Analytical Sciences

Tetramethylammonium Hydroxide-doped Starch Film as a Colorimetric Sensor for Trinitrotoluene Detection

Wilasinee SRIPROM,* Aree CHOODUM,* Chanadda PHAWACHALOTORN,** Worawit WONGNIRAMAIKUL,*,*** and Wadcharawadee LIMSAKUL*

*Integrated Science and Technology Research Center, Faculty of Technology and Environment, Prince of Songkla University, Phuket Campus, Kathu, Phuket 83120, Thailand
**Department of Applied Science and Business Management, King Mongkut’s Institute of Technology Ladkrabang, Prince of Chumphon Campus, Chumphon 86160, Thailand
***Research Program: The Development of Management System for Reduction and Control of Water Contamination and Distribution in Songkhla Lake Basin and the Western Coastline of the South of Thailand, Center of Excellence on Hazardous Substance Management (HSM), Bangkok 10330, Thailand

A tetramethylammonium hydroxide (TMAH)-doped starch film was developed for trinitrotoluene (TNT) detection. A purple Janowsky anion was obtained from the reaction of TNT with released TMAH. When the film was used in conjunction with digital image colorimetry (DIC), rapid quantitative analysis of TNT was achieved. The Red-Green-Blue (RGB) intensities analyzed from digital photographs of the purple product were used to establish calibration curves for TNT. A wide linear range (2.5 to 50 mgL⁻¹) with good linearity (R² > 0.99) was achieved for the quantification of TNT. Good precision (1.73 to 3.74%RSD) was obtained for inter-day tests (n = 5). The films were applied to test four post-blast soil samples and two positive results were observed. The concentrations quantified by DIC were in good agreement with spectrophotometry. The film was able to be stored in a freezer for 3 months with <4.3% change in performance.

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