Experts in Particle Characterization


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NanoBrook 90Plus PALS

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 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 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.


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.

Surface Zeta Potential - Principles of Operation

The Surface Zeta Potential feature allows the user to measure the electrical charge on materials like coated glass, plastic, tape, or other flexible surfaces. A series of measurements are taken on probe particles at different distances from a surface and the Surface Zeta Potential is calculated as shown:

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.

Principles of Operation - Particle Sizing using DLS

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.


Narrow latex with Particle Solutions

InstrumentNom. 90Nom. 273Nom. 111Nom. 400
A 91±1 276±1 110±1 404±4
B 90±1 279±1 108±1 391±3
C 90±1 276±1 109±1 399±3
D 90±1 277±1 110±1 397±3
E - - 112±1 394±3
Std. Err±0.3%±0.3%±0.6%±0.6%
Test Results from Brookhaven Instruments Particle Size Analyzers(diameters, in nm)

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.

90Plus 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

Principles of Operation - Phase Analysis Light Scattering (PALS)

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 m 2/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 graphing with Particle Solutions
Figure 1

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.

Electrophoretic Mobilities Determined with the NanoBrook 90Plus PALS
(units 10-8 m2 /V·s)
SamplePALS ResultLit. ValueComments
NIST 1980 2.51 ± 0.11 2.53 ± 0.12 Electrophoretic mobility standard.
Blood Cells -1.081 ± 0.015 -1.08 ± 0.02 Dispersed in physiological saline
Fe2O3 0.013 ± 0.0015 N.A. Dispersed in dodecane
TiO2 0.255 ± 0.010 N.A. Dispersed in toluene - not dried
TiO2 0.155 ± 0.011 N.A. Dispersed in toluene - dried
TiO2 -0.503 ± 0.015 N.A. Dispersed in ethanol
Casein -0.025 ± 0.002 N.A. Dispersed in PEG - viscous
SiO2 -0.73 ± 0.04 N.A. Dispersed in 2.0 M KCl - High salt

Table 1

Custom Columns

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

Custom columns with Particle Solutions
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.


Typical Applications

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
  • Specifications


    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 10 µm, 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.

    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 40 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
    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

    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.
    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.
    BI-SZP Surface Zeta Potential
    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-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 PALS may upgrade to include backscatter provided their instrument has the necessary mechanics, optics and hardware. Contact the factory for more information.


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