GCMS resolution

[fdana]

Hi, GCMS Eexperts,

I am trying to resolve GCMS EI spec, I have one spec that has 4 signals of 105, 77, 75 and 45, no library match in NIST and Wiley, anyone has experience with it and can tell me what this is? is it a SPME fiber?

Thanks a lot for info!

fdana

[James_Ball]

Hi, GCMS Eexperts,

I am trying to resolve GCMS EI spec, I have one spec that has 4 signals of 105, 77, 75 and 45, no library match in NIST and Wiley, anyone has experience with it and can tell me what this is? is it a SPME fiber?

Thanks a lot for info!

fdana

Many of the substituted Benzene compounds have 77 as a major ion. Ethylbenzene also has the 105 but the major ion for that is 91, sec-butyl and tert-butyl benzene have 134, 105, 91 and 77. But unless the tune of the MS is way off, those should be found in the library searches.

[Peter Apps]

Can you be sure that there is only one compound in the peak ?

Peter

[fdana]

Hi, Peter and James,

Thanks a lot for reply!

It is one compound peak, it appears in quite some samples, and it remains to be unknown in lab history.

I wonder it is a SPME fiber related stuff release.

fdana

[Peter Apps]

Have you run a blank ?

Peter

[JMB]

1. Do mass chromatograms of m/z 105, 77, 75 and 45 match EXACTLY ??

2. From memory, SPME fibres are polydimethylsiloxane (NO aromatic content)--please check.

3. Most importantly, an MS spectrum CANNOT be fully interpreted in the absence of the molecular ion. Suggest you run GC/MS in chemical ionization +ve mode.

4. If MW 105, then by the N rule, your molecule has an ODD (1,3,5 etc) number of N atoms. If MW is EVEN, then N atom count is even (0, 2, 4 etc).