Another idea was that the characterisWc pa]ern obtained for NEDC analysis is connected with the matrix characterisWcs that overlap the glucose ion map. Similar case is presented in figure . Here, an analysis for glucose (A, C) and glucose isotope 221 (B, D) is presented. The round area of measurements on the lew side of each brain Wssue slice represents the slices of Wssue homogenate: upper -where homogenate was mixed with a glucose isotope 221, and lower -plain homogenate, containing naWve glucose from the Wssue. We should see naWve glucose in the A, and C part of the picture. In the B (betaine aldehyde derivaWzaWon), we see a glucose isotope only in the upper "homogenate" region of interest. Control and Wssue slices are black. In the D part (NEDC matrix), the upper, "homogenate" region of interest has high intensity, but we see the signal on the control spot and on the Wssue as well. Moreover, we see characterisWc pa]erns on the Wssue, while it should not be there -the picture should be black as in the case of betaine aldehyde derivaWzaWon. Such evidence leads to the conclusion that there must be an addiWonal substance or and addiWonal effect that produce overlapping ion map and interfere with glucose isotope analysis. The similar situaWon probably occurs for naWve glucose analysis. It is possible that the matrix may generate isobaric ions with chlorinated naWve glucose species, which seems to be inseparable since the experiments menWoned in the literature review were done with a high-resoluWon system: Bruker SolariX FT-ICR mass spectrometer . Another idea is that we could observe different pa]ern of crystallizaWon, depending on the area of the Wssue. In such a case the distribution of the certain solutions could follow specific patterns, and do not cover the surface uniformly. Maybe one of the matrices crystallizes better where there is less glucose or where there is less of another substance correlated to the real glucose distribution?