[Clinho]

When it comes to application of Lambert-Beer law, above which particle sizes this method is useless, i.e. is there a size limit of particles, concentration of which can be determined with reliability?

Is that limit based on empirical evidence, or purely on theoretical considerations (e.g. because Rayleigh scattering takes place for too large particles)?

[Clinho]

Anyone knows?

[the inquisitor]

Well as far as I know, most laboratories consider particles < 0.45 um (micrometre) as dissolved and those particles that are > 0.45 um are suspended solids.

Turbid samples will definitely scatter the light due to large particles in the sample and lead to a higher result.

Hope this helps.

Kind regards.

[Babcock_Hall]

All I can add to this discussion is that bacterial growth is often judged by turbidity.  The absolute concentration of bacteria is not typically sought, but the relative concentrations are important.