Task-specific ionic liquid-enabled mercury sensor for sensitive detection of total mercury in food digestion solution

Abstract

Heavy metal sensors are limited to the applications for environmental and drinking waters due to matrix interference. We report here a task-specific ionic liquid enabled DNAzyme-based mercury sensor (TSIL-Hg-sensor), allowing the sensitive detection of mercury in solid food samples. In TSIL-Hg-sensor, TSILs sequentially extracted mercury ion from microwave acid digestion solution with high efficiency, and then peroxidase-mimicking DNAzyme (PMD) that was used for the following signal amplification. Hg2+ and PMD shared the extraction capacity of TSILs. The greater amount of Hg2+ extracted from the first extraction would results in the less PMD from the second extraction, enabling the signal-on colorimetric detection of mercury. The detection of limit was 0.5 nM when [OMIM][PF6] was used for the extractions, 100 times more sensitive than the previously reported PMD-based signal-off sensor. The sensor with [Opy][BF4] was less sensitive, but highly specific for Hg2+. The practical applications were demonstrated by challenging TSIL-Hg-sensor with 5 standard solid foods containing mercury from 5.3 to 850 μg/kg with the recover percentage of 102 ˜115%. TSILs are designable for almost any molecules besides metal ions. Nucleic acids are compatible with numerous signal amplification means. TSIL-Hg-sensor therefore represents a universal design for sensors with high matrix interference resistance.