Enthalpies
of solution and densities of glycylglycine in aqueous
solutions of NaNO3, NaClO4, and Na2SO4 were measured at 298.15 K. Standard transfer enthalpies
(Δtr
H
0), standard transfer
partial molar volume (Δtr
V
ϕ
0), and hydration
numbers (N
h) have been determined for
glycylglycine. All of the Δtr
H
0 values are negative in the three salt solutions. The relative
order of Δtr
H
0 in the
same concentration of 1–1 type salts is NaNO3 >
NaClO4. The Δtr
H
0 in low concentration of Na2SO4 solutions
is between the corresponding values in NaNO3 and NaClO4 solutions. With increasing Na2SO4 concentration,
the Δtr
H
0 values exceed
that in NaNO3 solutions. The Δtr
V
ϕ
0 values are positive and vary in the sequence Na2SO4 > NaNO3 > NaClO4. The
results
were discussed in terms of various interactions.
Butyl-methacrylate-based porous monoliths were rapidly prepared in the fused-silica capillary with a 10-cm stripe of polyimide removed from its exterior. The photopolymerization could be carried out in 150 s using ethylene glycol dimethacrylate as a cross-linking agent; 1-propanol, 1,4-butanediol, and water as tri-porogenic solvents; and Irgacure 1800 as a photo-initiator. The effect of different morphologies on the efficiency and retention properties was investigated using pressure-assisted CEC (p-CEC), CEC, and low pressure-assisted liquid chromatography modes (LPLC). Baseline separation of the model analytes was respectively achieved including thiourea, toluene, naphthalene, and biphenyl with the lowest theoretical height up to 8.0 microm for thiourea in the mode of p-CEC. Furthermore, the influence of the tri-porogenic solvents on the morphology of methacrylate-based monoliths was systematically studied with mercury intrusion porosimetry and scanning electron microscopy.
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