To confirm that we measure glucose form the Wssue we have decided to perform MS/MS analysis. We have prepared the samples of glucose (0,5 mg/ml), and glucose derivaWzed with betaine aldehyde in the soluWon (0,5 mg/ml) and performed dried droplet analysis with CHCA (5mg/ml ACN:H2O, 2:1; 0,2% TFA) and NEDC matrix (7mg/ml, 70% MeOH) respecWvely. Obtained MS/MS spectra were compared to respecWve MS/MS spectra from the Wssue (see: figure ). In both cases it is possible to detect characterisWc m/z values, but some addiWonal peaks are also present, especially in the case of NEDC matrix, as there was some addiWonal substance that ionize from the Wssue in this extracWon window that cannot be resolved from the glucose ion (see: figure ).