extraction of docetaxel from lactated ringers for LC/MS

[w-c]

Hi guys I am new to LC/MS and heard this is the place to get answers. I am trying to detect docetaxel/paclitaxel in a sample of lactated ringers. The lactated ringer's is a solution of electrolytes (NaCl, KCl, Ca, lactate). I have been getting ion suppression of the docetaxel peak. I am trying to use solid phase extraction but I cannot seem to get the ion suppression/ electrolytes to go away. Has anybody had experience with lactated ringers or a better desalting extraction?

[Uwe Neue]

On a reversed-phase column or even reversed-phase SPE, the ions should separate readily from the analytes. What are your chromatography conditions?

[w-c]

Chromatography and detection:
-waters 2695 hplc
-micromass zq2000 single quad MS using positive ESI; 3.5kV cap voltage; 25V cone; 120C source temp; 450 desolvation temp
-quantifying the sodium adduct since it was the biggest peak during tuning (830.25 m/z)
-waters xterra c18 3.5um 2.1x100mm colum/ guard column 2.1x20mm 3.5um c18
-mobile phase 50% 40uM sodium acetate with 3.4 mM acetic acid/ 50% ACN; added sodium to force only 1 adduct formation rather than K or NH
-isocratic flow rate 0.2 ml/min

Extraction:
-discovery 96 well SPE plate with 50 mg C18
-method is still being changed using different wash solvents/volumes
-???

I think the problem is that the electrolyte concentrations are very high in lactated ringers compared to my drug concentrations that I spike. mg/ml vs. ng/ml

[Keaka]

Isocratic conditions is likely to be your problem.

Switch to gradient conditions and allow for a brief period of high aqueous at the beginning of your run to wash out all of the salts with a quick ramp to high organic (methanol).