Q:

When performing a Lonza Bacterial Endotoxin Test (BET), LAL or PyroGene™ Recombinant Factor C (rFC), endotoxin detection assay how should I prepare my sample for testing?

A:
There are a few ways in which your sample can be prepared before testing it. Most samples only need to be diluted before they are tested with one of our endotoxin detection kits. In order to determine how far out you should dilute your sample, you should calculate the MVD (Maximum Valid Dilution) for the sample. The MVD of a sample is its endotoxin limit in EU/ml divided by lambda, the lowest standard of the standard curve you are using (for gel-clot, lambda is the labeled sensitivity of the lysate). You should not exceed the MVD for your sample, and to ensure a margin of safety, we recommend that you do not dilute past ½ MVD whenever possible. We recommend heat inactivation of the sample if you suspect that proteases are interfering and causing a false positive result. This can be achieved by heating a dilution of the sample at 70 degrees C for 5-15 minutes. Further dilutions can be made from the inactivated sample. We recommend using our beta glucan blocker if you suspect contamination by beta glucans. This contaminant can come from yeast and cellulosic materials. A common dilution/response pattern is seen in the LAL test with samples that been contaminated by beta glucans. This includes a negative response with concentrated samples, a positive response with increasing dilution and an eventual negative response at the highest dilution. Additionally, with kinetic methods, a synergistic response (enhancement) is frequently seen in beta glucan contaminated samples. We recommend using PYROSPERSE™ with samples for which endotoxin binding is a suspected source of inhibition. Some examples of samples that PYROSPERSE™ can be used with are lipid emulsions, electrolyte solutions, normal serum albumin and plasma protein fraction.
Related URLs:
Categories:
Endotoxin Detection
Research Areas:
Endotoxin Testing