El nuevo molino ultracentrífugo ZM 200 de RETSCH es un molino de rotor no sólo extremadamente rápido y cuidadoso con el material molido, sino también de uso universal gracias a su amplia gama de accesorios.
Planeten-Kugelmühlen haben seit jeher einen festen Platz in der täglichen Laborpraxis zur Feinzerkleinerung unterschiedlichster Materialien. Neben dem Mischen und Zerkleinern hat sich in den letzten Jahren auch im mechanischen Legieren z.B. thermoelektrischer oder hochkoerzitiver Materialien ein weiteres Anwendungsgebiet ergeben.
Das Michael Rout Labor, welches an der New Yorker Rockefeller Universität beheimatet ist, nahm erstmals 2006 Kontakt zu RETSCH in den USA auf, um die Möglichkeit der kryogenen Vermahlung von Hefezellen mit einer Planeten-Kugelmühle zu diskutieren. Das Ziel ihrer Untersuchungen war die Erforschung der „Bauweise“ von Komplexen, welche an den Zellwänden von Hefezellen zu finden sind. Für den Einsatz einer Planeten-Kugelmühle sprach in erster Linie, dass sehr feine Partikelgrößen erreicht werden können, was eine wichtige Voraussetzung für fundierte Analysen an den Hefezellen ist. Eine Partikelgröße im Submikron-Bereich begünstigt eine hohe Ausbeute für die nachfolgende Proteinreinigung.
In zahlreichen Labors werden täglich viele unterschiedliche Probenmaterialien aufbereitet. Für die Zerkleinerung von Feststoffproben auf Analysenfeinheit wird eine Mühle benötigt, die nicht nur vielseitig einsetzbar und leicht zu reinigen ist, sondern die auch eine reproduzierbare Probenvorbereitung – und damit zuverlässige Analysenergebnisse - garantiert. Mit der Ultra-Zentrifugalmühle ZM 200 bietet RETSCH eine Rotormühle an, die nicht nur sehr schnell, sondern auch äußerst materialschonend zerkleinert und, dank einer umfangreichen Zubehörpalette, universell einsetzbar ist. Mit ihrem kraftvollen Powerdrive-Antrieb vermahlt die ZM 200 weiche bis mittelharte und faserige Materialien extrem schnell auf Endfeinheiten bis unter 100 µm und steigert so den Probendurchsatz im Labor.
Die Entwicklung von Arzneimitteln mit schwer löslichen bis unlöslichen Wirkstoffen stellt eine große Herausforderung für die pharmazeutische Industrie dar. So ist die Bioverfügbarkeit oral verabreichter Wirkstoffe, das heißt in welchem Umfang und in welcher Zeit der Wirkstoff vom Körper aufgenommen wird und am Wirkort zur Verfügung steht, in entscheidendem Maße von deren gelöstem Anteil im Magen-Darm-Trakt abhängig. Eine Möglichkeit zur Verbesserung der Auflösungseigenschaften und somit der Bioverfügbarkeit von Wirkstoffen stellt die Zerkleinerung von Wirkstoffpartikeln dar. Durch Minimierung der Partikelgröße schwer löslicher Wirkstoffe wird das Oberflächen-Volumen-Verhältnis vergrößert. Dadurch lassen sich die mikronisierten oder nanoisierten Partikel besser in Lösung bringen. Die zerkleinerten Partikel können in unterschiedlichsten Arzneiformen eingesetzt werden, wie z. B. klassisch in Tabletten oder Kapseln.
Modern analytical methods increase precision and push detection limits to make even the smallest traces of sample components detectable. Despite this development sample preparation, which is carried out prior to the actual analysis, is frequently neglected. Errors caused by lacking accuracy in sample preparation have a much bigger impact than errors made during analysis. Just like an iceberg which is mostly hidden under water, only a small part of the sum of errors is perceived whereas the major part of potential errors is not taken into account (fig. 1). One of the reasons may be the fact that sampling and sample preparation have always been done in a traditional way which has become a routine over the years and is no longer considered as having a critical influence on the subsequent analyses.
A solid sample material should always be sufficiently prepared by size
reduction and homogenization before it is subjected to chemical or physical analysis. Care should be taken that the analysis sample fully represents the original material and that the sample preparation process is carried out reproducibly. Only then are meaningful results guaranteed. Most sample materials can be reduced to the required analytical fineness at room temperature by choosing a mill with a suitable size reduction principle (impact, pressure, friction, shearing, cutting).
How are nano particles produced? The “Bottom-Up” method synthesizes particles from atoms or molecules. The “Top-Down” method involves reducing the size of larger particles to nanoscale, for example with laboratory mills. Due to their significantly enlarged surface in relation to the volume, small particles are drawn to each other by their electrostatic charges. Nano particles are produced by colloidal grinding which involves dispersion of the particles in liquid to neutralize the surface charges. Both water and alcohol can be used as dispersion medium, depending on the sample material. Factors such as energy input and size reduction principle make ball mills the best choice for the production of nanoparticles.
Use of laboratory grinders for size reduction of human bones and bioceramics
Bone implants and substances for bone regeneration are used in surgery to replace degenerated bone material by implants or to “re-build” it with specific substances. The material used in implants varies from autogeneic (supplied by the patient) through allogeneic (supplied by a donor) bones to replacement materials such as hydroxylapatite (HA) and tricalcium phosphate (TCP). Bovine bones and corals are used in conjunction with synthetically produced foamed materials to form a basis for the regeneration of bone substance. Various RETSCH mills are suitable for the preliminary and fine grinding of human bones as well as bioceramic materials.
In the analysis of solid material, the popular adage that “bigger is better” certainly does not apply. The goal is to produce particles that are sufficiently small to satisfy the requirements of the analysis while ensuring that the final sample accurately represents the original material. The “particles” of interest to the analyst generally range from 10 µm to 2mm. Additionally there are many application, where even finer sizes are needed. One example are active ingredients, where it is necessary to grind in the submicron range. Finally for DNA or RNA extraction mechanical cell lysis is well-established.
Materials differ widely in their composition and physical properties. Hence, there are many different grinding principles that can be applied, and this, together with other variables such as initial feed or “lump” size, fineness needed and amount of sample available, results in a wide range of models available to the researcher.
A faultless and comparable analysis is closely linked to an accurate sample handling. Only a sample representative of the initial material can provide meaningful analysis results. Rotating dividers and rotary tube dividers are an important means to ensure the representativeness of a sample and thus the reproducibility of the analysis. Correct sample handling consequently minimizes the probability of a production stop due to incorrect analysis results. Thus correct sample handling is the key to effective quality control.
Some sample materials have properties which make size reduction at ambient temperature impossible. If, for example, very elastic materials need to be ground or volatile components have to be preserved for further analysis, it is essential to carry out cryogenic grinding. The use of liquid nitrogen helps to embrittle the sample, thus improving its breaking properties, and preventing volatile substances from escaping due to the frictional heat produced by the grinding process.
The SM 300 excels especially in the tough jobs where other cutting mills fail. It has a freely selectable speed range from 700 to 3,000 rpm with high torque. The mill is convenient to operate and easy to clean. Reliable and extremely efficient sample preparation in the laboratory is now guaranteed with the SM 300.
Scientists have been studying nano particles (extremely small particles of less than 100 nanometers in diameter) for many years. On the basis of nano particles, new and innovative properties are developed, e. g. semiconducting or surface properties, such as the lotus effect, which open up possibilities previously unknown. There are various methods to produce nano particles. The “bottom up” technique involves synthesizing the particles from atoms and molecules. With the “top down” method, the particles are reduced to nanometer size by grinding. A suitable tool for this method is a planetary ball mill, such as RETSCH’s PM 100, PM 200 or PM 400, which provides the necessary energy input for grinding down to the nanometer range.
The detection of illegal drugs and pharmaceuticals plays a role in various fields, for example in forensic science, road traffic accidents, in competitive sports or at the workplace. Chemical substances can be detected in blood, saliva, urine and in hair. Hair has the great advantage of storing the substances for a long period, which means that detection is still possible several months after consumption of the drug. In addition to the detection of drugs, hair samples are also used for DNA analysis as well as for the analysis of heavy metals and minerals.
For the size reduction of many materials it is more suitable to use a cryogenic mill than a laboratory mill which operates at room temperature. The sample is embrittled by liquid nitrogen which improves its breaking behavior when submitted to impact, pressure and friction; moreover, volatile components of the sample are preserved. The RETSCH CryoMill is not only the most modern and safest cryogenic mill in the market, it also provides excellent grinding results.
An efficient sample preparation procedure for rapid, reliable and reproducible analytical results is becoming increasingly important today. Ever more stringent requirements are being set both in research and production, e.g. for product monitoring and quality control.
The following situation is typical for many production plants: After a routine quality check, the production process is stopped or an already produced batch is suspended, because the analysis results were not within the relevant critical values. But does the tested product really deviate from the specifications? The quality control managers are convinced of this because modern analysis instruments provide results with very low tolerances. The sample in question was tested several times and the result was confirmed. The question is why the product does not match the specifications although the production parameters have not been changed in any way. The possibility that the tested product is indeed deficient cannot be excluded. However, it is often not the product itself which causes irregular analysis results but a lack of understanding of the steps which come before the analysis.
Air jet sieving is usually the method of choice for dry sieving of materials with particle sizes below 40 microns. However, it is also a faster alternative to vibratory sieving of materials of up to 250 microns.
Particle size analysis and particle size distribution are important criteria for the quality control of bulk materials. In a running production process, the results of a quality check must be available quickly to allow for immediate adjustment of the production parameters. Depending on the expected particle size and sample volume, different sieving methods and sieving machines are suitable for analysis. The method used for particle size analysis is primarily determined by the fineness of the material to be sieved. For dry sieving of samples with particle sizes below 40 microns, air jet sieving is the method of choice.