[sofia@]

Hello everybody,
 i have one drug that is poorly soluble in aqueous solution and Soluble in DMSO, approximately 100 mg/mL.
I have to find the solubility of this in media. How can i set up this experiment? Could you please suggest me a protocol and explain me? (i m gonna use a spectrophotometer)
thank you!
p.s. for the majority of you this is an easy question, but im not a chemist. 

[Arkcon]

I guess we can assume the media is mostly aqueous, unless you're able to put some DMSO into it.  However, if your active has a know absorbance wavelength, you should be able to figure out how to measure it in solution.  Why don't you try, and we'll see what help you need.

[sofia@]

i have already made od scan in both dmso and media and i know the absorbance wavelength!

[Vidya]

You can convert wavelength of the absorbance into concentration in the given solution
A=εcl
 

[Borek]

You can convert wavelength of the absorbance into concentration

You can't. You can convert absorbance into concentration, not wavelength into concentration

[Vidya]

You can convert wavelength of the absorbance into concentration

You can't. You can convert absorbance into concentration, not wavelength into concentration

In the spectrophotometer while performing the experiment you note down the max absorbance  and wavelength so both the values can be observed during the experiment. 

[Borek]

In the spectrophotometer while performing the experiment you note down the max absorbance  and wavelength so both the values can be observed during the experiment. 

Both are observed, but you don't use wavelength to determine concentration. The equation you listed (correctly) - A=εcl - doesn't contain wavelength.

[Vidya]

In the spectrophotometer while performing the experiment you note down the max absorbance  and wavelength so both the values can be observed during the experiment. 

Both are observed, but you don't use wavelength to determine concentration. The equation you listed (correctly) - A=εcl - doesn't contain wavelength.

You select the max absorbance and it is at particular wavelength.
Use the equation and get the concentrations.It is a very simple experiment.

[Borek]

You select the max absorbance and it is at particular wavelength.
Use the equation and get the concentrations.It is a very simple experiment.

Please explain what is "wavelength of the absorbance" that you mentioned in your original post:

You can convert wavelength of the absorbance into concentration in the given solution
A=εcl

I have no doubt you know what the Lambert-Beer's law is and I agree it is a pretty simple experiment. It doesn't make your original statement correct.

And the longer you argue the more I think you are just trolling.

[Vidya]

it is the wavelength of maximum absorbance and max absorbance value is used in calculations.So wavelength is important as every compound has a specific λmax.I have done this experiment many times so please we can stop this argument now.

[Arkcon]

it is the wavelength of maximum absorbance and max absorbance value is used in calculations.So wavelength is important as every compound has a specific λmax.I have done this experiment many times so please we can stop this argument now.

Sorry to prolong the argument, however, I would also like to see the formula used in the calculations that uses lambda max.  For example, when selecting wavelength in a detector for an HPLC run, we will often select a wavelength other than lambda max.  If lambda max is crucial for calculations, we should be required to compansate somehow.  But again, I don't use wavelength in my calculations.

[Vidya]

I am also not using the wavelength but I used the value of A at a particular wavelength.So when I replied may be it was in my mind about the wavelength because no doubt its value is important and should be mention in the experiment.I gave the right formula also in which wavelength is not mentioned.
A=εcl

[Vidya]

actually I should have written
absorbance at λmax into concentration

[Borek]

actually I should have written
absorbance at λmax into concentration

And that would be OK.