The rate of sample deposition is also adjustable to accommodate sample solutions of different volatility or viscosity. The advantages of band application for scanning densitometry are that the sample band can be made longer than the slit length of the light source, which minimizes quantification errors due to positioning of the sample within the light beam,and different volumes of a single standard solution can be applied for calibration. In addition, the standard addition method for quantification is facilitated by overspraying the sample already appliedto the layer with a solution of the standard. Reactive reagents can be applied in the same way for prechromatographic derivatization. Similarly, matrix solutions to prepare layers for evaluationby MALDI mass spectrometry can be applied in this way. Spray-on sample applicators such as the Linomat 5 (Camag, Muttenz,Switzerland), Fig. 3,