Preconcentration Zone

Figure 5 Progressive separation on a preconcentration zone plate.

One of the most useful tools designed into a thin layer plate is the preconcentration or pre-spotting zone (Figure 5). This is a 2.5-4 cm area at the bottom of a plate, composed of diatomaceous earth or wide-pore silica gel, to allow heavy loading or vertical (horizonal if doing preparative work) streaking of the sample. As the mobile phase passes though this special material, the sample does two things. If a circular spot, it changes to a band (an oblong circle). If a dilute sample, it also concentrates itself in this band. In this portion of the plate, no separation occurs. The separation begins only after the band transfers from the preconcentration zone into the silica (or, in some cases, the RP18 or other bonded-phase) layer. This

Figure 5 Progressive separation on a preconcentration zone plate.

reforming of the sample (from a spot to a band) gives a more efficient separation, since the band is narrower along the direction of development.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment