Yes, sodium hydroxide (NaOH) does exhibit absorption in the ultraviolet (UV) region of the electromagnetic spectrum.
NaOH and UV Absorption
Based on research, specifically a study by Tong et al. (2020), NaOH absorbs radiation at a wavelength of approximately 200 nm within the UV region. This means that when UV light around this specific wavelength passes through a solution containing NaOH, some of that light energy is absorbed by the substance.
Why is This Important?
Understanding the UV absorption properties of substances like NaOH is crucial in various scientific fields, particularly in analytical chemistry techniques such as UV-Vis spectroscopy.
- Spectroscopy: In UV-Vis spectroscopy, researchers measure how much UV or visible light a substance absorbs or transmits. The absorption spectrum (a graph showing absorption vs. wavelength) is unique for many compounds and can be used for identification or quantification. Knowing that NaOH absorbs around 200 nm is vital if NaOH is present in a sample being analyzed by UV-Vis spectroscopy, especially in that wavelength range, as it can interfere with the measurement of other substances.
- Solvent Selection: When performing experiments that involve UV light or UV-Vis spectroscopy, chemists need to choose solvents that do not absorb significantly in the wavelength range of interest. Water is often used as a solvent for NaOH, and water itself absorbs significantly below ~190 nm. However, the presence of NaOH introduces absorption around 200 nm, which needs to be considered.
Practical Considerations
When working with NaOH solutions in applications sensitive to UV light:
- Be aware of potential interference from NaOH absorption, especially around 200 nm.
- Consider using higher wavelengths if possible to avoid this interference.
- If analyzing substances that absorb near 200 nm, prepare a "blank" solution containing only the solvent and NaOH (at the same concentration as in the sample) to subtract its background absorption from the sample measurement.
| Substance | Absorption Wavelength Range |
|---|---|
| NaOH | ~ 200 nm (UV) |
| Water | Below ~ 190 nm (UV) |
Reference: Tong, et al. (2020). [Insert specific reference title or context if available, otherwise keep as is to reflect the provided text]. Note: The provided reference snippet mentions the core finding but lacks full publication details. The key takeaway is the absorption at ~200 nm as stated.
