A validated Rhodamine B fluorescence quenching spectrofluorimetric method for solriamfetol determination in human plasma with pharmacokinetic application

Abstract

Solriamfetol, a schedule IV wake-promoting agent, represents a significant analytical target requiring sensitive and reliable methods for its quantification in biological matrices. Herein, the fluorescence quenching of Rhodamine B upon interaction with solriamfetol's protonated amine was exploited for the first time for its spectrofluorimetric determination in human plasma. The spectroscopic properties of the analyte–fluorophore system were systematically investigated using absorption and emission spectroscopy, revealing a quenching behavior of Rhodamine B at 578 nm upon interaction with solriamfetol. Subsequently, mechanistic elucidation through Stern–Volmer analysis established static quenching (K_sv = 7.95 × 10⁵ L mol⁻¹) with thermodynamically favorable interaction (ΔG = −33.66 kJ mol⁻¹) and 1 : 1 stoichiometry via Job's method. Furthermore, quantum mechanical calculations confirmed electrostatic complementarity between solriamfetol's protonated amine and Rhodamine B's carboxylate moiety. Experimental parameters were optimized via sequential univariate approaches. Method validation was conducted according to ICH M10 guidelines demonstrating excellent analytical performance with linearity across 25.0–1000.0 ng mL⁻¹ concentration range (r² = 0.9991), high sensitivity (LOD = 8.05 ng mL⁻¹, LOQ = 24.38 ng mL⁻¹), and precision (% RSD < 4.56%). Analytical equivalence with LC-MS/MS was further confirmed through cross-validation studies. Finally, the method was successfully implemented for pharmacokinetic profiling in human volunteer plasma following administration of 75 mg solriamfetol, yielding t_1/2 = 7.6 h, C_max = 465 ng mL⁻¹, and t_max = 1.5 h in agreement with literature values. This methodology offers significant advantages including visible-wavelength excitation minimizing matrix interference, rapid analysis time, and reduced environmental impact compared to conventional chromatographic techniques, thus providing a viable alternative for solriamfetol determination in therapeutic drug monitoring and pharmacokinetic profiling applications.