High-performance liquid chromatographic determination of urinary 2,5-hexanedione as mono-2,4-dinitrophenylhydrazone using ultraviolet detection

Free and total 2,5-hexanedione in biological monitoring of workers exposed to n-hexane in the shoe industry

OBJECTIVES

To analyse the role of total 2,5-hexanedione (2,5-HD) compared with free 2,5-HD as a biological indicator of exposure to n-hexane at work.

METHODS

One-hundred and thirty two workers in contact with this solvent during their occupation in the shoe industry in the province of Alicante (Spain) were studied. Environmental and biological tests were carried out analysing variations of the concentration of the metabolite in urine corresponding to different working conditions. Environmental exposure was evaluated in each work place using active personal monitors and measured by gas chromatography (GC). Dichloromethane extracts of the urine samples collected at the end of the working shifts were analysed, before (determining free 2,5-HD, the toxic metabolite) and after acid hydrolysis (pH 0.1) (yielding the total 2,5-HD) and also by GC. The concentration of conjugated metabolite 4,5-dihydroxy-2-hexanone was calculated from the difference between total and free 2,5-HD.

RESULTS

Free 2,5-HD represented an average of 14.2% of the total 2,5-HD determined in urine, and this percentage increased significantly (P<0.01) with higher environmental levels of acetone. Other factors, such as absorption through the skin (depending on the use of gloves) and the day on which samples were taken also significantly affected the relation between the two indicators and their respective relationships with environmental concentrations of n-hexane.

CONCLUSION

Although analyses of the relationship between the levels of atmospheric n-hexane and those of metabolites in urine show a greater correlation for total 2,5-HD than for free 2,5-HD, our results suggest that free 2,5-HD could be a better indicator in evaluating risk of exposure to n-hexane, since the concentration is directly related to the neurotoxic effect.

Analytical derivatizations of volatile and hydrophilic carbonyls from aqueous matrix onto a solid phase of a polystyrene-divinylbenzene macroreticular resin

Extraction and derivatization of carbonyls to benzyloximes, pentafluorobenzyloximes or 2,4-dinitrophenylhydrazones is simplified and reaction times are substantially reduced by simultaneous sorption and derivatization from aqueous solution onto a solid phase. In this reaction a macroreticular polystyrene-divinylbenzene resin acts as a sorbent and catalyst to allow simultaneous extraction and derivatization of hydrophilic and lipophilic aldehydes and ketones from simple as well as complex matrices including plasma. Conversion to the 2,4-dinitrophenylhydrazones or pentafluorobenzyloximation at ambient temperature requires 10 and 20 min, respectively. These reaction conditions correspond to at least a 6-fold reduction in reaction times for derivatization of the reactive aldelhydes and a 36-72-fold reduction for preparation of derivatives for the slower reacting ketones.