Simultaneous quantification of 11 antiepileptic drugs using limited isotope-labeled internal standards in LC-MS/MS:...

This study aims to establish an LC-MS/MS method to simultaneously analyze 11 antiepileptic drugs with a particular focus on maintaining accuracy while reducing the number of isotope-labeled internal standards employed for cost-effectiveness. By applying a water/acetonitrile gradient elution containing 0.1 % formic acid and 2 mM ammonium formate as the mobile phase, optimal sensitivity for the target drugs could be obtained in positive ESI mode in LC-MS/MS. After optimizing various extraction techniques, extraction with 70 % acetonitrile was selected as it provided good recoveries (>93 %) for all targets without matrix effects. Accuracies within 3 % were achieved from the combination of six internal standards, while accuracies of 5 % and 10 % were obtained by reducing the number of internal standards to four and two, respectively, for more economical analysis. The accuracy of the established method was maintained in hyperglycemia, hyperlipidemia, and hyperalbuminemia sera, suggesting that it can be successfully applied to individual serum samples with various properties.