A new kinetic single-stage Limulus amoebocyte lysate method for the detection of endotoxin in water and plasma

A convenient kinetic chromogenic Limulus amoebocyte lysate (LAL) method, based on components originally intended for a two-stage end-point method, has been developed. The components (LAL and chromogenic substrate) can be pooled and subsequently used in a single-stage kinetic procedure adapted to microplates. With the help of a kinetic software, it is possible to measure over the three log range 0.005-12 EU/ml in one test run--a range considerably wider than the range of the end-point procedure. A good linearity of the log-log standard curve, reflected by coefficients of regression between 0.997 and 1.0, is shown as well as a high-resolution (> 700 s) between the negative control and the lowest standard point. Moreover a good precision (C.V. < 10%) is obtained in both water and plasma, showing the usefulness of the method in different applications. Finally, a strong correlation (r = 0.95-0.99) to other LAL methods is demonstrated.