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  • Reversible and high accuracy pH colorimetric sensor array based on a single acid-base indicator working in a wide pH interval.

Reversible and high accuracy pH colorimetric sensor array based on a single acid-base indicator working in a wide pH interval.

Talanta (2020-09-06)
Andrea Pastore, Denis Badocco, Paolo Pastore
ABSTRACT

A pH colorimetric sensor array (CSA) with fast response time (<1 min) using only one acid-base indicator, Bromothymol Blue (BB), was prepared and characterized by modulating the amount, C, of the surfactant Hexadecyltrimethylammonium p-toluenesulfonate between 0 and 0.3725 gCTApTs/gprecursor with a constant amount of the OrMoSil precursors. The effect of the C increase is a continuous acidic shift of the calibration position, i.e. a huge variation of the pKa value of BB in the pH range 5.80-13.50. The precision error decreased with increasing C from 0.096 pH units (lower C values) to 0.023 pH units (larger C values). This result led to the development of a model to determine the number of spots with suitable C values required for having a similar value of precision in the entire working interval of the CSA. By selecting only 4 spots the precision error is < 0.100 pH units in the pH range 5.80-13.50. With 256 spots (diameter of each spot ≈ 3 mm), the model predicted an error almost constant (≈0.010) in the entire pH range.

MATERIALS
Product Number
Brand
Product Description

Supelco
Crimp seals with PTFE/silicone septa, silver aluminum seal, open center, diam. × total thickness × PTFE thickness 20 mm × 3.2 mm × 2 mil, white PTFE/silicone, pkg of 100 ea
Sigma-Aldrich
Bromothymol Blue, ACS reagent, Dye content 95 %
Sigma-Aldrich
Tetraethyl orthosilicate, ≥99.0% (GC)
Sigma-Aldrich
Sodium hydroxide, ACS reagent, ≥97.0%, pellets
Sigma-Aldrich
Hexadecyltrimethylammonium p-toluenesulfonate
Sigma-Aldrich
Dodecyltriethoxysilane, technical