Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
39, Number 10, October 2001, pp. 200-204
Photolysis of NSAIDs. I. Photodegradation Products of Carprofen
Determined by LC–ESI–MS
Ming-Thau Sheu[1], Hsiu-O Ho[2], Po-Yu Wang[1],[3], Yi-Bo Liou[1],
and An-Bang Wu[1]
[1]Graduate Institute of Pharmaceutical Sciences and
[2]Department of Pharmacy,
Taipei Medical University, Taipei 110, Taiwan, R.O.C and
[3] National Laboratories of Foods and Drugs, Department of Health, Executive
Yuan, Nankang 115, Taipei, Taiwan, R.O.C.
A solution of carprofen in methanol at a concentration of 2.74 ¥ 10–2
mg/mL is subjected to photoirradiation using a Hanovia 200-W high-pressure
Hg lamp for 9 h. In total, seven photodegradation products are separated, and
their quasimolecular ions are subsequently determined online using a liquid
chromatography (LC)–electrospray ionization (ESI)–mass spectrometry
(MS) method. The high-performance LC consists of an Inertsil 5 ODS-80A (2.1- ¥ 150-mm)
column. The mobile phase is initially CH3CN. NH4OAc (20mM in de-ionized H2O)
is 43:57 (v/v), and after 14 min it is CH3CN. NH4OAc (20mM in de-ionized H2O)
is 54: 46 (v/v). The UV detector was set at 260 nm. The parameters of LC–MS
for mass determination involves an atmospheric pressure ionization electron
spray interface with a negative mode of polarity (ESI–). The chemical
structures of the degradants are elucidated based on the mass-to-charge ratio
of the quasimolecular ions and the molecular weight changes by comparison with
the parent drug (carprofen). The degradation proceeds via an initial dechlorination.
A dechlorination or esterification reaction is competed with decarboxylation.
This finding is in accordance with our previously reported result of first
order photodecomposition kinetics for carprofen.
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