Determination of Methamphetamine Hydrochloride by highly fluorescent polyfluorene with NH2-terminated side chains

Three different poly{9,9-bis[6′(–NHBoc, –NH3+ and –NH2)hexyl]fluorene}s (PF-NHBoc, PF-NH3+ and PF-NH2) have been synthesized and characterized. Both UV–Vis and fluorescence spectroscopic results supported the interaction between the polyfluorenes and Methamphetamine Hydrochloride (MAPA) was derived from the different terminals of hexyl side chains. Among the three polyfluorenes, PF-NH2 exhibited the best sensory response to Methamphetamine Hydrochloride (MAPA) in THF arising from its –NH2 terminals. The fluorescence of PF-NH2 was immediately quenched once the MAPA was added, and the detection limit of MAPA was determined to be ∼25 ng/mL. Fluorescence quenching experiments of PF-NH2 by NH4Cl and other metal ions confirmed that electrostatic interaction should make contributions to the quenching behavior, in addition, upward non-linear curvature and much higher quenching constant (Ksv) in the Stern–Volmer plots for MAPA suggested some other interactions such as hydrophobic or/and hydrogen-bonding interactions dominated the analyte-induced aggregation, and such hydrophobic interaction was responsible for the sensitive selectivity. The fluorescent quenching experiments upon adding other drugs such as Pethidine Hydrochloride (PTD) and Ephedrine Hydrochloride (EPD) confirmed such selectivity, especially under the high concentration of the Stern–Volmer plots. The high sensitivity, selectivity, and its simple and fast character, made it a new and effective way for drug detection.