Determination of the histamine metabolite tele-methylimidazoleacetic acid and of creatinine in urine by the same HPLC system

Abstract.

Objective and Design: To develop an HPLC method with UV detection for determination of tele-methylimidazoleacetic acid (t-MeImAA) in urine of man or animals, which is reliable, simple and less expensive than existing GC/MS techniques.¶Method: The elaborated procedure enables separation of t-MeImAA from its pros-isomer (p-MeImAA) as well as from imidazoleacetic acid. As an internal standard tele-ethylimidazoleacetic acid (t-EtImAA) is used. The acids, after being converted to their stable isopropylesters, are extracted at pH 6.0–6.5. The further separation prior to HPLC utilises a small cellulose phosphate column. The HPLC system is isocratic with a C18 column and mobile phase consisting of an aqueous solution of SDS at pH 3.5 mixed with acetonitrile (65:35). An advantage of this system is that it can be used to determine the urine creatinine concentration to express excreted t-MeImAA in mmol/mol creatinine.¶Results and Conclusions: The method applicability is demonstrated in repeated studies in mastocytosis patients. The broad range of excretion values, from normal up to a high level (0.9 to 30 mmol/mol creatinine), indicates that it can be satisfactorily used for evaluation of histamine turnover under various clinical conditions. The method appears to be a good alternative to GC/MS based ones.