Figure 3: Mass spectrometry (MS)/MS response of peripheral blood mononuclear cell extract with 50 ng nevirapine and efavirenz, including their respective internal standards: The two left most peaks illustrate the MS/MS response of nevirapine (m/z = 267.4 > 267.4, Rt = 2.23, C) and its internal standard (BIRH-414) (m/z = 255 > 255, Rt = 3.00, A). The right most peaks represent the response of efavirenz (m/z = 316 > 272, Rt = 7.56, B) and its internal standard (d4-EFV) (m/z = 320 > 276, Rt = 7.47, D).