LC-MS/MS Method for the Quantitative Determination of Tanespimycin and its Active Metabolite in Human Plasma: Method Validation and Overcoming an Insidious APCI Source Phenomenon

Abstract

RESULTS: A sensitive method was developed and validated for the measurement of tanespimycin and its active 17-AG in human plasma using tanespimycin -C3, 15N as an internal standard. The assay was validated over the concentration range of 10.0 to 2500 ng/mL for tanespimycin and 5.00 to 1250 ng/mL for 17-AG. During method development, an internal standard variability due to an in-source reduction of the quinone moiety during ionization was observed. The in-source reduction was mitigated by selection of appropriate mobile phases, internal standard concentration, injection volume, source temperature, and continuous maintenance of the source between runs.