Today, met a general question: how to improve the ESI Sensitivity? So I would like to answer this question from the preparation of sample.(1) Select appropriate chromatography grade HPLC solvents
(2) Avoid exotic solvent mixes (MeOH, MeCN, Water, 0.1% formic work best for 98% of LC/MS applications)
(3) Avoid adding excessive modifiers (eg amm.acetate @ 10mM not 50mM)
Choose the right column chemistry (C-8 vs. C-18); change column chemistry before changing solvent mix or composition.
(4) 2.1mm column or lower, flow rates of 200-400 uL/min
(5) Peak widths for quantification not greater than 8-10 secs
(6) Dissolve sample in start mobile phase solvent (weakest solvent possible).
Here is a schematic drawing of the Finnigan MAT 900S electrospray ion source (kindly provided by EPA/Dr. Helmut Muenster.)
