Elimination of Interferences in the Mercury(II) Determination with a Dithizone Nanofiber-coated Test Strip Based on Filtration–Enrichment

Abstract

This paper reports the selectivity of dithizone dye nanofiber-coated test strip (Dith DNTS) for the detection of Hg^II at ppb level. The Dith DNTS having thin layer (less than 500 nm) composed of 100% dithizone ensures highly sensitive Hg^II detection in the range of 0.1 to 20 ppb with the 3 σ detection limit of 0.057 ppb within 17 min by filtration enrichment of 100 mL of sample solution and subsequent reflection absorption measurement. The detection method has been shown to possess high tolerance to various cations and anions based on solid-liquid separation between dithizone layer and aqueous solutions in the presence of suitable reagents. Consequently, the allowable limits for reliable detection of 10 ppb of Hg^II with their removal requirements were as follows : Na⁺ (10000 ppm), K⁺ (5000 ppm), Ca^II (5000 ppm), Al^III (500 ppm), Cr^III (200 ppm), Cr^VI (3 ppm), Mn^II (100 ppm), Fe^III (100 ppm), Ni^II (100 ppm), Cd^II (10 ppm) and Pb^II (100 ppm) under acidic conditions, Cu^II (6.4 ppm) and Zn^II (100 ppm) using EDTA as a masking reagent to form water-soluble chelates, Fe^II (70 ppm) with KBrO₃ to oxidize Fe^II to Fe^III, and Ag⁺ (50 ppb) by filtration a sample solution containing NaI through a membrane filter to remove AgI precipitates. This highly sensitive and selective detection system is a promising method for simple and reliable on-site monitoring of Hg^II in real water samples.