Optimized procedures for simultaneous quantitation of low concentration levels of morphine and codeine in urine using gas chromatography–mass spectrometry

Abstract

Background: Detection techniques with high specificity, precision and accuracy are required for evidence of illicit drug intake. The study aim was to develop a low-concentration drug testing method for morphine and codeine in urine samples using gas chromatography-mass spectrometry (GC-MS) to establish a precise quantitative analytical method that improves upon limit of detection (LOD), limit of quantitation (LOQ), precision, and accuracy of currently available detection methods. Methods: Using a 300 ng/mL urine sample, solid phase extraction was performed using an automated solid phase method. All analyses were performed using a Hewlett-Packard (Palo Alto, CA) HP 6890 gas chromatograph interfaced to a HP 5973 mass selective detector (MSD) equipped with a DB-5MS column to acquire full-scan and SIM mass spectrometric data. Solid phase extraction was optimal at pH 9.0 in a 2 ml sample volume. An internal standard concentration of 100 ng/mL yielded optimal results. Results: Standard solution ranges (40-450 and 40-1500 ng/mL) significantly influenced LOQ. Calibration methods were not associated with LOD and LOQ for either MOR or COD. The intra- and inter-day precision values did not exceed 2% and were not different within groups. The accuracy of the examined method ranged from 97.8% to 103.3%. All parameters were validated in 33 clinical urine specimens. Conclusions: This developed method was successfully used for the determination of morphine and codeine in human urine for forensic identification. The examined protocol can be applied to simultaneous quantification of morphine and codeine at low concentration levels in urine.

Keywords

• gas chromatography–mass spectrometry
• urine specimen
• internal standard method
• limit of detection
• limit of quantitation
• morphine; codeine