![]() I measured the size of QDs using Zetasizer Nano ZS90. The solution was then sonicated for 40 minutes to break up any possible aggregates. Before each measurement the QDs were diluted in ddH2O (the finial concentration of the solution was 0.03ppm,0.1ppm,1ppm,10ppm,50ppm). The excitation and emission wavelength (EX/EM)of the QDs were 340/440nm and 271/580nm respectively, and the concentration of the two different QDs both were 1mg/mL. Two types of Water- soluble carboxyl quantum dots-a carbon quantum dot and a CdTe/ZnS/CdS quantum dot were used in my measurement. Peter Cullis and Marcel Balley did a lot of research on this in the late 80s early 90s. Also, freezing and thawing prior to extrusion can reduce the number of internal lamella and depending on the lipid composition, convert from multilamellar to oligolamellar. Vortexing at maximum speed for 0.5 minutes vs 5 minutes can reduce the size distribution. Also the comment regarding microscopic evaluation using wetmount can also yield telling results. Laser diffraction is an alternative for micro size particles. ![]() Measurements outside of the recommended range, such as PDI >7, are not representative of the sample. For example, some DLS instruments supply guidelines for quality factors, such as polydispersity index (PDI) or if the amount of scatter is too high or too low. With regard to measuring a lipid suspension with DLS, it is dependent on the instrument. If bubbles are indeed the issue and not aggregation, applying a light vacuum to the sample after extrusion can eliminate the bubbles. No pre-filtering of the sample is required by the user.Ĭontact us for a quote or to discuss your particle sizing needs.The lipid composition, the composition of the hydration buffer and any steps between hydration and extrusion would be need to comment on the potential for aggregation. Particles larger than the nanoconstriction are removed before reaching it by filters that are built into the cartridge. The heart of the instrument is the microfluidic cartridge, which allows the electrical detection of nanoparticles as they pass one by one through a nanoconstriction. Spectradyne’s nCS1 instrument and associated analysis cartridges, are based on Spectradyne’s patented nanoparticle analyzer (NPA) technology. Not relying on optical technology, the Spectradyne system can be used for protein aggregation studies, extracellular vesicle analysis, nanomedicine, virus studies etc.ĭisposable microfluidic cartridges eliminate cross contamination and make operation simple and straightforward from just 2-3µl of sample. The instrument measures individual nanoparticles to produce particle size distributions with quantitative concentration information for particles from 40nm to 2000nm in size. The Spectradyne nCS1 TM instrument provides a unique platform for the rapid quantitative measurement of Nanoparticle size in solution. The Spectradyne’s nCS1 TM has taken the Coulter Counter method and re-engineered the principle, it is now possible to count and size individual particles down to 50nm. The most Modern Beckman Coulter LS 13320 XR system can now produce real data down to 10nm using the Patented PIDS system. The approach has been validated by many of the other manufacturers trying to partially copy this by adding additional wavelength measurements. By combining vertically and horizontally polarised light with multi-wavelength measurements, a much more accurate and reliable measurement can be made below 0.4µm. Particles scatter polarised light by differing amounts. Beckman Coulter developed a patented detection system ‘Polarisation Intensity Differential Scattering’ (PIDS) to overcome the limitations of laser diffraction in this region. Some manufacturers take the intensity data down to this size level and then make effectively an educated guess at the data below in order to show something down to 0.1µm. However, once the size gets below 1µm, there is little or any discernible shape to the intensity ‘curve’ making the discernment of any angular variation virtually impossible below approx. For relatively large particles such as 20µm, this is relatively easy as the intensity minima are well defined, see below: The technique of laser diffraction requires the ability to measure the angle of diffraction of the laser light in order to ascribe a size to the particle. ![]() ![]() The material is analysed using its laser scatter pattern. The particles are placed in a flow cell between the laser and its focal point. The angle of the laser beam and particle size have an inversely proportional relationship, where the laser beam angle increases as particle size decreases and vice versa. The intensity of light scattered by a particle is directly proportional to the particle size. Laser diffraction analysis is based on the Fraunhofer diffraction theory. ![]()
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