Determination of hydroxypropylhistidine in haemoglobin as a measure of exposure to propylene oxide using high resolution gas chromatography mass spectrometry.

The alkylating agent propylene oxide is a potential carcinogen. Exposure to this compound leads to the formation of N-3'-(2-hydroxypropyl)histidine in protein. A sensitive and specific method has been developed for the determination of this alkylated amino acid in rat and human haemoglobin using high resolution gas chromatography with selected ion monitoring. Globin isolated from blood was hydrolysed with 6 M HCl and the protein hydrolysate chromatographed on a Dowex 50W H+ column. The amino acids in the partially purified extract were analysed as N-heptafluorobutyryl methyl esters using an SE-52 fused silica capillary column. Quantification was made by monitoring the ion m/z 560 [M-COOCH3)+ derived from the derivatized hydroxypropylhistidine in the sample and the corresponding ion at m/z 565 from the pentadeutero analogue of the alkylated amino acid added initially to the globin as an internal standard. The method has been used to quantify hydroxypropylhistidine down to levels of 2 microgram gm-1 haemoglobin and has been applied to studies in rats exposed to propylene oxide.