Malvern Mastersizer 2000 laser particle size analyzer is one of Malvern's most attention-grabbing products. It perfectly combines advanced laser diffraction technology with highly practical routine particle characterization, and has become the best choice for particle size analysis in laboratories worldwide. Then, what is the principle of Malvern laser particle size analyzer? Why can't the Malvern 2000 testing software be opened after downloading and installation? To help everyone have a basic understanding of Malvern laser particle size analyzer, this article sorts out the principle, usage method and precautions of Malvern laser particle size analyzer. Let's learn together. Malvern Mastersizer 2000, a laser particle size analyzer, is a product produced by Malvern Panalytical in the UK. It is mainly used for wet particle size measurement of unlithified sediments (sediments that have not turned into stones, such as soil; most Quaternary sediments are unlithified) and other disperse materials (which means putting a small amount of soil sample in water to measure their particle size). This laser particle size analyzer is currently an advanced instrument for measuring particle size and is often seen in papers. Except for instrument errors, its measurement accuracy is relatively high. Working Principle of Malvern Laser Particle Size Analyzer Malvern laser particle size analyzer is designed based on the phenomenon of light diffraction. When light passes through particles, diffraction occurs (essentially the interaction between electromagnetic waves and matter). The angle of diffracted light is inversely proportional to the particle size. Particles of different sizes will cause their diffracted light to fall at different positions when passing through the laser beam, and the position information reflects the particle size; particles of the same size will cause their diffracted light to fall at the same position when passing through the laser beam. The information on the intensity of diffracted light reflects the percentage of particles of the same size in the sample. The laser diffraction method uses a series of photosensitive detectors to measure the intensity of diffracted light at different angles by particles of different sizes. By using a diffraction model and mathematical inversion, the particle size distribution of the sample is obtained. The percentage content of particles corresponding to the particle size is obtained through the intensity of diffracted light received by the position detector. The dependence of the intensity of particle diffracted light on the angle decreases as the particle size becomes smaller. When the particles are as small as several hundred nanometers, the diffracted light intensity almost completely loses its dependence on the angle, that is, the diffracted light will be distributed over a wide range of angles, and the light intensity per unit area is very weak, which increases the difficulty of detection. Structural Composition of Malvern Laser Particle Size Analyzer The instrument is mainly composed of three parts: 1. Main unit (including optical components): marked as Mastersizer 2000. The main unit is used to collect raw data for measuring the particle size in the sample. 2. Accessory (sampler): a part like a stirrer with a tube in the middle. In academic terms, it is marked as Hydro 2000G. The accessory is used for sample dispersion (like the fan blades at the bottom), thorough mixing and delivery to the main unit. 3. Computer and Malvern measurement software: Malvern measurement software is used to define and control the entire measurement process, as well as process the measured particle size distribution data, display results and print reports. Performance Indicators 1. Measurement range: particle diameter in the range of 0.02~2000μm in a single measurement. 2. Measurement speed: complete 2000 standard information collections within 4 seconds and draw a 3D particle size distribution map. 3. Form of measurement report: can provide a large amount of information such as particle size distribution data, graphics, average value, median particle size, peak particle size, etc. Usage Method of Malvern Laser Particle Size Analyzer 1. Sample Preparation Sample Collection Sampling in materials generally follows the following 3 principles: - It is best to sample during the movement of materials (or during the production process). - Multi-point sampling. Sample at different positions and depths. For each sampling, mix the samples collected from various points as the bulk sample. - The sampling method should be fixed. Sample Reduction Since the actual amount of sample required for instrument analysis is very small, it is necessary to reduce the collected bulk sample. The process is: bulk sample - laboratory sample - analysis sample. Dry Test Some samples are easy to react with wet dispersants, such as dissolving or swelling when in contact with liquids, so they can only be measured in a dry state. If the sample is agglomerated, it only needs to be dried in an oven. However, fine substances may be damaged when dried in an oven. To remove moisture, the oven should be adjusted to the maximum temperature, but not higher than the melting point of the sample. If the oven has an obvious impact on the sample, a desiccator can be used. Wet Test Wet dispersion technology is adopted. Mechanical stirring makes the sample spread evenly, ultrasonic high-frequency oscillation makes the agglomerated particles fully dispersed, and the electromagnetic circulation pump makes the particles of different sizes evenly distributed in the entire circulation system, thus fundamentally ensuring the accurate repetition of the test for samples with a wide distribution. Selection and Preparation of Dispersion Medium An important principle for selecting the dispersion medium is that the sample cannot dissolve in the dispersion medium. If the sample dissolves, the turbidity will decrease when the sample is analyzed and the turbidity is observed. In addition, if there are bubbles in the dispersion medium, errors will also occur in the calculation results, so degassing should be considered before use. Generally, ultrasonic or boiling methods are used (for volatile dispersion media, gas cannot be removed by heating the dispersant). Surfactant Adding surfactant helps in sample preparation. Surfactant can transfer the charge effect that acts on the sample and causes the sample to float on the surface or agglomerate. Add the activator by the small amount addition method, with the standard of one drop per liter. If excessive, bubbles will be generated, which will affect the measurement results. Use of Ultrasound Ultrasound can not only remove bubbles in the dispersion medium but also help the sample disperse in the dispersion medium. If there are a lot of agglomerated particles at the bottom of the beaker, putting the slurry and its beaker into an ultrasonic bath for dispersion for two minutes will have a very obvious effect. Note Be careful when using ultrasound on fragile particles, as ultrasound may cause particle separation. If there is any doubt about the effect before and after using ultrasound, a microscope can be used for observation. A sample is generally measured repeatedly 3 times, and the average value is taken as the measurement result. If the reproducibility is poor, abnormal results should be eliminated or the sample should be re-sampled for measurement. If problems are encountered in sample dispersion, refer to the following table for analysis. 2. Data Processing The data tested on MS2000 is saved in a file with the suffix .mea, which can be viewed, edited, and reported on any computer installed with MS2000 software. For users who want to make their own particle size distribution charts, they need to use the "Export Data" function in the software to export the original particle size data to Excel. The steps are as follows: 1. First, confirm whether the particle size distribution grade table at the bottom of the "Result Report" is in the default grade - only in this way can the same chart as in the MS2000 software be made. The default distribution grade should be a logarithmic grade from 0.02 to 2000μm. If it is found that the particle size column in the table is not such a grade, go to "Edit" - "User Size" and change it to "Default" format. 2. Select a single or multiple records to be exported in the record view, select "File" - "Export Data" to open the dialog box, and select the corresponding "Template" at the top of the dialog box. 3. Open an empty Excel document, right-click "Paste" in the first cell, and you can see that the previously selected record data is exported. The abscissa we need for drawing is the particle size, i.e., a row of numbers from 0.02 to 2000, and the ordinate is the corresponding numbers in another row, which means the volume fraction corresponding to the particle size grade. 4. When drawing, select all the values of the corresponding abscissa and ordinate at the same time to make an xy scatter plot. Change the format of the abscissa to logarithmic, and you can get the same chart as in the MS2000 software. Precautions for Using Malvern Laser Particle Size Analyzer 1. General Pretreatment Since sediments preserve a large amount of organic matter and calcium carbonate during deposition, which have a great impact on particle size measurement, it is necessary to find ways to remove them, and this process of removing impurities is called pretreatment. Experience in sample pretreatment (for reference only, specific to samples): - Soak the sample in water and add hydrogen peroxide to remove organic matter. - Add hydrochloric acid solution to remove calcium. - If the sample solution is cleaned until it is neutral. - Ultrasonic oscillation is performed on the sample before loading to eliminate the cementation in the sample. - Add a dispersant to reduce the agglomeration of particles. - Select the appropriate ultrasonic time and intensity, and perform ultrasonic again before measurement to ensure that the sample particles are in a dispersed state. - Adjust the pump speed so that particles of different sizes enter the sampler evenly. 2. Instrument Use - Take a small amount of sample (about the size of a mung bean) and put it into a beaker containing 50ml. - Stir evenly with a glass rod. If it is not uniform, it can be oscillated in an ultrasonic cleaner. - Put the sample into a large beaker and start the instrument. - Modify the name of the experimental sample on the computer and save it. Experience in Using Malvern Mastersizer 2000 (Wet Sampling) After several months of actual operation of particle size determination, the following experience is summarized: 1. Sampling Of course, the sample must be representative, and sampling should be reduced by the quartering method or other appropriate methods. These are known to laboratory technicians, so I won't go into details. Just pay attention to the details. The reason for mentioning the sampling problem again is to emphasize that sampling is an important but easily overlooked problem. 2. Sample Preparation Since we use wet sampling, the preparation of the sample involves a dispersion problem. The sample should be prepared into a sample with relatively dispersed stability. I remember that during the installation training, we asked the installation engineer to make a sample for us. Due to the lack of a ready-made method and limited time, the engineer gave us a simple demonstration. As a result, the sample dispersion was not good, and it was easy to agglomerate and precipitate (the turbidity was decreasing). The sample was also easy to adsorb on the sample window, silicone tube, beaker, stirring paddle and other accessories, and the laser intensity decreased rapidly. Later, we conducted experiments on the screening of dispersant concentration and sample concentration. After selecting the dispersant concentration and sample concentration with stable sample dispersion, the sample was not easy to agglomerate and precipitate, and the laser intensity decreased slowly. 3. Background Determination A good background is the basis for obtaining correct and accurate results. The main factors affecting background measurement include: dispersion medium, bubbles, dust, temperature difference, stirring speed, ultrasound, amount of dispersant, sample window, etc. Selection of dispersion medium (including dispersant): select according to product performance and relevant manuals. For example, when choosing water, it is not necessarily the purer the better. The purer it is, the easier it is to get dirty and dissolve more gas, and bubbles are easy to generate during stirring. Fresh distilled water is good. Bubbles: Bubbles come from the dispersion medium. If the dispersion medium can be degassed, the effect will be better. Common degassing methods include vacuum filtration, ultrasonic degassing, and heating and boiling. The wet sampler is equipped with an ultrasonic processor, which is convenient, but the ultrasonic degassing effect is the worst. Bubbles generated by ultrasound are easy to adhere to the stirring paddle, beaker wall, sampling pipeline and sample cell window; it is recommended to use newly distilled water cooled to room temperature. Dust: Dust is everywhere. Try to avoid weighing samples in the instrument room to avoid generating more dust. Keep the instrument room as clean as possible, such as mopping the floor with wet water and wiping tables and chairs; if conditions permit, change shoes and use a clean room. Temperature difference: Preheat the instrument for 15-30 minutes, and balance the dispersion medium and dispersant in the instrument room in advance. It is recommended to install an air conditioner (and use it). Stirring speed: It should be such that the sample does not precipitate and no bubbles are generated; if bubbles are generated by stirring, stop stirring first and start stirring after the bubbles escape. Ultrasound: It is recommended to use external ultrasound treatment before adding to the sampling beaker. Do not use ultrasound during measurement. Amount of dispersion medium: It is recommended to use more than 900ml to avoid easy generation of bubbles during stirring. Sample window: The problem of the sample window is almost the problem of bubbles and dust. Note that after cleaning, do not tighten it too much when installing, as long as the dispersion medium does not leak. If it is tightened too much, the second column of the background will be higher than the first column. 4. Data Collection The sampling problem is also mentioned here. When sampling, attention should be paid to fully mixing the sample, which can be repeatedly sucked and flushed with a syringe to obtain a representative sample. For data collection, attention should be paid to selecting optical physical constants such as refractive index (RI) and sample absorbance that meet the characteristics of the sample and dispersant. In addition, attention should be paid to screening and optimizing the turbidity and sampling time. 5. Data Processing and Reporting If the relevant parameters are not selected properly, the relevant parameters such as RI, absorbance, and data analysis model can be revised through "Edit Results"; the report results can be edited with a report designer to meet the requirements of oneself (company) for the report template. Malvern 2000 Testing Software Fails to Open If other versions have been installed before, uninstall the software, delete the installation directory and registration information, and then start over. If it still doesn't work, there may be a conflict with the operating system, and the system needs to be reinstalled. By now, I believe everyone has a basic understanding of Malvern laser particle size analyzer. In the process of using Malvern laser particle size analyzer, the sample collection work must be careful, which has a direct impact on the results. This article is comprehensively compiled from online sources such as Lu Jiaxin Quaternary Team, Materialren Official Account, and Analysis and Testing Encyclopedia Network.