Why Are My Liquid Analyzing Device Results Inconsistent at Low Concentrations?

In summary, the person is experiencing inconsistent results with their liquid analyzing device based on the Beer-Lambert law when using low concentrations of colored liquids. They have tried cleaning the cuvette and varying the room temperature, but the results are still inconsistent. The inconsistency may be due to small contaminants becoming more noticeable at lower concentrations. Generally, spectrophotometers are more reliable at higher absorbance levels. The person is seeking advice on how to improve their results at low concentrations.
  • #1
surepic
I made liquid analyzing device based on beer lambert law. I am getting very accurate results when using rich colored liquids but when concentration of colored liquid is dropping beyond certain level I am getting non consistent results. Example:
Mixing 2 liquids with concentration 10:1 or 30:1 I am getting same results even after 200times testing but when concentration is falling to 50:1 60:1 I am starting to get different results.
My question is what can effect results at low concentration? Fingerprints? Room temperature?
Im cleaning cuvette with 99% isopropyl alcohol. After that no stains are visually detectable. Toom temperature can vary 5c degrees. So what is causing results to vary?
 
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  • #2
Welcome to the PF. :smile:
surepic said:
I made liquid analyzing device based on beer lambert law.
Can you post a schematic of your device, as well as drawings and pictures of it? That may help us to figure out what issues may be causing problems.
 
  • #3
surepic said:
I made liquid analyzing device based on beer lambert law. I am getting very accurate results ...
How cool.

What @berkeman said.
 
  • #4
Sorry I think I posted in wrong branch of the forum. Problem is not in design or in electrical part its more chemistry related problem.
 
  • #6
Well, if you are getting inconsistent results for diluted solutions (→ strong signal because of a weak absorbance) then perhaps problem does lie in the electrical part.
 
  • #7
Low absorbance solutions can often give inconsistent results because you can begin to see the effects of small contaminants (dust, fingerprints on the cuvette window, imperfections in the cuvette, etc.) whereas these effects are not noticible when the absorbance of the solution is higher. Generally, spectrophotometers are reliable around the 0.1-1.0 Absorbance range.

What absorbance readings are you getting with your different dilutions?
 

1. What is a liquid concentration problem?

A liquid concentration problem is a mathematical problem that involves determining the amount or concentration of a substance dissolved in a liquid solution. It typically involves using the known quantities of the solution and the substance to calculate the unknown concentration.

2. How is liquid concentration typically expressed?

Liquid concentration is typically expressed as a ratio or a percentage. For example, a concentration of 0.5 M would mean that there is 0.5 moles of the substance per liter of solution, while a concentration of 25% would mean that there is 25 grams of the substance per 100 milliliters of solution.

3. What is the formula for calculating liquid concentration?

The formula for calculating liquid concentration is: C = m/V, where C is the concentration, m is the mass of the substance, and V is the volume of the solution. This formula can be rearranged to find any of the three variables, depending on which is known and which is unknown.

4. How can I determine the concentration of a solution without knowing the volume?

If you know the mass of the substance and the concentration, you can use the formula C = m/V to solve for the volume. If you know the mass of the substance and the volume, you can use the formula C = m/V to solve for the concentration. And if you know the concentration and the volume, you can use the formula C = m/V to solve for the mass of the substance.

5. What are some real-world applications of liquid concentration problems?

Liquid concentration problems are commonly used in chemistry, biology, and environmental science to determine the amount of a substance present in a solution. For example, in a chemistry lab, you may need to calculate the concentration of a certain chemical in a solution to ensure that the experiment is conducted accurately. In environmental science, liquid concentration problems can be used to measure pollution levels in water sources. Additionally, in the food and beverage industry, liquid concentration problems are used to ensure that products have the desired taste and consistency.

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