Quality control of histamine and methacholine in diagnostic solutions with capillary electrophoresis

Solutions of histamine and methacholine bromide in different matrices for diagnostic purposes were analyzed for stability and quality control using capillary electrophoresis. Histamine (2-[4-imidazolyl]ethylamine) [CAS No. 51-45-6] was determined using a 0.1 M Tris-borate buffer of pH 8.3 with 5·10-5 M cetyltrimethylammonium bromide (CTAB) and 0.005% poly(vinyl alcohol) (PVA) and detected at 214 nm using clenbuterol [4-amino-a-(tert.-butylaminomethyl)-3,5-dichlorobenzyl alcohol] [37148-27-9] as an internal standard. Metacholine bromide (acetyl-ß-methacholine bromide) [333-31-3] was determined with a 0.01 M creatinine-chloride buffer of pH 4.85 and detected with indirect UV at 230 nm using potassium as an internal standard. Histamine solutions were stable for a prolonged period of time, whereas under enforced degradation conditions methacholine was hydrolyzed, yielding acetic acid and (tentatively) ß-methylcholine as reaction products.