the invention relates to a method for the detection of incorrect deposition on a maldi sample support with several separate sample sites , where after the preparation on the sample support , an area located between two sample sites is sampled with a desorption laser , and a signal of an ion detector in a mass spectrometer is acquired in temporal relation to the sampling . the signal is examined for the presence of a signal which indicates incorrect deposition . an advantage of the method is particularly that it can be carried out using a maldi ion source and a connected mass analyzer , and that it requires little procedural effort .