Photothermal lens microfluidic sensor for femtomole detection of 2,4,6-trinitrotoluene based on Meisenheimer complexation

Abstract

Since the simple and accurate quantification of 2,4,6-trinitrotoluene (TNT) traces is still a challenge for analytical chemists, we employed a recently developed crossed-beam photothermal lens spectrometer for highly sensitive and selective determination of TNT through a well-known Meisenheimer complexation with n-butylamine (nBA). The colorless solution of TNT in dimethyl sulfoxide (DMSO) was changed to deep-red after the addition of nBA. Hence, we used a 532 nm diode laser as excitation source in photothermal lens investigations. All the instrumental parameters and chemical conditions such as chopper frequency, sample flow velocity, amine concentration and etc. were optimized. Photothermal lens measurements yielded a linear signal dependence on TNT quantity from 5 to 100 nM. The limit of detection (LOD) was 1.6 nM (˜5 fmol). The method was successfully carried out for determination of the TNT vapor extracted into the 300 μL dimethyl sulfoxide (DMSO).