This is about spectrometry.
How would the presence of salicylic acid affect the results of the spectrophotometric determination of the purity of ASA? Why?
I don't know how you conducted the experiment but I assume you measured a peak in the absorption spectrum of ASA. Since ASA is made from salicylic acid, there would be extra absorbance at the peak you are using. I expect it may shift somewhat, due to the groups added to SA, but, none-the-less, it won't shift enough that there will be no intrerference; therefore, the SA will have you thinking there is more ASA there than is actually there.
Check my thinking.
I take this is uv/visible? The absorbance in the UV/Visible spectrum of ASA is due to the aromatic ring. As this is present in both SA and ASA you will not be able to easily determine the purity of ASA from the UV/visible spectrum.
The better spectrometry way to do this is either infra-red or nmr.
You are correct in your thinking that the presence of salicylic acid (SA) can affect the results of the spectrophotometric determination of the purity of acetylsalicylic acid (ASA), also known as aspirin.
In UV/Visible spectrophotometry, the absorbance of a substance is measured at specific wavelengths in the UV or visible range. ASA and SA both contain an aromatic ring, which contributes to their absorbance in this range. This means that when you measure the absorbance of a sample containing ASA, you will not only be measuring the absorbance of ASA itself but also the absorbance of the SA present. This can make it difficult to accurately determine the purity of ASA, as the absorbance of SA can interfere with the measurement.
Additionally, the slight differences in the chemical structure of ASA compared to SA can cause a shift in the absorption peak, but it is unlikely to be significant enough to completely eliminate interference.
To overcome this issue, it is recommended to use other spectroscopic techniques such as infrared (IR) or nuclear magnetic resonance (NMR) spectroscopy. These techniques can provide more specific information about the chemical structure of the compounds, allowing for a more accurate determination of purity. IR spectroscopy analyzes the vibrational modes of the molecules, while NMR spectroscopy analyzes the interactions of atomic nuclei.
By using IR or NMR spectroscopy, you can differentiate between the specific functional groups present in ASA and SA, enabling a more precise determination of the purity of ASA without interference from SA.