iPhone in TNT test

The digital image from an iPhone has been used to estimate the concentration of TNT in soil following a colorimetric test, performing better than a digital SLR camera. This application of a smart phone in scientific applications is one of several announced recently and paves the way for an inexpensive, portable field test for the explosive.

The process was described in Talanta by scientists from Prince of Songkla University, Thailand and the University of Strathclyde, UK. The test involves mixing suspect soil with the reagent dicyclohexylamine. If TNT is present, a red-violet colour appears rapidly. The solution was photographed within one minute and the image was transferred to a computer where Adobe Photoshop was used to generate the red-green-blue intensities from the image. These were correlated with the concentration of TNT.

In comparisons with a DSLR camera, the iPhone was more sensitive and the results had lower relative error and better precision. Since many people possess this type of camera, it is a more convenient way to process the test colour than a stand-alone camera. Other types of smart phone might also give satisfactory results.

The research team involved in this work suggested that their work could lead to the development of an app for the phone which could provide a readout in the field without the requirement for separate downloading and processing.