Matrix effects in collision cell

<p>I see some strange effects with direct injection on column of brackish water.</p><p></p><p>Briefly: When I directly inject brackish water on column, the response of the MRM is significantly lower than the same injection of tap water. What I see is that the product ion enhances (no adducts are formed) but the response of fragments in the collision cell decreases. See the example below</p><p></p><p>Some things i allready tested:</p><p>- The collision energy has no influence on the effect. At higher energies, both product ion and fragments decreases.</p><p>- The compounds involved are pesticides and especially phosphorous pesticides and phenyl urea herbicides. Triazines are not influenced!</p><p>- When I use Offline SPE and inject 90% organic extract, the effects are gone.</p><p></p><p></p><p></p><p>example:</p><p><img height="794" src="" width="1446"/></p><p></p><p>System: I_CLass FTN UPLC coupled to Xevo-TQS. 250µl extention loop.</p><p>Column: Xselect HSS-T3 75x2.1mm, 2.5µm</p><p>Mobile Phase A: 95% H2O, 5% MeOH, 0.05% FA</p><p>Mobile Phase B: 100%acetonitril, 0.05% FA</p><p></p><p>water sample from North Sea estuary.</p><p></p><p></p><p>My question is why it happens and off course how to loose the effects.</p>


  • Have you tried running in full scan 'daughter ion' mode to see if the population of fragments is different?

    Different matrix conditions as your sample elute can cause the  likelihood of protonation at different sites on the molecule to change.

    This may lead to a different relative distribution of fragments at a given collision energy.

    Someone more knowledgable on mass spec or environmental analysis might give you a better answer.

  • I tried the daughter scan and it looks like there is indeed a different energy change on the molecule. The parent ion is more intense while the fragments are lower in intensity (see image attached). There is however no change in optimal collision energy or fragmentation pattern. When I increase the energy, all ions decreases in intensity.