Extraction and determination of opium alkaloids in urine samples using dispersive liquid–liquid microextraction followed by high-performance liquid chromatography

► Liquid–liquid microextraction-high performance liquid chromatography method for opium alkaloids. ► Determination of morphine, codeine, papaverine, noscapine and thebaine in urine samples. ► Study of optimum experimental conditions for extraction process. ► Linear calibration over 0.50–500 μg L −1 and limit of detections in the ranges 0.2–10 μg L −1. A simple, rapid and sensitive method based on dispersive liquid–liquid microextraction (DLLME) combined with high-performance liquid chromatography–ultraviolet detection (HPLC-UV) was used to determine opium alkaloids in urine samples. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, enrichment factors and recoveries for different opiates are in the range of 63.0–104.5 and 31.5–52.2%, respectively. The calibration graphs are linear in the range of 0.50–500 μg L −1 and limit of detections (LODs) are in the range of 0.2–10 μg L −1. The relative standard deviations (RSDs) for 200 μg L −1 of morphine, codeine and thebaine, 5.0 μg L −1 of papaverine and 10.0 μg L −1 of noscapine in diluted urine sample are in the range of 2.8–6.1% ( n = 7). The relative recoveries of urine samples spiked with alkaloids are 84.3–106.0%. The obtained results show that DLLME combined with HPLC-UV is a fast and simple method for the determination of opium alkaloids in urine samples.