Finally we are done with the tapping trials of 5 different kinds of lactose powder! The final lactose powder used was SuperTab30GR(125-150um). The powder was still steeply sloped with a higher relative humidity, so I had to turn the cylinder a few times during the trial. At the end, I put all the files into Andy’s flashdrive and made sure that none of the files was missing. Now ready to move onto the next step. 🙂 I’m going to research about AFM(Atomic Force Microscopy) before starting on a new project.
10/02: Relative Humidity 46%.
Finished tapping trials with the one ranging 63-125um and <45um&>212um. Both kinds of the powder generated fine results – the <45um&>212um one was actually not as level as seen in the images, but I can say it had “almost” flat surface.
10/03: Relative Humidity 48%.
Did the tapping trials with the one ranging 125-150um. The first trial “failed” because the camera was found out to have moved during the trial, but the next one was okay. The powder got sloped by some degree. I had to turn the cylinder a few times in order to visualize it, but later the slope became quite stabilized. I’d like to find out if a different relative humidity would affect the slope of the powder, so I would continue the rest of the trials for this powder tomorrow. So far, this one is the only lactose powder with which the tapping trials are not finished.
Finally got the new connecting part for the camera – Matt had to use the two aluminum ones for another experiment, so I have found a metal one somewhere in the lab. At first, there was still a problem with completely fixing the camera, but I got that problem solved as well. Because of that, even though I put all the images of the tapped powder into Andy’s flashdrive, the one taken on September 27th is a little “unstable,” which means that the camera moved a little bit during the tapping(and I realized this after finishing that trial). The other two were fine; even though the powder got tilted and I had to change its position a couple of times, the slope was visualized in the frames.
As I had written on my last post, I sieved the lactose SuperTab30GR ranging from 63um to 150um again using more sievers in order to “narrow” down the ranges even a little bit. My hypothesis was that the reason the powder got sloped after some taps was the big difference between the small and big particles – I wanted another siever between 63um and 150um ones.
So for this sieving, 45um(just in case), 63um, 125um, 150um were used. I sieved the whole amount of the powder(63-150um) for about 9-10 minutes(3 times with 3 minutes of each interval). Someone had “torn” the 150um siever and there was a tiny hole which was not big but definitely bigger than the 150um diameter, so I sieved the powder 125-150um once again for about 5 minutes. The powder ranging between 45-63um and the one ranging from 150um were thrown away, since their amounts were not a lot and we already had enough samples for those ranges.
And the results are 1) 125-150um may be a too narrow size range for tapping; the powder in that range doesn’t get compressed at all even after a few tappings. 2) 63-125um WORKS. Well, there is still a slight slope but we can visualize it & it is negligible in my opinion. I could not do a tapping trial for that because Matt is still using the connecting part for the camera in order for another kind of experiment, but hopefully soon we can solve the “sloping” issue for the last powder samples left. 🙂
Since it is too hard to take the data from SuperTab30GR ranging from 63 to 150um, I wonder that if this difficulty is due to the big difference between small and big particles. I would like to suggest about sieving it once more and narrow the range of its size.
SuperTab21AN(<45 & >212) today had surprisingly stable slopes; the images taken today show a big contrast to the ones taken a week ago, since in my previous post, I wrote that it was quite “out of control.” I had not been able to expect the direction of the slope, but today, it was different; even though the powder was still tilted, I was able to visualize the slope onto the shadow. At first, I assumed that the relative humidity would be one of the factors which affect the powder, but one weird thing is that the relative humidity of August 16th and today were the same with 49%. And the weight of the one for the last week was 25.4g and the one for today 24.3g.
Pharmatose125M has no problem with its data-taking process. Great compressibility. 🙂
SuperTab30GR was stable at first, but later it turned out to be the same result as the issue Damian pointed out. The image on the left is the 73rd one of today’s trial, and I stopped taking all the images after this one. In the video clip, you can see that the compression was stable at first and later the shape of the top becomes a little bit ragged. I’ll try this one again tomorrow in order to “complete” the tapping trials.
SuperTab11SD <45um & >212um: Stable & great compaction rate
SuperTab21AN <45um & >212um: Hard to expect its pattern(the direction of its slopes). We have to use the method Andy told us to do. I had to loosen & retighten the cylinder almost 100 times.
Pharmatose 125M <45um: Stable & great compaction rate. A little bit sloped after it was almost done with compressing, but the directions of the slopes were all the same and I did not have to loosen and retighten the cylinder to visualize the slope.
SuperTab 30GR <45um & >212um: quite stable. A slight hump(which is negligible in my opinion) kept coming up during the tapping trial.
Changed filenames for Pharmatose125M and SuperTab11SD
(did not take the data; just played with it around in a loosened setting)
- marked lines on the bottom part of the cylinder. Finally figured out that it did not generate a constant set of data because of its unstableness.
Had a conclusion that it did not actually reflect “true” tapped volumes.
– Moved SuperTab21AN to Andy’s Flashdrive
– Took data Pharmatose450M 45-63um (48%RH, 16.4g) and SuperTab11SD 150-212um (48%RH, 21.2g)
Since I was(and am still) not familiar with computer science, changing all the iterated filenames was quite a challenge for me. I knew how to change the name of a file one by one but not the whole group of files at once. Later the command line I finally found was:
ex) x=1; for i in *.png; do mv “$i” “$x.png”; x=$(($x+1));done
And here is the command I exactly used for one set of files:
x=1; for i in 080212_SuperTab_21AN_150-212um_47%_take2-*.png; do mv “$i” “SuperTab21AN–150_212–47%RH–08_02_2012_2-$x.png”; x=$(($x+1));done
– About the tapping trial of SuperTab11SD 150-212um
At first the top surface was quite ragged and later became more and more sloped; I cannot still think of the way to visualize the slope to its shadow.
This powder was the last lactose sample to be sieved – and on the sample bag, it was written that it had 80% of 20-90um particles and 20% of <20um ones. Since there was some time gap of sieving between this one and the other kinds of powder, when I went downstairs to sieve it, someone may have mistakenly torn the 150um siever and there was a tiny hole on it (about 1/8 inch – or smaller – diameter). Because of that and since I needed to make sure that the information on the bag was correct, I put an ‘additional’ 125um siever between the 150um and 63um sievers. After 3 times of sieving, there was almost none on the 150um siever (and I don’t think it was all because of that small hole) and there was nothing between 150um and 125um ones as well. As a result, now we have a new range of particle size, 63-125um. (The sievers used were 45um, 63um, 125um, 150um, and 212um.)
A couple of questions were arisen after the sieving and a few tapping trials.
1) Why so fluffy?
The lactose powder contained high moisture from the beginning, even though I used all-dried sievers. According to the manual issued by DFE Pharma, Pharmatose 450M has a large surface area for excellent wettability, even though Pharmatose in general shows low moisture absorption. I am not sure if this would be the answer for this question, though, since its general characteristic and specific one seem quite different.
2) After a few tapping trials, I found it interesting that 45-63um particles had less compression rate than <45 or 63-125um ones. I should probably do more trials, though, in order to be sure about this.
It has been a long time since I wrote my last post about tap density. The data-taking process is still going on, and I think we finally got a setting we had wanted. Andy’s idea was awesome – taking the images of the shadows of the cylinder works really well. Compared to the previous ones, the current setting generates much clearer images.
There are a couple of problems I found out about the device, though.
1) I always try to keep the cylinder level, but still the lactose in it keeps getting sloped even a little bit.
2) When I tap the cylinder, there is a slight “friction” problem – the cylinder sometimes comes down really slowly after I remove a ruler.
I am not sure if these are big issues to be considered or not – please comment any ideas about it. 🙂