Surfactant-Modified Dispersive Liquid–Liquid Microextraction for the Determination of Salbutamol or Dapsone via Reciprocal Derivatization

Salbutamol (SAL) and dapsone (DPSN) derivatization reactions and analysis procedures were established and improved in this study. SAL was used as a derivatization agent for DPSN, and DPSN was a derivatization agent for SAL. The method of derivatization, the diazonium coupling of SAL and DPSN, was optimized. The optimum parameters were 12 mM hydrochloric acid and 2.4 mM sodium nitrite for diazotization and 24 mM potassium hydroxide for azo coupling. Surfactant-modified dispersive liquid‒liquid microextraction (SM-DLLME) was optimized using a new solvent mixture: an aqueous dye derivative sample mixture, 600 µL of butanol as the extracting solvent, 1.05 wt.% Triton X-100 as the dispersive solvent, and 42 mM potassium chloride. Compared to existing methods, the linearity, correlation coefficients, limits of detection, and molar absorptivities were improved when SM-DLLME followed by HPLC-UV was employed. The proposed technique can detect pharmacological, environmental, and medicinal trace concentrations of SAL and DPSN.