I have prepared a clear colourless solution of BPA using Dimethyl Sulfoxide (DMSO) as an organic solvent.
I have seen in the papers that the maxim lambda for the better absorbance of UV for BPA (in aqueous solutions) was about 230 nm or 270 nm, however when I try to get the UV spectra of the dissolved BPA in DMSO, there would be a maximum absorbance of about 2.5 at the wavelength of 300 nm, while the absorbance at about 230 and 270 nm would be very low and around 0.1
Now I am wondering whether we can say that 300 nm is the maximum lambda for the BPA or not?
If yes, why I can not see anywhere else to nominate this wavelength as the lambda max?
If no, what would be that maximum absorbance for?
Thanks for your advices
Kind regards
Aghil
Hi Marius,
Thanks for your response and comprehensive explanation.
Yes as you mentioned the UV absorption of BPA in at 227 and 275 nm, however when I am trying to find the λmax of BPA in my samples I see that this is at about 300 nm using plastic cuvettes and 285 nm using quartz cuvettes, with the maximum absorbance of above 2.5. I have repeated the tests but got the same results. I have also used DMSO as blank as you said.
Now I am wondering which one can be considered as the λmax of my samples ? 285 or 300 nm?
Why I should see different λmax using different types of cuvettes?
if it is the case which cuvettes is better to be used?
About using ethanol, I would say due to the next steps I need my samples to be in the DMSO or DMF solutions, rather than ethanol, because I need to make a disodium salt of BPA which I think would be decomposed while using ethanol.
Actually as a clarification, at this step, by the fact that I do not have any specific information about the λmax of disodium salt of BPA I am trying to firstly be sure of the accuracy of the UV-VIS instrument and the cuvettes, by calibrating the instrument with a specified λmax which can be BPA here. after ensuring the accuracy of the instrument I want to use the wavelength scanning to figure out the accurate λmax of the disodium salt of BPA.
I appreciate your attention and any specific suggestion in this regard.
I have also another (maybe silly) question; what absorbance should be seen at the λmax to be accepted as the maximum accepted absorbance; 1< or >1?! I am asking this question because I am seeing 2.5 molarity absorbance in my samples while I have seen somewhere that this should be below 1. I know that I can get the lower absorbance by using low concentrated samples, however I just want to know what if I want to keep the concentration ?!
Sorry for the long story and explanations :-)
Thanks so much
Dear Marius,
Thanks for your answers.
Yes I use the same cuvettes or normally use the cuvettes which are matched to each other.
Thank you again for your comments.
Regards
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