Comparative Technologies

Technical Note: M111C Comparison: NTA Vs DLS.pdf (Right Click, Save As)

Competing or complementary technologies include Dynamic Light scattering (DLS), also referred to as Photon Correlation Spectroscopy (PCS), and Electron Microscopy (EM).

DLS works on a similar principal to NTA and relates the rate of Brownian movement to particle size. However, rather than giving the particle size on a particle-by-particle basis, it produces an average particle size. It does not provide a visualisation of the particles and simply detects the rate of change of scattered interference resulting from particle Brownian motion. It is a very strong technique for looking at samples with a very narrow range of particle sizes (monodisperse) but has problems with samples with a range of sizes (polydisperse) where the large particles dominate the average produced and hence bias the technique towards a few larger or contaminant particles.

EM, in its wide range of presesentations is a very exact method of measuring particles and is also complemented by NanoSight's NTA technology. Unlike EM, NTA can visualise the particles within a liquid, does not require any significant pre-treatment, is much faster and significantly cheaper.

Nanoparticle Research

Many NanoSight NTA systems are to be found in research laboratories that already have particle sizing instruments and are interested in general particle sizing. Users often find NTA to be a valuable complementary measurement technology and a unique tool in the characterisation of their samples.

Below is a table comparing some of the features of the NanoSight system to other common techniques which may be found in laboratories performing general particle sizing:

*By resolution ratio we mean the ability of the technique to resolve particles of different sizes where the smaller the ratio the better the resolution capacity. DLS has a resolution ratio of about 4, meaning mixed populations of 100 nm and 400 nm particles can be resolved (but not 100 nm and 200 nm). NanoSight's NTA is approximately six-eight times better at 1.5, being able to resolve 100 nm and 150 nm populations. Both techniques require optimal concentrations of the two sizes in the mix to get the best resolution, although NTA is less sensitive to imbalanced ratios of particle size than DLS.

In comparison to DLS, the principle differences to NTA are: 

1. NanoSight conducts particle-by-particle analysis, compared to DLS's average.
2. NTA avoids DLS's bias towards larger particles and better deals with poly-disperse systems.
3. NTA has a resolution of 3:2 vs DLS.
4. NanoSight can detect at much lower concentrations, down to 107 particles per ml, and can estimate concentration.
5. NanoSight analysis does not require refractive index data.
6. NanoSight has a unique image which validates the results and provides additional insight into the sample. The image is information rich and provides a quick and easy way to check a sample.

DLS users understand these limitations and often buy NanoSight to complement or validate their results.