Hello,
What causes a high amplitude (intercept) value in the autocorrelation function in DLS?
I was reading this "Correlation intercept – what is it and what does it mean? | Malvern Panalytical" but it only mentions one reason as to why the intercept would be high.
I am using Wyatt instrument and when the amplitude is higher than 1 it will mention that it is an error because the amplitude is not theoretically possible to be greater than 1.
Any input would be appreciated.
Thank you
She
Shei S. Multiple scattering (too high a concentration for measurement: ideally in DLS the sample is in 'infinite dilution' to eliminate particle-particle interactions and only examine random Brownian motion) and fluorescence are the 2 most common causes of a non-1.00 intercept value (which ideally is an indication of signal-to-noise in the system) in my experience. Number fluctuations may cause an intercept > 1 but this is unusual in my experience.
What is the system you are measuring?
Shei S.
The parameters of settings, which are selected by the device automatic system, are the important criteria of reliability of measurements. Check out the article
Article Structure of Micelles of Sodium Dodecyl Sulphate in Water: a...
Yes, your result is most likely number fluctuations. Or in more general terms: the statistics in your correlation functions are not as expected for a Gaussian signal, in other words you would have to measure longer (much longer) to get the expected intercept. There are some larger particles/aggregates/air bubbles/dust in your sample that lead to this result. Try to clean (centrifuge, filter) the sample to improve.
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