Eco-friendly screening method for sulfonamides using a 3D handheld smartphone-based fluorescence detection device and graphene nanoplatelet-packed pipette tip microextraction

A sensitive, miniaturized, and low-cost method combining pipette tip solid-phase microextraction and smartphone-based fluorescent detection has been developed for the determination of total sulfonamides in water samples. Sulfonamides antibiotics (SAs) are contaminants commonly found in water matrices, leading to antibiotic-resistant bacteria and risks to human health and the environment. Thus, its real-time monitoring is essential to the risk assessment, and the subsequent management of any water supply. Sample preparation consisted of extraction/preconcentration of SAs using graphene nanoplatelets packed inside a pipette tip, followed by fluorescent derivatization using fluorescamine inside the microplate reader, both 3D printed. Subsequently, a 3D printed detection platform that houses monochromatic LED strips as radiation source and a smartphone as detector have been used for determination total SAs. Digital image processing was based on the RGB colour model using image J software with its Readplate plugin and the green intensity channel was used as analytical signal due to its higher sensitivity. Several factors that affect the extraction efficiency and detection have been optimized. Under the optimized conditions, good linearity for SAs studied were obtained in a range of 10-60 µg L-1 with r ≥0.990 and limits of detection between 2.5-3.1 µg L-1 for a sample volume of 10 mL. The recoveries of sulfamethoxazole (as a model compound to express total SAs) spiked in diverse water matrices were tested at two different levels showed good recoveries from 94% to 102% with RSD ≤ 7.6%. The results obtained with the proposed method were satisfactorily compared with those obtained with a conventional spectrofluorometer (P≥0.13). This easy-to-operate system features a simple extraction procedure (up to 20-fold enrichment), excellent sensitivity and precision, which is very useful and practical for on-site analysis. Furthermore, three greenness evaluation methodologies (GAPI, AGREE, and AGREEprep) were used to assess the environmental friendliness of the proposed method, demonstrating its superior performance compared to previously published HPLC and spectrophotometric methods.