The new ZS Xplorer software is here!
Modern, flexible and different from the classic Zetasizer software, the novel ZS Xplorer interface was developed specifically for the latest generation of Zetasizer systems: the Zetasizer Pro and the Zetasizer Ultra. If you missed the launch, check out the exciting launch recording and Q&A session.
In order to help you easily adapt to the new interface, here are a few commonly encountered tips to help you become familiar with the entirely new software architecture. The main difference is that data are now saved in one …

Join us for the next User group meeting!
User Group Meeting Announcement 19 Oct 2018 1pm-4pm EDT

We are pleased to announce the first virtual Zetasizer User Meeting ZUM-1! This initiative is an effort to foster the diffusion of knowledge and experience between our support group and those researchers that regularly evaluate light scattering data from the Zetasizer. The Zetasizer Users Community is invited to present and share data with specific questions. Get live feedback from our panel of experts.
The meeting will be live-streamed via Webex and is limited to 3.0 hours. …

Debye Screening – what is it?
 
In colloidal samples (and this spans the whole range from molecules in solution to particles in a dispersion) the movement of and forces between objects are often governed by the charge affecting neighbors. When we measure zeta potential (by electrophoretic light scattering), the determination of the effective charge of particles is really what is probed. In other words: zeta potential (or electrophoretic mobility) is a measure of how the charge of a particle/molecule is influencing the movement of another particle/molecule. The full potential as a …

How can we obtain the applied field strength?
When performing electrophoretic light scattering (ELS) measurements, the sample is exposed to an externally applied electric field, and we observe the extra movement that the particles undergo as a result of the applied field with the changes in the phase difference between the un-scattered reference laser beam and the scattering from the particles. The electrophoretic mobility µ is the particle velocity v divided by the electric field strength E, where the field strength is the applied voltage over the distance between the electrodes [typically …

Launching the latest Zetasizer in Mexico!
 
June was a special month at our Mexico City office. We held a specific launch party organized for the latest addition to our Zetasizer family of instruments – the Zetasizer Pro and the Zetasizer Ultra. One of the groundbreaking novelties in the new system is adaptive correlation, a new method to perform dynamic light scattering (DLS) measurements, where rapid correlation functions are classified as being steady state or transient. Steady-state data sets describe particles that are consistently part of the measurement volume and hence characteristic of …

How good can a gold standard be?
 
When performing dynamic light scattering (DLS) measurements, we sometimes encounter especially nice data. An interesting issue to consider is the level of data quality one can expect to achieve, under ideal circumstances, when all other interferences are minimized. This is especially relevant at the smaller nanoscale where fewer standards are available, and to those who have less practical experience with sizing colloidal nanoparticles by DLS. How monodisperse can a good sample be? What are achievable polydispersity index (PDI) values to aspire to?
What is the …

Where is the Zetasizer used?
 
For around two decades, the Zetasizer range has been the de facto standard for performing dynamic light scattering (DLS) measurements on a wide range of particles and materials.
Today’s launch of the Zetasizer Pro and Zetasizer Ultra – which took place earlier today on May 23rd, 2018 – provides a good reason to summarize the key application areas for light scattering technology: both dynamic and electrophoretic! Where are these Zetasizers used? Where can we find them, in the real world?
Below is a list of key application focus areas:

Bioscience and biopharmaceuticals: …

The peaks in your distribution are out of order?
We recently received an email about the order of peaks in the Zetasizer software:
For data evaluation, is it possible to rearrange the NNLS results by order of particle size populations?”
How the peaks are shown (by area)

Size measurement results are typically viewed in the Intensity PSD (M) tab. This is part of the standard Size and Summary workspaces.  When a record contains more than one peak, these results will be tabulated in the table above the intensity size distribution. The default ordering in …

Will the zeta potential of my vesicles vary in different buffers?
 

The short answer is: Yes, it will. In select cases, the value of the measured zeta potential may remain close to the same. However, that is the exception rather than the rule. This is no different for vesicles than for other nanoparticles, biomolecules, polyelectrolytes, etc.
How does zeta change with salt concentration?
The zeta potential of a colloidal particle in solution is a description of the overall effective net charge of the particle under the sample system conditions. Thus the effective net …

… and receiving a Zetasizer
 
In North America, this time of the year is the busiest period for shipping companies like DHL, Federal Express or the US Postal Service. Malvern Panalytical does not rest either, in fact, our systems are part of the global shipping growth in this busy season. As a global company certified in ISO 14001 we are conscious of our role and take measures to minimize the use of resources. One of these efforts resulted in the design of a new reusable shipping box for the Zetasizer. An …

Measuring aggregation temperature using the Zetasizer

In dynamic light scattering (DLS), the hydrodynamic size and size distribution of particles in solution can be obtained.  It may be of interest to examine this measurement as a function of time and temperature, or as a ‘trend’, as it is called in the Malvern Zetasizer software.  For biological protein samples, this temperature trend is particularly interesting: although at low temperatures a protein may be stable and show repeatable size (and scattering intensity) measurements, typically at some elevated temperature (Tagg), protein molecules will show a tendency …

Molecular weight measurements with the Zetasizer software?
First a few words of caution: molecular weight or Mw measurements in general are not easy, require time, good sample preparation skills as well as patience. If you are new to the Malvern Zetasizer it might be best to familiarize yourself first with the rapid, user-friendly, and quite forgiving technique of dynamic light scattering (DLS). {{If you are experienced and want to skip to a Brainshark narrated screen recording of the steps, best viewed in Chrome, go ahead to https://www.brainshark.com/malvern/sls-with-zetasizer }}.
OK, with that out …

The term polydispersity (or more recently dispersity without the poly, as per IUPAC recommendation) is used to describe the degree of “non-uniformity” of a distribution.  In the field of molecular/nanoparticular characterization, there are in principle two different definitions of polydispersity, depending on the underlying property of interest.
In Gel Permeation Chromatography (GPC) and Size Exclusion Chromatography (SEC), we are interested in the molecular weight of the sample. The distribution obtained from GPC/SEC is typically a molecular weight distribution describing how much material there is present of the various molecular weight “slices.”  …

Is there a maximum viscosity for DLS measurements?
 
The Malvern Zetasizer can determine particle size by dynamic light scattering (DLS). In this technique, the intensity fluctuations are analyzed to find the corresponding diffusion coefficient that led to the fluctuations. The translational diffusion coefficient Dt of a particle is inversely related to its size and the viscosity of the dispersant (or more accurately the hydrodynamic radius rH and viscosity η).

This relationship can be used to predict detectability limits of the technique in general, and this is how we explore the idea of …

Zetasizer: What is the zeta potential deviation?
 
The Malvern Zetasizer software report for zeta potential shows a parameter that is called Zeta deviation. This parameter is shown directly below the mean Zeta potential.

The mean zeta potential is derived from the fast field reversal (FFR) phase analysis light scattering (PALS) technique.
The fast field reversal provides a single number from the analysis. This single number is the mean zeta potential. The slow field reversal [also known as SFR] can be used to determine the zeta distribution, a distribution of different charge values from …

Zetasizer: 21CFR? Electronic Record/Electronic Signature? Test Schedule?
 

The Malvern Zetasizer is an extremely versatile measurement system. By far the most systems are used in academic and industry research laboratories, for example in fundamental research, drug discovery, or formulation optimization. However, a significant number of installations are in operation in “controlled” environments, such as for quality control in pharmaceutical companies. Here documentation and compliance with good manufacturing standards GMP is critically important, and a specific version of the operating software exist that locks down standard operating procedures (SOP) with limited ability (based …

Intralipid-Lipid emulsions

Lipid emulsions are administered intravenously for a variety of purposes:

To help feed patients with temporary difficulty in ingesting food orally
For better transport of lipophilic drugs (fat-friendly active ingredient (API) which is not soluble in water)
For controlled release of drugs (size related to uptake and retention)
To decreasing adverse reactions to drugs
To improve targeting of drugs
In emerging gene therapies for cellular and gene delivery, and personalized medicine

Control and understanding of colloidal properties – such as droplet size and zeta potential – enable the design and optimization of appropriately stable emulsions. The …

Nanomaterial isoelectric points IEPs
 
In a recent webinar presented by Ana Morfesis titled “Characterizing the zeta potential & Isoelectric Point of Nanomaterials” we got such a good turnout that we were not able to address the numerous questions asked during the event.
Thank you for the participation!
Since there was such strong interest, we have provided the following list of questions and answers to benefit all who are interested.  We have also provided a table of common metal oxide IEPs, as shown to the left.
 
 
For those who were not able to attend the live event, the session was recorded and is …

Monoclonal Antibodies – or mAbs for short

Since many of these mAbs require refrigeration we had used dynamic light scattering (with a Zetasizer) to show the formation of aggregates after freeze-thaw cycles (for details see application note “Effect of storage conditions on Immunoglobulin“). These could be seen both in the increased polydispersity index (PDI) and the appearance of a large-size aggregate peak in the intensity size distribution as shown to the right. The area under the peak gives an indication of the presence of the large aggregates but is not suited for …

Three methods to verify dynamic light scattering systems
If you are a meticulous researcher you may want to test your new Zetasizer. Is it really providing the correct size? One of the advantages of dynamic light scattering is that there are no tweakable adjustments, it is all physics: laser wave length, scattering angle, refractive index of the dispersant are all known in advance and are given parameters for the optical setup and sample. Nevertheless, it is a good idea to check and verify the performance of the system. One of the …