Prof. Takashi KANETA
Okayama University, JAPAN
Takashi Kaneta was born in Hokkaido, Japan, on April 27, 1963. He obtained his B.Sc. in Chemistry from the Hokkaido University of Education, Sapporo College, in 1987, and his Ph.D. from the Faculty of Sciences, Hokkaido University, in 1992. He currently works in the Department of Chemistry, Okayama University. His research interests are in the development and application of paper-based analytical devices, capillary electrophoresis, and laser-induced fluorometry for analyzing environmental and biochemical substances. He published more than 100 papers in refereed journals and obtained more than 2,000 citations.
Paper-based analytical devices for remote and onsite environmental analysis
Takashi Kaneta*
Department of Chemistry, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan
*kaneta@okayama-u.ac.jp
Paper-based analytical devices (PADs) are an attractive platform for onsite environmental analysis because of their inexpensiveness, portability, simple detection scheme, and user-friendly operations. However, PADs need improvement in stability, sensitivity, and operations to achieve onsite analysis in the real world. Therefore, we have attempted to address several issues that could potentially prevent onsite analysis.
The PADs consist of a hydrophobic barrier surrounding hydrophilic channels where aqueous solutions flow spontaneously via capillary force in the cellulose network. A commercially available wax printer fabricates the hydrophobic barriers. Fig. 1 displays an example of the PAD for the determination of Fe(III).1 The green color indicates hydrophobic wax that prevents penetration of aqueous solutions. The device consists of an introduction zone connected with four detection zones. The detection zones contain hydroxylamine to reduce Fe(III) to Fe(II) and a colorimetric reagent, o-phenanthroline. When adding a sample solution to the introduction zone, it flows into the detection zones via capillary action, resulting in a color change in the detection zones. We also developed the PADs that permit acid-base titration and chelate titration of calcium and magnesium ions.2,3 The PADs for measuring Fe(III) and acid-base titration were able to measure the levels of Fe(III) and acid in a sample of hot spring water on-site. The results are similar to those found using standard spectrophotometry and acid-base titration. Conversely, the PAD for chelate titration was applicable to measurements of calcium and magnesium ions in natural and mineral water samples.
Although these PADs permit onsite analysis, only experts would be able to use them because we need a micropipette which is unfamiliar to people who have no experience with chemical experiments. To overcome this issue, we proposed two types of sample introduction methods: one dipping method and another, a PAD equipped with a volume gauge.4-6 Users can introduce samples into these PADs without the need for a micropipette, making them user-friendly.
Furthermore, we need to address additional challenges to enhance the sensitivity of PADs for onsite analyses. To improve the sensitivity of the PAD measurements, we introduced a large volume and coupled it with preconcentration techniques to target onsite analysis of environmental contaminants.
References:
- Ogawa, K.; Kaneta, T. Anal. Sci. 2016, 32, 31.
- Karita, S.; Kaneta, T. Anal. Chem. 2014, 86, 12108.
- Karita, S.; Kaneta, T. Anal. Chim. Acta 2016, 924, 60.
- Seetasang, S.; Kaneta, T. ACS Sensors 2022, 7, 1194.
- Danchana, K.; Iwasaki, H.; Ochiai, K.; Namba, H.; Kaneta, T. Microchem. J. 2022, 179, 107513.
- Danchana, K.; Iwasaki, H.; Thayawutthikun, Y.; Saetear, P.; Kaneta, T. ACS Omega 2023, 8, 11213.
