Determination of acid dissociation constants of Alizarin Red S, Methyl Orange, Bromothymol Blue and Bromophenol Blue using a digital camera

Abstract

Acid dissociation constants (pK a ) are important parameters for the characterization of organic and inorganic compounds. They play a crucial role in different physical, chemical, and biological studies. Herein, we introduce a new approach for the determination of acid dissociation constant based on digital image analysis using a low-cost, precise, accurate, sensitive, and portable home-made, camera-based platform. Digital images of Alizarin Red S, Bromophenol Blue, Bromothymol Blue, and Methyl Orange solutions were captured at various pH values. The captured images were analysed to obtain the RGB (Red, Green, and Blue) colour intensities that are used to calculate the RGB colour absorbances. The pK a values were calculated from the RGB colour absorbance-pH relationship using graphical and mathematical methods, and with the aid of DATAN software. For the four studied dyes, the results obtained from digital image analysis were in excellent agreement with the data of sophisticated spectrophotometers and the previously reported literature data.

Selective Removal of Anionic Dyes by Metal–Organic Framework-Anchored CoAl-Layered Double Hydroxide Nanosheets

“…Therefore, the CoAl-LDH/Cu-(tpa) MOF nanocomposite shows the maximum anionic methyl orange dye adsorption efficiency at pH = ∼6.5. Also, the high adsorption efficiency at pH = ∼6.5, suggests the adsorption of undissociated methyl orange dye in the form of an azo structure (pKa of methyl orange is 3.36) rather than a quinoid structure …”

Modeling the Dichromatic Behavior of Bromophenol Blue to Enhance the Analytical Performance of pH Colorimetric Sensor Arrays

“…The difficulty in correlating RGB colors with spectroscopic changes can be solved using the hue, saturation, and value color space (HSV) [12,13]. The H coordinate [14][15][16][17] is the most suitable, since it is an analytical signal characterized by high robustness. Its value is separated from the V coordinate linked to the lighting conditions and the variability of the background of the acquired image.…”

pH-Dependent fluorescence of [La(OH)2]+[ARS]− hybrid nanoparticles for intracellular pH-sensing

“…5,14 Here, a suitable emissive nanoprobe that allows to indicate such acidic pH ranges is highly The pH-indicator ARS is generally known to change its absorption both in the acidic range (pK a = 5.5) and in the basic range (pK a = 10.8). 18 To evaluate the pH-dependent properties of the [La(OH) 2 ] + [ARS] -IOH-NPs, first of all, the absorption of the nanoparticle suspension was examined and compared to solutions of freely dissolved ARS (Figure 4; ESI: Figure S1). Accordingly, the IOH-NPs show a considerable colour shift from pink (pH = 5.0-9.0) to violet (pH > 9.0), and most important to pale yellow (pH < 4.5) (Figure 4a).…”

“…The pH-indicator ARS is generally known to change its absorption both in the acidic range (p K a = 5.5) and in the basic range (p K a = 10.8). 17 To evaluate the pH-dependent properties of the [La(OH) 2 ] + [ARS] − IOH-NPs, first of all, the absorption of the nanoparticle suspension was examined and compared to solutions of freely dissolved ARS (Fig. 3; ESI:† Fig.…”