The gel-clot technique

Preparatory testing

Test for Labeled Lysate Sensitivity

• Test is performed in 4 replicates. In each of these replicates, the labeled sensitivity, expressed, λ, in EU/mL.
• Standard solutions of four concentrations ( 2 λ, λ, 0.5 λ, and 0.25 λ) are prepared by diluting the USP Endotoxin RS with Water for BET.
• Equal volumes of Standard Endotoxin Solutions ( 0.1 mL aliquots) from each test tube are mixed with Lysate TS.
• Reaction mixture is incubated at 37 ± 1°C for 60 ± 2 min or as per manufacturer’s recommendation, avoiding vibration.
• To check the integrity of gel, individually remove each tube from the incubator and invert it 180 degrees in a single fluid motion.
• If gel remains intact upon inversion, test results are considered as positive. On the other hand, the results are negative if intact gel is not formed. The test is valid when the lowest concentration of the standard solutions displays a negative result in all replicate tests.
• The endpoint refers to the lowest concentration among the descending series of standard endotoxin concentrations that causes the lysate to clot.
• Geometric mean endpoint is measured by calculating the average value of logarithm of the endpoint concentrations of the four replicate series.

Acceptance criteria – The geometric mean endpoint concentration determines the lysate sensitivity.