Spray-on devices employ a motor dri

Spray-on devices employ a motor driven syringe as the samplereservoir and a nitrogen (or compressed air) atomizer to spray thesample onto the layer in the form of spots, bands or rectangles.The position of the atomizer is fixed and the plate is moved on amotorized stage beneath it to apply bands of any length between 0(spots) and the maximum transit length of the atomizer (190 mm).Recommended default values for analytical separations are 8 mmfor complex samples and those dissolved in aqueous solution and6 mm for relatively simple mixtures in volatile organic solventsWith a zigzag motion of the layer, samples can be applied over a rectangular area, useful for preparative applications and for sam-ples dissolved in solvents of low volatility. The rectangular samplezones are dried and focused into narrow bands by one or more shortdevelopments with a strong solvent prior to their separation. Thisprocess is automated if automated multiple development is usedfor the separation (Section 3.1.3).