Continuous Flow Injection Analysis: Quenched continuous fluorescence of ۵-hydroxy tryptamine for the determination of paracetamol using a blue-purple laser diode fluorimeter and a photodiode as a detector at ۰- ۹۰° angle

A flow injection–fluorescence quenching method was developed for the determination of paracetamol using serotonin hydrochloride as a native fluorophore. To the best of our knowledge, no prior FIA system has used serotonin hydrochloride as a quenching fluorophore for paracetamol. Continuous fluorescence was excited by a ۴۰۵ nm laser diode in a custom-built laser diode fluorimeter equipped with a ۹۰° photodetector aligned for emission measurement at ۵۲۵ nm. The system demonstrated a stable signal response under dynamic flow conditions, enabling rapid and reproducible analysis. The calibration curve was linear over the range of ۰.۱–۴۵ µmol L⁻¹, with a correlation coefficient of r = ۰.۹۹۸۰. The detection limit was ۵۰ nmol L-۱ (۰.۴۹۱۳ ng/sample), and precision studies yielded RSD% values below ۰.۵% for target concentrations of ۱ and ۵ µmol L-۱ (n = ۶). Analytical results from the developed method showed no significant deviation from the labelled dose (۵۰۰ mg/tablet) as confirmed by a one-sample t-test. However, a paired t-test comparing the developed method with a conventional Spectrofluorometric technique produced a significant difference, highlighting the improved performance of the FIA approach. The technique combines minimal reagent use, high sampling throughput (۶۰ samples/hour), and nanomolar detection, making it valuable for routine pharmaceutical analysis at trace levels.

کلیدواژه ها:

Flow injection analysis ، Fluorescence quenching ، Paracetamol ، Serotonin hydrochloride ، Laser diode fluorimeter