Microwave-induced plasma optical emission spectrometry (MIP-OES) has been attracting growing interest since the introduction of a commercial instrument based on a Hammer cavity and resonant iris system (4100 MP-AES, Agilent...
Liquid−liquid equilibrium data were obtained for aqueous two-phase system (ATPS) composed of [poly(ethylene oxide) (PEO1500), poly(propylene oxide) (PPO425), poly(ethylene oxide) 11 −poly(propylene oxide) 17 −poly(ethylene oxide) 11 (L35), or poly(propylene oxide) 8 −poly(ethylene oxide) 22 −poly(propylene oxide) 8 (10R5)] + ammonium thiosulfate + water, at 283.2, 298.2, and 313.2 K. The consistencies of the all tie-line experimental compositions were improved by applying the Othmer− Tobias and Bancroft equations, resulting in linear correlation coefficients (R 2 ) ≥ 0.95. For all the ATPS, an increase in the temperature resulted in increases in the biphasic region and the tie-line slope, indicating that the phase separation process was entropically driven. Among the macromolecules studied, PPO425 produced the largest biphasic region, due to its greater hydrophobicity, followed by L35 ≈ 10R5 > PEO1500.
In
extraction procedures, the more commonly used aqueous two-phase
systems (ATPS) comprise mainly water, salt, and macromolecule, particularly
the macromolecule poly(ethylene oxide) (PEO). However, one limitation
of such ATPS is their capacity to separate compounds that are more
hydrophobic. One possible solution to overcome this restriction is
the use of ATPS formed with triblock copolymers, which are more hydrophobic
and therefore enable the extraction of hydrophobic solutes. In addition,
the range of applications of ATPS formed with thiocyanate salts can
be broader, mainly to extract metal ions. In view of this, equilibrium
data were acquired in this work by constructing phase diagrams for
ATPS comprising macromolecules [poly(ethylene oxide), PEO, or (poly(ethylene
oxide))-(poly(propylene oxide))-(poly(ethylene oxide)) triblock copolymers,
F68 or L64] + thiocyanate salts (ammonium, sodium, or potassium) +
water at 25.0 °C. The influence of the nature of the cation on
the formation of the ATPS was investigated and followed the order
K+ > Na+ > NH4
+.
The capacity
of different macromolecules to enable ATPS formation was also examined
and followed the order L64 > F68 > PEO1500. Phase inversion
occurred
with the (L64 or F68) + NH4SCN + water ATPS, in that the
top phase is rich in salt and the bottom phase is rich in macromolecule.
This aspect is different in most ATPS that are typically described
in the literature.
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