Clinical Pathology: Clinical Chemistry

217)

A urine sample of a 34-year-old female patient is examined by gas chromatography–mass spectrometry (GC-MS) after deglucuronidation, liquid/liquid extraction, and derivatization.

Substance RT (min) Characteristic ions (m/z) LLOD (ng/mL) LLOQ (ng/mL)
Cocaine-D3 3.596 185, 201, 306
EDDP-TMS 3.201 277, 262, 220, 200 100 200
Methadone 3.445 72, 165, 223, 294 10 25
Pentazocine-TMS 3.734 274, 289, 342, 357 10 25
Cocaine 3.613 182, 198, 272, 303 10 25
Cocaethylene 3.758 196, 82, 317 10 25
BEG-D3-TMS 3.775 243, 259, 364
BEG-TMS 3.784 240, 361, 256 25 50
Morphine-D3-2TMS 4.351 432, 404, 417
Codeine-TMS 4.236 178, 196, 234, 371 10 25
Morphine-2TMS 4.360 429, 236, 414, 401 10 25
O-6-MAM-TMS 4.499 399, 287, 340, 355 10 25
Norbuprenorphine-2TMS 5.627 468, 500, 510, 524, 557 2 5
Buprenorphine-TMS 6.065 450, 482, 506, 524, 539 2 5
THC-COOH-D3-2TMS 4.770 374, 476, 491
THC-COOH-2TMS 4.777 371, 473, 488 5 10
Fentanyl-D5 4.798 250, 194
Norfentanyl-TMS 3.230 155, 154, 247, 289, 304 10 25
Fentanyl 4.800 245, 146, 189, 202 5 10
Sufentanyl 4.927 289, 140, 187, 238, 289 2 5
Alfentanyl 5.185 289, 222, 268, 359 5 10

From Strano-Rossi S, Bermejo AM, de la Torre X, Botrè F. Fast GC-MS method for the simultaneous screening of THC-COOH, cocaine, opiates and analogues including buprenorphine and fentanyl, and their metabolites in urine. Anal Bioanal Chem 2011;399:1623–1630.

Which one of the following compounds was definitely present in this patient’s urine?

• Urine screens by gas chromatography–mass spectrometry (GC-MS) are usually preceded by immunoassay screenings.

• Confirmation by GC-MS is based on a combination of retention time and the mass spectrum.

• The mass spectrum shows peaks at varying m/z (mass-to-charge ratios) and is fairly unique for certain molecules.

• Many drugsare excreted into urine as glucuronides.

• Glucuronides are usually deglucuronidated before GC-MS.

• Most compounds need to be derivatized before GC-MS analysis in order to be retained.

• Mass spectra are derivatization specific.

 
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