The rate of sample depositionis also adjustable to accommodate sample solutions of differentvolatility or viscosity. The advantages of band application for scan-ning densitometry are that the sample band can be made longerthan the slit length of the light source, which minimizes quantifi-cation errors due to positioning of the sample within the light beam,and different volumes of a single standard solution can be appliedfor calibration. In addition, the standard addition method for quan-tification is facilitated by overspraying the sample already appliedto the layer with a solution of the standard. Reactive reagents canbe applied in the same way for prechromatographic derivatiza-tion. 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,