Problems with testing

[Steven Ramiro]

Team,

So our chip is in solution.  I put it in the shaker at 5:30pm and Eric and I came in at midnight to do a reading. 

The UV vis was giving me and Eric weird readings tonight... it kept saying that we reached max absorbance (4.000ABS), even after I diluted it 10,000x. This would indicate that all of the drug has been released and more, which doesn't make sense. 

Yesterday afternoon, I was trying to make a characteristic curve for the ibu:PBS solution, so that I could see how the absorbance should change as I change the concentration.  I created a solution of 14mg/100mL (0.14mg/mL) {I had trouble dissolving it all even with head and stirring but that's another story}, and took absorbance readings as I diluted the samples 10x, 100x, etc.... I saw that the absorbance was decreasing from 3.135ABS for the 1/10, to 3.068 for 1/100, and 3.010 for 1/1000... So I was expecting to see a tiny absorbance when we ran it tonight. BUT even after 10,000x dilution, the machine was still maxing out.  I don't get why it's doing this. >_<

It might be a machine problem? But we doublechecked with by putting in a blank, and it seemed to be working okay....
Or maybe we're reading at the wrong wavelength? Literature seems to suggest 225nm, and I did a couple of scans across a range of wavelengths (with the solution and its subsequent dilutions) and there was a definite huge peak at 225nm that went out of the range of the screen....
Or maybe there's something going on with the PLA/PLGA/glue that is giving us a weird peak that's interfering with our data?  But I remember seeing in the literature that PLGA/PLA shouldn't interfere with this wavelength.....
Any thoughts or ideas?
Do we have access to any other UV vis machines?

In the meantime, ALEX if doing a 10x or 100x dilution doesn't give you a good reading below 4.000ABS, then take 360mL and put it in a microcentrifuge tube. I left a fresh one lying on top of the UV vis machine with the micropipettes

I'm hoping it was just a machine issue that'll go away when you restart it tomorrow. So see what happens and let me know. My ID is in the lounge.

ALSO, we will not be placing my ID card in the brick outside.  My boss has requested that we not do this for security purposes.  We will not be allowed to the use the equipment if we leave my ID lying around.  Until we figure out something better, we will have to coordinate with each other.

Steven
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Steven Ramiro
B.S. Materials Science and Engineering
A. James Clark School of Engineering
University of Maryland, College Park

[Doug Trigg]

Its likely the plga/pla/glue that is throwing the readings.  Did you guys measure the mass of the chip as well?  We might need to do mass measurements instead.  Can you put some glue in one beaker, some pla in another and some plga in another and do a UV vis reading for each (probably should wait like 1 day to get things to disovle)?