Photolysis of NSAIDs. II. Online LC-MS Determination of Photodegradants from Carprofen
FU-AN CHEN1, PO-YU WANG2,3, KUO-CHING WEN3, CHAU-YANG CHEN1 AND AN-BANG WU2*
1. Department of Pharmacy, Tajen Institute of Technology, No.20, Weisin Rd., Yanpu Township, Pingtung County 907, Taiwan (R.O.C.)
2. Graduate Institute of Pharmaceutical Sciences, Taipei Medical University, No.250, Wusing St., Sinyi District, Taipei City 110, Taiwan (R.O.C.)
3. Bureau of Food and Drug Analysis, Department of Health, Executive Yuan, No.161-2, Kunyang St., Nangang District, Taipei City 115, Taiwan (R.O.C.)
(Received: October 23, 2002; Accepted: January 13, 2003)
ABSTRACT
(Received: October 23, 2002; Accepted: January 13, 2003)
Carprofen in a 10% aqueous ethanol solution at a concentration of 0.10 mg/mL was subjected to photo-irradiation under sunlight for 24 hr. Four photodegradants were separated and subsequently followed an online determination of their quasi molecular ions using an LC-MS method. The HPLC consisted an Inertsil 5 ODS-80A (2.1 mm i.d. x 150 mm) column, and the mobile phase was initially CH3CN: NH4OAc (20 mM in D.I. H2O) = 43: 57 (v/v). After 14 min, CH3CN: NH4OAc (20 mM in D.I. H2O) was changed to 54: 46 (v/v). The UV detector was set at 260 nm. The parameters of LC-MS for mass determination were optimized with an API electron spray interface with negative mode of polarity (ESI-). The chemical structures of the degradants were elucidated based on the m/z of the quasi molecular ions. Two degradants were found to proceed via an initial dechlorination with C-Cl cleavage. Dechlorination was observed to be competing with decarboxylation, i.e. either reaction is in accord with our previously reported result with a first-order photodecomposition kinetics of carprofen.
Key words: photolysis, carprofen, NSAIDs, LC-MS, dechlorination