Accuracy and precision have distinct meanings in the world of particle sizing technology. Generally, accuracy refers to the ability of an analytical device to provide a measurement that is within a defined error from an established, true, and verifiable value. Precision is a measure of the recurrence of a value whether it is accurate or not. Two types of precision can be described: repeatability and reproducibility. In terms of particle size measurement, repeatability refers to the ability of an instrument to repeat its own measurement while the same sample resides in the circulating system. Reproducibility, on the other hand, is related to the comparison of two or more instruments in which representative (repeatable sampling assumed) samples are introduced to each of the instruments. Repeatability is statistically more variation-free than reproducibility because a single instrument measures the same recirculating sample.

Blue Laser Technology is applied to the Microtrac Unified Scatter Technique for Full-Range Particle Size Measurement.  Microtrac development team (owned by L&N at the time) introduced during the 1990's a new "Unified Scatter Technique". This replaced the older differential polarization method with its associated problem of discontinuities when combining two different scatter methods into one integrated particle size distribution. This new method incorporated the use of both a forward and a high-angle detector array in conjunction with a new and unique TRI-LASER System, which effectively multiplies the number of logarithmic detectors available for scattered light detection. The three laser arrangement produced scattered light through an angular range from very close to zero degrees up to 160 degrees, in one continuous pattern. The Tri-laser system has been upgraded to include blue lasers to provide advances in resolution and sensitivity in the submicron and nanosize ranges. The concept of utilizing logarithmic detector design to provide shift-invariance described for tri-laser systems is maintained and extended to the combined use of blue and near-infrared lasers.

Particle Size Measurement of Cement by Laser Diffraction Using Microtrac S3500. The manufacture of Portland cement depends upon many factors, including chemical composition of raw materials, firing temperatures, and particle size. Of particular interest in this note is particle size measurement, since it can affect the efficiency of process grinding and quality of the final product. While there is continuing progress in automated process control, many plants throughout the world control grinding manually and measuring particle size by Blaine air permeability, Wagner photo-sedimentation, and sieve particle size techniques. Blaine and Wagner values are generally related empirically to surface area, which is an indicator of fineness while sieve values provide information on the coarser portion of the particle distribution. These methods do not lend themselves to timely measurements and, therefore, lag various stages of production. The Microtrac particle size analyzer has been used for over 20 years to shorten the time between measurement of particles and process intervention indicated by particle size while aiding the quality control efforts.

Using Microtrac Particle Sizing Analysis to help turn Electric Power Generation By-Products into Wallboard, Cement and Plastics. Coal represents a major contributor to the production of electric power. It also provides coke for production  of steel, gasified coal for production of carbon monoxide and hydrogen to produce Tylenol and NutraSweet, and coal tar for light oils and ammonia. The large amount of coal used for power generation produces byproducts that are deemed deleterious: sulfur dioxide contributes to production of acid rain; nitrogen oxides contribute to acid rain, ozone, and smog; particulates contribute to production of smog; CO2 is believed by some scientists to contribute to global warming. The Clean Air Act of 1970 advanced a beginning to reduce the quantities of these substances emitted to the environment. Subsequent acts placed further requirements to reduce environmental exposure to acid rain (1990) or to adopt Clean-Coal Technology (2005). This paper provides a short outline of some of the advances and positive actions taken by the electric power companies to comply with these acts by using by-products of coal burning for electric power.

This document explains how Microtrac, Inc FLEX software has been designed to satisfy and comply with FDA regulations in 21 CFR Part 11 for electronic records and electronic signatures.

Particle size measurement is an important consideration in modern industrial processes including paints, pigments, cement, pharmaceuticals, sediments, abrasives, coatings and many more. Quite possibly it could be said that there is little that can be touched that has not had some measurement of particle size analysis performed. The increased emphasis on size measurement with concomitant requirement for speed of analysis, serves to enhance productivity and quality. Numerous methods for particle size measurement are presently in use and may number as many as 450 or more, although many of these techniques are not commercially available. The most widely used methods employ laser light scattering, sieves, sedimentation, microscopy, surface area and counting devices. Each method is based upon a specific physical principle causing each to provide data which may be different from others. Often, confusion erupts as to which answer is “correct”. Since the methods rely on implementation of different principles that are based upon certain assumptions, shape factor, bias of a device toward a particular particle feature and other factors prevent the various methods from agreeing. As a result of these effects it may be necessary to compare the data from one method with data from another method. One useful method is to develop a correlation between methods using linear regression techniques.

High-Concentration Submicron Particle Size Distribution by Dynamic Light Scattering: Power spectrum development with heterodyne technology advances biotechnology and nanotechnology measurements. DYNAMIC LIGHT SCATTERING (DLS) is a well-established technique for measuring particle size over the size range of a few nanometers to a few microns; however, at high sample concentrations severe limitations are placed on the DLS measurement. This paper discusses the causes of the high concentration limitations, the means of overcoming the limitations, and the results of measurements at high concentrations. DLS determines particle size from the analysis of the Brownian motion of suspended particles. Light scattered from a moving particle has a Doppler light frequency shift imparted to it. Scattering from a group of particles will have a distribution of shifts from the randomly moving particles. Figure 1 illustrates two measurement configurations that can be employed to extract the Brownian motion information from the frequency shifted, scattered light. Homodyne detection shown on the left extracts the shifts by the interference between the light scattered from each particle with the light scattered by the rest of the particles. The interference or self-referencing removes the high optical frequency, leaving the lower shift frequencies. This is the conventional photon correlation spectroscopy (PCS) geometry, usually measured at a 90° scattering angle.

Recalculation of Microtrac Data to Emulate Data from Sieves, Sedimentation and Other Methods. There are multiple methods that can be used to provide particle size distributions. These include dynamic light scattering (quasi-elastic light scattering) which includes the well known Microtrac method of frequency spectrum analysis (Power Spectrum analysis). Other methods include sedimentation (gravitational and centrifugation), surface area measurement, diffraction (static light scattering), air permeability, sieves (shakers, “tappers”, air-propelled), and counters (image analysis, conductometric, light obscuration). There are many variations of these methods and each can provide a view of the distribution and statistical values associated with a powder or particle slurry. An issue that can arise involves the effects of the material on the measurement. Each measurement is designed upon the premise that particles are spherical. Since most materials are not truly spherical (round particles are not necessarily spheres) each method may be influenced slightly differently. The result is that one method may not provide the identical size and distribution that another method or variation of a method produces. This note addresses the issue of converting data from one method to another. As an example, the widely used sieve method will be compared to Microtrac data while attempting to explain why the differences exist between the methods.

Explanation of Data Reported by Microtrac Instruments (Terminology, abbreviations and calculations shown on reports). Microtrac data include many values that are essential to developing particle size distribution specifications and evaluating data. Each of these items is explained as well as changes to be expected: Sizes, Percentiles, Mean Diameter, Molecular Weight, Calculated Surface, Standard Deviation, Kurtosis, Skewness, etc.

Zeta potential measurements are subject to many influences.The list provided shows several of the most important aspects of parameters that require control to achieve repeatable measurements (Viscosity, Temperature, Conductivity, Concentration). The values requested are voluntary and are not required for zeta potential or mobility measurements to be conducted successfully. The values become a permanent record with any saved data and allow easy record keeping of conditions imposed for the measurement.

Evaluation of Fine Particles in Distributions and the Relationship to Microscopic Evidence.  Microscopy is a technique that has been used for many years to determine the chemical composition, shape, morphology and size of particles. Many types of microscope exist including light microscopy, electron microscopy (useful in determining elemental composition) and atomic force microscopy. Their application encompasses many materials including examination of tissue, bacteria, fungi, minerals, liposomes, pigments, blood cells, viruses, and nanoparticles. Of special concern to this discussion is its use in the determination of particle size distributions especially within the context of the presence of distribution tails or fines when compared to laser light scattering data. This paper describes an experiment in which Microtrac data and competitive light scattering data were evaluated and com ared to optical microscopy and the issues that arise. It is important to note that volume distributions explain more relatively about weight or mass of product. One definition of size that it is the amount of space taken up by an object and can be expressed in terms of volume. Thus volume may be considered a more important indicator of size than the number of particles present. The volume is important in particle size since product amount is generally determined by weight and not by how many particles are present. It would be sorely difficult to specify an amount needed in a formulation by counting particles when it is much more easily accomplished by weighing. An analogy to this is in chemistry where the use of moles substitutes for the laborious need to count molecules related to Avogadro’s number (6.02E 23 molecules/mole). Using moles assists calculations in stoichiometry and is directly related to mass (weight) of a compound. This is akin to using weight rather than count when product quantities are determined. Modern light scattering instruments afford a direct relationship to weight through the volume distribution.