Valerian tablet (coated)

For the desired Knife Mill PULVERISETTE 11, we recommend the usage of our single-use-technology vessels, when only 35 grams of tablets should be ground.

We used a 100 ml vessel to weigh in the sample. Surely also a 40 ml vessel would fit for these coated tablets, too.We ground the sample in short intervals (2 seconds of grinding at maximum speed, followed by one second of programmed pausing time). After 30 seconds, the maximum fineness achievable seemed to be reached.

Test wise, we proceeded grinding for a complete minute, but still some coating fragments of ~ 1 mm length were spotted, too. Surely also a Vibratory Micro Mill PULVERISETTE 0 could be used to comminute such a type of sample as well (see result 3).

Probably the shell of the tablets can become embrittled to comminute to a fine powder. Liquid nitrogen (-196 °C) would work best for a rapid embrittlement. Person safety equipment is recommended for the preparation. The rest of tablets was split in half (~ 11 grams) was placed in the lid of a single-use-grinding vessel. A portion of liquid nitrogen was poured into the lid and after the LN2 evaporated completely, the grinding vessel was closed and fixed onto the adapter.

The mill was programmed to start with maximum speed (14.000 rpm) to comminute with three intervals of 10 seconds. Afterwards, still a few fragments up to 1 mm length were spotted.

We placed the sample into a mortar made of zirconium oxide for a metal free grinding of the tablets. The mortar with grinding ball was fixed onto the vibrating disk and we started the grinding process for first five minutes with ~ 2,5 mm amplitude.

After five minutes, the output was almost similar to result one; some of the shell fragments were attached to the grinding ball. We proceeded grinding for further 15 minutes. After a total grinding time of 20 minutes, an almost homogenously ground sample was found. A few tiny particles were found with a Thread Counter (magnifies 10x).

Because the sample wasn’t sticking yet, surely a longer dry grinding is possible to improve the grinding result. Only when a certain fineness was reached, when a particles own g-force would become weaker that interacting surface forces, a dry ground sample will become compressed and requires a grinding in suspension to improve the level of fineness.