Statistical Design Approach for Optimizing the Spectrofluorimetric Method for Quantifying Trazodone Hydrochloride

A sensitive spectrofluorimetric method was developed to determine trazodone hydrochloride in its formulation and urine sample. The principle of the developed method is based on the formation of an ion pair complex at a pH of 4.27 between the analyte drug and eosin Y, followed by its extraction into dichloromethane and subsequent fluorescence measurement. The fluorescence of the extracted trazodone-eosin Y complex was recorded at 450 nm with an excitation wavelength of 350 nm. Recording the fluorescence was utilized to construct the calibration plot, which was found to be linear in the range of 32.0–1.50 × 103 ng/mL of trazodone hydrochloride. The influences of experimental variables, namely pH, volumes of eosin Y (2.90 × 10–3 M), and buffer solution (pH 4.27), on the fluorescence intensity were examined and optimized by response surface methodology via Box−Behnken design. The limits of detection and the limit of quantitation of the reported method are 9.50 and 28.79 ng/mL, respectively. The accuracy of the proposed method was evaluated for intra-day and inter-day precision in the range of 0.46 to 0.77% RSD. The content of trazodone hydrochloride in its dosage forms was determined by the developed method using the standard addition technique, and the results showed good recovery between 96.50 and 99.25%, with a standard analytical error of 1.54 × 10–5 to 2.86 × 10–4. Interval hypothesis testing confirmed that it is lower than ±2%; hence, there was no bias between the developed and reference methods. No interference was observed from the common excipients present in tablet formulations. The developed method was also successfully applied for the determination of trazodone in urine samples, and recovery of the drug was observed in the range of 90–98%.