Poly vinyl alcohol cryogel as a selective test kit for pre and post blast trinitrotoluene

A cryogel test kit was successfully developed for the detection of trinitrotoluene (TNT). Tetramethylammonium hydroxide (TMAH) entrapped within a polyvinyl alcohol (PVA) cryogel matrix acted as the colourimetric reagent. The PVA cryogel TNT test kit was fabricated within a micro-PCR tube to which the sample solution could be directly added for in-tube detection. This made the developed test kit small and easily portable. The test kit was used to demonstrate the rapid quantitative analysis of TNT in soil sample in conjunction with digital image colourimetry. The digital image of the colourimetric product from the test kit was captured using the built-in digital camera of a mobile phone. Red-Green-Blue (RGB) colour data from the digital image was used as the analytical data to establish a calibration graph for the target analyte using a series of TNT standard solutions. The concentrations of TNT detected in post-blast soil samples by the test kit were in good agreement to values obtained using spectrophotometric detection and method validation indicated good precision both for intra- and inter-day (2.77-4.21%RSD and 3.34-7.82%RSD, respectively). The TNT test kit could be stored for almost 3 months in a freezer exhibiting only a -0.73% change in intensity of green channel. The test kit was also reusable and after nine uses only a 0.8% change in intensity of green channel was evident. These results demonstrate that the PVA cryogel TNT test kit has the potential to be used for TNT detection in a complex sample matrix. When the test kit was used in combination with digital image colourimetry, it provided an ideal novel platform for the rapid quantitative analysis of TNT in post blast samples.