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In this paper, a novel azo Schiff base chemosensor was synthesized via condensation reaction of 4-Aminoantipyrine with 1-(3-Formyl-4-hydroxyphenylazo)-3-nitrobenzene. The imine sensor was studied via spectroscopic methods IR, 1HNMR and UV-Vis. The chromogenic behavior of colorimetric chemosensor toward various anions was investigated by UV–Vis spectroscopic. The chemosensor show abrupt changes towards CN− and OAC−anions in DMF/H2O solution in comparison with other anions. Upon the addition of CN− and OAC− ions to the receptor, the color of the L solution was changed from yellow to purple that was detectable with naked-eye and without any optical instrument. No color changes towards other anions were observed. The detection limits of the azo-azomethin sensor for OAC− and CN− anions were 2.6 ×10-5 and 1.4 ×10-6 mol L-1, respectively. Using the association constant value for sensor towards OAC− and CN− anions was calculated to be 4.2 ×103 and 3.07 ×104 M-1.

In this paper, a novel azo Schiff base chemosensor was synthesized via condensation reaction of 4-Aminoantipyrine with 1-(3-Formyl-4-hydroxyphenylazo)-3-nitrobenzene. The imine sensor was studied via spectroscopic methods IR, 1HNMR and UV-Vis. The chromogenic behavior of colorimetric chemosensor toward various anions was investigated by UV--Vis spectroscopic. The chemosensor show abrupt changes towards CN- and OAC--anions in DMF/H2O solution in comparison with other anions. Upon the addition of CN- and OAC- ions to the receptor, the color of the L solution was changed from yellow to purple that was detectable with naked-eye and without any optical instrument. No color changes towards other anions were observed. The detection limits of the azo-azomethin sensor for OAC- and CN- anions were 2.6 ×10-5 and 1.4 ×10-6 mol L-1, respectively. Using the association constant value for sensor towards OAC- and CN- anions was calculated to be 4.2 ×10³ and 3.07 ×104 M-1. [ABSTRACT FROM AUTHOR]

In this study, a colorimetric sensor was introduced to determine citric acid by the indicator displacement assay(IDA) method. The sensor was made from the complex formation reaction between the Chromeazurol S and the gadolinium ions in aqueous solutions. At optimum pH(pH =7.00), Chromeazurol S (yellow) was reacted with gadolinium (III) in a 1: 1 ratio, and the Chromeazurol S-gadolinium color complex solution changed to purple. With the addition of citric acid to the designed sensor, citric acid replaces Chromeazurol S and reacts with gadolinium ion in a 1: 1 ratio. The reason for the displacement of the indicator by the analyte in combination with the gadolinium ion acceptor is that it has a larger citric acid-gadolinium complex formation constant (logKF = 6.86) than the Chromeazurol S-gadolinium formation constant (logKF = 5.67). The linear range of this measurement and detection limit of this sensor (S/N=3) were determined 2.27×10-6 to 112.90×10-6 M and 2.08×10-6, respectively. To determine the selectivity of the designed sensor, the effect of different anions such as pyrophosphate, salicylic acid, periodic acid, benzoic acid, and other compounds on the sensor response under similar conditions was investigated, and no significant color change was observed. It was indicating that the sensor has a high selectivity to measure this analyte. The efficiency of the method was evaluated by measuring citric acid in the orange juice sample by the standard addition method.