Optical sensors and the salt effect: a dual-transducer approach to acidity determination in a salt-containing concentrated strong acid.
A dual-transducer approach has been developed to decompose the optical signals of acid sensors in salt-containing concentrated acid solutions and to give acid and salt concentrations in concentrated LiCl-HCl, CaCl2-HCl, and AICl3-HCl solutions, respectively. The optical acid sensors in this approach are films of porous sol-gel SiO2 or SiO2-Nafion composite doped with low-pKa indicators. A novel linear relationship (dA/dCsalt)cCacid = beta x (dA0/dCacid)Csalt = 0 (A = absorbance of the sensor in a salt-containing HCl solution; A0 = absorbance of the sensor in a salt-free acid solution) was found, and the current approach is based on a set of nonlinear equations derived from this relationship.
Allain
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Department of Chemistry, The University of Tennessee, Knoxville, 37996-1600, USA.
Canada
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