Abstract
A method based on the direct injection of diluted urine for the identification and quantification of morphine, morphine‐3‐glucuronide, morphine‐6‐glucuronide, codeine, codeine‐6‐glucuronide, ethylmorphine, ethylmorphine‐6‐glucuronide and 6‐acetylmorphine (6AM) in human urine by electrospray ionisation liquid chromatography‐tandem mass spectrometry was validated for use as a confirmation procedure in urine drug testing. Four deuterium labelled analogues were used as internal standards: morphine‐3‐glucuronide‐D3, morphine‐D3, codeine‐D3 and 6AM‐D3. Twenty microlitre aliquots of urine were mixed with 80 μl of the internal standard solution in autosampler vials and 10 μl was injected. The chromatographic system consisted of a 2.0 × 100 mm C18 column and the gradient elution buffers used acetonitrile and 25 mmol/l formic acid. Two product ions produced from the protonated molecular ions were monitored in the selected reaction monitoring mode. The intra‐ and inter‐assay variability (coefficient of variation) was below 10% at higher levels for all analytes, but at the reporting limits the variation was above 20% for 6AM, morphine‐3‐glucuronide and codeine‐6‐glucuronide. Ion suppression occurred early after injection but did not affect the identification and quantification of the analytes in authentic samples. The method was further validated by comparison with a reference gas chromatographic‐mass spectrometric method using authentic urine samples. The two methods agreed almost completely (99%) regarding the identified analytes, but for the quantitative results there were slightly lower levels when measuring glucuronides directly as compared to total determination after hydrolysis by gas chromatography‐mass spectrometry.
We conclude that the presented liquid chromatographic‐tandem mass spectrometric method is robust and reliable, and suitable for use as a confirmation method in urine drug testing for opiates
Copyright © 2007 John Wiley & Sons, Ltd.