UV Spectrophotometry - anyone got experience sourcing UV-C compatible diffraction gratings?

General
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Hi All

I’m working with a team of students to design and document a UV-Vis spectrophotometer that can measure microlitre quantities of DNA/RNA, which means it needs to get down to UV-C, at least as low as 220 nm wavelength.

There aren’t many diffractrion gratings that reach those wavelengths (for example, all the available ones from ThorLabs and Edmund Optics only reach 250 nm) and they are quite pricey - if you have any experience with sourcing components for UV spectrophotometry please let me know. Also more generally, if you have experience of trying to do this previously or thoughts on design then get in touch, we are still in the design and planning phase for the project!

Jenny

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Hi Jenny,
I’m developing a multispectral colorimeter for wine analysis. I need to measure in the UV-C so I’ve been doing some research on that. As far as I know, there are no solid state devices that work in that region of the spectrum (LEDs or photodiodes). The lowest you can go is 280nm. I would like to know what light source are you planning to use and what detector.
Regarding diffraction gratings, you should go for a reflection type (look here).
It would be great to have a talk about this when you are in Mendoza!

Best regards

1 Like
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Hi Pablo

We’re planning on using a xenon light source (Excelitas Technologies Miniature Xenon / RSL-3101-3) and a linear photodiode array sensor (S8378-512Q CMOS Linear Image Sensor from Hamamatsu) - the interim parts are to be determined!

Jenny

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I would ask Francis @few, he’s the person I could imagine would have the best thoughts on this. Francis any ideas here?

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I haven’t worked with UV C spectrometers. Definitely a metallized reflective first surface grating and a detector (with window) that is UV sensitive. Sounds like they’re on a good track already.

Richardson Grating Labs (now part of Newport) is a pretty well known grating source. They have UV compatible gratings. https://www.gratinglab.com/Products/Product_Tables/A1.aspx

From what I have heard, UV C is generally an expensive spectral range to work in. Everything gets tricky. All your optics need to be reflective (like UV aluminum coatings, https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=12393) or UV transparent (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3569).

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We’re definitely finding that UV-C complicates everything! Luckily one of the team members is doing a PhD in optoelectronics and knows a lot about optical fibres which is very helpful for that part.

Thanks for the supplier links! We’ll look into those.

One thing that would be good to try is UV-C LEDs but for DNA quantitiation and quality the key values are 230 nm, 260 nm and 280 nm and many contaminants absorb at 225 nm so a broader spectrum allows better analysis of your sample quantity. 235 nm is the lowest LED wavelength I’ve found and even those are still “engineering samples” e.g. Optan (https://www.optanled.com/) offer 280 nm, 260 nm and 235 nm LEDs. They are $100s each.

Jenny