Microextraction by Packed Sorbent as a Novel Strategy for Sample Clean-Up in the Determination of Methadone and Eddp in Hair.

A microextraction by packed sorbent (MEPS) procedure for rapid concentration of methadone and its primary metabolite (EDDP) in hair samples was developed. The miniaturized approach coupled to gas chromatography with tandem mass spectrometry (GC-MS-MS) was successfully validated. Hair samples (50 mg) were incubated with 1 mL of 1 M sodium hydroxide for 45 minutes at 50 °C, time after which the extract was neutralized by adding 100 μL of 20% formic acid. Subsequently, MEPS was applied using a M1 sorbent (4 mg; 80% C8 and 20% SCX), first conditioned with three 250 μL cycles of methanol and three 250 μL cycles of 2% formic acid. The extract load occurred with nine 150 μL cycles followed by a washing step involving three 50 μL cycles with 3.36% formic acid. For the elution of the analytes, six 100 μL cycles of 2.36% ammonium hydroxide in methanol were applied. The method was linear from 0.01 to 5 ng/mg, for both compounds, presenting determination coefficients greater than 0.99. Precision and accuracy were in accordance with the statements of international guidelines for method validation. This new miniaturized approach allowed obtaining recoveries ranging from 73 to 109% for methadone and 84 to 110% for EDDP, proving to be an excellent alternative to classic approaches, as well as other miniaturized procedures.