ABSTRACT
Pretreatment is needed to extract drugs from the hair cortex. Incubation overnight in buffers is generally preferred to ultrasonic bath in solvents, which tend to give dirty extracts. Basic or acidic digestion is also used, depending on molecular properties and stability. Liquid-liquid and solid-phase extractions are the preferred extraction methods, while solid-phase microextraction is not widely used because of its poor accuracy for quantification.
