Prior pH History of the Hair Specimen

Effect of pH on the incorporation of cocaine, benzoylecgonine, and morphine into hair. Caucasian brown hair was exposed to the drug (5 pg/mL) containing a radioactive tracer in 10 mM phosphate buffer at the indicated pH for 1-h, The hair was rinsed three times with water and dried. A 30-min ethanol decontamination was followed by six phosphate decontamination washes. The hair was then digested with sodium hydroxide and the drug concentration measured by scintillation counting. 

Effect of acid/base pretreatment on cocaine incorporation into Caucasian brown hair. The hair was exposed to the solutions listed for 3 h at 37°C and then washed with water until the water was pH neutral. The hair was rinsed two times with 10 mM phosphate buffer, pH 5.6. The hair was then exposed to cocaine (5 pg/mL), decontaminated, and analyzed. To restore the hair, each sample was soaked in 10 mM phosphate buffer, pH 5.6, for 5 d before exposure and analysis. 

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