Summary:
In the present work, novel organic compounds were synthesized especially
designed for analytical applications. Among those compounds synthesized
wasasquaraine dye based on indole, whichshowed remarkable bleaching in the
presence of small, water soluble thiols. Additionally, in presence of mercury
ions, this squaraine, tended to form colored precipitates.
A spectrophotometric method was developed and validated for the determination
of thiols in aqueous solutions. This method was based on the decrease in the
absorbance of the squaraine caused by the thiols, at a wavelength of λ = 538 nm.
According to the optimization experiments, the optimum solvent for the method
was the mixture acetonitrile :water 30 : 70 v/v. The optimalsquaraine
concentration was 7.010–6 Μ in 0.01 M phosphate buffer, pH = 6.8. The method
validated thelinearity of the calibration curves, limit of detection (eg.
L-cysteine LoD = 8.710–7 Μ), selectivity, precision, ruggedness and
uncertainty.
Meanwhile, a paper–based technique was developed, with the squaraineon
cellulose membranes, to detect the presence of Hg2+ions in aqueous solutions.
This method allows forstraightforward “naked-eye” monitoring of the Hg2+ at
concentrations higher than 50 ng mL–1 Hg2+.
Keywords:
Squaraines, Thiols, Mercury, Photometry, Paper based techniques
