This chapter provides information on wet and dry measurement sample preparation.
Overview
in
Particle size test
Preparation of the pre-sample is very important, encountered in the measurement
most
The problem is caused by insufficient sample preparation,
such as
The sample agglomerates, dissolves, floats on the surface, or does not get a typical sample, and the result is an error.
So to find
An effective way to ensure the sample is fully prepared. Once the appropriate dispersion technique is found, the procedure is standardized to compare the two samples.
Typical sampling
When measuring the sample, make sure that the sample used is representative. If the sample is taken from a bottle or container, it must be ensured that the sample is thoroughly mixed. If the sample is powdery, large particles tend to float on the surface of the container, and small particles tend to sink to the bottom.
Most samples will have some large particles, and some small particles, but most of them are in the middle of the two extremes, the sample is taken from the surface of the container, most of the measurements are large particles, if compared with the sample taken from the middle of the container, The results will be significantly different.
If the sample is stored in a container, the sample should be thoroughly mixed before measurement. Do not shake the container as this will speed up particle separation. Instead, hold the container with both hands and gently roll it to change direction.
20
Second, this method is better when the container is half full. Liquid samples may also be separated in the presence of the container, with large particles sinking into the bottom. To extract a typical sample, the sample should be thoroughly mixed. It should be noted that when the magnetic stirrer mixes the liquid sample, large particles are easily moved outside the container due to centrifugal separation, which tends to cause sample deviation.
Dry sample should pay attention to the problem
The first step in measuring a sample for the first time is to decide whether to analyze the sample in wet or dry conditions. This is determined by what sample is ultimately used. If the sample is used or stored in a dry condition, a dry analysis method is preferred.
Some samples tend to react with wet dispersants, such as may dissolve or swell upon contact with liquids, so they can only be measured in a dry state.
Another consideration is whether the material can flow freely in a dry state. A good performance is a non-adhesive dry powder sample that can be fully decomposed in the feeder, while a highly viscous material is easily bonded, causing deviations in the measurement.
The sample agglomerates only need to be dried in the oven. However, when the fine substance is dried in an oven, the sample will be damaged. In order to remove moisture, the oven should be adjusted to the highest temperature, but not higher than the melting point of the sample.
If the oven has a significant effect on the sample, a dryer can be used. New samples that are not damp in the air are very useful and often have good results. Moisture absorbing samples should be packaged as soon as possible
Into the bag to avoid moisture absorption.
Wet sample should pay attention to the problem
The above considerations are the analysis of dry samples, and care should be taken when analyzing samples in wet conditions, as there are more options, and the latter part of this chapter is a problem to be aware of when preparing wet samples.
Dispersant selection and preparation
The first option is the choice of suspension medium (dispersant) when measuring wet samples. When the sample is first analyzed, it is best to check the dispersion beforehand, and the selected dispersant (initial measurement usually used with water) is added to a beaker containing a small sample and the result is observed. The sample may be dissolved, which can be observed. If not determined, the sample can be analyzed and the opacity observed. If a decrease in opacity is observed, the sample is being dissolved. It is worth noting if the dispersant itself contains impurities or particles.
. The problem of safe handling of samples after measurement must also be considered, following local policies and using the correct procedures for handling samples and dispersants. Most local regulations prohibit hazardous samples and dispersants from being released into the water.
Surfactants and mixtures
The addition of surfactants and mixtures is useful when encountering problems such as sample floating on the surface of the dispersant, and the next section briefly explains the usefulness of such additives.
Surfactant
The addition of a surfactant can aid in sample preparation, and the surfactant can transfer the charge effect that acts on the sample to cause the sample to float on the surface or agglomerate. The activator is added by a small amount of addition, the standard is one drop per liter. If too much is added, foam will be generated when stirring or taking samples, and foam may be considered as particles in the system, which will affect the test results.
Ultrasonic use
In addition to the above process, ultrasound can be used to aid dispersion, whether or not it contains a surfactant. When the sample is mixed in a suspension medium, it is possible to visually observe whether or not an ultrasonic wave is required. If there is a lot of grain agglomeration at the bottom of the beaker,
a beaker containing the sample
Disperse in the ultrasonic bath for two minutes, the effect will be very obvious. If needed, when the sample is added
Sample cell
Ultrasound can also be used, which will prevent re-agglomeration.
note
Be careful when using ultrasonic waves on fragile particles, as ultrasonic waves may separate the particles. If there is any doubt about the effect before and after the use of ultrasound, it can be observed with a microscope.
Dongguan Guancheng Precision Plastic Manufacturing Co., Ltd. , https://www.dpowergo.com