Producción a pequeña escala - extracción de aceite de CBD

La extracción de aceite de CBD a partir de flores de cannabis gana cada vez más interés en todo el mundo para cumplir los requisitos médicos. Los métodos de extracción típicos son mediante etanol o CO2 supercrítico. En ambos casos, el material de la muestra debe triturarse para aumentar la densidad de la muestra en la unidad de extracción. Por regla general, los tamaños de muestra más adecuados son de 2 a 5 mm o de 1 a 2 mm.

El molino de corte SM 300 316L de Retsch cumple los requisitos para la preparación de muestras antes del proceso de extracción, sin efectos de calentamiento, es decir, sin pérdida de ingredientes volátiles y sin efectos de adherencia. Es posible un caudal de muestras de más de 40 kg/h, y la finura final puede adaptarse a los requisitos del usuario seleccionando la abertura de malla de los tamices de fondo.  Gracias a su sofisticado diseño, el SM 300 316L puede desmontarse en segundos y es muy fácil de limpiar. 

El vídeo de la derecha muestra lo fácil que es moler flores secas de cannabis con el SM 300 durante la preparación de muestras para la extracción de aceite de CBD. El molino lo consigue con un rendimiento de más de 40 kg/h y una finura de 1-2 mm (también son posibles otras finuras seleccionando el tamiz de fondo) y sin calentamiento a 700 rpm. Todas las piezas en contacto con el producto son de acero inoxidable 316L y pueden limpiarse rápida y fácilmente gracias a sus superficies especialmente lisas.

Método de extracción de THC / Cannabinoides Método mejorado, derivado del protocolo Shimadzu

Solution for Potency Testing

For potency testing, the Mixer Mill MM 400 with the falcon tube adapter can be used to simultaneously homogenize up to 8 samples. For this purpose, the dried flowers are deep-frozen at -20°C and then 4 g are filled in each tube. After adding 2 x 15 mm steel grinding balls, homogenization can take place at 30 Hz for 3 minutes. A grind size of 1-2 mm can be achieved in this way. This method leads to highly reproducible analysis values with minimized sample loss for CBD, CBDA, THC and THCA and also saves time due to high sample throughput, short grinding times and disposable tubes which don’t require cleaning. After grinding, a portion of 500 mg can be used for the subsequent steps like extartion. This method is also suitable for homogenizing samples for pesticide analysis.

Heavy Metal Analysis

During their growth, cannabis plants can absorb toxic heavy metals such as lead, cadmium, arsenic and mercury from the soil. If samples are analyzed for heavy metals, the Knife Mill GM 200 is also suitable in addition to ball mills and the ZM 300 rotor mill. It is particularly easy to use and homogenizes samples up to 200 ml in one go. A particle size of <1 mm is sufficient to achieve very good reproducibility. The standard deviation was below 5 % for all analyzed elements. If a shorter grinding time is selected, which results in larger (2 mm) particles, standard deviations of up to 12 % can be expected. Appropriate care in the homogenization process therefore pays off by minimizing such particle size effects.

^{Grain size effects on the reproducibility of heavy metal analysis in cannabis flowers: After 10 s grinding (interval at 4000 rpm) in the Knife Mill GM 200, fibers remain, the corresponding standard deviations in heavy metal analysis are higher than with samples ground for 20 s with a final fineness < 1 mm (10 s interval, 4000 rpm + 10 s 10000 rpm).}

In the case of heavy metal analysis, special attention must be paid to choosing the right grinding tools. Since mechanical particle size reduction is always associated with abrasion of the grinding tool, the use of steel tools inevitably leads to a falsification (increase) of the heavy metal values in the sample. This can be avoided by choosing, for example, zirconium oxide tools in the case of ball mills or titanium tools in the case of GM 200 or ZM 300. Steel tools increase the measured concentration of heavy metals and lead to incorrect results.

^{Effects of the grinding tool material on analysis results. Abrasion from steel tools leads to increased values of heavy metals and thus falsifies the analysis. This falsification can be avoided by using zirconium oxide or titanium tools.}

There are different methods for determining trace metals in plant material such as cannabis and hemp or edibles. All require mineral acid digestion to destroy the organic matrix and dissolve trace metals to obtain a liquid sample. For microwave systems, 0.5 g ground sample are sufficient.

Molinos adecuados para el control de la calidad de muestras de cannabis

Hemp is a versatile plant material that has gained increasing attention in recent years due to its numerous applications and industrial importance. Hemp is a variety of the cannabis sativa plant species and is known for its high levels of cannabidiol and low levels of tetrahydrocannabinol. Hemp has been used for centuries for a variety of purposes including fiber, food, and medicine. However, in the last three years, there has been a significant development in the use of hemp for industrial purposes such as building materials, biofuels, and textiles.

The RETSCH Cutting Mill SM 300 was used for grinding pre-cut stem parts of the plants down to 1 mm particles without too long fiber parts > 10 mm. The 6-disc rotor and a 0.75 mm bottom sieve were employed, and the mill was operated at 3000 rpm. Depending on the individual sample, a throughput of 1 kg in 5 min was possible, resulting in an average throughput of ~7.5 kg / h. It is strongly recommended to use the cyclone unit to improve the sample discharge from the grinding chamber and prevent clogging of the sieve with fine particles. Glass bottles of various sizes or receptacles of 5 l or 30 l can be attached to the cyclone for sample collection.

Pre-cut stems of hemp plants before (left) and after grinding in the Cutting Mill SM 300 (right)

Cutting Mill SM 300 with cyclone

To obtain finer particles, a two-step grinding process using the Cutting Mill SM 300 for-precutting and the Rotor Beater Mill SR 300 for fine grinding is recommended. While the SM 300 grinds the sample much quicker, the SR 300 produces much finer particles. Therefore, combining the two milling systems greatly improves the process. This is demonstrated in the following with two samples, hemp hurd and hemp fibers.

The hemp hurd sample was slowly poured into the funnel of the mill whereas the hemp fibers were fed as bundles to the machine. Both samples were pre-cut in the SM 300 using the V-rotor and a 1 mm bottom sieve. To facilitate sample discharge, the cyclone was used as described above. The sample was ground in both cases to fibers sized approximately 1-10 mm.

The fine-grinding step was done for both samples in the SR 300 at 10.000 rpm using a 360° ring sieve with aperture size 0.08 mm. Again, the cyclone was employed to improve sample discharge. The hemp hurd was pulverized to 86 % < 100 μm, the hemp fibers to 76 % < 100 μm. The required grinding times for 1 kg of sample are shown in table 1.

Hemp hurd (above) and hemp fibers (below) after pre-cutting in the SM 300 and subsequent pulverization in the SR 300.

The Retsch Cutting Mill SM 300 and Rotor Beater Mill SR 300 are versatile laboratory-scale mills for grinding hemp and similar materials to a fine powder or flour. Both mills can handle a wide range of fibrous samples and produce consistent particle sizes. While these mills are designed for laboratory-scale applications, they are also suitable for grinding at least 2-3 kg/h in pilot-scale applications. Safe and user-friendly operation and a wide range of accessories of different materials make both mills easy to use in many application fields.