Sample Treatments That Solve Low Endotoxin Recovery Issues.

Area of Science:

• Biochemistry
• Analytical Chemistry
• Microbiology

Background:

• Low endotoxin recovery (LER) is a significant challenge in the bacterial endotoxins test (BET), particularly with pharmaceutical formulations containing chelating agents and detergents.
• The standard water dilution method for BET can lead to inaccurate endotoxin activity measurements in samples exhibiting LER.
• Accurate endotoxin quantification is critical for ensuring the safety of parenteral drugs and medical devices.

Purpose of the Study:

• To evaluate the appropriateness of different dilution methods for endotoxin activity measurement in samples with LER.
• To identify optimal conditions for the magnesium dilution method for endotoxin testing.
• To investigate factors that mitigate LER effects.

Main Methods:

• Comparison of water dilution, magnesium dilution (2 mM MgSO4), and direct methods for endotoxin activity measurement.
• Assessment of endotoxin stability in LER solutions under different conditions.
• Evaluation of LER effects with varying concentrations of chelating agents, detergents, and proteins.

Main Results:

• The water dilution method yielded low endotoxin recovery (LER), while the magnesium dilution and direct methods provided accurate endotoxin activity values.
• Endotoxin activity remained stable for over a month at 4°C when measured by the magnesium dilution or direct methods.
• Optimal magnesium concentration in the diluent should exceed the sample's chelating agent concentration; human serum albumin was identified as an LER mitigating factor.

Conclusions:

• The magnesium dilution method is the most appropriate technique for endotoxin measurement in LER solutions.
• Understanding and mitigating LER is essential for reliable endotoxin testing in complex sample matrices.
• This study provides practical guidance for improving the accuracy of the bacterial endotoxins test.