I am pretty sure that no LAL nor the rabbit assay can handle higher concentrations of benzyl alcohol. For some substances which cannot be tested, we used the monocyte activation test with whole blood, in really difficult cases with an adsorption step for the pyrogens and then removing the product.

Here are the papers;

Schindler S, Rosenberg U, Schlote D, Panse K, Kempe A, Fennrich S and Hartung T. Pyrogen testing of lipidic parenterals with a novel in vitro test. PharmEuropa Sci. Notes 2006, 1-7.

Daneshian M, Guenther A, Wendel A, Hartung T and von Aulock S. In vitro pyrogen test for toxic or immunomodulatory drugs. J. Immunol. Meth. 2006, 313:169-175.

As Thomas Hartung mentioned, i don't think LAL can handle high concentration of benzyl alcohol. My idea is try GC-MS but you may want to derivatize the endotoxin compound or evaporize benzyl alcohol and re-suspend the endotoxin with pyrogen-free water then GC-MS.. many papers have done this technique to test endotoxin..

One possibility would be to inoculate 11 day chick embryos intravenously

J.Infect. Dis. 116:529-536, 1966

Here are a few simple options:

• Blow your sample down under a gentle stream of nitrogen and re-suspend in water to the original volume.  A warm heat block could help speed the drying process. Then test via LAL as originally planned.  
• If you have access to a lyophilizer, you can dilute your sample in water to freeze it, then lyophilize it overnight and re-suspend in the original volume of water.    Then test via LAL as originally planned.  

If you were to do GC/MS, you would have to extract the LPS, as if you went straight to FAME derivitization, you would also derivitize any other fatty acids present in the sample which could throw off your results. Also, you would still need to get it out of Benzyl alcohol and put it into methanolic HCL.  

Let me know if this helped or if you have any other question!

Thank you so much all of you for your valuable answers and surely it will help me in analysis.

I acknowledge the receipt of your valuable replay. However, we want to check endotoxin from gram negative bacteria not pyrogen.

Please follow the advice of Thomas. He succinctly and convincingly explained the advantages and disadvantages of modern methods for the determination of endotoxin. We have seen that a lot also depends on the professionalism of the expert, who owns the methods of data.