Analysis of hexoses by dried droplet approach 1mg/ml of glucose, galactose, mannose, fructose and D-glucose 13 C6 isotope in water were prepared. Sugars soluWons were measured with dried droplet approach in two ways. First way: sugars soluWons were mixed with betaine aldehyde soluWon (1 mg/ml ACN:H2O, 2:1 v/v), 1:1 and analysed by dried droplet approach with CHCA matrix (5mg/ml ACN:H2O, 2:1; 0,2% TFA) in the posiWve ionisaWon mode. Second way: sugars soluWons were mixed with water (1:1) -to obtain the same concentraWon and analysed by dried droplet approach with NEDC matrix (7mg/ml, 70% MeOH) in the negaWve ionisaWon mode. MS/MS analysis of all hexoses was performed by LIFT approach in both cases. D-glucose 13 C6 isotope analysis in the Wssue homogenate The brain Wssue was iniWally cut with the scalpel and then homogenized in the glass homogenizer (Wheaton, Bionovo). Then, 5 µl of D-glucose 13 C6 in water (20 mg/ml) was added to the Wssue. To obtain perfectly homogenous mixture, Wssue homogenate was mixed with glucose soluWon with the aid of PTFE pestle. The final concentraWon of D-glucose 13 C6 in homogenate was: 1,91 µg/mg of Wssue. Such prepared material was introduced into the inert material, placed in the cryotome chamber, frozen, cut into 12 μm slices and placed on the ITO glasses together with the slices of measured Wssue.