Brookhaven - NanoBrook 90Plus Zeta Potential Analyzer

NanoBrook 90Plus

Zeta Potential Analyzer Utilizing Phase Analysis Light Scattering

Features at a glance


Rapid and accurate particle size distributions

Multimodal & unimodal size distribution software

ISO 13321 and ISO 22412 compliant results

Range > 0.3 nm to 6 µm

Customizable reports

Ideal for fast, routine sizing applications in research or quality control

High power 35 mW diode laser

Dynamic light scattering at 90°

Temperature control, -5 °C to 110 °C

Compact bench top unit, USB connection


Zeta potential for the difficult cases

For proteins, peptides, mAb, RNA, and other biological samples

For zeta potential in organic solvents

For oily or viscous media

For high-salt suspensions

For samples near the I.E.P.

1,000 times more sensitive than other techniques

Disposable cuvettes, no contamination or alignment

Built in automatic procedures and parameters (SOP)

Easy to use

Brookhaven's NanoBrook 90Plus PALS instrument combines our NanoBrook 90Plus and NanoBrook ZetaPALS instruments in to one powerful package for sizing and zeta potential analysis. With over a decade of proven records in diverse applications, Brookhaven's pioneer Phase Analysis Light Scattering (PALS) technology remains a step ahead of the competition. This package delivers unparalleled zeta potential (surface charge) measurement sensitivity and accuracy. It also provides unique real-time (in-situ) monitoring capability for electrophoretic response of particles/molecules under an electric field, a valuable tool ONLY from Brookhaven for delicate biological entities like proteins and exosomes. It has been successfully utilized in nearly every possible suspension environment from high salts such as PBS and sea water to organic solvents and of course aqueous solutions.

Reliable, Accurate, and Easy to Use

The new NanoBrook 90Plus PALS particle size and zeta potential analyzer incorporates all you need for fast, routine, sub-micron measurements of size and zeta potential. Based on the principles of Dynamic Light Scattering (DLS) for particle sizing and distribution, and based on phase analysis light scattering for zeta potential measurements; most measurements only take a minute or two.

Two Scattering Angles:

Particle sizing measurements will be made at the 90° scattering angle. Zeta potential measurements are always done using the 15° detection angle to minimize diffusion broadening.

Dilute suspensions, on the order of 0.0001 to 1.0% v/v are prepared, using suitable wetting and/or dispersing agents. A small ultrasonicator is sometimes useful in breaking up loosely-held agglomerates. Two or three mL of suspension are required to make the measurements. Disposable, polystyrene square cells are used for aqueous and simple alcohol suspensions. Disposable, glass round cells with reusable Teflon stoppers are used for aggressive solvent suspensions. Just a few minutes are required for the sample and cell to equilibrate with the actively controlled temperature environment inside the NanoBrook 90Plus PALS. A square glass cell is available if desired and special small-volume cells may be used to reduce the volume of material needed to just 50 µL or 10 µL. For aqueous samples the 50 µL is a disposable cuvette. In all cases the sample is recoverable. For very small particles the high-sensitivity BI-APD detector is invaluable.

90Plus Narrow Latex


Perhaps the most important benefit for users is the reproducibility from sample-to-sample, operator-to-operator, and instrument-to-instrument. The table to the right shows the results obtained for polystyrene latex. Notice the Std. Error of the Effective (or Average) Diameter is less than 1% of the mean of the 10 repeated runs. Such excellent repeatability is typical of the NanoBrook 90Plus particle size analyzer for QC analysis and ensures product quality time-after-time. The table also shows several aspects of the inter-instrument repeatibility found with routine Brookhaven dynamic light scattering equipment. To test the reliability of the information obtained with Brookhaven Instruments a customer subjected five instruments in five locationswith different operators and using four different samples for examination. The table above shows excellent reproducibility with recognized standard materials and superb internal agreement. You can be confident of the results you get with your NanoBrook 90Plus!

Data Presentation

The NanoBrook 90Plus PALS particle size and zeta potential analyzer offers three choices. For routine determinations an average diameter (Eff. Dia.) and a measure of the distribution width (Polydispersity) are sufficient for many applications. The second choice is to fit these values to a lognormal distribution, allowing the user to visualize the size distribution and to interpolate cumulative and differential results at 5% intervals.

92 and 269 bimodal

Results from Test Bimodal Sample on NanoBrook 90Plus PALS (diameters, in nm)

The figure above shows an example of the third choice, suitable for more complicated, multimodal size distributions. Here, a numerical algorithm, including Mie theory, is used. These results are for a mixture of known latex particles. Positions of the measured particle sizes on the accompanying graph are in excellent agreement with the known sizes of 92 and 269 nm.

During a measurement, the display can be switched interactively between any one of these -- correlation function, lognormal, or multimodal -- each shown "live" as data are accumulated. The live display is particularly useful in determining the end-point of a measurement where multimodal distribution shape may be important

For measurements of very low mobilities, the NanoBrook 90Plus PALS is the answer. The only answer! With concepts developed at Bristol University and Brookhaven Instruments, the NanoBrook 90Plus PALS determines zeta potential using Phase Analysis Light Scattering: A technique that is up to 1,000 times more sensitive than traditional light scattering methods based on the shifted frequency spectrum.

Electrostatic repulsion of colloidal particles is often the key to understanding the stability of any dispersion. A simple, easy measurement of the electrophoretic mobility "even in nonpolar liquids" yields valuable information. Measurements made in water and other polar liquids are easy and fast with the NanoBrook ZetaPlus. Such measurements cover the range of typically ± (6 to 100) mV, corresponding to mobilities of ± 10-11 to 10-7 m2/V·s. The NanoBrook 90Plus PALS covers this full range, of course, and extends it by a factor of 1000 in sensitivity!

The NanoBrook 90Plus PALS utilizes phase analysis light scattering to determine the electrophoretic mobility of charged, colloidal suspensions. Unlike its cousin, Laser Doppler Velocimetry (LDV) (sometimes called Laser Doppler Electrophoresis (LDE)), the PALS technique does not require the application of large fields which may result in thermal problems or denaturation. This is due to the fact that the measurement analyzes the phase shift. The particles need only to move a fraction of their own diameter to yield good results. In salt concentrations up to 2 molar and with electric fields as small as 1 or 2 V/cm enough movement is induced to get excellent results. In addition, the Autotracking feature compensates for thermal drift.

zetapals ps graph

Simple Clear Presentation

Figure 1 above shows the results of an actual experiment with a NanoBrook 90Plus PALS instrument. The important parameters and results are seen at a glance. The excellent agreement of the five runs in this experiment is obvious as is the match of expermental curve (red, bold) and it's fitted version (red, thin). As with all Brookhaven instruments the user can simply produce a customized report.

Multiple Sample Types

Table 1 below shows a variety of difficult to measure samples, all of which were easily measured with the NanoBrook 90Plus PALS. Some were measured in high salt concentration; some in low dielectric constant non-polar solvents; and one in a viscous liquid.

Custom Columns

The software can be easily customized to display the columns needed for a quick review of the important parameters as shown below

zetapals ps columns

Figure 2

Something More Challenging

Of course the NanoBrook 90Plus PALS can quickly and easily yield results from all "regular" samples but its real strength is in the difficult cases and to demonstrate the performance of this premium instrument where others fail, we offer the following table:

Biological samples such as proteins, antibodies, peptides, DNA/RNA are easily denatured by electrical fields. The NanoBrook 90Plus PALS can successfully measure the mobility of biological samples with typical voltages from 2 to 4 Volts. In Figure 1 above, Lysozyme was measured with 2.5 Volts applied.

Aggressive Solventssuch as DMF, THF, DMSO, MET, etc. are easily accomodated by Brookhaven's NanoBrook 90Plus PALS system with the use of our special solvent resistant electrodes and glass sample cells. The extension of zeta potential measurements into the realm of such systems is just another standout property of the NanoBrook 90Plus PALS. Some examples of this are shown in Table 1.

High salt concentrations difficult to measure due to the Joule heating and energy dissipated. The power applied in high salt has to be kept low in order to avoid affecting the sample. Only Brookhaven's NanoBrook 90Plus PALS can measure in salt conditions up to 2 Molar. An example is shown in Table 1.

Unusual solvent? If your solvent is unusual then it's dielectric constant is probably unknown. In thise case our BI-870 Dielectric Constant Meter will quickly, easily, and accurately provide the information necessary for a zeta potential determination.

Sample Type: Sizing:  nanoparticle and colloidal-sized materials, in any non-absorbing liquid., Zeta potential: proteins, nanoparticle, polymer and colloidal-sized materials, suspended in any non-absorbing liquid, with relative permittivity (dielectric constant) > 1.5 and viscosity < 30 cP.

Size Range: Sizing:  0.3 nm to 6 µm diameter, depending on refractive index and concentration, Zeta potential: 1 nm to 100 µm, sample dependent

Mobility range: 10-11 to 10-7 m2 / V * s

Zeta potential range: -500 mV to 500 mV, sample dependent

Maximum sample conductivity: Sizing: unlimited, Zeta potential: 220 mS/cm, covering saline and PBS solutions for proteins; sample dependent

Sample cells: Sizing: 1 to 3 mL disposable plastic, 50 µL disposable, 40 µL quartz flow cell, 10 µL quartz minimum, Zeta potential: 180 µL, 600 µL, 1250 µL

Concentration range: Sizing: 2 ppm to 50 mg/mL, depending on refractive index and concentration, Zeta potential: 40% v/v, sample dependent

Signal processing: Sizing: Dynamic Light Scattering, DLS, Zeta potential: Electrophoretic & true Phase Analysis Light Scattering, ELS & PALS

Correlator: Brookhaven's TurboCorr, multitau, research grade with 510 hardware channels, covering the equivalent of 1010 linearly-spaced channels, 100% efficiency, real-time operation over the entire delay-time range.

Precision: Sizing:  ± 1% typical, Zeta Potential: ± 3% typical

Temperature control range: -5 °C to 110 °C ± 0.1 °C

Condensation control: Purge facility using dry air, nitrogen preferred

Standard laser: 35 mW red diode laser, nominal 640 nm wavelength

Scattering angle: 15° & 90°

Data Presentation: Average & width, lognormal fit, and multimodal size distribution for sizing., Doppler Frequency Shift, electrophoretic mobility, zeta potential using Smoluchowski, Hückel, or Henry

Compliance: ISO 13321 and ISO 22412 compliant results for sizing

Power Requirements: 100/115/220/240 VAC, 50/60 Hz, 150 Watts

Dimensions: 23.3 x 42.7 x 48.1 cm (HWD)

Weight: 15 kg

Environmental Characteristics: Temperature 10 °C to 75 °C, Humidity 0% to 95%, non-condensing

CE certification: Class I laser product, EN 60825-1:2001, CDRH

Options for particle sizing at 90°

BI-APD: Avalanche photo diode, up to 10 times the sensitivity

90PDP: Absolute molecular weights of polymers in solution. Option includes µL flow cell (90PFC) and Debye plot software, requires BI-APD. Relative molecular weight calculated from the DLS determination of the diffusion coefficient is standard.

BI-PSD21: 21 CFR Part 11 software to assist ERES compliance sizing only.

BI-IQOQPQ: Qualification for installation, operation and performance for sizing and zeta.

BI-SFS: Sample filtration system provides fast and convenient way to clean your light scattering samples, a necessity for samples smaller than 20 nm. Utilizing Teflon® tubing and nonreactive components, the BI-SFS is compatible with most sample filtration needs provided there is at least 5 mL of liquid. For protein and other rare samples, use 20 nm BI-DF20AQ Anatop filters instead.

Lasers: 5 and 10 mW, HeNe laser at 632.8 nm wavelength, 50 mW and higher powered, frequency-doubled solid state lasers at 532 nm wavelength

Accessories for particle sizing at 90°


BI-SCP: Box of 100 plastic cells with caps, 2.2 to 4.5 mL volume. Use with water, for sizing and zeta.

BI-RCG: Box of 250 round glass cells with 25 reusable Teflon caps, 1.9 to 4 mL volume. Use with solvents, requires BI-RCH.

BI-RCH: One round cell holder for use with BI-RCH

BI-SM50: Box of 80 plastic cells, disposable, 50 µL volume, sample retrievable, requires Bi-SM50A. Use with water.

BI-SM50A: One sample cell adaptor for use with BI-SM50.

BI-SM10: One 10 µL quartz cell for sizing of small and rare samples, sample is retrievable.

90PFC: Additional 40 µL quartz flow cell for use with 90PDP

Reference Materials 

BI-LTX92: Latex reference material for validation of sizing, 15 mL, 92 ± 3 nm.

BI-SVK92: Starters validation kit for sizing, 2 mL, 92 ± 3 nm.

BI-CC: Nitrogen-purge facility for condensation control.

Options for zeta potential

BI-ZTU: Autotitrator, 4-pump, pH, temp, conductance for use with acids, bases, surfactants, dispersing agents, salts and other additives to determine the IEP and trend of zeta potential with concentration of additive. BI-ZTU includes one BI-ZELF-P and one BI-ZELF-P/B for use with aqueous samples.

BI-ZELF-P: Plastic electrode assembly for use with BI-ZTU in flow mode, including one BI-ZELF-P/B

BI-ZELF-P/B: Box of 2 plastic flow cells for use with BI-ZELF-P

BI-ZELF-G: Solvent resistant electrode assembly for use with BI-ZTU in flow mode, including one BI-ZELF-G/B glass cell, for use in solvents

BI-ZELF-G/B: Additional glass cell for use with BI-ZELF-G

BI-870: Dielectric constant meter improves accuracy when calculating zeta potential in solvent mixtures and speciality solvents.

BI-PALS21: 21 CFR Part 11 software to assist ERES compliance.

Accessories for zeta potential

BI-SREL: Solvent resistant electrode assembly for use with BI-SCGO glass cells, inconvenient for use with BI-SCP cells.

BI-SCGO: Box of 10, open-topped glass cells for use with solvents.

When working in saline and other high salt concentrations use one of these electrodes*:

BI-ZEL: Electrode assembly for aqueous systems, use BI-SCP cell, 1.25 mL sample volume.

BI-ZEL2: Electrode assembly for aqueous systems, use BI-SCP cell, 450 µL sample volume.


BI-SVE175: Electrode assembly for aqueous systems, with BI-SCP cell, 175 µL sample volume

BI-ELECCK: Electrode cleaning kit including wand and polishing strip, for use with BI-ZEL and BI-SREL

BI-ZR5: Zeta reference material for validation, blue pigment for use in water, - (44 ± 8) mV.

While it is tempting to buy just the solvent resistant electrode assembly and use it with the glass cells (BI-SCGO) in solvents and the plastic cell (BI-SCP) if measuring in saline or other aqueous environments, it is a mistake on two accounts. First, cross-contamination is a problem with small sample volumes such as those found in zeta potential determinations. Second, the solvent resistant assembly has to be small enough to clear the inside dimensions of the glass cells to prevent cracking. It is less convenient when removing the assembly and cells. But the standard BI-ZEL electrode can fit snugly into the BI-SCP cells and so both are convenient to remove when measuring in aqueous-based samples.

Note: current users of the 90Plus PALS may upgrade to include backscatter provided their instrument has the necessary mechanics, optics and hardware. Contact the factory for more information.


Polymer latexes

Pharmaceutical preparations

Micelles, Liposomes, Exosomes

Oil/Water and Water/Oil emulsions

Proteins, IgG, peptides, RNA/DNA

Paints and pigments



Pigments, inks and toners

Cosmetic Formulation

Liposomes and biocolloids

Ceramics and refractories

Emulsions (foodstuffs, cosmetics)

Wastewater treatment monitoring

Carbon blacks

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