I do not think there is any other way than to filter the decalin regularly. Even if you would somehow manage to close the VAT unit perfectly, you still introduce some dust into the decalin (toluene) every time when you insert the meassuring cuvette with the sample into the VAT unit. We have different instrument than you, but yes, we use such filtering pump regularly. If one keeps the filtration (pump) speed low enough, so that no air bubbles are formed in the decalin, one can use such filtration even befor every DLS or SLS measurement - during the time used for sample filling and exchange. We were used to use 20 nm filters for this purpose, but lately I have figured out that using 200 nm filter and regular filtration of decalin satisfies our needs.

Cheers!

Thank you for the suggestion. I just realized that is hard to find a pipe of a material which is resistant to toluene but soft enough for a peristaltic pump. As far as I understood, you filled your bath with decalin (which is slightly less agressive). Did you have any corrosion problems?

Thanks again,

Leo

With our setup I improvised a bit. Ii took an old collon for gas chromatography (GP) that I got from a colleague from the department of the analytical chemistry, emptied it with compressed air and cleaned it - in this way i obtained a nice thin metal tube that I used as a pipe connecting decalin bath with the pump.They also have nice fittings to conect such tubes.

We use KNF LAb Liquiport(R) pump. Maybe you ask there and they should be able to suggest you also where to get an appropriate tube (if you do not wish to improvise):

http://www.knf.com/products/laboratory-pumps/product/products/diaphragm-liquid-pumps-1/transfer-pumps/

I am convinced that you could find a setup also for the toluene, but maybe you rather switch to decalin that is also in broad use in the VAT units.

Glad that I could help. Cheers!

You already called up an ALV application engineer?

This was a question that came up repeatedly when we had a CGS3 several years ago. The advice given then was that pumping toluene was not recommended due to the low flashpoint. If pumping at all, then decalin was better due to its higher flashpoint. In practice, dust was not that critical in our experience because we did not use the system that frequently, so big dust could settle to the bottom of the index matching VAT, and we dipped every cuvette into toluene before insertion into the sample holder. For extracare the outside of the cuvette could even be rinsed with clean toluene. Encouraging all users to take special cleaning precautions did help. Fortunately, the alignment system of the CGS3 is so solid that the dissambly with the provided tools made it relatively easy after having done it a few times. (Yes, delicate, and you do not want to break the VAT, but amazing how often the system would require no adjustment at all after re-assembly).

Before the 'clean outside with toluene' protocol we had one time where water had formed micelles in the bath: this showed up as an increased countrate at 90 degrees and DLS showed nice correlation functions from the index matching fluid alone...

Unless you need to use toluene for some reason, suggest you switch to decalin. Much safer, less volatile, and easy to pump and filter. We had an old Brookhaven system with a peristaltic pump and in-line filter. Just ran it periodically to clean the decalin. Get rid of the toluene and do yourself a favor. I don't recall which pump tubing we used, but there are tubings that are resistant to decaline as it is much less aggressive solvent. Good luck.