“…Several methods lack coelution of the internal standard and the analyte, which is necessary to help compensate for potential matrix effects or for varying ionization efficiency due to mobile-phase gradients (7,10,11,14 ). Laborious sample preparation (8,15 ), large sample volumes (8,(11)(12)(13), time-consuming derivatization procedures (15 ), and a lack of sufficient validation (8 -11 ) exclude these methods from routine analysis. Only one methodology exists for combined measurement of LPA and S1P (11 ).…”