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There is a significant difference in the separation of the peaks in the electrochemical detection of catecholamines depending on the elution method from the urine. We have found that eluting the CATS from urine on Amberlite, followed by their elution from the column with boric acid, results in a superior HPLC separation with little or no interferences. The elution with alumina does not result in the same "clean" peaks and we were confronted with frequent interferences before we moved to Amberlite. In the Amberlite method, the metanephrines are generally not eluted from the column with boric acid, although sometimes a small amount is released (in fact, if eluted the normetanephrine peak is seen just after the DHBA internal standard peak). In order to release the metanephrines the column is subsequently washed (after the boric acid wash for elution of the catecholamines) with an ammonia solution. The eluted metanephrines are conjugated and have to be deconjugated prior to running them on the HPLC. Since moving to the Amberlite elution method, we have never had interference problems with our DHBA internal standard peak. The determination of the metanephrines, rather than catecholamines, however, is seen by many as the most sensitive and specific test for the diagnosis of pheochromocytoma. Oren Zinder Department of Clinical Biochemistry Rambam Medical Center Haifa, Israel 31096 Prof. Oren Zinder Department of Clinical Biochemistry Rambam Medical Center Haifa, ISRAEL 31096 Tel: +972-4-854-3767 Fax: +972-4-854-2409 email: [log in to unmask] ##################################################################################### This e-mail message has been scanned for Viruses and Content and cleared by MailMarshal ##################################################################################### ------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/