Not mass friendlycompound

[mk12]

I have to develop method for detecting raspberry ketone in our cell extracts. this molecule is not very mass freindly. LOD right now is 10ug/ml with Single ion mode in neg mode.

What should i do to increase the sensitivity for this molecule..help is highly appreciated

[Don_Hilton]

Whatn kind of technique are you using (LC/MS? GC/MS?)? If GC/MS, I would expect to find this fairly eaisly at this concentraiton. But without even knowing what kind of instrument, never mind conditions, it is a bit difficult to offer somethign to obtain an improvement.

[mk12]

Hi! Don thanks for replying We do not have GCMS what I have is Shimadzu IT_TOF (ESI) and WaterS UPLC SQ(ESI).

I can see ion 165(M+H) and 163 (M-H) in uplc SQ but there is no positive or neg ion in shimadzu but do see a huge peak with weird ions. . In UPLC if I use single ion mode i can have LOD of 10ug/ml but can not verify or quantify because can not have MSMS in UPLC is SQ.

For gradient I am using 5% to 100 ACN (0.1% formic acid) in both mobile phase A and B , C18 ,5 micron column. In Shimadzu my interface voltage is -3.5 for neg, CDL temp is 200C, Nebulizer gas flow is 1.5 L/min, Heat block temp is 200C, Dec voltage is 1.55 KV.

Both UPLC and Shimadzu has ESI mode but why I only see M+H and M-H in UPLC.

[orcicdejan]

So, you get [M-H]- with Waters instrument, but weird ions with Shimadzu? What are those weird ions? Is there a possibility that the system is contaminated and you're getting various adduct ions - [M+HCOO]-, [M+Cl]-, [M+H2PO4]- etc. in NI, and [M+ NH4]+, [M+Na]+, [M+K]+, [2M+Na]+ etc. in PI?

[Jeff Dahl]

If formic acid didn't work, you might try ammonium acetate or ammonium formate at 5 mM and see if you can get better signal intensity.

[lmh]

(1) tell us what the weird masses are! Someone might be able to work out their relation to your ketone.

(2) My guess is that your ketone has some volatility, especially in the half-vacuum conditions it will meet half way down a heated capillary on the way into a mass spec, and it may be being lost by the same mechanism as removes the solvent! You could try reducing capillary temperatures and drying gas temperatures as low as you dare... Spray chamber conditions are one of those things that varies most between different manufacturers.