Measuring Formaldehyde Concentration: The Role of NaOH

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In summary, Albert is looking for a method to measure the concentration of formaldehyde in a diluted solution. Lisab suggests a wet chemistry method using commonly available chemicals and provides step-by-step instructions. Albert asks about the concentration of NaOH and later mentions having access to gas chromatography instruments but prefers a quick and simple method with an accuracy of +/- 0.5%. Lisab clarifies that 1.0 M NaOH is needed for the procedure.
  • #1
biobird
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Hello all,

In order to re-use formaldehyde from a dilluted solution (in water) I need to know the concentration of formaldehyde in the dilluted solution.
Can anyone tell me how to measure this concentration? It does not have to be very accurate.

thanks in advance,
Albert
 
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  • #2
Hi biobird -

I'm not sure what equipment you have available to you, but here's a wet chemistry method that uses commonly available chemicals. It's from a commonly used test method to measure HCHO from wood products.

You'll need the following solutions:

0.05 M iodine
0.1 M sodium thiosulfate
1.0 M sulfuric acid
starch solution ~1%

Mix 25ml iodine + 10ml NaOH + 20ml of the solution you're testing. Let it sit 15 minutes away from light. Add 15ml H2SO4 and titrate immediately with the Na2S2O3. When the solution starts to become pale yellow add a few drops of starch solution as an indicator.

Do the same titration procedure on 20ml water (blank).

Calculate the HCHO concentration:

c[HCHO] = (Vo – V) * 750 * c[Na2S2O3]

Where

Vo = volume of Na2S2O3 used in blank titration, in ml
V = volume of Na2S2O3 used titrating the solution you're testing, in ml
c[Na2S2O3] = concentration of sodium thiosulfate in M (0.1 in this case)
c[HCHO] = concentration of HCHO in mg/L
 
  • #3
Hello Lisab,

Thank you very much for your description of this procedure.
I will try it soon.
Does the concentration of the NaOH matter?

greetings, Albert
 
  • #4
Also what kind of instrumentations do you have e.g. Gas Chromatography ?
 
  • #5
Well, I guess we have this kind of instruments at the lab, but I never worked with it. I was actually looking for a quick and simple method with an accuracy of -let's say- plus/minus 0.5 percent. After all, I'm just a simple biologist:confused:
 
  • #6
biobird said:
Hello Lisab,

Thank you very much for your description of this procedure.
I will try it soon.
Does the concentration of the NaOH matter?

greetings, Albert

Ooops, left that out!

1.0 M NaOH will do.
 
  • #7
hi. may i know why NaOH has to be added? - just asking!

thnks
 

1. How do I measure formaldehyde in the air?

To measure formaldehyde in the air, you can use an air sampling device such as a passive diffusive sampler or a real-time monitor. These devices collect air samples and provide a reading of the formaldehyde concentration in parts per million (ppm). It is important to follow the manufacturer's instructions for proper use and calibration of these devices.

2. What is the best method for measuring formaldehyde in water?

The most commonly used method for measuring formaldehyde in water is the colorimetric method. This method involves adding a reagent to the water sample, which reacts with formaldehyde to produce a color change. The intensity of the color is then measured using a spectrophotometer, and the formaldehyde concentration can be determined based on a calibration curve.

3. Can I measure formaldehyde in solid materials?

Yes, formaldehyde can be measured in solid materials such as wood, furniture, or clothing. The most common method for measuring formaldehyde in solids is the desiccator method, which involves placing the material in a sealed container with a desiccant and measuring the formaldehyde concentration in the headspace after a set amount of time.

4. How do I interpret formaldehyde measurement results?

The interpretation of formaldehyde measurement results depends on the type of sample being tested and the method used for measurement. In general, the results will be reported in parts per million (ppm) or milligrams per cubic meter (mg/m3). It is important to compare the results to regulatory limits or guidelines to determine if the levels are safe for human exposure.

5. Are there any safety precautions I should take when measuring formaldehyde?

Yes, formaldehyde is a known carcinogen and should be handled with caution. It is important to wear appropriate personal protective equipment, such as gloves and a respirator, when handling formaldehyde samples. Additionally, proper ventilation should be ensured to prevent exposure to high levels of formaldehyde during the measurement process.

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