An unexpected albumin-bilirubin band in cellulose acetate electrophoresis for alkaline phosphatase isoenzymes.

In 4 out of 202 consecutive electrophoretic patterns for serum alkaline phosphatase isoenzymes, an extra band was observed in the albumin zone. Subsequent heat inactivation tests and comparison studies with an albumin-based bilirubin standard indicated that the band was due to staining of an albumin-bilirubin complex. The band should not be mistaken for an isoenzyme of alkaline phosphatase.