Monitoring of environmental cancer initiators through hemoglobin adducts by a modified Edman degradation method.

Tissue doses of cancer initiators/mutagens are suitably monitored through hemoglobin adducts formed in vivo, but the use of this method has been hampered by a lack of sufficiently simple and fast procedures. It was previously observed that when the N-terminal amino acid in hemoglobin, valine, is alkylated it is cleaved off by the Edman sequencing reagent, phenyl isothiocyanate, in the neutral-alkaline coupling medium, as opposed to the acidic medium required by normal amino acids. Based on this principle, conditions for a functioning procedure for gas chromatography/mass spectrometry (GC/MS) determination of N-terminal alkylvalines in hemoglobin were worked out. Derivatizing the protein in formamide solution with pentafluorophenyl isothiocyanate, using a 2H-alkylated protein as internal standard, and applying on-column injection during analysis, permit reproducible determination of hydroxyethylvaline and other adducts down into the dose range where cancer risks may be considered acceptably low.