Liquid without phase separation

Integrating liquid-liquid extraction and detection is far from easy, as reflected in the few attempts made so far. Many of the devices developed for this purpose fail to comply with the definition of sensor. Such is the case with continuous liquid-liquid extraction systems without phase separation, where programmed switching of the propulsion system (a peristaltic pump) allows the extracting phase to be passed iteratively by the detection point in a back-and-forth motion that enriches it gradually with the extracted species [9-11]. This type of system is much too Complex to be considered a sensor, though in addition, the extraction process is not completely simultaneous with detection. 

Heterogeneous liquid-liquid systems are quite common place in analytical chemistry, which uses them for a variety of purposes, including the following in relation to sample preparation (1) analyte transfer from one phase to another, followed by (a) phase separation in order to feed only the phase enriched with the analyte to the detector or subject it to some other operational step prior to detection, or (b) continuous monitoring of the enriched phase without phase separation (2) the formation of a heterogeneous medium, — small droplets of one phase in another — which is the usual purpose of homogenization and emulsification. Ultrasound (US) has been used to improve the outcome of (1) and (2), albeit with rather disparate results and frequency. 

Liquid—liquid extraction, as exemplified by the spectrophotometric determination of paracetamol in suppositories [149] without phase separation (8.5.1.3). A pronounced speeding up of analyte extraction and hydrolysis was attained with several iterative flow reversals. 

F. Priego-Capote, M.D. Luque de Castro, Ultrasound-assisted continuous liquid—liquid extraction without phase separation and hydrolysis of paracetamol in suppositories, Anal. Chim. Acta 489 (2003) 223. 

F. Canete, A. Rios, M.D. Luque de Castro, M. Valcarcel, Liquid-liquid extraction in continuous flow systems without phase separation, Anal. Chem. 60 (1988) 2354. 

In the cases of the hydrogen-bonded materials described in the previous sections, single homogeneous liquid-crystalline phases without phase separation are displayed by the formation of intermolecular hydrogen bonds. Here, liquid-crystalline physical gels, anisotropic functional materials with heterogeneous self-organized structures (Type B in Fig. 2), are discussed. 

Although most FI determinations involving liquid-liquid extractions are made after separation of the two phases, in some of the more recent contributions, determinations are also made without phase separation, therefore excluding phase separators from the system. 

FI Iterative Flow Reversal Liquid-liquid Extraction System without Phase Separation... 

We have developed a fluorous super-Bronsted acid catalyst, 4-(lH,lH-perfluoro-tetradecanoxy)-2,3,5,6-tetra Luorophenylbis(trifluoromethanesulfonyl)methane (8), which can be recycled by applying liquid/solid phase separation without fluorous solvents [8] and an organic-solvent-swellable resin-bound super-Br0nsted acid, polystyrene-bound tetrafluorophenylbis(trifluoromethanesulfonyl)methane (9) [9]. 

Some atypical FI liquid-liquid extraction systems do not use any proper separation unit, but an emulsion, an organized medium, a minicolumn capable of retaining one of the phases involved in the extraction process, or a reversed-flow system. A number of ingenious approaches for FI liquid-liquid extraction without phase separation have been designed. 

Ruiz-Jimenez J, Luque de Castro MD (2003) Flow injectimi manifolds fin liquid—hquid extraction without phase separation assisted by ultrasound. Anal Chim Acta 489 1—11... 

We can define the solubility of B in A as the maximum amount of B that can dissolve without phase separation in a given amount of A at the given temperature and pressure. Treating B as a solute, we can express its solubility as the mole fraction of B in the phase at the point of phase separation. The addition of any more B to the system will result in two coexisting liquid phases of fixed composition, one of which will have mole fraction xb equal to its solubility. 

The oppositely charged polymers and surfactants may form a single phase without complex formation, or may form a soluble surfactant-polymer complex, or may result in phase separation (Piculell and Lindman 1992 Wang et al. 1999,2000). If the interaction leads to liquid-liquid phase separation, the process is called coacervation. If the interaction leads to a liquid-solid phase separation, then the process is named precipitation. Many factors affect the interaction of oppositely charged surfactants and polymers that consequently have an effect on the possible phase separation phenomena. Extensive studies have been done on both theoretical and practical aspects of phase separation. It is important to know the conditions under which coacervation occurs in applications dealing with the formulation of cosmetics and pharmaceuticals. 

In comparison with catalytic reactions in compressed CO2 alone, many transition metal complexes are much more soluble in ionic liquids without the need for special ligands. Moreover, the ionic liquid catalyst phase provides the potential to activate and tune the organometallic catalyst. Furthermore, product separation from the catalyst is now possible without exposure of the catalyst to changes of temperature, pressure, or substrate concentration. 

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