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Posted: February 8, 2008

Russian laser aids in defining nanoparticles

(Nanowerk News) Russian scientists have created a device that determines micro- and nano-particle size using a laser technology that claims to be more accurate than methods currently used in the laboratory and could find a role in pharmaceutical quality control. Most of the technological development in the area of particle size analysis has been in the sub micron area and news of this novel device raises hope of a viable and cheaper alternative to current techniques.
Microscopy with optical scanning and image analysis, sieving, and particle counting by optical and electrical counters are the current standards although each has limitations that make it difficult or impossible to use in certain laboratory scenarios.
Specialists of the St. Petersburg Research-and-Production Firm for Analytical Instrument-Making (LUMEX) in Moscow, Russia, have designed and produced an analyser that not only measures the average diameter of particles, but also determines quantities of a specified particle size within a mixture.
This is particularly important in the drug discovery and diagnostic processes as control or monitoring of operations such as crystallisation, filtration and preparation of the degree of reaction often depend on the ability to measure the size and concentration of small particles that are components of the liquid.
The device, known as Laska, measures the angle of diffused light deflected by the microparticle. The multielement detector records this scattered radiation, allowing the intensity to be measured. The angle of deflection is determined by the size of each particle.
"Our device already enables to perform analysis of particles of up to 500 nanometres in size, i.e., up to half a micron," commented Vladimir Krivoshlyk, head developer at LUMEX.
"Laska was intended for the analysis of rather big particles, with their diameter being no less than a micron. However, we are working now on the analyser modification, which would allow to measure sizes of smaller particles," he added.
The device may potentially have its uses in aspects of quality control for pharmaceuticals where knowledge of particle size distribution and particle shape of pulverised material or suspensions can be a vital factor in filtering out substandard drugs.
The analytical instrument market has struggled to fill this niche area in which current methods battle with each other to become the industry standard. Techniques such as sieve analysis involve passing the material being sized through openings of a particular standard size in a screen.
The particle-size distribution is then reported as the weight percentage retained on each of a series of standard sieves of decreasing size and the percentage passed of the finest size.
Surface Area Analysis involves measurement of the exposed external area of a particle and is achieved by detecting the amount of nitrogen given off after absorption, considering one atomic layer of nitrogen adsorbed. The technique is normally used for characterisation of non-spherical and porous particles.
Particle shape can also be documented with a microphotograph. Particle shape can be quantified by using image analysis in conjunction with SEM. The image analysis unit has the capability to generate an array of chords across the particle to arithmetically define the shape of the particle.
Source: LabTechnologist.com (Wai Lang Chu)
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