Pharmaceutical dosage forms are the forms in which drugs are present and administered to the body. In today's various conventional pharmaceutical dosage forms, 70% of the active ingredients are present in tablets and capsules in powder form. For other forms, intermediate products or excipients are often present in dry powder form. In addition, from the perspective of new formulations such as microcapsules, microspheres, powders, liposomes, new emulsions, and nanoparticles, which have developed rapidly in recent years, the physical properties of various pharmaceutical particles are key parameters that affect the quality of drugs. Therefore, as the authoritative technology for measuring various physical properties of particulate matter-laser particle size technology, more and more attention has been paid to engineering technicians and drug inspectors in the quality assurance and control of pharmaceutical formulation research and production processes.
Many users are very embarrassed when choosing a laser particle size analyzer. On the one hand, there is not much knowledge about the laser particle size analyzer; on the other hand, various manufacturers say that their particle size analyzer is the best, and I do n’t know who is good. This article gives some references here:
First, the selection of laser particle size analyzer must first pay great attention to the accuracy and repeatability of the instrument. Because the particle size analyzer is a precision instrument for testing the particle size range, if its test accuracy is not good and the repeatability is poor, then you should not choose a laser particle size analyzer. Because this will give you the wrong data, can not give guidance to your production and process, and thus delay your processing technology. More importantly, an inaccurate laser particle size analyzer can cause you and your supplier to return goods, sue, or ruin you.
Second, the choice of laser particle size analyzer depends on the manufacturer's technical strength, how to judge the manufacturer's technical strength? First of all, who is the main inventor, how well is it known in the particle industry? Is it an expert in this area, if the manufacturer says no You need to be careful about the name of the inventor and what level of technology you have. Some of them may be infringing products. The purchase of such products will also amount to infringement in the future. And this kind of manufacturer does not do long, you are affected by the purchase of this product, it is impossible to get long-term technical support.
3. The better theory for testing submicron and micron laser particle size analyzers is the full-range Mie scattering theory. It is impossible to develop a digital model of the full-range Mie theory if the manufacturer does not have a relatively high level of technical personnel. Something can't solve the fundamental problem. It can be distinguished by testing with submicron standard particles.
Fourth, we must understand how it is dispersed. A sample must obtain an objective test result. Only when the sample is well dispersed can the correct result be measured. If the dispersion system cannot keep the sample in the dynamic test, or the pipeline through which the particles pass is too long, the large particles are quickly precipitated, the information captured by the large particles is less, and the information of the small particles is relatively more, the actual measured data It will be too small, it is not objective data, and there is no practical guidance. Some manufacturers hope that the data measured by their products is as small as possible, but if it is not objective data, it may lead to economic disputes.
5. Several key test points of product pros and cons.
The laser particle size analyzer has several key test points, as follows:
1 Particle size measurement range
Wide particle size range, suitable for a wide range of applications. Not only depends on the range reported by its instrument, but also on how to detect the scattering of small particles beyond the area of ​​the main detector.
The best way is to directly detect the full range, so as to ensure the consistency of the background deduction. The mixed test of different methods, and then fitted into a map by computer, will definitely bring errors. The detection range of the LS laser particle size analyzer (Beckman Coulter, USA) is between 40nm and 2000μm, which plays an important role in the particle analysis in the research of new dosage forms.
2 laser light source
Generally, a 2mW laser is used. If the power is too small, the scattered light energy is low, resulting in low sensitivity. In addition, the gas light source has a short wavelength and stability is better than the solid light source.
3 Detector Because the larger the radius of the laser diffraction halo, the weaker the light intensity, it is easy to miss the detection of the signal / noise ratio of small particles, so the detection of the distribution of small particles can reflect the quality of the instrument. The development of the detector has gone through several stages of circle, semicircle and sector.
3.1 The latest generation of detectors from Malvern, UK
The patented non-uniform cross-arrangement three-dimensional fan-shaped detection system has the highest actual resolution and no signal dead zone. It is equivalent to 175 in a circular or cross-star arrangement and 93 in a semi-circular arrangement, enabling a direct detection angle of 135 degrees.
3.2 Number of channels
In the laser particle size analyzer, unlike the concept of the existence of channels in the counter, it is actually the number of light receiving areas of the detector. It has a theoretical and practical optimization value: too little: insufficient scattered light received, poor accuracy; too much: too high sensitivity, resulting in poor reproducibility.
In order to make up for the shortcomings of the slow sampling speed, some manufacturers only use more channels to meet the sensitivity requirements with loss of reproducibility, so the measurement time is 20 seconds or more than 1 minute.
The latest generation of Mastercizer2000 laser particle size analyzer from Malvern Instruments in the UK samples 1000 times per second, and the measurement time is only 2 seconds (the average of 2000 results), which can optimize the accuracy and repeatability.
4 Whether to use complete Mie theory
Because Mie's dispersion theory is very complicated and the amount of data processing is large, some manufacturers ignore the optical properties of the particles themselves such as refraction and absorption, and use the approximate Mie theory, resulting in problems such as limited application range and increased probability of missed detection.
5 Accuracy and repeatability indicators
The higher the accuracy and repeatability indicators, the better. Adopt NIST standard particle detection.
6 Stability
The stability of the instrument includes the stability of the optical path and the stability of the dispersion system and the influence of the surrounding environment. Generally speaking, gas lasers and optical platforms are used to help stabilize the optical path. Internal heat-generating components (such as a 50-watt tungsten lamp) will affect the environment around the light path.
The stability index is not included in the manufacturer's instrument description. The user can only judge by judging the structure of the instrument and visiting or asking other users who have used it for a long time.
7 Scanning speed
Fast scanning speed can improve data accuracy, repeatability and stability. Different manufacturers have different scanning speeds, ranging from 1 time / second to 1000 times / second. Generally speaking, the greater the number of cyclic scan tests, the better the accuracy of the average result, so the higher the speed, the better; the spray dry method and spray require higher speed, the better; although the free fall dry method is not fast, but Since the particles only pass through the sample area once, the speed is faster and better. The amount of samples that users need to process each day is also a factor of speed.
8 Automatic alignment, no need to change lens, automatic correction
9 ease of use and maintenance
On this point, it is often overlooked before buying, but in fact directly determines the efficiency and life of the instrument. The method of understanding is the understanding of the structure of the instrument and the reflection of other existing users.
Is it convenient to disassemble and clean: the particle size analyzer is divided into two parts: the host and the diffuser. The sample flow cell always needs to be cleaned regularly, and the cleaning interval depends on the nature of the sample. For an instrument combining a host and a disperser, the sample cell is often placed deep inside the instrument. It is cumbersome to take out and disassemble, and it is very easy to damage the optical path system.
10Whether it meets international standards
The ISO13320 standard is the basic requirement for a laser particle size analyzer. But not all manufacturers comply with this standard. In the process of measuring the distribution of submicron particles, the non-laser diffraction method does not comply with the ISO13320 standard.
11 diffuser
11.1 Wet method
Whether it has physical dispersion functions such as ultrasound and agitation, and whether the ultrasonic power and agitation speed are continuously adjustable is the key to ensuring the repeatability of the analysis results.
11.2 Dry method
Is it a closed measurement, is the sample easy to disperse? If not, has a jet disperser been selected? An impinging airflow of 300 m / s is a prerequisite to ensure that the sample can be fully dispersed to obtain true analysis results.
Article link: China Chemical Instrument Network http: //
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