Frans_M_Everaerts_Isotachophoresis_378342.pdf

128 DETECTION SYSTEMS
the zone boundaries is required. The other two isotachopherograms contain both the
qualitative and the quantitative information.
In Table 6.3 the results of the separation are given. The time interval between two
peaks, measured with a stop-watch. is given in seconds. The use of electronic equipment
for measuring the time intervals more accurately decreases the detection limit. The
detection limit can be decreased further by using a leading electrolyte with a lower
concentration, because all other zones will adjust their concentrations in the zones
according to the concentration of the leading electrolyte. It must be emphasized, however,
that a decrease in the concentration of the leading electrolyte automatically implies that
the pH limits between which experiments according to the isotachophoretic principle can
be carried out safely are narrower. While at a concentration of the leading electrolyte of
lo-* N a pH of about 3.5 is the lower limit and a pH of about 10 is the upper limit, at
TABLE 6.3
QUANTITATIVE INFORMATION THAT CAN BE DERIVED FROM A THERMOMETRIC
DETECTOR
The figures given are zone lengths, expressed in seconds. The quantitative information that can be
derived from conductivity and W detectors is discussed in Chapter 10, where the quantitative aspects
of the thermometric detector are also discussed in more detail.
Compound Amount injected (nmoles)
Oxalate 20 43 64
21 43 64
21 43 63
43 64
64
Average 21 43 64
Formate
Acetate
Average
Average
5 10 15 20 30 45
20
20
19
20
22
22
21
22
39 62
41 61
41 61
40 61
63
40 61.5
47 72
47 72
47 71
47 71
72
47 71.5
0-Chloropropiona te 37 71 111
37 74 108
39 73 107
73 108
110
Average 38 73 109