Validación de un método analítico por cromatografía de gas-líquido y reacción colorida para la identificación de cocaína y metanfetamina en muestras decomisadas

In Mexico there is an increase in morbidity and mortality rates due to cocaine and methamphetamine consumption, which has become a main public health issue. Thus, new strategies against traffic and use of narcotics must be developed in order to reduce drug demand. This study proposes a two-step method to analyze seized drug samples containing cocaine or methamphetamine by means of color and chromatographic techniques. The preliminary test consists of color reactions to distinguish between secondary and tertiary amines by using sodium nitroferricyanide and cobalt thiocyanate, respectively. The next step requires a gas-liquid chromatograph equipped with a flame ionization detector that is universally available and affordable for most forensic laboratories. The results showed that there are no interferences of common adulterants, such as acetaminophen, caffeine, acetylsalicylic acid, benzocaine and phenacetin. The limit of detection for color tests was 20 ?g and 4 ?g for cocaine and methamphetamine, respectively. The limit for chromatographic technique was 2 mg/mL for both substances. Carryover effect was not seen with drug concentration up to one order of magnitude. The qualitative method was validated and found to be simple, economic and selective for identification of cocaine and methamphetamine in seized drug samples.