1) The mixture of extracting and dispersing solvents is rapidly injected to a water sample. A dispersion is formed and facilitates fast extraction of analytes from the water sample.
(2) The dispersion is removed by centrifugation and the extracting solvent containing analytes is taken for analysis with a microsyringe.
In the first example, carbon tetrachloride was used as the extracting solvent and it was collected from the bottom of a centrifuge tube for injection into the GC instrument [5] (see Fig. 1).
In general, several requirements have to be met to perform sample isolation using DLLME. The dispersing solvent has to be fully soluble with the water phase. Usually acetone, acetonitrile and methanol are used for this purpose. The extracting solvent has to fulfill several requirements. It has to have potential for extracting analytes. Also, it has to be soluble in the dispersing solvent while its solubility in water has to be very low. Finally, the density of the extracting solvent has to differ greatly from the density of water to enable phase sepa- ration.
Selection of both extracting and dispersing solvents is important to obtain a high enrichment factor (EF), defined as the ratio of the concentration of analyte in the sedimented phase to the initial concentration of analyte in the sample. Moreover, the volumes of these solvents have to be optimized, and that is usually performed in step-by-step approach although a central composite design is also used for this purpose.
1) The mixture of extracting and dispersing solvents is rapidly injected to a water sample. A dispersion is formed and facilitates fast extraction of analytes from the water sample.(2) The dispersion is removed by centrifugation and the extracting solvent containing analytes is taken for analysis with a microsyringe.In the first example, carbon tetrachloride was used as the extracting solvent and it was collected from the bottom of a centrifuge tube for injection into the GC instrument [5] (see Fig. 1).In general, several requirements have to be met to perform sample isolation using DLLME. The dispersing solvent has to be fully soluble with the water phase. Usually acetone, acetonitrile and methanol are used for this purpose. The extracting solvent has to fulfill several requirements. It has to have potential for extracting analytes. Also, it has to be soluble in the dispersing solvent while its solubility in water has to be very low. Finally, the density of the extracting solvent has to differ greatly from the density of water to enable phase sepa- ration.Selection of both extracting and dispersing solvents is important to obtain a high enrichment factor (EF), defined as the ratio of the concentration of analyte in the sedimented phase to the initial concentration of analyte in the sample. Moreover, the volumes of these solvents have to be optimized, and that is usually performed in step-by-step approach although a central composite design is also used for this purpose.
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