I have been trying to determine some carbamtae derivatives using LC/MS, I am using ESI/positive ion mode ; gradient elution: water+0.1 % TFA then acetonitrile+ 0.1 % TFA but no ionization is observed, any suggestions?
did you try other eluents? I used to to with formic acid (0.2%) in both eluents ; A: water and B : methanol/acetonitrile (80/20, v/v). But for multiresidue analysis also works A: water (0.2%formic acid) and B methanol/acetonitrile (80/20, v/v) with 3 to 5 mM ammonium acetate. hoping to have helped you
Agreed with Lounes Haroune, but for chromatography separation i have got good results in multi residues analysis using Mobile phase A : 0.1% formic acid in H2O / Acetonitrile // 90/10 (V/V) and Mobile phase B : 0.1% formic acid in H2O / Acetonitrile // 10/90 (V/V) using C18 column of 1.8um.
Gradient program can be optimized by trial and error method depending on no. of analytes.