Determination of pKa values of anthraquinone compounds by capillary electrophoresis

Abstract

In this paper, the dissociation constants (pKa1, pKa2) of five anthraquinones were determined from the relation between the effective mobility at different pH values and the buffer pH value, which was derived from the basic electrophoresis theory and the dissociation equilibrium of a binary acid. In addition, the changes of pKa values of the five compounds were also investigated when organic modifiers were added to the buffer system.

Microwave assisted synthesis of metal‐organic framework MIL‐101 nanocrystals as sorbent and pseudostationary phase in capillary electrophoresis for the separation of anthraquinones in environmental water samples

“…Thus the result in the changes in anthraquinones’ partition between PSP and aqueous phase. Physcion, chrysophanol and aloe‐emodin have poor resolution in CZE , since their pK a ranged only from 8.49 to 8.51. In the presence of nMIL‐101, the migration sequence was approximately the same as that in CZE without nMIL‐101, with a descending order of the pK a .…”

Rapid separation and determination of structurally related anthraquinones in Rhubarb by pressurized capillary electrochromatography

“…The chemical structures of these analytes studied show that their apparent charged depends on their pK a values tested to be approximately 8.5 for physcion, chrysophanol and aloe-emodin, 5.7 for emodin, and 4.7 for rhein in the aqueous solution, respectively [28]. The mobile phase containing 10 mmol/L phosphate at different pH values ranging from 4.9 to 7.0 was investigated to study the effect of pH value on the separation.…”

Rapid pKa estimation using vacuum‐assisted multiplexed capillary electrophoresis (VAMCE) with ultraviolet detection

“…In the past decade a number of groups have demonstrated capillary electrophoresis (CE) with UV detection as an alternative approach for pK a determinations 1–6,9,12–29. The advantages of CE for pK a determinations include a microgram sample requirement due to the small injection volume; no need for high compound purity because CE provides a separation, and no weighing of the sample because only migration times are needed to calculate the pK a 1–3,5,6,12…”