Sulfites are used as preservatives in many consumer products to prevent browning and microbial growth. However, many individuals have adverse reactions to sulfites especially at higher doses. This creates the need for sulfite regulation in consumer products, and a way to chemically quantify the amount of sulfites present. Usually wineries use the Monier-Williams test to determine the amount of sulfites present in wine, but this process is tedious, requires a trained chemist, and is not particularly accurate. However, wineries are required by the Alcohol and Tobacco Tax and Trade Bureau, to indicate that the item “contains sulfites” at concentrations of 10 ppm and above, so inadequate labeling leads to significant health issues in uninformed consumers. To remediate these challenges, anion sensors are employed which provide higher sensitivity and selectivity to their target analytes. While anion sensors have gained notable momentum in recent years, there is a considerable lack in the amount of selective, optical, and water-soluble sensors. Small molecule and metal-free chemosensors are of increasing demand due to their relatively simple synthesis, and their ability to be employed in a variety of solvents while remaining highly selective to their analyte of interest. This group has made a small organic molecule sensor, 4-(1H-pyrrol-2-yl)pyridine, with aqueous solubility that has gained recognition for its acute sensitivity for sulfite anions in solution. This sensor can detect sulfites with a limit of detection of 3.69 nM. In a competitive anion study, the sensor exhibited bleaching when selectively interacting with sulfite and bisulfite with a 20-fold higher concentration of various anions present in solution. Here, the increased sensitivity and selectivity of the sensor to detect sulfites in solution can prevent severe health hazards to consumers by accurately determining the concentration of sulfites present in consumer goods. Additionally, the sensor and the mechanism through which it functions, have been studied by UV-vis, IR, and 1H NMR spectroscopy. Through this analysis, new methods in food science and regulation can be created to increase accuracy in product labeling, ensure the safety of the consumer, and efficiency in testing consumer products. This presentation reveals new insight into the chemistry of this important new sensor molecule, a newly synthesized anion sensor of similar chemical structure, and the mechanism of its action.

Synthesis of 4-(1H-pyrrol-2-yl)pyridine, related compounds, and their application in sulfite sensing

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