Conventional methods for analyzing heavy metal contamination in soil and water generally require laboratory equipped instruments, complex procedures, skilled personnel and a significant amount of time. With the advancement in computing and multitasking performances, smartphone-based sensors potentially allow the transition of the laboratory-based analytical processes to field applicable, simple methods. In the present work, we demonstrate the novel miniaturized setup for simultaneous sample preparation and smartphone-based optical sensing of arsenic As(III) in the contaminated soil. Colorimetric detection protocol utilizing aptamers, gold nanoparticles and NaCl have been optimized and tested on the PDMS-chip to obtain the high sensitivity with the limit of detection of 0.71 ppm (in the sample) and a correlation coefficient of 0.98. The performance of the device is further demonstrated through the comparative analysis of arsenic-spiked soil samples with standard laboratory method, and a good agreement with a correlation coefficient of 0.9917 and the average difference of 0.37 ppm, are experimentally achieved. With the android application on the device to run the experiment, the whole process from sample preparation to detection is completed within 3 hours without the necessity of skilled personnel. The approximate cost of setup is estimated around 1 USD, weight 55 g. Therefore, the presented method offers the simple, rapid, portable and cost-effective means for onsite sensing of arsenic in soil. Combined with the geometric information inside the smartphones, the system will allow the monitoring of the contamination status of soils in a nation-wide manner.
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Supplementary Materials Figure S1: I) a) Dimensions of PDMS chip b) Fabricated PDMS chip. II) Different chip designs with control(C) and test (T) wells, showing diameter, length, breadth and thickness: a) 2.5,22,22, and 8 mm. b) 4,22,22, and 6mm c) 6,22,22, and 4mm d) 8,22,22, and 4mm. III) Images of chips tested on the device, representing: 1) Reflection with shadow effect 2) Shadow effect at the corners 3) High intensity with no reflection and shadow effect 4) Reflection with poor intensity Acknowledgments: This subject is supported by Korea Ministry of Environment (MOE) as “Geo-Advanced Innovative Action Project” (2015000540008), the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1C1A1A01054762), and Korea University of Technology and Education as “Professor’s Education and Research Promotion Fund 2015”.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering