I have a compound which absorbs at about 213 nm. I want to find its molar extinction coefficient by preparing a calibration curve. The problem is that I do not know if the value I will obtain could be treated as a true value, since the compound dissolves only in solvents with a cut-off above compound's absorbance maximum (n-butanol, DCM, CHCL3).
Is there a way to find it?
Hi Olga, you are doing a solvent only Abs control without your compound, right?
You could make films of different thicknesses, determine their extinction coefficients and create a calibration plot.
V. N. Ravi Kishore V. I have, in fact, prepared films of different thickness, though, how do I find out the mass of the material on the film? As I understood from the literature, the density of the organic material on the surface is usualy different from its density in a single crystal.
Hi Olga, first, when you measure the molar extinction coefficient in such range (200-250 nm) you need to consider solvent cut-off as most of the solvent you mentioned has interference in this region. Second, if you are measuring in thin films with different thickness, you need to make the samples in quartz plates as normal glass slides has absorption below 350 nm. And if you make you thin films with different from same stock solution the measurement should be alright (However, spin coating is advisable for uniform thickness of the film).
If you are depositing your films by vapor deposition, then it is possible to determine its thickness using a quartz crystal oscillator.
Initially you need to create a calibration curve of frequency of quartz oscillator vs film thickness, film thickness being measured independently using some other technique and later use this for all other experiments.
- Badges
- Science method
- Similar topics
- Methodology
- Absorption Spectroscopy