Dual fluorescence enhancement of loratidine by photoinduced electron transfer blocking and micellization: Application to the development of novel highly sensitive microwell spectrofluorimetric assay for analysis of dosage forms and urine samples.

This study describes the enhancement of the weak native fluorescence of loratadine (LOR) by dual strategy via photoinduced electron transfer (PET) blocking followed by micellization into sodium dodecyl sulfate micelles. The enhanced fluorescence was employed as a basis for the development of a novel microwell spectrofluorimetric assay (MW-SFA) for the determination of LOR in its pharmaceutical dosage forms and urine samples. The assay was conducted in 96-microwell assay plates, and the enhanced fluorescence signals were measured by a microplate reader at 290 and 435 nm for excitation and emission, respectively. The optimum conditions of the assay were established, calibration curve was generated, and the linear regression equation was computed. The relation between the fluorescence signals and LOR concentrations was linear with good determination coefficients (0.9992) in the range of 10 - 2000 ng mL. The assay limits of detection and quantitation were 4.1 and 12.5 ng mL, respectively. The precision was satisfactory, with values of relative standard deviation not exceeding 1.68%, and the assay's accuracy was ≥ 99.1%. The proposed was successfully applied to the analysis of LOR in its pharmaceutical dosage forms with acceptable accuracy and precision. The label claims were 99.3 - 100.5% (±0.95 - 1.59%). Statistical analysis comparing the results of the proposed assay with those obtained by a reported pre-validated assay revealed no significant difference between both methods in terms of the accuracy and precision at the 95% confidence level. The assay was also applied to the analysis of urine samples containing LOR with accuracy ≥ 98.24%. The greenness of the proposed assay was confirmed by three efficient metric tools. In overall conclusion, the proposed assay is characterized by high sensitivity, procedure simplicity, and high throughput, enabling the simultaneous analysis of many samples in a short time. Therefore, it is a valuable tool for rapid routine application in pharmaceutical quality control units and clinical laboratories for the determination of LOR.