Investigation of the spectrofluorimetric behavior of azelastine and nepafenac: Determination in ophthalmic dosage forms Marwa A.A. Ragab ⁎, Eman I. El-Kimary Faculty of Pharmacy, Department of Pharmaceutical Analytical Chemistry, University of Alexandria, El-Messalah, Alexandria 21521, Egypt abstract article info Article history: Received 21 March 2018 Received in revised form 3 June 2018 Accepted 14 June 2018 Available online 15 June 2018 The first spectrofluorimetric report investigating the fluorimetric behavior of the antihistaminic drug, azelastine (AZEL), and the non-steroidal anti-inflammatory drug, nepafenac (NEP), either in bulk or in their dosage forms, eye drops and ophthalmic suspension. After a full investigation of the factors that may influence their spectrofluorimetric behavior: pH, different organized media and organic solvents, the optimum factors were set in order to enable the analysis of each drug with maximum sensitivity. The AZEL spectrofluorimetric analysis was set at 286/364 (λ ex /λ em) in distilled water while for NEP, the analysis was set at 228/303 (λ ex /λ em) in meth- anol. The linearity range for AZEL was from 0.1 to 1.5 μg/mL while that of NEP was from 0.2 to 1.5 μg/mL. The lin- earity yielded good regression parameters with low LOD (0.022 and 0.032 μg/mL for AZEL and NEP, respectively) and LOQ (0.073 and 1.08 μg/mL for AZEL and NEP, respectively) when compared with those obtained from many previous spectroscopic and chromatographic reports in literature. The method was ICH validated and was ap- plied to the analysis of AZEL and NEP with good selectivity regarding the inactive ingredients. © 2018 Elsevier B.V. All rights reserved. Keywords: Emission spectrofluorimetry Azelastine Nepafenac Spectrofluorimetric behavior Ophthalmic dosage forms 1. Introduction Nepafenac (NEP) is a non-steroidal anti-inflammatory (NSAID) which is marketed as eye drops. It is used prior to cataract surgeries to decrease inflammation and pain [1]. As can be seen in Fig. 1, NEP is con- sidered to be benzophenone. Benzophenones are organic compounds containing a ketone attached to two phenyl groups. Moreover, its struc- ture contains benzene ring connected with electron donating group. Al- though this chemical structure suggests having a fluorimetric activity, no spectrofluorimetric report was found investigating its fluorimetric behavior or using a spectrofluorimetric based method for its analysis. Chromatographic and spectrophotometric methods were found in liter- ature for analyzing NEP in eye preparations [2–9]. Azelastine (AZEL) which is a phthalazine derivative is an antihista- mine eye drops used to treat allergic conjunctivitis [1]. The chemical structure of AZEL (Fig. 1) suggests that it possess fluorescence response which is confirmed by one report [10] which aimed at studying the pharmaco kinetics of the drug in guinea big plasma and lung tissues using HPLC-FD with no discussion or details mentioned about the fluo- rimetric behavior of the drug. This report applies exhausting extraction procedures for analysis of AZEL in biological matrices. Some reports were found in literature analyzing AZEL in pharmaceuticals using chro- matographic and spectrophotometric methods [11–19]. Luminescence spectroscopy is an adaptable analytical technique that offers higher sensitivity and selectivity than other detection systems such as classical UV absorption, fewer expenses than LC-MS/MS detec- tion, and time saving compared with HPLC. These advantages imply that luminescence spectroscopy is a suitable technique for analysis of drugs in simple matrices (pharmaceutical preparations) [20–24] and/ or complex ones (biological samples) [25]. Also, being a spectroscopic technique with carefully selecting the diluting solvent, it is considered to be an eco-friendly technique. No reports till now were found investigating the fluorescence be- havior of each one of the proposed drugs in the present study. It is worth saying that the proposed spectrofluorimetric method for AZEL analysis shows the lowest LOD, LOQ and linearity ranges than the re- ported HPLC [11–14] and spectrophotometric methods [14–19] found in literature for its analysis in pharmaceuticals. The same could be stated about the proposed spectrofluorimetric method of NEP analysis as the LOD, LOQ and linearity ranges yielded by the proposed method were lower than that obtained by some HPLC [6, 8, 9] and spectrophotometric [2–6] reported methods. A clear tabulated comparison of the proposed method with these reported methods including their conditions of anal- ysis and/or solvents used will be presented in the Results and Discussion section. However, one stability indicating spectrofluorimetric report [26] has been recently found for analyzing AZEL in pharmaceuticals. Al- though the report succeeded in reaching lower LOD and LOQ than the proposed one, it used 0.2 M H 2 SO 4 as a diluting solvent which is human carcinogen, corrosive and irritant when inhaled to nose, throat and lungs [27, 28]. The present work uses distilled water as a diluting Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 204 (2018) 260–266 ⁎ Corresponding author. E-mail address: marmed_2001@yahoo.com (M.A.A. Ragab). https://doi.org/10.1016/j.saa.2018.06.057 1386-1425/© 2018 Elsevier B.V. All rights reserved. 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