How to report the chemical composition of a sample via

[@asmaashakir4732]

Thank you very much

[@javadpourrezaei.j]

Thank you very much, it was beneficial.

[@fislimohammedislam4158]

Thank you so much Dr

[@javajoe4]

My 'Select Signal to Load' option is grayed out.

[@shirwansany8706]

Hello @javajoe4, thank you for your comment. The 'select signal' will activate if you set the GC/MS to record the chromatogram in both scan and sim modes. If you do not select the sim mode before analyzing the sample, the GC/MS will record the chromatogram in scan mode by default.

[@haniffhanafy5011]

Thank you Dr Shirwan.

[@zafarfarooqofficial3685]

How can I find the molar mass of an oil sample?

[@wild_durian]

if the final results of metabolites after GC-MS analysis in ug/mg, and raw results in ug/ml, then how to convert the individual metabolites concentration into wt%? Please reply

[@abdullahimuhammad6591]

Quit interesting.But can someone use relative abundance instead of using area to get a % composition?

[@shirwansany8706]

Hi @abdullahimuhammad6591, thank you for your comment. Hello, yes possible to use relative abundance instead of area.

[@raahis8256]

I have data of GCMS how can identify each compound without digital library or how can i identify that

[@shirwansany8706]

Hi @raahis8256, thank you for your comment. I recommend you analyse both blank and sample. Then, the blank chromatogram is deducted to get clean mass spectra. From the mass spectra, you could deduce the possible compound based on the mass spectra.

[@somiaafzal6807]

Jzak ALLAH. It's very informative. Can you please share a video/guidance on matching the Kovats index??

[@shirwansany8706]

Salam, Thank you for the question. I have not recorded the video on the index calculation, but I have published the work here: link.springer.com/article/10.1007/s41664-020-00118-z. Shall you need the paper, please request via [e-mail]

[@somiaafzal6807]

@@shirwansany8706 jzak ALLAH for response. Can we match our calculated Kovat retention index for (HP-5) with the theoretical/literature retention index (HP-5) of Kratz?

[@shirwansany8706]

@@somiaafzal6807 possible; However, you may need to follow the GC similar setting from the previously reported retention index. Also, please allow some deviation from the previously reported retention index.

[@somiaafzal6807]

@@shirwansany8706 Jzak Allah for the answer. So the point that is confusing me is that the calculated retention index (Kovats' RI) can be matched with the previously reported/theoretical/NIST chem book etc. Van Den Dool and Kratz RI retention index OR with the Normal alkane RI. So only need to match our GC setting and column type (like HP5 / DB wax type etc.) and find the nearest RI?

[@shirwansany8706]

@@somiaafzal6807 The approach is as follows: 1. Find the original work the calculate the Van den Dool and Kratz RI 2. Follow the GC setting and procedure to get the RI. 3. Compare your calculated RI with the published Van Den Dool and Kratz RI. Else, you also can compare with NIST, Chem Book RIs. The NIST and Chem Book RIs have stated with column they used. Compare the RI of compunds that are separated using the similar column.

[@beautysddewanti6395]

The percentage area is equal to % composition of compound in the sample?

[@shirwansany8706]

Theoretically yes; the limitation is, that the detected peaks whose mass spectra do not match against the NIST library are omitted in this reporting.

[@beautysddewanti6395]

@@shirwansany8706 Thank you Dr Shirwan