A sol-gel colorimetric sensor was successfully developed for the detection of methamphetamine (MA). Simon's reagents were entrapped within the polymeric network of the sol-gel matrix. The sol-gel MA sensor was fabricated within a micro-PCR tube to which the sample solution could be directly added for in-tube detection. This resulted in a small and easy to carry sensor. The sensor was used to demonstrate the rapid quantitative analysis of MA in illicit methamphetamine tablets (Yaba) in conjunction with digital image colorimetry. Real-time Red-Green-Blue (RGB) basic color data of the colorimetric product from the sensor was obtained using an application installed on a mobile phone. The concentrations of MA detected in the illicit tablets by the sol-gel sensor were comparable to values obtained from gas chromatograph-flame ionization detector (GC-FID) analysis. Method validation indicated good precision both intra- and inter-day (0.85-2.41% and 1.76-4.51%, respectively). The sensor was also applied to spiked urine samples and low relative errors in the range of +4 to -9% were obtained. The sol-gel sensor was capable of being stored for almost 3 months (84 days) in a freezer (-18°C) with only a +4.89% change in the results compared to analysis carried out on the day of preparation. These results demonstrate that the sol-gel MA sensor has the potential to be used as a colorimetric sensor for MA detection in a variety of media. When the sensor was used in combination with a color analysis application installed on a mobile phone, it provided an ideal novel platform for the rapid quantitative analysis of MA.
- Digital image colorimetry
- iPhone app