Frans_M_Everaerts_Isotachophoresis_378342.pdf

THERMOMETRIC MEASUREMENTS
TABLE 10.2
CALIBRATION CONSTANTS, Kcal, AND ZONE LENGTHS WITH IMIDAZOLE/IMIDAZOLE
HYDROCHLORIDE AS THE LEADING ELECTROLYTE
The experimental values were measured with a thermometric detector.
lonic species Concen- Concen- lnjected Detected Calibra- Deviation from
tration tration volume zone tion average Kca,
in the
sample
in the
zone
(bl) length
(set)
constant
w~~,. to4) A K ~ 106 ~ ~ % -
(mole/l) (mole/l)
Ace tic acid
Adipic acid
Formic acid
Hydrofluoric acid
Iodic acid
Lac tic acid
Maleic acid
Tartaric acid
Acetic acid
Formic acid
Maleic acid
Acetic acid
Formic acid
0.05
0.025
0.05
0.05
0.05
0.0343
0.05
0.025
0.05
0.05
0.05
0.05
0.05
0.0075
0.0042
0.0087
0.0087
0.0074
0.0069
0.0046
0.0042
0.0075
0.0087
0.0046
0.0075
0.0087
1
1
467
407
398
409
465
340
735
416
308
255
491
154
129
0.4283
0.4388
0.4327
0.4215
0.4364
0.4386
0.4437
0.4290
0.4329
0.4508
0.4428
0.4329
0.4455
-0.82
0.23
-0.38
-1.50
-0.01
0.21
0.72
-0.75
-0.36
1.43
0.63
-0.36
0.90
277
-1.9
0.5
-0.8
-3.4
0.0
0.5
1.6
-1.7
-0.8
3.3
1.4
Average 0.4365 0.64 1.5
metric detector'. This value can vary, depending on the heat production in the adjacent
zones, the electric current, the type of solvent used and the cross-section of the narrowbore
tube. The concentration of an anionic species in the narrow-bore tube is about
0.01 g-equiv./l under the conditions used and the cross-section of the narrow-bore tube
is about 1.6 - 1 0-3 cmz . This means the minimum amount of an ionic species that can be
detected is about 8 *
g-equiv. If the volume of the sample injected is 3 pl, the
minimum concentration in the sample that can be detected is about 2.7 * g-equiv./l.
In order to illustrate this, the separation of a mixture of 0.005Noxalate, 0.01 N
formate, 0.01 N acetate and 0.01 5NP-chloropropionate in the system described above
at pH 6.02 was carried out. The results are shown in Fig.lO.1. Traces (a), (b) and (c)
correspond to injected volumes of 1,2 and 31.11, respectively. The amounts detected were
5 * and 1.5 - lo-' g-equiv., respectively, for the different anions, when
1 1.11 was injected. It can be stated that a complete separation of the mixture is obtained,
both qualitatively and quantitatively, in traces (b) and (c). All quantitative information
can be deduced from trace (a), for it should be remembered that for quantitative analyses
the transition of zone boundaries is required, once the sequence is known. Trace (a) shows
-0.8
2.1
*This means that a difference of about 100 sec is needed between two successive peaks, the differential
trace of the linear temperature response.