Published: Journal of Analytical Toxicology, Volume 20, Number 4, July/August 1996, pp. 269-270.

Lack of Hydrocodone and Hydromorphone Interference in the GC–MS Detection of Morphine and Codeine
K.E. Brooks and N.B. Smith

To the Editor:
Fenton et al. (1) recently reported that hydrocodone and hydromorphone interfere with gas chromatographic–mass spectrometric (GC–MS) assays for codeine and morphine, respectively, when they are analyzed as acetates or as trimethylsilyl ethers. In addition to their own remedy, which consisted of pretreating the sample with sodium borohydride, they mentioned several other possible solutions (2–4) to this problem. As a simple alternative to sample pretreatments, we describe here an extraction method in which both hydrocodone and hydromorphone form single peaks that do not interfere with either codeine or morphine. We first developed our method for the extraction of a wide range of drugs from urine for GC–MS analysis in a clinical setting (5), which requires that all of the drugs in a sample be identified, not just the drugs of abuse. We did not report its ability to identify the various opiates because, at the time, we were unaware that hydromorphone and hydrocodone interference was a problem.

In our method, sodium bicarbonate and acetic anhydride were added to the urine sample, which was then allowed to react at room temperature. Under these mild aqueous conditions, the acetic anhydride formed acetates with primary and secondary amino groups and with phenolic (but not alcoholic) hydroxyl groups. Thus, codeine and hydrocodone did not react, and morphine and hydromorphone were converted to their respective 3-monoacetates. After acetylation, the sample was extracted with a dichloromethane–acetone (1:1, v/v) mixture, and the extract was evaporated to dryness before being reconstituted in a small amount of injection solvent for GC–MS analysis.

Figure 1 shows the total-ion chromatogram and mass spectrum of hydrocodone isolated from the 1995 College of American Pathologists (CAP) urine sample UT-7. Hydrocodone chromatographed as a single peak at 18.3 min, which was well after the retention time for codeine (17.4 min). The mass spectrum of the peak was that of underivatized hydrocodone. Figure 2 is the total-ion chromatogram and mass spectrum of hydromorphone from the 1995 CAP urine sample T-14. Hydromorphone chromatographed as a single peak at 20.6 min, which was well after the retention time of 3-acetylmorphine (19.2 min). The mass spectrum of the hydromorphone peak was that of the 3-monoacetate of hydromorphone.

The fact that hydrocodone and hydromorphone both chromatographed as single peaks, well away from codeine and morphine retention times, indicates that tautomerization, which would result in the appearance of additional peaks, did not occur with either drug under the mild derivatization conditions of this method. Indeed, codeine, hydrocodone, hydromorphone, and morphine can all be identified in the presence of each other. Thus, with our procedure, detection of codeine and morphine is completely free of interference from hydrocodone and hydromorphone. The detection of oxycodone (retention time, 19.5 min) is free of these interferences as well.

Klazina E. Brooks¹ and Norman B. Smith^1,2
1Department of Clinical Biochemistry, University Hospital, P.O. Box 5339, London, Ontario, Canada N6A 5A5 and ²Department of Biochemistry, University of Western Ontario, London, Ontario, Canada

References

1. J. Fenton, J. Mummert, and M. Childers. Hydromorphone and hydrocodone interference in GC/MS assays for morphine and codeine.
   J. Anal. Toxicol. 18: 159–64 (1994).
2. R.D. Miller and D.R. McKean. Preparation of chlorotrimethylsilyl enol ethers from a-chloroketones using trimethylsilyl iodide.
   Synth. Commun. 12: 319–22 (1982).
3. R.D. Miller and D.R. McKean. The facile silylation of aldehydes and ketones using trimethylsilyl iodide: an exceptionally simple procedure for the generation of thermodynamically equilibrated trimethylsilyl enol ethers. Synthesis 9: 730–32 (1979).
4. D.C. Fuller and W.H. Anderson. A simplified procedure for the determination of free codeine, free morphine, and 6-acetylmorphine in urine. Presented at the 22nd Annual Meeting of the Society of Forensic Toxicologists, Cromwell, CT, October 13–16, 1992.
5. K.E. Brooks and N.B. Smith. Versatile, efficient system for extracting drugs from urine for gas chromatographic/mass spectrometric analysis. Clin. Chem. 35: 2100–2103 (1989).

Reproduction of editorial content of this journal is prohibited without publisher’s permission.

| Home | Subscribe | Current Issue | Back Issues | Search | Advertise | Other Publications |