Hi Ajeet, identification of unknown GC/MS-peaks can be done by using mass spectral libraries (e.g. NIST 17, Wiley registry; look here: http://www.sisweb.com/software/ms/wiley.htm). If you are experienced in interpreting EI mass spectra you can narrow the selection of possible structures. For this purpose I recommend you the book 'Interpretation of Mass Spectra' by Fred W. McLafferty and Frantisek Turecek (https://www.amazon.de/Interpretation-Mass-Spectra-Fred-McLafferty/dp/0935702253). To determine the M+-radical you can use soft ionization techniques (e.g. ionization with methanol or methane). Halogenes (Cl, Br) can be easily determined by their isotopic pattern. Number of N atoms (even or odd) can be determined by using the N-rule. Alkanes show a fragmentation pattern with a characteristic mass difference of 14. Acrylates show a chararcteristic ion with m/z = 55. Phthalates show m/z = 149. Aromatic benzyl rings often show m/z = 91 (Tropylium cation). You see, that different classes show very characteristic ions. For learning I recommend you to study the EI spectra of common structures and try to explain the characteristic ion pattern. Greetings Markus
Hi Ajeet, identification of unknown GC/MS-peaks can be done by using mass spectral libraries (e.g. NIST 17, Wiley registry; look here: http://www.sisweb.com/software/ms/wiley.htm). If you are experienced in interpreting EI mass spectra you can narrow the selection of possible structures. For this purpose I recommend you the book 'Interpretation of Mass Spectra' by Fred W. McLafferty and Frantisek Turecek (https://www.amazon.de/Interpretation-Mass-Spectra-Fred-McLafferty/dp/0935702253). To determine the M+-radical you can use soft ionization techniques (e.g. ionization with methanol or methane). Halogenes (Cl, Br) can be easily determined by their isotopic pattern. Number of N atoms (even or odd) can be determined by using the N-rule. Alkanes show a fragmentation pattern with a characteristic mass difference of 14. Acrylates show a chararcteristic ion with m/z = 55. Phthalates show m/z = 149. Aromatic benzyl rings often show m/z = 91 (Tropylium cation). You see, that different classes show very characteristic ions. For learning I recommend you to study the EI spectra of common structures and try to explain the characteristic ion pattern. Greetings Markus
Hi Ajeet, a good software package for interpreting EI-MS spectra is the following: http://www.acdlabs.com/products/adh/ms/
Greetings Markus
Commonly, the GC/MS have a software to do that. However, you cant try to have information from papers on the same topic. Besides, you can use model chemicals.
Best Regards
SAM
you can identify the GC-MS peaks by searching in the NIST Library and also confirmed with known standards.
There are a lot of good comments listed, such as using the manufacturer software. Also, as mentioned above by using the NIST Library search is probably the easiest way to narrow your identification. But another way is to concentrate on the base peak and molecular ion of your MS and there are textbooks as well as the internet that might guide you in your identification. Of course this is a little more work than just pushing a button. Again verification against a known standard is also a must, as mentioned by Vimala Vimala. The most simple step is to purchase a search program and library that can be used on your instrument.
this link works
https://www.researchgate.net/deref/http%3A%2F%2Fwww.acdlabs.com%2Fproducts%2Fadh%2Fms%2F
- Badges
- Science topic
- Similar topics
- Computer Science and Engineering
- Software