Hi Ravi, As mentioned above dust may be a problem and will show large objects typically in the micron range. However, if you just leave your sample for 5 minutes on the bench the dust should settle to the bottom of the cuvette and shouldn't interfere with the laser anymore. There could be other things going on, if your nanoparticles have a very low zeta potential (i.e. close to 0) they could be aggregating thus causing results to differ over time. Also, if the concentration of the nanoparticles is too low then you may not be collecting enough runs to get a proper average result, you could try increasing the concentration or alternatively increasing the run time or number of runs. There are other possibilities, which are too numerous to mention. However, if you would like a more detailed response I would be more than happy to look at your data directly. If you would like this then send me a direct message, or email, and attach your results. For full analysis I would need the distributions and correlation functions to get a sense of what is happening.

Best wishes,

Chris

Dear Mr Reddy, it is a good question. If you have excellent skills with synthetic procedure and in preparing colloidally stable nanoparticles, I am sure the Malvern zetasizer would be a reliable one to reproduce the data. It would also be a matter with zeta-size analyzer that how much the cleanliness (means - avoiding dust particles) would be achieved in your lab atmosphere. If you can overcome the problem caused by dust particles, you can easily achieve the reproducibility. All the best for your research.

Hi Ravi, As mentioned above dust may be a problem and will show large objects typically in the micron range. However, if you just leave your sample for 5 minutes on the bench the dust should settle to the bottom of the cuvette and shouldn't interfere with the laser anymore. There could be other things going on, if your nanoparticles have a very low zeta potential (i.e. close to 0) they could be aggregating thus causing results to differ over time. Also, if the concentration of the nanoparticles is too low then you may not be collecting enough runs to get a proper average result, you could try increasing the concentration or alternatively increasing the run time or number of runs. There are other possibilities, which are too numerous to mention. However, if you would like a more detailed response I would be more than happy to look at your data directly. If you would like this then send me a direct message, or email, and attach your results. For full analysis I would need the distributions and correlation functions to get a sense of what is happening.

Best wishes,

Chris

Hi Ravi, DLS by Zetasizer is a robust technique unlike many analytical methods. If there is a problem with dust, you would see it on the intensity or volume distribution graphs as a large peak in micron range. As Christopher mentioned, there could be an y number of reasons such as low zeta potential or concentration or settling down of your particles during measurement, etc, Try to filter your samples and run independent samples. Also think that the phenomenon you are seeing could be real. That means your stock nanoparticles might be degrading or changing somehow during storage leading to those results.

Chitosan nanoparticles aggregate together if not properly stabilized. If your particles showing an increase in particle size with time this can be the reason. Have you done sonication before measurement?

My approach to nanoparticles synthesizing results in strongly reproducible results both in catalytic properties and size and shape. Hydrolysis of Fe Cl3 6H2O in water with ethanol was used for sythesising.

I am sure that the size of nano particles can be reproduced. If the method and fundamentals/boundaries conditions to synthesize the materials is same with all aspects. To avoid the contamination is also a good approach to reproduce the data.

Ya if you can do experiments with very very carefully then you will get similar results in zeta sizeser nano ZS. after preparation sample was characterise particles size without filter and with filter (if you expecting particles size below 500 nm then filter it with 500 nm syrenge filter) if there is chage in particles was observed it indicates that your sample containe dust particles.

i am also worked on drug nanoparticles synthesis for 6 months was taken to optimize experimental parameter to get similar size particles in different batches. i feel many researchers due to hurry about publication then simply doing DLS size analysis then going to SEM whichever DLS results matches well with SEM results they reporting it. many researchers just reporting numbers as size of the particles but not giving intensity and volume distribution of particles which was observed in DLS, this is due to same problem which was your facing they are not interested to optimize the parameter they want publications as soon as possible.

I strongly recommend you to carefully control the experimental parameters. I work with chitosan nanoparticles and I could get reproducible both mean size and charge. You should fileter chitosan solution before making nanoparticles as there is some chitosan insoluble that may affect to the final product. In addition, the polydispserity index can tell you the size distribution of your formulation. I hope you can solve this problem.

Nanoparticle size and morphology are reproducible if you control perfectly all the synthesis parametes (temperature, time; concentration of the precursors, agitation speeding,....).

I would further add that if you are using the malvern zetasizer you should look at the Number PSD option rather than volume or intensity PSD. Intensity PSD will flare up with aggregates even if they aren't the main component of your suspension. It's tricky to get to it but you essentially have to add a new column to your data sheet and then you will have the number PSD (average particle size). I've found this to be more accurate and reproducible than the Z-average. Regardless, I agree with the other responders, dust, microbubbles, concentration, temperature... all of these parameters need to be well controlled. Also, I would suggest you do more than 3 runs for more variable particles I do 20-minute measurements and this provides more data to smooth out any outlier measurement that was unduely affected by aggregates or other conditions.

Best of luck.

A good recipe (correct chemical system matched to appropriate shear) yields reproducible results. I use a NICOMP 380ZLS (same principle as the Malvern) both to develop products and to track the commercial batches we make, and the technology works great. When you get proficient at reading the output, the results tell you where you are in your development. The final metric we use to determine if we have a good product (beyond the primary driver of size distribution and stability) is the reproducibility. Nice answer by Raj Kumar.