Second order advantage applied to the spectrophotometric analysis of ciprofloxacin and dexamethasone in ophthalmic drops; automatic green method using on-line photodegradation.

On-line photodegradation and spectrophotometric analysis assisted by multivariate curve resolution-alternating least squares (MCR-ALS) was developed the simultaneous determination of ciprofloxacin (CIP) and dexamethasone (DEX) in ophthalmic suspensions using an automated flow-batch analysis (FBA) system. CIP and DEX have strongly overlapped UV spectra. Overcoming this lack of selectivity involves augmenting data dimensionality. This could be performed by adding information about the sample photodegradation to obtain the so-called second order advantage. Commercial sample analysis was successfully performed and no statistical differences (α = 0.05) with respect to pharmacopeia methods were obtained. The proposed method offers several advantages over the methods developed to date. In agreement with the principles of green chemistry, only water was used as solvent, low amounts of waste were generated and on-line waste treatment was included in the system. Moreover, the cost per analysis was significantly reduced compared to methods that employ separative techniques.