Fluorescent sensor based on solid-phase extraction with negligible depletion: A proof-of-concept study with amines as analytes

This paper describes the development and proof-of-concept testing of an easy-to-use trace analysis technique, namely F-SPE, by coupling fluorescent sensor with solid phase extraction (SPE). F-SPE is a two-step methodology that concentrates an analyte from a liquid sample onto a fluorophore-modified membrane and measures the amount of analyte from the extent the extracted analyte quenches the emission of the fluorophore. By applying the principle of negligible depletion (ND) intrinsic to SPE, the procedure of F-SPE for analyzing a sample can be markedly simplified while maintaining the ability to detect analytes at low limits of detection (LOD). The merits of this approach are demonstrated by impregnating a SPE membrane with a perylene diimide (PDI) fluorophore, N,N′-di(nonyldecyl)-perylene-3,4,9,10-tetracarboxylic diimide (C9/9-PDI), for the low-level detection of organic amines (e.g., aniline) and amine-containing drugs (e.g., Kanamycin). The sensing mechanism is based on the donor-acceptor quenching of PDI by amines, which, when coupled with the concentrative nature of SPE, yields LODs for aniline and Kanamycin of 67 nM (∼6 ppb) and 32 nM (∼16 ppb), respectively. [Display omitted] •A novel fluorescent sensor, namely F-SPE, is developed from solid-phase extraction (SPE) disk modified with perylene diimide (PDI) fluorophore.•F-SPE demonstrates effective detection of aniline and Kanamycin, with limit of detection (LOD) down to 67 and 32 nM, respectively.•The sensing mechanism is based on the donor-acceptor fluorescence quenching of PDI by amines.•The high detection sensitivity of F-SPE is mainly due to the high porosity of SPE substrate that helps concentrate the analytes from solution phase.•F-SPE significantly simplifies the analysis process by eliminating the need to precisely meter the sample volume.