I am using malvern Zetasizer for the measurement of chitosan nanoparticles loaded with drug.
Hello,
Refer to the manual of the instrument (book) given with the instrument it has the information you are looking for. You can also download e-copy from Malvern website.
All measurements were performed with the automatic determination of optimum measurement conditions: the incident flux (Attenuator) and the volume of registration (Measurement Position).
Hi,
Well, Just according to my personal experience with Malverns:
I would not say that there is an optimum count rate, the count rate is directly related to the concentration of your sample (number of nano particles per sample). Since the count rate represents the average scattering intensity during the measurement with a particular sample under a specific optical settings of the experiment. Then you can judge the concentration of your sample and maybe dilute it. I would say a good count rate which allows the instrument to give a more precise reading of your sample would be 300-500 Kcps. with samples less than 150 kcps; the reading quality would be very low, while if more than 800 kcps, readings are not realistic and you would get wrong size and charge readings....
Count rate in DLS this is simply the number of photons detected and is usually
stated in a “per second” basis. This is useful for determining the sample
quality, by monitoring its stability as a function of time, and is also
used to set instrument parameters such as the attenuator setting and
sometimes analysis duration. The count rate needs to be above some
minimum value in order to have enough signal for analysis, however all
detectors have a maximum count rate where the response remains linear,
and if the count rate is not adjusted automatically, the manufacturer
recommendations for adjusting the count rate must be observed
In default automatic mode, the Malvern Zetasizer software will automatically attenuate the laser to reach an ideal count rate of between ~200 to ~500 kcps [kilo counts per second]. This means if your sample scatters more light, the input laser power will be reduced automatically to reach the ideal count rate. If your sample scatters less light, then the system will use 100% laser power, and in automatic mode the software will compensate by measuring over a longer time (and averaging more subruns).
Yes, you can also do all this manually in the setup of the experiments by changing the attenuator position (11 is 100% laser power, 1 is 0.001% laser power, evenly spaced, about a factor three for every position change). Caution: if the sensitive detector is exposed to too much light it could be permanently damaged, aim to stay below 1Mcps and always optimize from low counts upwards.
http://www.materials-talks.com/blog/2015/06/11/derived-count-rate-what-is-it/
Ulf Nobbmann sir i have recorded DLS of my four samples , is there a wayout to corelated the kcps values of these samples as they have different attenuator number.
Hi Manzoor,
Reported in the software for the Zetasizer is a “Mean Count Rate” and “Derived count rate”.
The mean count rate is the value that was detected, and the derived value is calculated to give the count rate is no attenuation was used, for comparison between measurements.
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