2007-02-17 00:23:31 · 5 answers · asked by rockfort 1 in Science & Mathematics ➔ Chemistry
Although the establishment of a pH scale and the determination of the pH in water is not problematic, it is not a straightforward task in non-aqueous solvents. As capillary zone electrophoresis (CZE) in organic solvents has gained increasing interest, it seems to be valuable to re-discuss the concept of the pH in such media, especially pointing to those aspects, which make pH measurement uncertain in non-aqueous solvents. In this review, the relevant aspects when dealing with primary standard (PS) and secondary standard (SS) as recommended by the International Union of Pure and Applied Chemistry (IUPAC), and the usage of the operational pH are discussed with special emphasis to non-aqueous solvents. Here, different liquid junction potentials, incomplete dissociation of the electrolytes (especially in solvents with low or moderate relative permittivity) and the occurrence of homo- and heteroconjugation must be taken into account. Problems arising in capillary zone electrophoresis practice are addressed, e.g. when the background electrolyte (BGE) consists of organic solvents, but the measuring electrode (normally the glass electrode) is calibrated with aqueous buffers, and the liquid junction potentials between the solvents do not cancel each other. The alternative concept of establishing a certain pH is described, using mixtures of reference acids or bases with known pKa in the organic solvent, and their respective salts, at a certain concentration ratio, relying to the Henderson-Hasselbalch equation. Special discussion is directed to those organic solvents most common in capillary zone electrophoresis, methanol (MeOH) and acetonitrile (ACN), but other solvents are included as well. The potential significance of small amounts of water present in the organic solvent on changes in pKa values, and thus on the pH of the buffering components is pointed out.
2007-02-17 00:36:57 · answer #1 · answered by stevieg 2 · 1⤊ 0⤋
yes. a pH factor can also be determined for solid compounds (primarily organic pastes *semi-solids) with no water present at all. The only dificulty is that the standard 0-14 pH scale may not nessisarilly be usable as that is for aqueos solutions... and some of the typical mesuring methods would have to be changed for more technical methods. to my knowledge the lowest pH & highest pHs of substances go beyond + and - 28 on the pH scale.
2016-05-23 22:16:38 · answer #2 · answered by ? 4 · 0⤊ 0⤋
normally only DMSO and water pka are really tabulated, you can find in the literature some other solvents pka of various acids but not enough to do a nice table.
BTW do you know what is the meaning of the measurement of pH in water ? if you discover it can I publish and earn a nobel with you ?
2007-02-17 00:47:33 · answer #3 · answered by scientific_boy3434 5 · 0⤊ 0⤋
As pH is thelogarithm of the inverse of H+ ions you must calculate these and apply the formula
2007-02-17 00:29:15 · answer #4 · answered by maussy 7 · 0⤊ 1⤋
7.... water is not aqueous
bromine is abit acidic
mercury too
2007-02-17 00:35:32 · answer #5 · answered by mike_goesblues 2 · 0⤊ 2⤋