Zetasizer dip cell kit, showing the dip stick, the glass cuvette, and two pipecleaners

Every once in a while we receive a Zetasizer question that we have heard before. Here is an example of such for the dip cell: “How do I clean the Zetasizer dip cell? What is a good cleaning protocol?” Most zeta potential measurements utilize the disposable (and reusable) capillary cell DTS1070. Occasionally the dip cell is the best choice. But how can you get the dip cell clean between different samples?




What is the dip cell?

The dip cell is available in our catalogue with the description “Universal Dip Cell Kit” (part number ZEN1002):
Universal dip cell kit for samples in aqueous and non-aqueous, i.e. non-polar dispersants such as hydrocarbons. Compatible with plastic DTS0012 and glass PCS1115 cuvettes. The kit includes electrode assembly with Palladium electrodes with 2mm spacing, one glass PCS1115 cuvette and cap. Compatible with all Zetasizer systems that can measure zeta potential.

The Zetasizer dip cell is really more of a dip stick, that you can place into a square cuvette. The electric field is centered between the two Palladium electrodes with a narrow 2mm spacing. This allows for a higher electric field strength. So it is ideal for electrophoretic mobility (zeta, ELS) measurements in dispersants with low dielectric constant.

How to clean the dip cell?

The dip cell stick is made of PEEK (Polyether ether keton) holding the Palladium electrodes. PEEK is resistant to many solvents and so ideal for many organic dispersants. There is a chemical compatibility statement in the manual, see screen image below. If you need to find the compatibility with a specific solvent, it might be best to just research/google that first.

The Dip-cell-cleaning-instructions in the manual describe ultrasonication. Here are some additional recommendations from my colleague Ana Morfesis:

Take care to not leave it in the sonicator for very long. So in the below instructions I would choose only having the sonicator on for maybe 15 seconds then leave the sonicator off for 30 seconds with the electrodes still in the cleaning solution and then sonicate another 15sec.
My usual cleaning procedure is to use a 25 or 50 mL Erlenmeyer flask and use 80:20 ethanol: water to sonicate for 30 seconds to one minute at a time. Then rinsing with ethanol or water and gently rub with a pipe cleaner in between sonication periods until the electrodes look clean.

The other cleaning liquids to consider in the Erlenmeyer are to go through a series of polar to non-polar solvents. An example would be to work through Ethanol, then Hexane and then Toluene and back to Hexane then Ethanol. You would sonicate for 30 seconds to 1 minute in each of these solvents. There is very little that withstands Toluene so if the electrodes are still unclean I would leave the electrodes during the Toluene step, in the Toluene (without sonication) for 30 minutes. I would suspect that the electrodes most likely become clean. Again, in between each solvent you would gently use a pipe cleaner.

So with the above tips you should not have trouble with the dip cell. Although, in general the preferred method is usually the capillary cell, whenever possible for running zeta potential measurements.

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If you have questions, please email ulf.nobbmann@malvernpanalytical.com. Thanks! While opinions are those of the author, some parts are not due to editing.