Photon correlation spectroscopy, particle size distribution

Methods for analysis of the particle size distribution in the aerosol cloud include techniques such as time of flight measurement (TOE), inertial impaction and laser diffraction. Dynamic light scattering (photon correlation spectroscopy) is confined to particles (in suspension) in the submicron range. In addition to the size distribution, the particle velocity distribution can be measured with the Phase Doppler technique. 

Each of the aforementioned techniques is capable of measuring powder that would be used in low-dose, solid oral dosage formulations. The technique must be compatible with the drug substance, and must be capable of producing the information that is needed. For example, if the particle size distribution is needed to ensure dose content uniformity, photon correlation spectroscopy can only provide an average particle size. In this instance, laser diffraction or image analysis would be more suitable techniques. Table 13.1 contains a comparison of the techniques that have been discussed. 

Photon correlation spectroscopy (PCS) has become a method of choice for sizing particles in the 3-3000nm range. Advances in the analysis of PCS data permit extraction of the particle size distribution as well as the mean diameter. 

Photon Correlation Spectroscopy, Transient Electric Birefringence, and Characterization of Particle Size Distributions in Colloidal Suspensions... 

In colloidal suspensions of anisotropic particles, the static structure factor plays a prominent role in particle size analysis. We have used transient electric birefringence (TEB) and electron microscopy, in addition to laser light scattering, to correlate our analysis of particle size distributions of bentonite suspensions. The complementary nature of TEB and photon correlation spectroscopy (PCS) in particle size analysis will be discussed. 

Beside of the progress in the theory of a particle movement in the zetameter measurement cell, there was progress in particle measurement techniques. New models of zetameters enable automatic measurement of electrophoretic mobility on the basis of the shift of light wave scattered on the particle that moves in the electric field [82]. This technique is called photon correlation spectroscopy (PCS). To increase the sensitivity of the measurement, it is supported by multiangle electrophoretic light scattering (ELS). This combination, allows one also to measure the particle size distribution of the dispersed phase [83]. 

Many papers report the fractionation of polystyrene latexes or mixtures thereof, as such commonly available spherical latex standards are an ideal system to test FFF setups or evaluations (for an example, see [362,401]). Recent coupling of Fl-FFF to MALLS enables a very high precision in particle size determinations. One example is shown in Fig. 31, where two Duke standard latex batches of a nominal size of 100 nm were investigated by Fl-FFF/M ALLS, underlining both separation power and resolution. Using traditional techniques such as photon correlation spectroscopy (PCS) and classic Fl-FFF detection, these samples seem to be identical. However, with Fl-FFF/MALLS, the batches could be separated as two discrete size distributions with a peak size that differed by 3 nm. However, it is not stated if a precise temperature control was maintained so that, critically considered, the observed differences could also have their origin in slight temperature... 

Microspheres intended for nasal administration need to be well characterized in terms of particle size distribution, since intranasal deposition of powder delivery systems is mostly determined by their aerodynamic properties and particle sizes. Commonly used methods for particle size determinations described in the literature are sieving methods [108], light microscopy [58], photon correlation spectroscopy [66], and laser diffractometry [25,41,53,93], The morphology of the microparticles (shape and surface) has been evaluated by optical, scanning, and transmission electron microscopy [66, 95],... 

The diffusion coefficient for a suspension of monosized particles can be measured directly by photon correlation spectroscopy [12] (quasielastic light scattering). For distributions of different particle sizes, the average diffusion coefficient is determined by photon correlation spectroscopy. 

The original Acoustosizer used a single frequency whereas a later development has a range of 13 frequencies between 0.3 and 13 MHz. This allows the measurement of the dynamic mobility spectrum and the determination of the zeta potential and particle size. In order to invert the mobility spectrum into a size distribution a log-normal distribution of particle size is assumed. A comparison with photon correlation spectroscopy for determining particle size and laser Doppler anemometry for particle charge eonfirmed the results using ACS [266]. These and additional sedimentation measurements confirmed that changes in particle size and zeta potential due to dilution effects are likely to occur in aqueous and non-stabilized systems. 

Recently,with respect to the importance of particle size distribution in terms of particle characterization and product physical stability testing, there has been interest in newer light-scattering methods for particle detection called photon correlation spectroscopy (PCS). PCS methods can be applied to both micro-and nanosuspensions. 

A total of 5 0 pL of the ARSL dispersions are diluted with 20 mL of filtered buffer (0.22-mm pore size, polycarbonate filters, Millipore, UK) and sized immediately by photon correlation spectroscopy (Model 4700C, Malvern Instruments, UK), which enables the mass distribution of particle size to be obtained, according to the manufacturer. Size distribution measurements are made at 25°C with a fixed angle of 90° and the sizes quoted are the z average mean (dz) for the ARSL hydrodynamic diameter. 

The measurement of particle size and molar mass distributions are typically carried out off-line with relatively expensive instruments. Techniques used for particle size include transmission electron microscopy, photon correlation spectroscopy, or capillary hydrodynamic fractionation and molar mass measurement with GPC. 

The particle size is measured using photon correlation spectroscopy (PCS) (10), a technique for measuring particle size distributions. When fine particles are suspended in a fluid, they are constantly in random motion as a result of collisions with the molecules of the fluid. This is known as "Brownian Motion," and was first observed in the 1820s. When the suspension is irradiated by a beam... 

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