Spectroflurometric Determination of Boron with Chromotropic Acid

Equilibrium and kinetic studies on the complexation of boric acid with chromotropic acid

“…On the basis of the boron complex-forming ability in acidic aqueous solutions, many useful methods for determining trace amounts of boron using chromotropic acid were developed by means of solvent extraction, high-performance liquid chromatography (HPLC), flow injection analysis (FIA) and so on. [18][19][20][21][22][23][24] It was proposed only later that the maximum sensitivity for boron measurement was obtained at a pH equal to or higher than 7. 25 Among most of the reports, the mechanism of the complexation has rarely been mentioned.…”

Ultrapure water blank for boron trace analysis

“…To evaluate medium-to-high range boron concentrations in tap and puri®ed water, a spectro¯uorimetric method was used. This method is based on the speci®c ¯uorescence of a complex between chromotropic acid and boron, following the protocol described by Lapid et al 15 and modi®ed by Motomizu et al 16 for high sensitivity and ¯ow injection methods. In this study, a new modi®ed method was developed to adapt it to the analysis of puri®ed water.…”

Anion exchanger as a reaction/separation medium—absorptiometric determination of trace amounts of boron in waters by on-line complexation with chromotropic acid presorbed on the anion-exchange column

“…Although the 1+2 complex has the highest molar absorptivity among the related species, the ultraviolet absorption spectra belonging to the 1+1 and 1+2 complexes are almost the same both in the shapes and the absorption maximum wavelengths and also resemble that of the undissociated reagent (pK a1 5.35), 23 whereas the dissociated chromotropic acid has a different absorption property when its spectrum maximum shifts to the longer wavelength. Taking the characteristics of the boric acid-chromotropic acid reaction into consideration, the optimum conditions of the methods for boron determination proposed so far [12][13][14][15][16][17][18][19] can fully be understood, and the equilibrium and kinetic information of the complexation will help us to develop further practical applications of the present system.…”

“…Based on the characteristics that both the reagent itself and its boron complexes absorb ultraviolet radiation and/or are fluorescent, many useful methods for the determination of boron have been developed. The spectrophotometric measurement for the 1+1 stoichiometric boron-chromotropic acid complex, which could not be carried out directly since the absorption spectrum of the complex is entirely overlapped by that of the ligand, has indirectly been accomplished by following the decrease in the reagent absorbance 12,13 or its fluorescence intensity [14][15][16] in neutral or basic solution. The methods tracing the 1+2 complex provided much higher sensitivity when a large excess of chromotropic acid was used.…”