Immunoassay for human serum albumin using capillary electrophoresis-semiconductor laser-induced fluorometry

Capillary electrophoresis combined with semiconductor laser-induced fluorom etry was applied to an immunoassay of human serum albumin. Human serum albu min was labeled with a fluorescent molecule (Cy5), which has an absorption maximum at 649 nm. The labeled albumin was purified by ultrafiltration in o rder to reduce signals, which are unreacted labeling reagent, product, and fragment products derived therefrom. After the purification, no signal for unreacted labeling reagent and fragment products was detectable in the elec tropherogram of the labeled albumin. The labeled albumin was then reacted w ith anti-albumin to form an immunocomplex, which was separated from the exc ess free albumin. The competitive immunoassay was used in the determination of human serum albumin in a controlled serum sample, using die labeled alb umin. The obtained value was found to be 0.21 +/-0.02 mg/ml, which is in go od agreement with other known values. (C) 2001 Elsevier Science B.V. All ri ghts reserved.