Fig. 10 The relationship between the chosen peaks’ intensities
and signal-to-noise ratio (s/n) in terms of the number of matrix layers
(A) and the spraying nozzle height (B) for the negative ionization mode
rat spinal cord tissue slices (matrix: 9AA 7 mg/ml 70% EtOH)
Nozzle height does not significantly affect the quality of the analysis,
but the peaks on the spectra are more intensive with the higher position
of the nozzle. S/n ratio is definitely higher for a higher nozzle
position. Thus z=5 was chosen as the best one. In the case of matrix
layers, we observe the increase in the peak’s intensity with increasing
number of layers (see: Fig. 10). Nevertheless, assessing the quality of
the picture, 14 layers seems to be a good choice. With the 16 layers,
the picture becomes a little bit blurred (see: Fig. 9). Thus, it is not
recommended when we are interested in looking for different brain
structures. Additionally, in the case of 14 layers, stable
picture is obtained with different normalization methods, which proves
the good quality of the measurement (see: Fig. 11).