DOI: 10.1002/elan.201400533 Electroanalytical Studies of Chromone Based Ionophores for the Selective Determination of Arsenite Ion Neha Gupta, [a] Ashok Kumar Singh,* [a] Shubhrajyotsna Bhardwaj, [a] and Divya Singhal [a] 1 Introduction Arsenic is the twentieth most abundant element occurs naturally in earth)s crust and also plays role as a compo- nent of more than 245 minerals. Arsenic is very toxic in nature in its inorganic form as arsenite, arsenate com- pound and its sulfide ores. Arsenic as arsenite is found in nature in trace amounts in water, rock, soil, air and plant tissues. Humans are exposed to arsenite primarily from air, food, water and prevalence of different types of can- cers. Mostly arsenic contaminations are found in ground water supply systems and are caused by the redox changes of geochemical environments [1]. Arsenite is widely used in herbicides, pigments and insecticides which represent its eminent source in water used for drinking. Arsenite concentration in water is mainly caused by human activities such as petroleum refining, mining wastes, sewage sludge, ceramic manufacturing in- dustries, agricultural chemicals, and coalfly ash [2,3]. Ar- senite disturbs ATP production through several mecha- nisms so the resulting energy supply in the cells have been reduced and finally cells are dead slowly. According to the WHO long exposure of inorganic ar- senic can cause harmful effects to human health, such as peripheral neuropathy, skin lesions, diabetes, pain, renal system effects, nausea, cardiovascular disease, vomiting, diarrhea, cancer and eventually leads to death [4–6]. Due to its high toxicity, WHO has lowered the maxi- mum contaminant level (MCL) for arsenic in drinking water from 50 to 10 mgL 1 [7]. The amount of arsenic present in drinking water is very less even lower than the calculated by modern analytical methods. There are sev- eral accepted analytical methods currently available for arsenic measurement in environmental samples. These in- clude solid ion selective electrode [8], whole-cell based biochip sensor [9], silica gel memberane electrode [10], potentiometric flow analysis [11], carbon paste electrode, liquid polymeric membrane based electrodes [12], vol- tammetric analysis [13] and atomic fluorescence spec- trometry [14]. Due to their easy preparation, low cost, fast response, high sensitivity, simple operation, wide linear dynamic range, and better selectivity, ion selective electrodes (ISE) have been found to be better tool than other analytical methods. However, there is a very few lit- erature on the use of potentiometric sensors selective to arsenic, and especially to arsenite [15]. 2 Experimental 2.1 Reagents All the ingredient used for the construction of polymeric membranes electrode i.e., poly(vinyl chloride) of high rel- ative molecular weight, plasticizers like o-nitrophenyloc- tyl ether (o-NPOE), dibutylphthalate (DBP), 1-chloro- naphthalene(1-CN), dioctylphthalate (DOP), tri-n-butyl- phosphate (TBP), and cation excluder hexadecyltrimethy- lammonium bromide (HTAB), potassium carbonate (K 2 CO 3 ), tetrahydrofuran (THF) and salts of all the anions were of analytical reagent and purchased from Sigma Aldrich and they were used as received. A 0.01 mol L 1 stock solution of arsenite was prepared by dissolving an appropriate, accurate amount of NaAsO 2 (E. Merck). A 5.0  10 10 –1.0  10 2 mol L 1 solution of ar- senite was prepared by sequential dilution of the appro- priate stock solution with doubly distilled water. [a] N. Gupta, A.K. Singh, S. Bhardwaj, D. Singhal Department of Chemistry, Indian Institute of Technology- Roorkee Roorkee-247667, India *e-mail: akscyfcy@iitr.ernet.in Abstract : Two chemosensors 4H-1-benzopyran-3-carbox- aldehyde, 4-oxo-, 3-(2-phenylhydrazone), [I 1 ] and 4H-1- benzopyran-3-carboxaldehyde, 4-oxo-, 3-[2-(2,4-dinitro- phenyl)hydrazone] , [I 2 ] with hydrazone-NH group as binding site have been shown excellent selectivity for ar- senite ion. It is confirmed by the UV-vis titration that I 2 is more selective than I 1 . The performance of the coated graphite electrode (CGE) was found to be better than polymeric membrane electrode (PME) in terms of linear range of 4.89  10 7 –1.0  10 1 mol L 1 , low detection limit of 8.31  10 8 mol L 1 and short response time. The pro- posed sensors were also used to determine the arsenite ion in different water samples. Keywords: Arsenite colorimetric sensor · Arsenite selective sensor · Coated graphite electrode · Polymeric membrane electrode www.electroanalysis.wiley-vch.de # 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2015, 27, 1166 – 1175 1166 Full Paper