Zeta Potential Analyzer validated by Leibniz Institute of Polymer Research

To ensure the quality of the Zeta Potential Analyzer ZPA 20 from DataPhysics Instruments, the Leibniz Institute of Polymer Research in Dresden has successfully validated the instrument's measurement results for streaming potential and streaming current analysis.

The Leibniz Institute of Polymer Research in Dresden has successfully validated the measurement results of the Zeta Potential Analyzer ZPA 20 from DataPhysics Instruments in Filderstadt. Many years of cooperation between the measuring instrument manufacturer and the institute ensured that the measuring system meets the highest quality standards. The bidirectional, oscillating measurement method of the Zeta Potential Analyzer ZPA 20 is patented and enables statistically high-quality data sets in the shortest measurement time.

The zeta potential is a measurable quantity that characterizes the charge situation at a solid surface in solution. It is measured at the boundary between the ion layer firmly adsorbed on the solid surface and the solution. Dr. Astrid Drechsler, a scientist at the Leibniz Institute of Polymer Research Dresden e.V. (IPF) and an expert in the characterization of polymer interfaces, explains why the zeta potential is an important parameter: "When a solid surface is immersed in an aqueous solution, it becomes electrically charged due to dissociated surface groups and the adsorption of ions and molecules. The zeta potential provides information about these chemical and charge formation processes. For example, it can be used to predict interactions such as adhesion between different surfaces." Zeta potential measurements are important in a variety of applications, such as the study of fuel cell membranes, fouling processes of filters, bacterial growth on food packaging and washing of textiles.

Depending on the size and shape of the samples, the zeta potential can be determined using different measurement methods. For small particles in the nanometer to lower micrometer range, electrophoretic methods are often used. For larger samples in the millimeter and centimeter range, streaming potential or streaming current analysis has proven beneficial. The new Zeta Potential Analyzer ZPA 20 from DataPhysics Instruments uses a patented measurement method based on such an analysis. It is therefore particularly suitable for examining samples in the macroscopic range. The instrument can be equipped with the MC-ZPA/S, a measuring cell for solids such as plates, membranes or films, and the MC-ZPA/PF, a measuring cell for fibers, powders and granulates.

Customers who are unsure whether the Zeta Potential Analyzer ZPA 20 is the right instrument for them can not only rely on the in-depth knowledge of the DataPhysics Instruments sales team, but also request test measurements with their samples. Dr. Sebastian Schaubach, Chief Innovation Officer at DataPhysics Instruments, says, "Our lab offers contract measurements for a wide variety of applications, both with the ZPA 20 and with all other instruments in our portfolio."

The Zeta Potential Analyzer ZPA 20 had to meet the highest quality standards right from the start. Therefore, the manufacturer DataPhysics Instruments cooperated with a partner that is known worldwide: the Leibniz Institute of Polymer Research Dresden e.V. (IPF). Dr. Astrid Drechsler is a scientist there who works on the physical chemistry of polymer surfaces, including zeta potentials.

Since 2017, Drechsler and her team have accompanied the development of the Zeta Potential Analyzer ZPA 20 in several project phases. "In the first phase, we validated data measured with the prototype," says Drechsler. In a second project phase, not only the device but also the measuring cells were further developed. "The aim was to simplify the handling of the measuring cells and to achieve reproducible sample preparation," explains Anja Caspari, a staff member at the IPF.

Streaming potential and streaming current analysis to investigate the zeta potential works as follows: An electrolyte solution is pumped through a measuring cell containing the sample material. Specifically, it is passed between two solid samples or through fiber or powder packing. In the process, the electrolyte solution separates ions that have collected near the surface and takes them with it. This creates a potential difference between the electrodes located on either side of the sample. This difference is measured as streaming potential or streaming current, depending on the sample geometry. These values, together with the pressure difference upstream and downstream of the measuring cell, allow the zeta potential to be calculated.

The Zeta Potential Analyzer ZPA 20 uses a patented measuring method to achieve fast results with high accuracy. Schaubach explains, "The Zeta Potential Analyzer ZPA 20 is the only measuring instrument on the market that uses a bidirectional and oscillating measurement of the streaming potential or streaming current." In this process, the electrolyte solution is pumped over or through the sample not only in one direction, but alternately in opposite directions. In addition, the flow rate of the electrolyte fluid changes in repeated cycles, resulting in pressure changes. The analyzer thus records up to 100 pressure values together with the corresponding streaming potential or streaming current in one second. This produces results with excellent statistical quality in a short time. The analysis software can easily process and evaluate large amounts of data.

The patented measurement method not only saves time during measurements, but also helps to reduce sources of error. The oscillating measurement generates both positive and negative pressure differences and thus positive and negative values of the flow potential or current. This can prevent polarization of the device electrodes. In addition, bidirectional flow can reveal sample surface asymmetries, such as inhomogeneous fiber or powder packing or inadequately fixed samples. The oscillating bidirectional flow of the electrolyte allows such sources of error to be detected and avoided.

During the development of the Zeta Potential Analyzer ZPA 20, special care was taken to ensure that all surfaces are easy to clean in order to avoid cross-contamination. This aspect is particularly important in order to perform accurate, time- and pH-dependent zeta potential measurements. In addition, the Zeta Potential Analyzer ZPA 20 can be extended with optional modules. For example, the LDU 25 liquid dosing system can be used to automatically change the electrolyte composition. This allows the isoelectric point or the adsorption of surfactants to be determined quickly and accurately.

"The cooperation with the IPF helped us to tailor the Zeta Potential Analyzer ZPA 20 to our customers' needs from the very beginning and to design it according to the highest scientific standards," says Schaubach. "We are especially proud that our patented measurement method makes Zeta Potential measurements faster, easier and more reliable than ever before." (OM-3/23)