title: Using ratiometric indicator-displacement assays in semi-quantitative colorimetric determination of chloride, bromide, and iodide anions.
abstract: A ratiometric indicator-displacement assay (RIDA) array has been developed for the semi-quantitative colorimetric determination of chloride, bromide, and iodide anions. Determinations of these halide anions follow the displacement reaction using the chelate compound of (2-(3,5-dibromo-2-pyridylazo)-5-(diethylamino)phenol) (3,5-Br2-PADAP) and heavy metal salts as colorimetric reagent. Different from regular silver nitrate titrations, the chloride, bromide, and iodide anions compete with the 3,5-Br2-PADAP ligand and change the colour of the 3,5-Br2-PADAP-metal chelate compound dramatically. These clearer colour changes make the semi-quantitative colorimetric determination of chloride, bromide, and iodide anions possible. The colour changes are imaged using a conventional flatbed scanner, and digitized. After statistical analysis, these colour changes in the RIDA array provide facile identification of chloride, bromide, and iodide anions at a wide concentration range (10 μM to 10 mM) without any misclassification. The RIDA array is able to discriminate without misclassifications among seven concentrations of chloride, bromide, and iodide anions. No shelf life issue exists because the chelating compounds react with halide anions directly without any pre-immobilizations.
authors: Laboratory of Instrumentation and Analytical Chemistry, Dalian Institute of Chemical Physics, CAS, Dalian, Liaoning 116023, P. R. China.
authors: Zheng
authors: Z
authors: Shen
authors: Hui
authors: H
authors: Li
authors: Liang
authors: L
authors: Feng
mesh_terms: D000838:Anions / Q000032:analysis / Q000737:chemistry; D001965:Bromides / Q000032:analysis* / Q000737:chemistry; D002712:Chlorides / Q000032:analysis* / Q000737:chemistry; D003124:Colorimetry / Q000379:methods*; D007202:Indicators and Reagents; D007454:Iodides / Q000032:analysis* / Q000737:chemistry
chemical_list: D000838:Anions; D001965:Bromides; D002712:Chlorides; D007202:Indicators and Reagents; D007454:Iodides