nitrophenols and 4-nitrophenyl-maltoheptaoside

Two commercial amylase methods which employ p-nitrophenol derivatives of blocked maltoheptaosides suffer from negative interference due to fresh haemolysate. Specimen storage at room temperature, or pre-incubation at 37 degrees C or 57 degrees C removes the effect. Incubation of amylase reagent at 37 degrees C with fresh haemolysate where the final haemoglobin concentration was 0.011 g/L, showed a rapid fall in absorption around 414 nm which became stable after 150 min. Since p-nitrophenol, the product of the amylase reaction, is measured at 405 nm it is concluded that the negative interference from fresh haemolysis is due to the transitory fall in absorption around 405 nm. It is recommended that amylase measurements using this technique, particularly those performed as an emergency, should not be done on haemolysed specimens.

Topics: Amylases; Blood Chemical Analysis; Chromogenic Compounds; Drug Storage; Enzyme Stability; Glucosides; Hemoglobins; Hemolysis; Humans; Nitrophenols; Spectrophotometry, Ultraviolet; Temperature; Time Factors