Ways of estimating waste and bacterial growth in Moina cultures

Ways of estimating waste and bacterial growth in Moina cultures

I am trying to wrap my mind around it but could you simplify a bit the principle and the process by which we use smartphones as colorimeter. I saw the apps but I didn’t understood this section of the reply.

I also didn’t got what you mean by NPK.

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Camera, lens, optical filters and image processing software vary widely between different phone models. Consequently an object photographed on one camera will look different on another.

The mitigation methods involve using a standard image-lightsources and generating a difference component, then using software to incorporate the difference so that one has the original image independent of the phone camera.
Using a regular camera that can give a raw image removes the need for such a complex calibration.

Here is a link about the method f calibration.
Colorimeter-cal-oe-27-14-19075.pdf (2.3 MB)

Nitrates, Phosphates, Potassium - nutrients in plant fertilizer.

Take a light source. Take a sample and add a suitable staining reagent. Shine the light source through the sample. Measure the light intensity passing through the sample using a sensor - your camera in this case. The camera has an app that takes the individual R,G,B values of the image and gives a quantitative measurement of light received and consequently the light absorbance characteristics of the sample. The rate of change of color provides quantitative information.
The first link page 32 onwards provides good explanation.

CAVEAT: My chemical and biology fun ended in school several decades ago.


Details for spectrometer

Several companies make light sensors - TI, Analog, Maxim, Vishay, Kingston etc . Datasheets of possible sensors for use in colorimeter and spectrometer.


A simpler approach :


Please give everyone a short summary on this video. @pratittodkar

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The Theory of the video

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Use this app

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Let’s try it out and identify advantages and disadvantages over a more conventional approach.

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I searched a little bit on the internet the only problem with this method is that the Beer’s Law fails for higher concentrations


Can everyone test this method on there own or is there a need for any further explanation?

what do you mean by Beers Lamberts law? What is it exactly?
How does it fail?
can it be coped up?

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It will be great if mobile can be made into a colorimeter @jtd @pratittodkar


@pratittodkar pls explain what is the purpose of this app?
How will it be useful?

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The only perpose of the app is to note the R G B values of the light coming after passing through the sample. And we can note down the values and then we can calculate absorbance using the intensities.


Beer-Lambart Law states that the absorbance is directly proportional to the length that the light travels through the container and the concentration of the absorbing compound in the medium.

Absorbance = epsilon (constant) * concentration * Length of the light that passes through the medium

Absorbance is an phenomena due to electrons ( hence a electric phenomena ). In higher concentration the charge density of the substance that is going to absorb is affected due to interaction with the solute and other potential molecules that might be present. Hence Beer’s Law fails for around >10mM

I haven’t found a source that makes it possible for us to cope with it.

We can either use that or the defination of absorbance which is
log [ I / I (with zero concentration) ]

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Ask for any explanation if needed and try the experiment as soon as possible.

Is it as simple as, when concentration of solute increases, there can no longer light pass through the solution, hence difference between higher concentrations cannot be determined…

In that case one can dilute the samples first and then detect the concentrations…


@jaikishan No actually it is a bit more complicated than that. See the electrons absorb and emit radiation as they jump between energy states. The whole spectrum of light when shown some of the parts in the spectrum will be missing which will be the radiation absorbed by the electrons of that particular element.

When charge distribution is affected we are talking about affecting electrons and hence affecting the absorption of light by that molecule. So there is error in our results and a divination from the law is observed.

Why not see is there a range of concentration where Beer Lamberts law works?
That will help to know sensitivity of colorimeter…

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