Breakthrough volume, solute being passed

Breakthrough volume can be measured by monitoring the ultraviolet (UV) signal of a water sample spiked with traces of a solute, 5, which has an initial absorbance, Aq. The spiked sample is passed through an SPE column. If the compound is retained by the sorbent, the effluent will have an absorbance of zero. A frontal or breakthrough curve is recorded (Fig. 4.9) beginning at a volume, V/, usually defined as 1 % of Aq, up to a volume of V, defined as 99% of Aq, where the effluent has the same composition as the spiked water sample (Hennion and Pichon, 1994). 

The separation of retained and nonretained solutes is not sharp, and a certain amount of solute with kf < fc cutoff will be concentrated along with the solute of interest. When twice the breakthrough volume for a particular solute, 2VE, has passed through the column (Figure 1), the concentration of solute in the effluent is equal to the concentration of solute in the influent, Cc, and the solute is completely broken through. At this point, one half of the total amount of solute applied to the resin has been retained (hatched area of Figure 1). This value is the maximum... 

A typical representation of column performance plots removal of the species from solution against the volume of effluent passed through the column. When measurable quantities of the cation to be removed exceed a predetermined level in the solution exiting the column, breakthrough is said to have occurred. 

Solutions (a) The breakthrough volume V of the solution to be passed through the column for the feed concentration to break through in equilibrium nondispersive operation is given by relation (7.1.16d) ... 

The physical extraction process, which takes place between the liquid phase (the liquid sample containing the dissolved analytes) and the solid phase (the adsorption material) is common to all SPEs. The analytes are usually extracted successfully because the interactions between them and the solid phase are stronger than those with the solvent or the matrix components. After the sample solution has been applied to the solid phase bed, the analytes become emiched on the surface of the SPE material. All other sample components pass unhindered through the bed and can be washed out. The maximum sample volume that can be applied is limited by the breakthrough volume (BTV) of the analyte. Elution is achieved by changing the solvent. For this, there must be a stronger interaction between the elution solvent and the analyte than between the latter and the solid phase. The elution volume should be as small as possible to prevent subsequent solvent evaporation. 

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