Determination of 2,4,6-Trinitrotoluene in Soil Samples Using a Paired Emitter-Detector Diode-Based Photometer

Light-emitting diodes (LEDs) can be used in paired emitter-detector diodes (PEDD) optical sensors as both the light source and the detector. PEDD-based photometers provide low fabrication cost, low power consumption, ease of miniaturization, and a high signal-noise ratio response in a wide wavelength range. This paper reports on developing a cheap but efficient PEDD-based photometer. The photometer consists of a white LED as the emitter diode, an RGB LED as the detector diode (for the first time), and a multimeter for recoding the signal. The developed PEDD-based photometer was utilized for the determination of 2,4,6-trinitrotoluene (TNT) in soil samples. A Meisenheimer complex of TNT with NaOH in acetonitrile was used as a probe to monitor the presence of residual TNT in soil samples. The calibration curve in the soil sample was linear in the concentration range of 0.86 to 110 µg g-1, with a detection limit of 0.27 µg g-1 and a quantification limit of 0.81 µg g-1. Analysis of the soil samples collected from the Iran Cinema and Television Town using the developed method showed trace residual of TNT.