SPE based soil processing and aptasensor integrated detection system for rapid on site screening of arsenic contamination in soil.

Rapid industrialization and urbanization have resulted in serious environmental deterioration, especially in terms of heavy metal contamination in soil. Arsenic is one of the primary heavy metal contaminants in the soil and possesses a severe threat to all the plants and animals including humans. The conventional methods for analyzing arsenic contamination in soil have tedious, time-consuming sample preparation steps and require laboratory equipped instruments and skilled personnel. The present work demonstrates a novel method for arsenic As(III) detection in the contaminated soil based on field applicable sample preparation and smartphone-based optical sensing. Soil sample preparation has been simplified and optimized using acid extraction and serial application of different solid phase extraction (SPE) cartridges for the removal of interfering ions with high arsenic yield in one step. The acidic extraction and SPE efficiencies were found to be 35.4% and 54.0%, respectively, for arsenic contaminated field soil samples. The quantification of As(III) was performed by aptamer-AuNPs based colorimetric assay with a smartphone coupled optical unit. This aptasensor integrated detection system (ADS) has shown a detection limit of 14.44 ppb for aqueous samples and 1.97 ppm for field soil samples. In the accuracy comparison with ICP-MS, arsenic contaminated field soils from various sources have been tested and the results depicted a highly significant correlation coefficient of 0.997 with an average difference of 1.67 ppm. By integrating all the required analytical steps into a portable format, the presented setup enables on-site tests of arsenic contamination in soil.