Instruments particle size

Most modem instrumental particle size analysers readily present data in a variety of forms, such as frequency, cumulative undersize or oversize, and interconvert between number, mass and other distributions. Acquisition of data in a suitable form is therefore not usually a problem. 

Unfortunately, this is not an atypical situation. APIs frequently exhibit rod- or needle-like morphology. Using laser diffraction instruments, particle size distributions of these materials appear as multimodal, making it difficult to assert that... 

Mean hydrodynamic diameters of vesicles (liposomes, nanospheres, nanobeads) can be determined by dynamic laser light scattering, e.g. the NICOMP 380 particle sizing instrument, Particle Sizing Systems (Sta. Barbara, CA, USA). 

Ohtsubo et al. have described a method to identify those parameters which determine the physical strength of PU microcapsules containing liquid insecticide (viz., fenitrothion) [45]. These microcapsules have been found to be effective in con-troUing household pests such as cockroaches. As expected, the strength of the microcapsule depends mainly on the microcapsule mass mean diameter (D), the thickness of the membrane wall (T), and particle size distribution expressed as polydispersity (e.g., D /DJ. The coefficient of variation of the particle size distribution (CV) is first determined using any suitable instrument (particle size analyzer) and method. Wall thickness T is calculated from the following equation ... 

An instrumental particle size analyzer, such as a laser diffraction or electro sensing zone counter, will be appropriate options for measuring particle size distributions. A rotational viscometer will be used to measure apparent viscosity if the suspension results are non-Newtonian. 

Measurements and Instruments. Particles size was measured by DLS Zetasizer Nano S90. Concentration of samples was 0,5 g/1, each sample was sonicated for at least 10 min before measurement. Elemental analysis was conducted to determine ATRP initiator amount on modified HAP particles. Molecular weights and molecular weights distribution of polymers after etching from particles were measured using GPC MIXED-C PLGel (5pm) methylene chloride was an eluent, at 30°C, with a flow rate 0,8 ml/min, polystyren was used as standard for columns calibration. 

The electrical aerosol analyzer and the optical counter are used to measure particle size distributions. Describe the size range and resolution characteristics of each of these instruments. 

Heuer, M. and Lesclioiiski, K., 1985. Results obtained with a new instrument for the measurement of particle size distributions from diffraction patterns. Particle Characterisation, 2, 7-15. 

Despite shortcomings, the Micromerograph in the early 1960 s was the only instrument generally available for determining particle size distribution of sub-sieve pro pint and pyrotechnic ingredients. 

In general, it appears that the Micromerograph, provided that frequent calibration checks are performed, is a good, reproducible instrument for size measurement. The operator time involved is less than with most other methods, and the calcns are not complicated. As in all sedimentation methods, only when the sample particles are spherical does the Stokes diameter that is measured become a measure of absolute particle size. Microscopic examination should be used to check on particle shape and the effect of deagglomeration... 

J.G. Day D.R. Dillehay, ibid, 277-285 3.0) D.E. Middlebrooks, S.M. Kaye, D.J. Edel-man G. Weingarten, Preliminary Evaluation of the Coulter Counter Particle Size Instrument , PATM 1054(1963) 31) J.A. Freitag, Four-... 

Silica gel 60 having particle sizes ranging from 0.063 to 0.200 mm. (70-230 mesh) is suitable. It may be purchased from Brinkmann Instruments, Inc., or E. Merck, Darmstadt, Germany. The submitters report that silica gel of this type normally contains ca. 5% water, which may be removed by drying at 300° for several hours. Somewhat better yields are obtained when the silica gel is dried in this manner before use. 

ALL METHODS FOR PRESENTING DATA FROM THE MEASUREMENT OF PARTICLE SIZE DISTRIBUTIONS, WHETHER INSTRUMENTAL, SEIVING, SEDIMENTATION, OR PHOTOMETRIC METHODS, MEASURE FRACTIONS OF THE TOTAL PARTICLE DISTRIBUTION. IF THE METHOD IS SENSITIVE, THE FRACTION-SEGMENTS CAN BE SMALL, AND THE MEASURED PARTICLE DISTRIBUTION WILL BE CLOSE TO THE ACTUAL ONE. IF THE MEASUREMENT IS LESS SENSITIVE, THERE MAY BE SIGNIFICANT DEVIATIONS FROM THE CORRECT PSD. 

This completes the types of particle distributions that we might encounter. It is now time to show how particle size counting-data are used. To do this, we must select an instrument that produces counts of size of particles correlated with numbers of particles in each size reuige. There are several types of such instruments whose nature will be delineated below. But, first, we must show how this is done. Let us now examine a method of calculating aparticel size distribution. 

Let us suppose that we have a particle counting instrument which sorts and counts the number of particles at a given particle size. The experimental data that we collect are ... 

Permeability is another method for obtaining information about pcirticle diameters. If one packs a tube with a weight of powder exactly equal to its density, and applies a calibrated gas pressure through the tube, the pressure drop can be equated to an average particle size. The instrument based on this principle is called the "Fisher Sub-Sieve Sizer ". Only one value can be obtained but the method is fast and reproducible. The instrument itself is not expensive and the method can be applied to quality control problems of powders. Permeametry is usefiil in the particle range of 0.5 to 50 n. 

Particle Size Laser Refractometiy is based upon Mie scattering of particles in a liquid medium. Up until about 1985, the power of computers supplied with laser diffraction instruments was not sufficient to utilize the rigorous solution for homogeneous spherical particles formulated by Gustave Mie in 1908. Laser particle instrument manufacturers therefore used approximations conceived by Fraunhofer. 

Fraunhofer rules do not include the influence of refraction, reflection, polarization and other optical effects. Early Iziser particle analyzers used Fraunhofer approximations because the computers of that time could not handle the storage cuid memory requirements of the Mie method. For example, it has been found that the Fraunhofer-based instrumentation cannot be used to measure the particle size of a suspension of lactose (R.I. = 1.533) in iso-octane (R.I. = 1.391) because the relative refractive index is 1.10, i.e.- 1.533/1.391. This is due to the fact that diffraction of light passing through the particles is nearly the same as that passing around the particles, creating a combined interference pattern which is not indicative of the true... 

In addition to instrument spreading, which is generally treated as being Gaussian in nature (15, 16), skewing can also be observed in SEC of latices because of entrapment of particles within the porous matrix. This effect generally increases with increasing particle size. 

This technique assumes a Gaussian spreading function and thus does not take into account skewness or kurtosis resulting from instrumental considerations. It can, however, be modified to accommodate these corrections. The particle size averages reported here have been derived usino the technique as proposed by Husain, Vlachopoulos, and Hamielec 23). 

The particle size analysis techniques outlined earlier show promise in the measurement of polydispersed particle suspensions. The asumption of Gaussian instrumental spreading function is valid except when the chromatograms of standard latices are appreciably skewed. Calc ll.ation of diameter averages indicate a fair degree of insensitivity to the value of the extinction coefficient. 

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