Development and validation of a GC-FID method for determination of cocaine in illicit drug samples

The objective of this study was to develop and validate a simple and reliable GC-FID method for quantitative determination of cocaine in illicit drug samples. Chromatographic conditions and detection parameters were optimized. Separation was performed on a HP-5 column (30 m-0.32 nm ID-0.25 μm) using an internal standard of n-tetracosan at the concentration of 0.25 mg/mL in methanol/chloroform (1:1) mixture. Validation of the method was performed by means of specificity, linearity, accuracy, precision, range, quantitation limit and detection limit. Method showed linearity with excellent correlation coefficients (r2=0.9992) for cocaine. The limit of detection and limit of quantification values of GC-FID method for cocaine analysis were 1.80 µg /mL and 5.57 µg /mL, respectively while limit of linearity was 1200 µg /mL. Mean recovery value obtained from spike study was 101.20%, and relative error calculated after CRM analysis was equal to 1.0%, indicating that method was accurate. Inter-day stability of the instrument was proven by use of the control chart. The procedure described is relatively fast, simple, precise, and applicable for routine illicit drug analysis in forensic laboratories.

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