ABSTRACT
A sulphide selective colorimetric metal complexing indicator-displacement assay has been developed using an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphthol printed by inkjetting on a nylon support. The change in colour measured from the image of the disposable membrane acquired by a digital camera using the H coordinate of the HSV colour space as the analytical parameter is able to sense sulphide in aqueous solution at pH 7.4 with a dynamic range up to 145 µM, a detection limit of 0.10 µM and a precision between 2 and 11%.
Subject(s)
Colorimetry/methods , Indicators and Reagents/chemistry , Ink , Organometallic Compounds/chemistry , Printing , Sulfides/analysis , Water/chemistry , Colorimetry/instrumentation , Copper/chemistry , Indicators and Reagents/chemical synthesis , Naphthols/chemistry , Nylons/chemistry , Organometallic Compounds/chemical synthesis , Photography/instrumentationABSTRACT
One of the main limiting factors in optical sensing arrays is the reproducibility in the preparation, typically by spin coating and drop casting techniques, which produce membranes that are not fully homogeneous. In this paper, we increase the discriminatory power of colorimetric arrays by increasing the reproducibility in the preparation by inkjet printing and measuring the color from the image of the array acquired by a digital camera, using the H coordinate of the HSV color space as the analytical parameter, which produces robust and precise measurements. A disposable 31 mm × 19 mm nylon membrane with 35 sensing areas with 7 commercial chromogenic reagents makes it possible to identify 13 metal ions and to determine mixtures with up to 5 ions using a two-stage neural network approach with higher accuracy than with previous approaches.
