Figure 2.

Extracted ionic chromatogram obtained from UHPLC-HRMS analysis of 0.2 ng/mg amobarbital and pentobarbital in spiked blank hair samples. A mixture of amobarbital and pentobarbital (10 ng each) was spiked into 50 mg of blank hair sample. The efficiency of gradient elution (A) and isocratic elution (B) was evaluated on Thermo Hypersil GOLD^TM C-18 column, Waters ACQUITY^® BEH C-18 column and Phenomenex Kinetex^® EVO column. The mobile phases for isocratic elution were 80% 10 mmol/L ammonium acetate (B-a) or pure water (B-b) and 20% acetonitrile.