A miniaturized assay for sensitive determination of Cu2+ ions on nanolitre arrayed 4-(2-pyridylazo)resorcinol (PAR) spots on polyethersulfone membrane platform

- 4-(2-pyridylazo)resorcinol (PAR) reagent spots were patterned on polyethersulfone membrane surface.
- One-step assay for rapid detection and/or quantitative determination of Cu2+ was demonstrated (t ≤ 10 min).
- An excellent LOD (10− 3 μg mL− 1) with good LDR of 10− 1-102 μg mL− 1 were achieved.
- The proposed method has a great potential for portability and field applicability.

Nanolitre arrays of 4-(2-pyridylazo)resorcinol (PAR) reagent produced on polyethersulfone (PES) membrane surface has been utilized as a platform for rapid and precise determination of Cu2+ ions in water. The topography of the membrane surface was characterized by atomic force microscopy whereas internal morphology was revealed by scanning electron microscopy. The water contact angle (θ) corresponding to ~ 82° confirmed that the prepared PES membrane is a low-wetting substrate. The computed value of limit of detection (10− 3 μg mL− 1) achieved by the proposed membrane-based sensor was 4-order of magnitude lower than that obtained on the pristine filter-paper (10 μg mL− 1). The proposed method showed high robustness towards slight changes in pH, temperature and analyte volume. The interference of commonly occurring cations and anions in water was also evaluated. The analytical utility of the developed method was successfully demonstrated for determination of Cu2+ ions in spiked domestic tap water samples. The proposed method demonstrated excellent recovery of representative Cu2+ ions in real samples that was also validated by comparing the results with ICP-OES data. A good agreement between the two results was obtained at 95% confidence level. The analytical utility of the proposed method was also extended for the estimation Cu2+ ions in sewage and industrial wastewater samples and results were compared with ICP-OES analysis. The ease of usability/readability, low reagent/analyte volume requirement and superior robustness confirms the applicability of the developed low-cost method towards point-of-use applications.

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