Page 198 - Illustrated Pocket Dictionary of Chromatography

TRIFLUOROACETIC ACID (TFA) 201

1,2,4-Trichlorobenzene Molecular weight: 181.5; boiling point:
213.5°C; refractive index (20°C): 1.5717; Density (20°C): 1.46g/mL; UV
cutoff: 308nm; solubility in water (20°C): 0.0025%; water solubility in
1,2,4-trichlorobenzene (20°C): 0.02%. 1,2,4-Trichlorobenzene is almost
exclusively used for high-temperature GPC work. It is nonreactive and
stable. The high cutoff precludes the use of 1,2,4-trichlorobenzene in
many HPLC UV methods.

Cl
Cl

Cl
1,2,4-Trichlorobenzene

triethylamine (TEA) Molecular weight: 101.2; boiling point:
89.5°C; refractive index (20°C): 1.4010; density (20°C): 0.73g/mL;
viscosity (25°C): 0.36cP; polarity index (P¢): 1.8; solubility in water
(20°C): 5.5%; water solubility in triethylamine (20°C): 4.6%. Triethy-
lamine is commonly used in reversed-phase HPLC as a basic mobile
phase modifier. TEA interacts with residual silanol groups on the
support surface and limits the interaction of a basic analyte with these
sites thereby decreasing peak tailing.

CH 2 CH 3

H 3 CH 2 C N

CH 2 CH 3
Triethylamine

trifluoroacetic acid (TFA) Molecular weight: 114.0; boiling
point: 71.8°C; refractive index (20°C): 1.2850; density (20°C): 1.53
g/mL; viscosity (20°C): 0.93cP; UV cutoff (0.1% solution in water): 210
nm. pK a : 0.3. Miscible with water. Very volatile with a strong pungent
smell. Avoid contact with skin and eyes. Trifluoroacetic acid is a
commonly used acidic mobile phase modifier in reversed-phase
HPLC. Because it is a very strong acid it is useful for protonating those