Chromatography Forum

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

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.

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

Peter

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

Have you run a blank ?

Peter

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).