Rapid and sensitive determination of Pb2+ in water using chromogenic reagent patterned on nail polish modified filter paper

Abstract

The current strategy extends the analytical utility of colorimetric spot assay for developing a simple one-step determination of Pb2+ in environmental water samples using the chromogenic reagent 2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol (5-Br-PADAP). The established assay was executed on Whatman filter paper modified with commercially available nail polish (NP). Goniometry analysis revealed that the surface of NP modified cellulose surface harbored hydrophobic character (θ ~111º). Scanning electron microscopy (SEM) and surface profilometry techniques satisfactorily recognized the changes in the morphology as well as the roughness upon surface modification. Under the optimized parameters, the assay could be concluded in less than 10 min upon formation of red-colored Pb-PADAP chelate. The figures of merits of the developed method were as follows; limit of detection (LOD=0.01 μg/mL), and linear dynamic range (LDR=0.5–10.0 μg/mL). The estimated assay sensitivity of the developed assay for Pb2+ determination corresponds to 11.4 ΔI/µg/mLPb2+/cm2. In addition to visual detection, data was also quantitated through scoring color intensity of the assay using image analysis software. Selectivity of the assay towards Pb2++ was greatly improved through addition of CN−, I− and F− that would eliminate the interference from most common diverse ions. The developed assay was satisfactorily extended for trace determination of Pb2+ in tap and wastewater samples. The reputable assay has several advantages; inexpensive modification/platform, low reagent/analyte volume requirement, improved specificity and simple read-out. Hence, the recognized assay can be widely implemented for point-of-use application especially in regions dealing with lead toxicity and limited laboratory facilities.