solvent?  You can use the vapor volume calculator in the acquisition software to see if more sample will fit into the liner.