Spectrophotometry as a Tool for Assaying Endotoxins

Biological Contamination of Nanoparticles and Its Manifestation in Optical Absorbance Measurements

“…Consider a colorimetric method for the determination of the biological contaminant using a bacterial lipopolysaccharide (endotoxin) as a typical example of such contamination. − Assuming the validity of the Beer–Lambert law, the optical absorbance (or optical density) can be written as eq : where σ BIO α is the extinction cross section of the biospecies, n BIO is their volume concentration, and d is the optical path length. By comparing the measured value of the optical absorbance to the standard (calibration) curve, the concentration of the biological contaminants can be easily determined. − The product, σ BIO α n BIO , determines the optical extinction coefficient, α BIO , of the biological contaminant.…”

“…Physical parameters used in simulations are listed in Table . The values of these parameters were selected to reasonably represent existing materials. − …”