This poster presents a novel combined method that allows quantification of formaldehyde (FA) in aqueous solution, and an efficient separation and identification of monosaccharides from formose reaction. Formose reaction (FR) is the base catalyzed oligomerization of formaldehyde, that produces more than 30 different compounds among linear and branched chain monosaccharides, sugar degradation products and organic acids. Separation and identification of all products is hardly possible, and a major effort has been put in developing efficient anal. methods. In this work, samples containing a mixture of monosaccharides and FA, as well as real samples from FR were analyzed. To achieve an efficient quantification, FA is derivatized with 2,4-dinitrophenylhydrazine (DNPH) and analyzed with a HPLC. Formose products are derivatized with O-ethylhydroxylamine hydrochloride (EtOx) and N,O-bis(trimethylsilyl)trifluoroacetamide (BTSFA) and analyzed using a gas chromatograph equipped with a mass detector. FR was carried out in a three necked round bottom flask, using Ca(OH)2 and glycolaldehyde as catalyst and initiator, resp. Two aliquots of 100μL were taken simultaneously from the reaction mixture, at different reaction times, and each sample was analyzed according to the method for FA quantification or for products identification. Samples for FA quantification were immediately derivatized and analyzed with HPLC. Samples for formose products identification were immediately frozen in liquid nitrogen to stop the reaction; water was removed by lyophilization, and the residue was dissolved in pyridine and derivatized according to the method. With this combined method, problems with the volatility of FA were overcome, and FA can be quantified at different reaction times. At the same time, reaction mixture can be analyzed, allowing us to follow the formation of different products in relation to FA conversion.