Determination of cocaine adulterants in human urine by dispersive liquid-liquid microextraction and high-performance liquid chromatography

• Published in: Analytical and bioanalytical chemistry Vol. 411; no. 16; pp. 3447 - 3461
• Main Authors: da Silva, Pedro Rafael, Sena, Laís Cristina Santana, Silva, Rubens Pedro Lorena, de Santana, Danielle Cristine Almeida Silva, de Santana, Fernando José Malagueño
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2019; Springer; Springer Nature B.V
• Subjects: Acetanilide; Acetonitrile; Acute intoxication; Adulterants; Alkalizing; Analytical Chemistry; Biochemistry; Caffeine; Characterization and Evaluation of Materials; Chemical properties; Chemistry; Chemistry and Materials Science; Chloroform; Chromatography; Cocaine; Dependence; Design of experiments; Diltiazem; Dispersion; Drug abuse; Elution; Experimental design; Extraction (Chemistry); Food Science; Freeze thaw cycles; Freeze-thawing; High performance liquid chromatography; Human wastes; Identification and classification; Intoxication; Ions; Laboratory Medicine; Lidocaine; Liquid chromatography; Liquid-liquid extraction; Methods; Monitoring/Environmental Analysis; pH effects; Phenacetin; Research Paper; Selectivity; Sodium chloride; Sodium phosphate; Solvents; Stability tests; Trifluoroacetic acid; Urine; Dispersive liquid-liquid microextraction; Urine drug testing; Liquid chromatography; Street cocaine; Drug adulteration
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-019-01797-z

This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human urine by dispersive liquid-liquid microextraction (DLLME) and high-performance liquid chromatography. The chromatographic separation was obtained in gradient elution mode using methanol:water plus trifluoroacetic acid 0.15% ( v / v ) (pH = 1.9) at 1 mL min −1 as mobile phase, at 25 °C, detection at 235 nm, and analysis time of 20 min. The effect of major DLLME operating parameters on extraction efficiency was explored using the multifactorial experimental design approach. The optimum extraction condition was set as 4 mL human urine sample alkalized with 0.5 M sodium phosphate buffer (pH 12), NaCl (15%, m / v ), 300 μL acetonitrile (dispersive solvent), and 800 μL chloroform (extraction solvent). Linear response ( r 2  ≥ 0.99) was obtained in the range of 180–1500 ng mL −1 with suitable selectivity, quantification limit (180 ng mL −1 ), mean recoveries (33.43–76.63%), and showing relative standard deviation and error (within and between-day assays) ≤15%. The analytes were stable after a freeze-thaw cycle and a short-term room temperature stability test. This method was successfully applied in real samples of cocaine users, suggesting that our study may contribute to the appropriate treatment of cocaine dependence or with the cases of cocaine acute intoxication.