A simple and sensitive liquid chromatography–tandem mass spectrometry assay for the quantification of ertapenem in microdialysate

A new liquid chromatography assay with isocratic elution and tandem mass spectrometry detection (LC–MS/MS) using an electrospray ionization interface in the multiple reaction monitoring mode was developed and validated for ertapenem determination in microdialysate samples. Linearity was demonstrated between 10 ng mL−1 (lower limit of quantification, LLoQ) and 160 ng mL−1. The precision (CV%) and accuracy (bias%) in microdialysates at the LLoQ were respectively 2.2% and 17.3% within-day and 10.6% and 2.7% between-days. Ertapenem was stable for 1 month at −20 °C and −80 °C but unstable at +4 °C. This new LC–MS/MS assay is simple, rapid and more sensitive than previously described assays.