Greeting fellow Chromatographers!!! I am a forensic chemist seeking advice on a method for the analysis suspected Nitrous Oxide. We have obtained a Nitrous Oxide standard from our local gas distributor. I am Currently using an HP GCMS (model 5890 GC and model 5970 MSD).Since we are attempting to obtain a spectrum of a gas, we are using a hamilton gas tight syringe to collect the sample.We also are using a relatively "cool" injection port ( 65 degrees ) and oven temperature ( 45 - 65 degrees over 15 min. ). Since Nitrous Oxide is a relatively low MW gas, we set the MSD to scan from 10 to 100 amu and we set the filament delay to 10 seconds. Thus far, after injecting ~4 ul of gas we get an error message. I believe we are overloading the detector with sample. Perhaps a smaller injection size or a cooler oven may help. Maybe the interface is too hot (280 degrees).
Any suggestions or comments would be helpful
By Ron on Thursday, November 8, 2001 - 06:17 am:
What concentration is the nitrous oxide? Although nitrous oxide can be analyzed by GC-MS, I would use an ECD with a PLOT column. An ECD can easily measure background levels of nitrous in air, and should have more than adequate sensitivity for you application. Some older MSs will overpressure with a gas injection, and a 5970 certainly does qualify as older. For gas injections to get a decent peak shape you need to do a split injection. I didn't see if you were doing split or splitless injections, but splitless injection will give very poor results.
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