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through the solute to the optical unit. In this way, the path length of the light through the sample is
effectively doubled. The disk is easily cleaned and is completely reusable. It is also easy to remove the
disk from one unit and insert it into the other. The interface consists of two modules, the coating
module and the optical module. Diagrams of the two modules are shown in Figure 8.15.
The LC column is connected to the chromatography module and eluent from the column passes into an
ultrasonic nebulizer. The nebulizer sprays the solvent in a tightly focused jet onto the surface of the
sample-collection disk. The temperatures of both the ultrasonic nebulizer and the collection disk are
carefully controlled.
Figure 8.15
The Coating and Optical Modules of the Interface
Courtesy of Lab Connections Inc.
The disk rests on a heated stage in an evacuated compartment that rotates slowly during the elution of
the sample. All the solvents evaporate leaving a deposit of solvent-free solutes on the disk surface. As a
consequence,
