Measuring the intensity of a non-fluorescent color

Hi everyone,
I have some solutions containing different concentrations (unknown) of a non-fluorescent color (red). Is it correct to measure the intensity of the solution and find out the concentration using the standard curve? actually I don’t know if the intensity measurement only works on fluorescent images or not.
I will be grateful if you can help me on this.

Have a look here:

Use a spectrophotometer to measure the absorbance.
As you can see from the above, it works for non-fluoerscent dyes because it measures absorbance.

Hi Gabriel

Thank you for your kind response! Yes I know about the spectrophotometer. We tried it before, but we have some limitations to use it now. we are using a microfluidic device and are not able to sampling from different parts of channels!


Hi Parinaz,

You can indeed measure non-fluorescent signals in ImageJ. There is juste a little tweaking to do on the data :wink:
If you don’t change anything, when you do your standard curve you will get a negative slope (your solution gets darker with higher concentrations). You can use it as it is, but it can get quite confusing.

Assuming you work with black&white pictures, it is quite easy to get a more intuitive standard curve: just invert the intensity values to get a negative image before doing your measurements (Edit > invert, or ctrl+shift+I).
note that this is different from inverting the LUT (image > Lookup Tables > invert LUT) which invert only the display, not the actual values.

If you already did your measurement, you can get the same results by subtracting the measured values from the maximum intensity (this depends on your file type).

I hope this is helpful !