Scan a range of UV-Vis wavelengths to identify absorption peaks for mercury nitrate, accounting for potential interference from nitrate ions. Consider alternative detection methods like silver nanoparticles or machine learning approaches to enhance accuracy.

You have to go for protocols that require the addition of reagents that produce color after a reaction with your analyte (mercury) for any spectrophotometric assays if the resulting solution is colorless.

Be aware that if you are going to be using crude samples with bacterial cells then there is likely to be a very high background of UV absorption from the cellular components (or from components in the growth medium if you are using rich medium).

Hello Dr. Michael J. Benedik ,

I'm still learning about this, and I'm wondering how this background absorption might specifically impact my experiment, since I'm planning to use UV-Vis spectrophotometry to measure mercury concentration in my bioremediation assays. I'll be measuring the mercury concentration in samples before and after the bacteria are introduced, to see how much mercury they remove. To do this, I am planning to create a calibration curve to know the wavelength that I'll be using in order to quantify the mercury in my samples. Could you explain how the background absorption from bacterial cells or the growth medium might affect these measurements, and if there are any steps I should take to minimize its impact?

It will depend upon how much mercury you have in your sample, or more precisely how much absorbance signal you will have. The protein and DNA in cells absorb very strongly from about 210 to 300 nm (and other molecules in the the cells absorb at other wavelengths). So if the signal from your mercury is less than the background signal from the cellular contents, you won't really see it.

Just take a bit of cell culture similar to what you might use in your experiments and do the UV-VIS scan of that and you will see what I mean.

You might be able to clean up the background a bit if you removed all the cells by centrifugation or filtration and just measured the supernatant. But there will still be some background from lysed cells.

Also what medium are you using? If minimal medium then you might be ok, but if it is some nutrient broth or LB then that will also have a very high UV absorption.

Thank you very much for this information Dr. Michael J. Benedik ! I will be using Nutrient Broth (NB). I understand that NB has a high UV absorption, which will contribute to significant background interference. I'm concerned this might affect my mercury measurements, especially since I'm analyzing samples before and after bioremediation. Apart from centrifugation and filtration, which I originally plan on doing, how else can I minimize this background absorbance, since these steps alone cannot completely eliminate the problem?

Should I consider using a different medium with lower UV absorption? Are there alternative analytical methods that would be more reliable for mercury detection in this setup? Also, do you have any published papers where I can read more about this issue? Thank you in advance for your response!

Since mercury nitrate is colorless, it does not absorb visible light, so traditional UV-Vis spectrophotometry in the visible range may not work. However, you can determine its absorption wavelength using the following approaches:

1. UV-Vis Spectroscopy in the Ultraviolet Range:

• Procedure: Prepare a diluted aqueous solution of mercury nitrate and run a UV-Vis scan in the range of 200-400 nm, focusing on the UV region.

• Rationale: Many colorless inorganic compounds, including metal nitrates, absorb light in the UV range due to electronic transitions, such as ligand-to-metal charge transfer (LMCT) or nitrate-related absorption.

2. Complexation with a Chromophore:

• Method: React mercury ions with a colorimetric reagent (e.g., diphenylcarbazone) to form a colored complex.

• Benefit: This shifts the absorption into the visible range, allowing for easier detection using UV-Vis spectroscopy.

3. Atomic Absorption Spectroscopy (AAS):

• Application: For mercury ions, AAS is a highly sensitive method that measures the absorption of light by mercury atoms, typically at 253.7 nm.

• Use Case: Especially useful for detecting mercury in various oxidation states, including from mercury nitrate.

4. Infrared (IR) Spectroscopy:

• Although not for absorption wavelength in the UV-Vis sense, IR spectroscopy can identify functional groups like nitrate (NO₃⁻) through characteristic vibrational bands.

Thank you very much for this response Dr. Shler Ali Khorshed ! Your insights on the different approaches for determining the absorption wavelength of mercury nitrate are very helpful!

I just want to ask if you have published any papers on this topic or related studies that I could cite in my undergraduate thesis methodology. It would really be great to reference your work as I proceed with my experiment to determine mercury nitrate's its absorption wavelength using UV-Vis Spectroscopy in the UV range.

Additionally, could you recommend some commonly used colorimetric reagents for mercury detection? Since you mentioned diphenylcarbazone, are there other common reagents that would work well for forming a colored complex with mercury ions?

On another note, I want to ensure laboratory safety while working with mercury nitrate under UV-Vis spectrophotometer. Based on my readings, mercury is sensitive to UV light and will volatilize, which raises concerns about potential mercury vapor exposure. Will mercury nitrate vaporize under these conditions?

Thank you very much for your time and expertise! Looking forward to your response.

Thank you Danny I am sorry I don’t have any paper tha you want good luck .

Kind regards

Dr.Shlet Ali Khorsheed