Q1 scan tuning type

[smkh]

Dear all;

My question is about tuning in Q1 scan type , either using manual or automatic optimization , if the molecular weight of my parent compound for example =280 g/mol and the result of automatic tuning in Q1 scan gives me 282 also when do manual tuning iget 282 as amost intense one , what dose this mean ?
Is 282 must be consider as aQ1 mass or imust intrest in the real one 280 and optimize it by manual tuning

[MH]

Without more information, there are a number of posibillities.
I'll give it a try:
1. Your instrument is out of calibration by 2 amu. Are you sure about the calibration?
2. Your compound contains some elements with "exotic" isotope distribution and the monoisotopic mass is not the most intense. Did you calculate the isotope model? Which peak should be the most intense?
3. A compound with m/z 282 is in the mixture. Are you injecting standards or (crude) mixtures?
4. How is the resolution set on your first quad? In other words: How sharp are your peaks?

Please provide more details!

Cheers,
MH

[smkh]

Hi; MH

Thanks alot for your intrest and replying
your informations are very useful to me ...
Calibration of instrument is ok,
my analyte contains Cl which explain the difference in the molecular weight.
I inject standard
Resolution not good in first quad and need Optimization......

thanks again

[MH]

Ok, so you are sure that m/z 282 comes from your analyte of interest.
In that case, there is nothing wrong to tune on 282 if that is the most intense peak. Just keep your monoisotopic mass in mind if you are going to fragment your analyte...

What kind of instrument are you using? QqQ? QTof? QTrap?

By the way: Did you see that one?
http://www.sepsci.com/chromforum/viewto ... hlight=282

[smkh]

My instrument is QqQ,Did you mean that Imust optimize the 280 if iwant to fragment it , I optimize it and fragment it to give daughter of 179 it is good and gives intense peak but there is another broad peak in this mass after 2.00 minute of my analyte, some times move.
my analyte have two metabolites , the internal standard is the detorieted analyte (analyte D6) is it possible to work on the same fragment to all these analytes.
it was very exiting to me to read the topics about m/z 282

thanks alot