Last time I did a bulk sieving of the powders in order to fractionate them into different distributions of grain sizes. From this initial sieving, I saw that the largest amount of powder in each of the sieved sizes was the 125–150 µm range. If the Pharmatose 150M lactose took approximately the same number of sieving cycles as the SuperTabs than I wouldn’t be doing this extra sieving step, however, because it took 8 cycles I am not convinced that the sieving is complete enough to give large cutoffs for the 125–150 µm size range. This is why I have decided to sieve each of the 125–150 µm sizes again to ensure that sieving is producing a strong cutoff between sizes. Like before, I’ve set up the following sieves:
- Lid
- 250 µm
- 125 µm
- 75 µm
- Bucket
this time ignoring the 45 µm sieve since it has a hole in it. I put the 125–150 µm size range in the top sieve and let it shake for 30 minutes. I’m only interested in the 125–250 µm range so this is the only one that I will be measuring.
SuperTab 30GR
Initial conditions:
- 2014-05-04
- Temperature = 22.9˚C
- Relative humidity = 22%
My first sieving for the second sieve cycle was:
- 125–250 µm = 218 g
I’ll note that the powder seemed to be have somewhat of a charge to it and as such, seemed to cling to the sieve. As seen in a previous post, this weight is significantly different than the one I ended with so, time for another sieve cycle.
My second sieving for the second sieve cycle was:
- 125–250 µm = 209 g
My third sieving for the second sieve cycle was:
- 125–250 µm = 202 g
My fourth sieving for the second sieve cycle was:
- 125–250 µm = 200 g
Pharmatose 150M
My first sieving for the second sieve cycle was:
- 125–250 µm = 75 g
Since the last sieving of the Pharmatose 150M was at 78 g, this change is within the 1–5% weight change and thus I will not be sieving it more.
SuperTab 11SD
I separated the SuperTab 125–250 µm fraction because it was quite large. So I started off with about 150 g of it in the sievers.
My first sieving for the second sieve cycle was:
- 125–250 µm = 130 g
My second sieving for the second sieve cycle was:
- 125–250 µm = 108 g
My third sieving for the second sieve cycle was:
- 125–250 µm = 99 g
My fourth sieving for the second sieve cycle was:
- 125–250 µm = 96 g
The powders are now within the arbitrarily decided 1–5% change of weight between sieving cycles. The next step is to size the particles to see if they actually are within these ranges.
Andy Maloney 