Chromatography Forum

Hello,

First of all, this is my first time here and nice to meet you all.

I am currently working on my research project using QTOF. Where I need to find the stability of synthetic Cannabinoids. Since synthetic cannabinoids are very expensive I am optimizing this method using benzocaine which has similar properties.

I have been using a 0.1% formic acid in water and 0.1% formic acid in acetonitrile(B) in positive mode. and the column I used was C18 column

The gradient I used was as follows with 2microliter injection of 10ppm benzocaine,
B increased until 0-100% over 10 mins time followed by a equilibrium step of 1 min, after that over another 1 minute B goes to the initial 0%.
This was done in positive mode and the mass spectrum was extracted at 166.

So far I haven't been able to witness peaks for benzocaine and I have been seeing other peaks interfering even in the BPI chromatogram. Any idea what I am doing wrong.

Thank you.

See the discussion on Cannabinoids. You probably need a stronger organic solvent like IPA in your mobile phase.

We need more info. like all your chromatographic conditions!

See the discussion on Cannabinoids. You probably need a stronger organic solvent like IPA in your mobile phase.

We need more info. like all your cinematographic conditions!

Thank you I will look into the cannabinoids discussion as well.

The column I have been using was C18 column (2.7 um, 100 x 2.1)
flow rate was 0.25ml/min.
and this was run in positive mode set to the lowest voltage and obtained a TIC. mass spectrum extracted at 166 (Benzocaine - 165g/mol)
column temp was kept at 40C

Is this enough or did I miss something?

Usually both mobile phases contain some organic solvent so the C18 wavy tendriles of the column do not collapse (its like going from fluffy hair to wet hair and thus affects the effectiveness of your separation, I'm an 'old chemist'). As an example, the mobile phases would be;

A; 0.1% Formic Acid in 95% Water/5% IPA

B; o.1% Formic Acid in 5% Water/95% IPA

Under your present scheme, molecules would be completely retained by the column and ACN is not strong enough to elute them.

Usually both mobile phases contain some organic solvent so the C18 wavy tendriles of the column do not collapse (its like going from fluffy hair to wet hair and thus affects the effectiveness of your separation, I'm an 'old chemist'). As an example, the mobile phases would be;

A; 0.1% Formic Acid in 95% Water/5% IPA

B; o.1% Formic Acid in 5% Water/95% IPA

Under your present scheme, molecules would be completely retained by the column and ACN is not strong enough to elute them.

Thank you so much. Ill keep this in mind.

Try starting at 25% B instead of 0%.

http://www.restek.com/chromatogram/view/LC_GN0553

Restek is using the same mobile phase here and they begin at 25%B. Flow is higher because they are using 4.6ID column and UV detection but you can scale the flow to match your column.