Highly stable pH-gradients formed by polyhydroxyl compounds, boric acid and borates

High-performance liquid chromatographic determination of electrically neutral carbohydrates with conductivity detection

“…The dissociation constant of PB is generally larger than that of boric acid (pKa = 9.2), e.g., the value is pKa = 4.5 in the presence of 0.5 M fructose and pKa = 5.3 in the presence of 4 M glycerol (17). This complexation has been utilized for anion-exchange chromatographic separation of sugars (14,15), titration of boric acid (20), and pH-gradient elution of peptides and amino acids (21)._ '…”

“…here has the great advantage to be more selective without the necessity to separate the fluorescent byproducts from the ALA derivative, combined with the highest sensitivity ever reported for the determination of ALA (detection limits: Ehrlich's reagent, 4 nmol (14); 2-amino-3-naphthol, 40 pmol (16); OPA/ME, 0.8 pmol). The OPA reagent has the outstanding property of being nonfluorescent until it reacts with the amines (21). A disadvantage may be the still potentially reactive excess of OPA remaining in solution.…”

IEF‐based multidimensional applications in proteomics: Toward higher resolution

“…gradients of a substance that do not possess any intrinsic acid‐base properties. As proposed by Troitskii et al , a gradient of dielectric permittivity, due to the presence of a gradient of organic solvent, creates a pH gradient simultaneously, even in the case of a uniform concentration of buffer compounds. There could be a possible advantage here in generation of ultra‐narrow and, perhaps, more stable and less expansive pH gradients.…”