Home-made fluorometer?

Dr E. Buxbaum EB15 at le.ac.uk
Mon Nov 4 06:47:49 EST 1996


Susan Jane Hogarth <sjhogart at unity.ncsu.edu> wrote:
>Hi,
>
>I'm thinking about making a fluorometer for myself. I'm not sure why the
>commercial ones are so expensive - is it the light source? Has anyone
>out there built one? In principle, it seems like a simple thing; any
>reason it couldn't be easily done with a half-decent machince shop and a
>pretty good knowledge of electronics (that would be my other half:)

That depends on the specification you expect from your maschine. The 
light source is usually a Xenon lamp of 150-200 W (a couple of 100 US$, 
depending on manufacturer, lifetime several hundred to thousend hours), 
but if you are interested only in visible light, a halogen lamp might do. 
The next stage would be a monochromator. If you always use the same 
fluorophore with known absorption and emission maxima, a filter set might 
do, otherwise you need a grating monochromator for the exitation and one 
for the emission beam. The light is then directed to a detector, usually 
a photomultiplier, but a photodiode may suffice, if low sensitivity and 
low speed is acceptable. The electrical signal is then amplified, 
measured or fed into a computer via an A/D converter. Part of the price 
is determined by the electronics: the faster, the more expensive. With 
good electronics and a good photomultiplier, you can get measurement 
times of about 100 usec (faster times are usually achieved with laser 
light sources). This is important for kinetic measurements (stopped flow, 
temperature jump ect). 

In short: a primitive fluorimeter can be build from the following 
components: An optical bench, a 200 W halogen bulb, a lens creating a 
parallel light beam, a high pass filter (which lets all light pass of 
wavelength shorter than the absorbance maximum of your label), a sample 
cell, and (at 90 degrees from the excitation beam) a low pass filter 
(which blocks all light of shorter wavelength than the emission maximum 
of the label), a lense focussing the emitted light onto a photodiode, an 
amplifier and a galvanometer. This could be build for less than US$ 1000 
in materials. However, you would be very limited in the applications. 
Nice high school project, though.




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