Introduction Furfural is an organic compound derived from a variety of agricultural products, and it is mainly used as petrochemical solvent and in rubber industries. In a wide range of food heating processes furfural may rise from 5-hydroxymethylfurfural (5-HMF), a product of dehydration of sugars and Maillard reactions. Our aim is the development of analytical approach to determine the common urinary metabolism of furfural and 5-HMF, by quantification of 2- and 3- furoic acids (FA), 5-HMF itself and its specific metabolite, 5-hydroxymethyl-2-furoic acid (HMFA).

Methods A group of healthy control subjects received an oral dose of 5-HMF in plum juice (780 mg) and its relative metabolites the investigated in urine within 24 hours. Analysis were carried out by solid-phase microextraction and gas chromatography/mass spectrometry. FAs were determined in head space after the conversion into their methyl esters derivatives by a reaction with trimethyloxonium tetrafluoroborate. HMFA tert-butyldimethylsilyl derivative was detected by direct immersion using N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide while 5-HMF quantification was perfomed by on sample derivatization with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine.

Results Data from 22 subjects were analysed. Mean daily concentrations of 2-FA, 5-HMF were quantified 46.1±15.1 mg/24 hour, 7.53±2.11 mg/24 hour. HMFA and 3-FA were not detected in all urine samples. 2-FA and 5-HMF concentration resulted particularly higher within 6 hours after the plum juice administration (mean of 37.1 mg/L and 5.3 mg/L respectively).

Conclusion Total urinary FAs may not discriminate a food intake or environmental exposures. Significant increases of 2- and 3-FA concentrations from professional exposure are identified, while high values of 2-FA alone are found after the intake of food with elevated quantity of HMF. Therefore total FA as Biological Exposure Index by the American Conference of Governmental Industrial Hygienists, could lead to unsuitable assessment of the level of furfural in the workplace.