FINGERPRINT OF ANIONS INVOLVING PK(A), MOBILITY AND CONCENTRATION ESTABLISHED BY USING CAPILLARY ISOTACHOPHORESIS

The suggested fingerprint of anions is constructed in a square, two si des of which form the pK(a) and absolute mobility, u(o), axis, the oth er two the concentrations axis in log scale. Every acid is demonstrate d by a pK(a)-u(o) point and by a dash to the point indicating concentr ation. The absorption in UV is marked by a small triangle. The suggest ed experimental procedure involves the isotachophoretic examination of the sample in four buffers of pH 3.25, 4.50, 6.25 and 6.25. The last one prepared from bis-tris propane is of use for discrimination betwee n mono-, di- and trivalent acids from the decrease of mobility. The pK (a) values of monovalent acids are found from the established relation ship between mobility ratio at different pH and pK(a). The pK(2) value s of divalent acids are calculated by assuming that pK(2) = pH at u = 0.75 u(o2). The quantity of an acid injected on the column n, nanomol, can be calculated from the equation, n = tiu(o)(96.5)(-1)(u + u(ap))( -1) where t = zone length (s), i = current (mu A), u and u(o) = effect ive and absolute mobility, u(ap) = apparent mobility of counter ion. B ased on the established equation, Delta u(max) = 0.35u(o) Delta pK(a) where Delta u(max) = maximum attainable difference between effective m obilities of two anions of the same absolute mobility as function of p H(L), Delta pK(a) = difference of pK(a) values. A new approach to the problem of resolution in isotachophoresis is demonstrated by marking a sphere of inseparability round the point in fingerprint system.