Agilent InfinityLab ELSD User Manual
57
4
Using the Module
General Considerations
Table 10
Volatile mobile additives compatible with ELS detection
Mobile Phase Additive
pKa
pKb
pH Range
Bp (°C)
Mp (°C)
Acids
Trifluoroacetic Acid (TFA)
0.3
13.70
72.4
-15.4
Formic Acid
3.75
10.25
100.7
8.3
Acetic Acid
4.75
9.25
116.0
16.6
Bases
Ammonia
9.25
4.75
-33.4
-77.7
Methylamine
10.66
3.34
-6.6
-94.0
Ethylamine
10.81
3.19
16.6
-81.0
Triethylamine
11.01
2.99
89.3
-114.7
Buffers
Ammonium Formate
3.8
9.2
3.0 – 5.0
8.2 – 10.2
120
Ammonium Acetate
4.8
9.2
3.8 – 5.8
8.2 – 10.2
111
Ammonium Bicarbonate
6.3
9.2
10.3
6.8 – 11.3
106
Ion-Pair Reagent
Pentafluoropropionic acid (PFPA)
~0.6
97
Heptafluorobutyric acid (HFBA)
~0.6
120
Nonafluoropropionic acid (NFPA)
~0.6
140
Tridecafluoroheptanoic acid
~0.6
175
