SYNCHRONOUS FLUORESCENCE SPECTROSCOPY COUPLED WITH CONTINUOUS WAVELET TRANSFORMS AND SAVITZKY-GOLAY DERIVATIZATION TECHNIQUE FOR THE SIMULTANEOUS DETERMINATION OF TADALAFIL AND DAPOXETINE HCl Original Article MAHA HEGAZY a , AMIRA KESSIBA b , MOHAMED ABDELKAWY a , AHMED ELGENDY b a Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini Street, 11562, Cairo, EGYPT, b Received: 26 Aug 2015 Revised and Accepted: 11 Feb 2016 Pharmaceutical Chemistry Department, Faculty of Pharmacy, Misr International University, KM 28, Cairo–Ismailia Road (Ahmed Orabi District), Cairo, Egypt Email: amira.kessiba@miuegypt.edu.eg ABSTRACT Objective: A novel combination of Tadalafil (TAD) and Dapoxetine HCl (DAP) has been recently introduced into the market for the treatment of premature ejaculation. The aim of this work is the development and validation of simple, sensitive and accurate analytical methods for the determination of TAD and DAP in their binary mixture without prior separation. Methods: Synchronous fluorescence spectroscopic (SFS) methods coupled with continuous wavelet transforms (CWT) and Savitzky-Golay (SAVGOL) derivatization technique have been developed. Results: Under optimum conditions, TAD and DAP were determined in the concentration ranges of 0.01–3 µg/ml and 0.01–1.2 µg/ml, respectively. Conclusion: The developed methods have the requisite accuracy, selectivity, sensitivity and precision and were satisfactorily applied for the simultaneous determination of TAD and DAP in bulk powder and pharmaceutical preparations. The results obtained for the analysis of both drugs in their pure forms by the proposed methods were statistically compared to those obtained by applying a reported high performance liquid chromatographic method (HPLC) method. The statistical comparison showed that there is no significant difference between the proposed methods and the reported one with respect to accuracy and precision. Keywords: Synchronous fluorescence spectroscopy, Tadalafil, Dapoxetine HCl, Continuous wavelet transforms, Savitzky-Golay technique © 2016 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/ ) INTRODUCTION Fluorescence Spectroscopy provides a major role in analysis owing to its high sensitivity and selectivity compared to UV-spectroscopy. Conventional fluorescence methods have limited practical applicability as most spectra of complex mixtures often cannot be resolved satisfactorily without previous separation. However, this can be overcome by using special techniques such as SFS [1]. In SFS, both the excitation and emission monochromators are scanned simultaneously. The main characteristics of SFS are narrowing of the spectral band [2], simplification of emission spectra by the choice of suitable Δ λ [3] and contraction of spectral range [4]. This result in sharp and narrow peaks compared to those of conventional spectrum. The combination of synchronous and derivative fluorimetry enhances minor spectral features and allows more reliable identification of chemical species. Wavelet transform (WT) was proposed for the approximate derivative calculation. It has a major advantage of enhancing the signal to noise ratio for calculations of the higher order derivatives in contrary to the derivative technique which has a major drawback in increasing the noise level in calculations of the higher order derivative [5]. WT contains two distinct parts, discrete and continuous which were developed independently in several fields [6-8]. WT methods have been successfully used for the resolution of overlapped spectra for the quantitative determination of multi- component mixtures by means of spectrophotometric methods [9-11]. An SAVGOL filter is a digital filter that can be applied to a set of digital data points for the purpose of smoothing the data, that is, to increase the signal-to-noise ratio without distorting the signal. The method is based on established mathematical procedures. It was first developed by Savitzky and Golay [12] who published tables of convolution coefficients for various polynomials and subset sizes [13]. Some errors in the tables have been corrected [14, 15]. The method has been extended for the treatment of 2-and 3-dimensional data. Tadalafil [fig. 1], is (6R, 12aS)-6-(1,3-benzodioxol-5-yl)-2,3,6, 7,12,12a- hexahydro-2-methylpyrazino[1’,2’:1,6] pyrido [3,4-b] indole-1,4-dione [16]. It is a selective, long-acting PDER5 Rinhibitor [17, 18]. Tadalafil has shown to be safe and effective in the treatment of erectile dysfunction across a variety of clinical populations [19-22]. Fig. 1: Chemical structure of Tadalafil Dapoxetine HCl (fig. 2), is a short-acting selective serotonin reuptake inhibitor (SSRI) developed for the treatment of premature ejaculation [23, 24]. Dapoxetine has a unique pharmacokinetic profile compared to other SSRIs as it is rapidly absorbed and eliminated after oral administration [25-28]. Dapoxetine doesn’t have pharmacokinetic interactions with PDE5 inhibitors which allow its combination with several PDE5 inhibitors for the treatment of premature ejaculation [29]. A survey of the literature showed that very few methods have been reported for the simultaneous determination of TAD and DAP in bulk powder and combined dosage form. The reported methods include HPLC coupled with UV detection [30, 31] and a single spectrophotometric method [32]. Both drugs were reported to be fluorescent [33-35], thus they could be determined by fluorescence detection. International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 8, Issue 4, 2016