When in size test，the zetasizer occur an error，and the log reveal：
Checking preset position
Seeking best attenuator at position 3.00mm...
Set attenuator: 11
Set attenuator: 11
Count rate: 0.13 kcps
Very high count rate. Continue with maximum attenuation.
Will use position 3.00 mm
Will use attenuator 11
Will perform 100 runs of 10 seconds
Starting run 1
[ATTENTION]: Data not suitable for analysis.
[ATTENTION]: Measurement aborted
Measurement aborted
the correlation function，count rate，log text，expert advice in the
Attachment.The free-dust sample can test last time，but the same test occur an error next time.
Interesting observation!
- Your correlation function has two peculiar characteristics:
- Based on these two characteristics it seems like your sample is sedimenting (sedimentation rate>Diffusion rate).
Are you characterizing a suspension or a colloid?
Laser diffraction size analyzers have an inbuilt dust cyclone/flow apparatus which will prevent particles from agglomerating.
The "correlation function" looks extremely strange. Part of the problem is perhaps that there is too much automation between you and the measurement, which makes it difficult to understand what is happening.
The first piece of the answer is that your count rate is zero. See the last panel. There is no signal. At a guess, for some reason instead of reporting the correlation function itself, your G(t) has been normalized by an estimator for G(0), the estimator is zero, and therefore the start number is something over zero, which in computer arithmetic may have a defined value.
Does your instrument report a photocount rate before it starts automatically adjusting things? What was that rate?
You have a dilute protein solution. The scattering intensity, if the sample is clear, should not be excessive. If the scattered intensity was originally huge, perhaps there was some artifact, the sort of thing you will likely find immediately so soon as you look for that rather than for meaning in the data analysis. (This is the sort of problem that can be very difficult to identify, until you find it, at which point it is only annoying and trivial.) Do you have a way of viewing the laser beam as it passes through the cell? Were you catching an edge of something, or a meniscus, or a scratch on the sample cell? These are all unlikely events that you likely checked for already, so my comments should be taken only to suggest a direction in which you might look, not that you would have missed any of these obvious points.
Hello Ci Qian,
sorry to hear about your issue. The most likely reason is that the cuvette is inserted incorrectly, or not fully pushed to the bottom of the cuvette holder. The count rate you measured is the dark count rate, and thus means there is no scattered light from your sample reaching the detector. Is the cuvette pushed all the way to the bottom of the sample holder? Is this a standard Malvern cuvette? When using other cuvettes, make sure that it is compatible with the optical setup. For any questions, contact your local Malvern help desk, or email the global help center at [email protected]
The software does have a count rate monitor, if you like to use just that go to: Tools - Count Rate Meter . The easiest is to observe the automatic adjustment steps in the live measurement window where the count rate trace, correlation function and any actions are displayed live. These are also logged in the log file
Hello ci Qian,
thanks for the clarification. Are you able to get good data with another sample in a different cuvette?
If yes: there may possibly be a small piece of glass in the bottom of the sample holder, preventing the cuvette from being fully inserted.
If not: I suggest to try using a standard plastic cuvette, put ~2mL of water in there and add a drop of milk. If you do not get any counts from that sample, then either the laser is blocked or the laser is broken. The broken laser would require a service visit.
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