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Abstract
Acetylsalicylic acid (ASA) and Codeine (CO) are two active ingredients usually found together in pharmaceutical preparations. A lot of procedures for determination of ASA are based on its previous hydrolysis to salicylic acid (SA). In this paper a procedure for both direct determination of CO and indirect determination of ASA in pharmaceuticals is proposed based on the measurements of the native fluorescence of CO and SA (obtained from hydrolysis of ASA). SA was determined in the range 0.1 -1.5 mg/L in the presence up to 10 mg/L of CO at λem 405 nm (λexc = 297nm). CO could not be determined at the low ratio usually found in pharmaceuticals with respect to ASA due to the spectral overlap, so a previous separation of SA was carried out by retention of this on an anion exchange resin. Thus CO was determined in the range 0.1-3 mg/L (λexc=215 nm, λem=350 nm.) in the presence of at least 520 mg/ L of ASA. The procedures were applied to the determination of CO and ASA in commercial pharmaceuticals with goods results, using an HPLC procedure as a reference method.
ACKNOWLEDGEMENTS
The authors are grateful to the Ministerio de Educación y Cultura, Dirección General de Enseńanza Superior (DGES) (Project No. PB98-0301), for financial support.