Analysis And Confirmation Of Urinary Drugs And Metabolytes By Cems

Interfacing a CE with a mass spectrometer (MS) has been shown to be an attractive approach, analogous to the use of LC-MS (9,10), to gather struc tural information of compounds, and to use the MS as a CE detector (70,71). Currently there are few published articles discussing CE-MS monitoring of drugs in urine. The best examples are CE-MS determination of urinary N-l-hydroxyethylflurazepam (the major metabolite of flurazepam) (72), halo-peridol (48), anti-inflammatory drugs (ibuprofen, flurbiprofen) and their metabolites (73), paracetamol and metabolites (24,25,74), nonopioid analgesics (24), methadone (30,36), and methylphenidate (75). In addition, the feasibility of using MS as the detector for the enantiomers of terbutaline spiked into a urine blank has been demonstrated (76). In this instance the use of the chiral selector (heptakis (2,6-di-0-methyl)-p-cyclodextrin) in addition to the use of MS gave the selectively needed to verify the chiral composition in complex matrices.

CE-MS instrumentation employed thus far for urinary confirmation testing of drugs of abuse and/or their metabolites uses CE interfaced to a MS with atmospheric pressure electrospray ionization. This is followed by identification of protonated molecular ions and/or their fragments using a triple quadrupole (30) or an ion trap (36) MS. In the first approach, fragmentation of methadone and EDDP was determined by MS-MS. Confirmation was achieved with in-source fragmentation. The first quadrupole was operated in the selected ion monitoring mode by switching between the respective parent/daughter ion masses for methadone (m/z = 310, 265) and EDDP (m/ z = 278, 249, 234). The CE-MS-MS approach has been successfully applied to the confirmation of methadone and EDDP in urines that were positive for methadone using CE-based immunoassays, FPIA, EMIT, and CE with UV absorption detection (30). Using an ion trap MS, the presence of amphetamine, MDMA, MDA, methadone, EDDP and morphine in urine could easily be confirmed by the full ion scan mode followed by MS-MS of the protonated molecular ions (36). An example is the alkaline extract of the quality control urine l06 in Fig. 7 where the presence of amphetamine, methadone, EDDP and morphine could unambiguously be confirmed by CE-MS. In addition, CE-MS was shown to be capable of detecting amphetamine and nicotine, compounds that co-migrated under the conditions employed. This was not the case using CZE with UV detection (Fig. 7A) (36). After sample extraction, urinary drug concentrations of 50-100 ng/mL can be detected by CE-MS, comparable to that observed by CE with UV detection. This sensitivity is sufficient for confirmatory testing of most urinary drugs of abuse. The use of a volatile buffer (Figure 7A) was not found to be a limitation in the separation. CE-MS instrumentation with a single quadru-pole MS does not permit unambiguous confirmation since no structural proof via fragmentation is possible. A single quadrupole MS can, however, be used as detector.

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