Porphyrin-based colorimetric sensing of perfluorooctanoic acid as proof of concept for perfluoroalkyl substance detection

Abstract

A color changing sensor for the pollutant perfluorooctanoic acid was developed. The pollutant was visually detected from soil at concentrations as low as 3 ppm.

Mobile Phone-based Colorimetric Detection of Perfluorocarboxylic Acids using Porphyrin Hosts

“…Host 1 α,α,α,10,15,aminophenyl]-21H,23H-porphyrin), host 1, was prepared according to the previously reported methods. (Taylor et al, 2021) Host 2 α,α,α,α-5,10,15,20-Tetrakis(2-aminophenyl)porphyrin (0.010 g, 1.5x10 -5 M) and pyridine (0.009 g, 1.2x10 -4 M) were combined in dry dichloromethane (10 mL) and stirred at ambient temperature for one hour. A solution of perfluorobutyryl chloride (0.014 g, 6.0x10 -5 M) in dry dichloromethane (5 mL) was added dropwise.…”

“…PFCAs appears to be due to the cumulative combination of both the carboxylate group and the fluorinated chain, as neutral fluorinated molecules and non-fluorinated carboxylates showed no colorimetric response (Taylor et al, 2021). Other works have shown the fluorophilic attraction of isomers of the same receptor (1) are able to bind neutral fluorinated molecules, and demonstrate trends based on fluorophilic affinities (Paleta et al, 2002).…”

“…In previous work, we presented the fluorinated "picket fence" amido-porphyrin, 1, that bound PFOA to produce a color change detectable by eye from soil at concentrations as low as 3 ppm. (Taylor et al, 2021) Here, we present two new modifications to this host molecule and investigate their responses to binding a range of PFCAs (Table 1).…”

“…UV-Vis spectroscopic analysis indicated host 1 bound PFOA with 1:1 binding in dichloromethane, with an association constant (K) in 10 the range of ca. 7.50×10 6 M -1 (logK = 6.88) (Taylor et al, 2021). By design, the fluorinated chains of the host were an equivalent length to the guest molecule PFOA.…”

Mobile Phone-based Colorimetric Detection of Perfluorocarboxylic Acids using Porphyrin Hosts

“…In previous work, we presented the fluorinated "picket fence" amido-porphyrin, 1, that bound PFOA to produce a color change detectable by eye from soil at concentrations as low as 3 ppm. 15 Here, we present two new modifications to this host molecule (Figure 1) and investigate their responses to binding a range of PFCAs (Table 1). The host molecules have a preference to bind PFCAs over other common PFAS such as perfluorooctanoic sulfonic acid, allowing for development of a colorimetric method for PFCA screening.…”