I have been working with GS dissolved in PBS to get a calibration curve using Thermo Scientific Nanodrop 2000 UV-Vis spectrophotometer. I derivatize the solutions with o-phthaldialdehyde and add isopropanol (to not precipitate the chromophores formed). The literature I've come across all say the max peak for GS absorbance is at 332 nm. But in all my UV-Vis runs, i've noticed 330 nm being the highest for most samples, 332 nm is seldom the highest. So am I right in assuming this is due to instrument variations & detection capacity? Is it appropriate to take the average of the abs values at 330 & 332 nm for each sample? Thanks in advance.
Dear Vidya,
I have just come across you post of June 2015.
It may be too late for you, but I would like to help others in similar situations.
Each spectrophotometer model has its own wavelength accuracy and wavelength precision specifications. The greater these specified figures in nm, the greater the chances of poorer method transfer and reproducibility.
It pays to check that your spectrophotometer is maintained in top condition, so that the spectrophotometer operates to the manufacturer’s published specifications.
Stray light would affect the accuracy of the Absorbance readings.
Kind regards,
Ade Kujore
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Vidya Jayaraman Hi! It´s already a long time you posted this question, but I hope you can help me. I am trying to find the max absorbance of gentamicin dissolved in PBS, however I cannot find a good peak. I found a slightly higher absorbance at about 250 nm. Is the peak you found well defined? I've read in a book (link bellow) that "The gentamicin complex does not posses ultraviolet light absorption properties".
Thank you.
Chapter Gentamicin Sulfate
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