NanoBrook 90Plus Zeta

Brookhaven’s NanoBrook 90Plus Zeta instrument combines our NanoBrook 90Plus with the Electrophoretic Light Scattering (ELS) technology of the NanoBrook ZetaPlus and is optimized for performance in aqueous suspensions and low salt environments.


Powerful Analyses at your Fingertips

Brookhaven’s NanoBrook 90Plus Zeta employs Dynamic Light Scattering (DLS) for particles/molecules size and Electrophoretic Light Scattering (ELS) for zeta potential determination. This package not only allows rapid measurements of the effective size and zeta potential of samples, but also provides further information on multi-modal distribution in size and zeta potential in polydisperse samples. Based on the proven technologies of Brookhaven, the NanoBrook 90Plus Zeta guarantees excellent mobility measurement performance in aqueous suspensions and low salt environments.

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 10 µm
  • Customizable reports
  • Ideal for fast, routine sizing applications in research or quality control
  • High power 40 mW diode laser
  • Dynamic light scattering at 90°
  • Temperature control, -5 °C to 110 °C
  • Compact bench top unit, USB connection


  • Zeta potential in low salt aqueous solutions/suspensions
  • Accurate, rapid, easy to make zeta potential determination
  • One piece, easy-fill disposable sample cells
  • No cell alignment or calibration
  • Zeta potential at 15°
  • Temperature control, -5 °C to 110 °C
  • Customizable reports, two parameter plots, graphical overlays
  • Can resolve multi-modals
  • Built in automatic procedures and parameters SOP

Measurement Principles


Simple fluids like water (low viscosity), glycerin (high viscosity) are Newtonian and exhibit viscosity effects, the dissipation of energy when particles move in such fluids. But dissolve macromolecules in these liquids –synthetic or biopolymers—and networks can form. In addition to viscosity effects, there are now elasticity effects, the storage of energy when embedded particle move. By following the mean square displacement (MSD) of tracer (probe) particles in such fluid and microrheological properties such as η*, the complex viscosity, G″, the viscous loss modulus, and G′, the elastic storage modulus, can be determined as a function of frequency.

Measurement of the autocorrelation function (ACF) using DLS techniques yields the MSD of tracer particles, which, under the right conditions, can be used to determine η*, G″, and G′ over a range of frequencies much higher than mechanical rheometers can attain. Much smaller sample volumes, in the microliters, are possible compared to mechanical instruments. Finally, since strains result from the thermally driven motion of tracer particles, these much smaller strains allow the study of fragile samples. The study of viscoelasticity in aggregating dilute protein solutions is a prime example of the benefits of DLS microrheology.

Reliable and Accurate Analysis

The new NanoBrook 90Plus Zeta particle 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 electrophoretic light scattering (ELS) for zeta potential measurements, most measurements only take a minute or two. Please see the 90Plus PALS for instruments combining sizing and PALS zeta potential.

Two Scattering Angles:

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

Principles of Operation – Particle Sizing using DLS

Dilute suspensions, on the order of 2 ppm to 50 mg/mL 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 is 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 Zeta.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.

image of summary statistics reportFigure 1



Perhaps the most important benefit for users is the reproducibility from sample-to-sample, operator-to-operator, and instrument-to-instrument. The figure above shows the repeatability of the results obtained by one instrument for a silica (LUDOX) sample. Notice the Std. Error of the Effective Diameter is less than ½% of the mean of the six repeated runs. Such excellent repeatability is typical of the NanoBrook 90Plus Zeta for even routine QC analysis and ensures product quality time-after-time.

Nom. 90 Nom. 273 Nom. 111 Nom. 400
91±1 276±1 110±1 404±4
90±1 279±1 108±1 391±3
90±1 276±1 109±1 399±3
90±1 277±1 110±1 397±3
112±1 394±3
90.3 277.0 109.8 397.0
Std. Err
±0.3% ±0.3% ±0.6% ±0.6%
Test Results from Brookhaven Instruments Particle Size Analyzers (diameter in nm)

The table to the right shows several aspects of the inter-instrument reproducibility 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 locations with different operators and using four different samples to examination. This table shows excellent reproducibility with recognized standard materials and superb internal agreement. You can be confident of the results you get with your NanoBrook 90Plus Zeta!

Data Presentation

The NanoBrook 90Plus Zeta 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.

image of results from bimodal test
Results from Test Bimodal Sample on NanoBrook 90Plus Zeta (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.

Reliable, Accurate, Easy to Use

The NanoBrook 90Plus Zeta is the simplest and most accurate particle electrophoresis system available. This revolutionary instrument has been designed to eliminate the shortcoming inherent in other zeta potential instruments. The 90Plus Zeta software is simple and intuitive to operate but yet offers flexibility and a full range of means for those that wish to tune their experiments to specific circumstances.

The screen image shown below indicates the clear and concise presentation. Information obtained from the sample is updated in real time and the user can select from several display formats. A literature of physical constants for many usual suspending fluids is provided but the user may provide their own values if desired. Printed reports are fully customizable.

image of surface zeta potential

Comprehensive Information

The NanoBrook 90Plus Zeta measures complete electrophoretic mobility distributions in seconds including multimodals (an example of bimodal zeta potential sample can be seen on the result screen from analyzing a created mixture of charged particles.)

In the example below the results of analyzing a mixture of alpha and gamma Aluminas in 1 mMolar KCI at pH10 is displayed. The left peak is identified with the green curosr and shown to have a zeta potential of -75 mV. If the other peak is chosen the value given is -5.00 mV. The ability of the NanoBrook 90Plus Zeta to provide this information distinguishes it from other methods which provide only an ensemble average.

image of test results

Derive Extended Information

The user can tabulate or graph any appropriate pair of parameters allowing, for example, the determination of the iso-electric point (IEP) as in the example below. The NanoBrook 90Plus Zeta is provided with a pH probe that can be used to measure this value.

image of iso-electric point

Unique Cell Design

The unique cell configuration eliminates the electroosmotic effect: No stationary levels, no alignment, and no calibration are required; as evidenced by the excellent agreement with NIST1980, a standard reference material. The NanoBrook 90Plus Zeta uses low cost, disposable sample cells. There is no assembly or maintenance required: Cross contamination is eliminated. Glass and quartz cells are available optionally. The same basic cell design is used with the NanoBrook 90Plus Zeta, ZetaPALS, 90Plus PALS, and Omni.

Typical Applications

  • Nanoparticles
  • Polymer latexes
  • Pharmaceutical preparations
  • Micelles, Liposomes, Exosomes
  • Oil/Water and Water/Oil emulsions
  • Proteins, IgG, peptides, RNA/DNA
  • Paints and pigments
  • Colloids
  • Polymers
  • Pigments, inks and toners
  • Cosmetic Formulation
  • Liposomes and biocolloids
  • Ceramics and refractories
  • Emulsions (foodstuffs, cosmetics)
  • Wastewater treatment monitoring
  • Carbon blacks




Sample Type Sizing: nanoparticle and colloidal-sized materials, in any non-absorbing liquid.

Zeta potential: nanoparticle, polymer and colloidal-sized materials, suspended in any non-absorbing liquid, with relative mermittivity (dielectric constant) > 20 and viscosity < 5 cP.

Size Range Sizing:  > 0.3 nm to 10 µm, dependinjg on refractive index and concentration.

Zeta potential: 1 nm to 100 µm, sample dependent.

Mobility range 10-9 to 10-7 m2 / V * s
Zeta potential range -220 mV to 220 mV, sample dependent
Maximum sample conductivity Sizing: Unlimited

Zeta potential: 7.5 mS/cm

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 Light Scattering, ELS

Correlator Brookhaven’s TurboCorr, multitau, research grade with 510 hardware channels, covering the equivalent of the 1010 linearly-spaced channels, 100% efficiency, real-time oepration over the entire delay-time range.
Precision Sizing: ± 1% typical

Zeta potential: ± 3% typical

Temperature control range -5 °C to 110 °C ± 0.2 °C
Condensation control Purge facility using dry air, nitrogen preferred
Standard Laser 40 mW red diode laser, nominal 640 nm wavelength
Scattering angle 15° & 90°
Data Presentation Average & wdith, 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
Diemensions 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

Notes: (*) Sample type dependant

A policy of continual improvement may lead to specification changes.

Options & Accessories

Options for particle sizing at 90°

BI-APDx Avalanche photodiode, up to 3 times the sensitivity of an APD and up to 5 times the sensitivity of a PMT
90PDP Absolute molecular weights of polymers in solution. Option includes µL flow cell (90PFC) and Debye plot software. 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 Additional options available; contact us for more information.

Accessories for particle sizing at 90°

Cells: BI-SCP Box of 100 plastic cells with caps, 2.2 to 4.5 mL volume. Use with water, for sizing and zeta.
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 and one BI-ZELF-B for use with aqueous samples.
BI-ZELF Plastic electrode assembly for use with BI-ZTU in flow mode, including one BI-ZELF-B
BI-ZELF-B Box of 2 plastic flow cells for use with BI-ZELF
BI-870 Dielectric constant meter improves accuracy when calculating zeta potential in solvent mixtures and speciality solvents.

Accessories for zeta potential

BI-SCP Box of 100 plastic cells, use with BI-ZEL electrode assembly and aqueous samples.
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.

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

Download Brochure

NanoBrook 90Plus Zeta Brochure PDF

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