sieving lactose 02

Continuing from yesterday, I am sieving the SuperTab 11SD lactose. Except today I have split the large fraction between 125–250 µm into two batches. I will sieve both batches for 30 minutes.

  • 23.1˚C
  • 47% relative humidity

SuperTab 11SD

My fourth sieving obtained the following:

  • > 250 µm = 8 g
  • 125–250 µm = 421 g
  • 75–125 µm = 14 g
  • 45–75 µm = < 1 g
  • < 45 µm = 37 g

My fifth sieving obtained the following:

  • > 250 µm = 7 g
  • 125–250 µm = 421 g
  • 75–125 µm = 13 g
  • 45–75 µm = < 1 g
  • < 45 µm = 39 g

This looks like a good stopping point as I’m wanting to use the 125–250 µm fraction and it hasn’t change appreciably.

Pharmatose 150M

This powder is much more cohesive than the SuperTab powders. I’ll also note that the bag of lactose, when received, was open in the jar. This is fine as the powder was exposed to the elements during shipping and thus may have more moisture content in it than the other powders. A comparison can now be made between powders and their moisture content—dependent on if the moisture content is greater in the pharmatose powder.

My first sieving obtained the following:

  • > 250 µm = 9 g
  • 125–250 µm = 205 g
  • 75–125 µm = 191 g
  • 45–75 µm = 21 g
  • < 45 µm = 68 g

My second sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 165 g
  • 75–125 µm = 209 g
  • 45–75 µm = 4 g
  • < 45 µm = 109 g

My third sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 103 g
  • 75–125 µm = 223 g
  • 45–75 µm = 4 g
  • < 45 µm = 153 g

Sieving the Pharmatose 150M is _very_ different than sieving the SuperTab powders. There seems to be a large amount of grains that are less than 45 µm in the batch and are for some reason getting stuck in the various sieves and powders in the sieves probably due to cohesiveness. Not sure though. I am making sure that the sieves are clear between each cycle. I suspect that more sieving sessions will refine the particle distributions but, I may end up with a bunch of powder with particle sizes less than 45 µm. I hope that the particles in the 125–250 µm range are for the most part separated nicely as this is the fraction that I wish to use in further experiments.

My fourth sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 90 g
  • 75–125 µm = 201 g
  • 45–75 µm = 14 g
  • < 45 µm = 175 g

As suspected, I lost more in the 125–250 µm range. There still seems to be enough for this project but I need to go through another cycle since there was a 10% change in weight between sieving 3 and 4. I’ll also note that the powder in the 125-250 µm range is flowing better out of the sieve and into the jar I am putting it in. I’m guessing because the number of smaller particles in this fraction are becoming less.

My fifth sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 85 g
  • 75–125 µm = 171 g
  • 45–75 µm = 2 g
  • < 45 µm = 207 g

My sixth sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 81 g
  • 75–125 µm = 144 g
  • 45–75 µm = 2 g
  • < 45 µm = 235 g

I will do one more since the diference between the 75–125 is still above a 10% change in weight. I do know why my 45–75 µm fraction is always small, it’s because there is a rip in the sieve where it meets the holder. No wonder why I was not getting any in that fraction for all the powders. This isn’t a problem, it just means that my smallest fraction is actually < 75 µm and not < 45 µm. I’ll fix my notes after the seventh sieving just so I stay consistent with what I started, i.e. so I don’t mess up with this final sieve.

My seventh sieving obtained the following:

  • > 250 µm = 5 g
  • 125–250 µm = 81 g
  • 75–125 µm = 144 g
  • 45–75 µm = 2 g
  • < 45 µm = 235 g

My eighth sieving obtained the following:

  • > 250 µm = 4 g
  • 125–250 µm = 78 g
  • 75–125 µm = 119 g
  • 45–75 µm = X g
  • < 45 µm = 262 g

I have to admit that this was fairly tedious and left me guessing if the sieving actually worked. I am wanting to ensure that the distribution in sizes of the particles are what I think they are so I may end up sieving the 125–250 µm fraction for all lactose types again and ensuring that the weight change between sieving cycles is less than 5%. I want to use the 125–250 µm particle size range as all three powders have > 50 g of powder in that range. So, I think I will end up sieving this range again just to make sure that the particle distribution is as narrow as I think it should be. Of course I will need to size the particles after the sieving process is complete.

I will also note that the Pharmatose 150M lactose in the 125–250 µm size range was pretty cohesive when I was trying to empty the powder out of the sieves for the first couple of cycles. After about the 5th one, the particles started flowing out much more smoothly and I think this is because the smaller particles were leaving this fraction. Still, I think I need to sieve the particles some more next time I’m in.

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  1. #1 by toms zapatos on June 6, 2013 - 11:33 pm

    Your article sieving lactose 02 | Andy Maloney write very well, thank you share!

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