mnick12
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Used uv vis experiences
Has anyone here ever purchased a used uv vis spectrometer?
The reason why I ask, is I am in the market for one to analyze tannin content in some of my cider apples. However most the ones one ebay say something
like "powers up but I don't know if it works" etc. Basically if anyone has ever purchased second hand equipment I would be curious to know what your
experience was like. Secondly, I would also like to know what you would advise against and for in the buying process. Thirdly, what about operating
software? In my limited spectroscopy experience there is software needed to run the instrument, how do you get that second hand?
Thanks
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phlogiston
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Especially in older instruments, a computer is often only optionally needed. Some machines (even modern ones) allow you to perform simple absorbence
measurements manually. They will have a user interface that allows you to adjust basic settings such as the wavelength manually and feature a display
that shows absorbance.
A computer offers benefits though, especially if you want to acquire spectra or want to use it to follow reactions in time. This could theoretically
be done manually as well but is much more convenient if it is automated. Computer-controlled machines may have settings that can only be changed via
the computer interface.
So, I would recomend checking to what extent it can be manually controlled.
Your concern that it may be difficult to obtain the instrument-specific control software is valid, especially for old instruments that may work only
with archaic versions of windows or even DOS or OS/2. So, if computer control is needed, make sure the seller can also provide the control software
and make sure you have a PC that can run it if it is old.
Another thing to note is that deuterium lamps (UV) have a limited life and can be costly to replace. For older machines replacements may be harder to
find. You'll eventually have to replace it if you use it, but if a new lamp was recently installed or it comes with spares, that is nice.
I have an old but functional machine that was given to me. The PC built into it failed. I reverse engineered the internal control signals from the
manual controls and built a simple USB interface that connects to my PC with simple software that I wrote to acquire spectra. It works, but took a bit
of work.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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mnick12
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Thanks phlogiston,
I would like the computer interface for a number of reasons. As you mentioned collecting spectra is part of my goal to monitor seasonal variances in
the fruit. Also I was considering using it for cell densities to monitor fermentation progress.
If I have to I will fork over the $, but for right now I don't really want to spend over 1k on the instrument.
I will be keeping an eye on university surplus, but right now the inventory is bunk
I wish I could find some seller that advertises something other than "powers on but no testing done, $500", like someone is going to pay $500 for a
broken POS.
How hard was it to interface the machine? I am not very literate in electronics.
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phlogiston
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Very old machines that may be functional but that look like junk should not cost more than $100-$200.
More modern ones that have a functional PC interface and pass a self test (which usually means that at least the lamps and detector work) will cost
more, but I would be surprised if it is impossible to find one well below $1k.
If a seller does not want to test it, perhaps you can ask if they might allow you to perform a few simple tests yourself, You could verify that it
takes spectra, and that it gives more or less the results you expect.
One more thing I forgot to mention: You are also going to need cuvettes. I don't know much about the spectrum of tannins, but I suspect that the area
<350 nm may be of interest to you. You might want to check, and it if it is, you will need quartz cuvettes for makgin measurements in the UV part
of the spectrum, because optical glass cuvettes are not sufficiently transparent at those wavelengths. Quartz cuvettes will add some cost.
For checking cell density, glass cuvettes will suffice and nearly any instruments will do. A flow-through cuvette would be a conventient assecoiry.
Interfacing the old machine was not particularly hard, but it does require some knowledge of electronics, both analog and digital, and some measuring
equipement (oscilloscope). I would say if you do not already feel confident that you could do it succsesfully, you probably don't want to go that
route. And you'd still need an instrument with known functional optics to work with
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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