Malvern ZetasizerNano
ZetasizerNano:
The zetasizer measures the size and zetapotentioal of particles in a liquid medium. The zetasizer utilizes the Brownian Motion of particles measured by Dynamic Light Scattering to calculate size, while molecular weight is measured using Static Light Scattering. Zeta potential, or the propensity of the particles within liquid will stick together, is measured via Laser Doppler Electrophoresis, where an electrical field is applied to the sample and the velocity of the particle is measure.
Important Reminders:
This is an optical measurement, care should be taken to use clean cuvettes and maintain a clean sample cell. A variety of cuvettes and sample cells are available. Glass/Quartz cuvettes should be used when using organic solvents.
The zetasizer should be turned on 30 minutes prior to measuring samples and turned off at the end of the day. The Power switch is located on the upper left side of the rear of the instrument.
Sample Preparation:
For sizing experiments place your sample in either a disposable or quartz cuvette, the depth of the sample should be between 10 and 15 mm. Overfilling the cuvette will adversely affect your results by creating thermal gradients in your sample. There is a full scale drawing on the lid of the sample chamber, that you can check your sample against. Before loading the cuvette into the chamber, make sure that the walls of the cuvette are free from dirt or fingerprints that could affect the light scattering. The beam path is from the front of the instrument to the back.
For zetapotential measurement, you have two cells options. For aqueous and alcohol-based solutions you can use the ‘folded capillary cell’ or organic and inorganic solvents you should use the universal dip cell. The folded capillary or zeta cells, while plastic can be reused by flushing solvent through them between measurements. For best results you should pre-wet the zeta cell, by flushing your solvent through the cell and pushing it out.
To fill a zeta cell you will need a 3 ml syringe filled with your sample. The syringe should be free from air, to remove air from your sample point the tip of the syringe up and slowly push the plunger up until all of the air is out of the syringe. With the syringe tip still pointing up, connect the zeta cell to the syringe. Slowly push the plunger up and introduce your sample into the cell. Continue filling the cell until the solution reaches the fold in the capillary then point the syringe tip down and continue filling. This will prevent air from being trapped in your sample, which will affect your results or prevent any data acquisition. Before loading the sample into the sample chamber, inspect for any air bubbles. If you see air bubbles, gently tap the cell on the table or flick it with your finger. If you cannot remove the air bubbles by tapping or flicking the cell, you should remove your sample with a syringe and flush the cells with your solvent and reload your sample. When the zeta cell is free from bubbles, close the cell with the included plugs and insert it into the sample chamber. The electrical contacts of the zeta cell should be touching the electrical contacts of the instrument. If the electrical contacts are not touching, you can gently push the tabs on the zeta cell outwards so they will make contact.
The universal dip cell should be used with solvents that are incompatible with plastic. You will need to fill the cuvette between 7 and 10 mm, using approximately 0.7-1.0 mL of solution. When the dip cell is inserted into the cuvette the depth of the solution should not be more than 15 mm, but the prongs of the dip cell should be covered with solution. Inspect the dip cell for any air bubbles and then place the cell into the chamber.
Software Interface:
The software is located on the desktop or under the Malvern Program file. You must first create (or open) a Measurement file from the File menu. A measurement file can hold many different measurements of the same type, size or zeta potential. If it is your first time running this type of sample, I recommend you start a manual measurement. To start your manual measurement, select Manual from the measure menu. This will open the Manual Measurement Settings; you will need to fill in each of the fields that are presented as you move through the file.
You choose the type of measurement you would like to make. After you choose the type of measurement you must also the cell type you are using. This is very important as choosing the wrong cell type can influence your results.
You will also need to know the Refractive index and absorption of your material. You may have to use the published data for the bulk material of your nanoparticles unless you have measured or found RI data for your material. You will also need to know the Viscosity and Refractive Index of your dispersant. If you are not measuring your sample at 25oC you should input the viscosity of your solvent at the temperature that you will be performing the measurement. You can add, delete or modify existing materials/dispersants by entering the dispersant list or manager and choosing to modify or add. Materials and dispersants with green triangles next to them are Malvern defined and cannot be modified.
Next you will need to set up the parameters for the measurement. This includes how many acquisition runs will be used per measurement. When using the automatic mode, the software determines the acquisition duration. If you want to determine the number and duration acquisition runs choose Manual and input your parameters. The number of measurements allows you to automatically run the sample in multiple times without further interaction. You can also choose a time delay between measurements. Multiple measurements are useful if you are interested in a time-course study or are looking to prove repeatability in your analysis.
Once your parameters are set, you will click ok and the measurement window will open. If your measurement parameters are correct and the sample is loaded into the instrument you can click the large green triangle at the start of the screen this will start the measurement.
The software will adjust the optics to yield the best results for your samples and will then start the data acquisition runs. At the end of the measurements, the data will be put into the Measurement file you opened when you started the software.
Once the data has been collected, you will be able to access the distribution plots, correlation graphs and measurement statistics. You will also be able to extract an SOP to save if you wish to run similar samples again in the future.
To extract the SOP from a manual measurement, right click on a measurement in your measurement file and choose ‘Extract SOP’, you will then be able to choose the file name and directory of your SOP. To run your SOP in the future, select ‘Start SOP’ from the measurement menu and select the SOP of interest. An SOP screen will display the type of cell that is to be used with the measurement and the measurement parameters, when you’ve check your sample and cell against the SOP file you can click ok and insert your sample into the sample chamber and Click Start (green triangle) and the measurement will proceed.
Please refer to the tables below when preparing your samples: