Calculating Iron (Fe) PPM from mL Lab Sample

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In summary, the conversation discussed a lab where the amount of iron in a vitamin was determined through absorbance measurements. A standard Fe solution with a concentration of 0.04 mg/mL (40 ppm) was prepared and used to create a calibration curve. The conversion from mL to concentration was clarified, and it was determined that the concentration of the 10mL standard solution was 4 ppm after being diluted in 100mL. There was also a question about accounting for dilution, which was confirmed to be necessary.
  • #1

Homework Statement

Hi. I just did a lab where we are to determine the amount of iron present in a vitamin based on its absorbance (after reacting it with hydroquinon and o-phenanthroline) and I am having trouble making a conversion.

At the beginning of lab, we prepared a " .04 mg/mL = 40 ppm " standard Fe solution.

For our calibration curve, we made 1 sample using 10 mL of standard Fe mixed with some citrate (to adjust ph i think), 2mL of hydroquinone, and 3 mL of o-phenanthroline and then diluted with water to 100mL.

Then, samples was made using 5, 2, 1 and 0 standard iron.

I took absorbances and now need to construct my calibration curve, but I am to use concentration, not mL.

Let's say, for the 10mL standard Fe sample. Am I supposed to just say that for every mL, there are .04 mg of iron and for every .04 mg of iron it is 40 ppm. So 10 mL is .04*10=.4mg of iron and .4 mg of iron is 400 ppm ?

is this the correct way to convert?

So I would have

1mL std Fe --> 40 ppm
2mL std Fe --> 80 ppm
5mL std Fe --> 200 ppm
10mL std Fe --> 400 ppm

Is this right? I'm not sure if I need to account for the fact that it was diluted? I'm confused.Thank you!
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  • #2
ppm (parts per million) is a unit of concentration. For water, 1 g = 1 mL, so one part per million is equal to one millionth of a gram per mL (i.e. 1 µg/mL = 0.001 mg/mL).

Your standard solution has a concentration of 0.04 mg/mL = 40 ppm. You then dilute 10mL of the 40 ppm solution into 100mL total solution. What concentration is this 100mL solution?
  • #3
ok, so for the 10mL standard, would it be 4 ppm since it is diluted in 100mL? 10mL * .04mg/mL *(1/100mL)= .004 mg/mL = 4 micro g /mL = 4 ppm ?
  • #5


Based on the information provided, it seems like you are on the right track with your calculations. To confirm, you are correct in saying that for every 1 mL of your standard Fe solution, there is 0.04 mg of iron. And since the initial concentration of your standard Fe solution was 40 ppm, this means that for every 0.04 mg of iron, there is 40 ppm. So, for your 10 mL standard Fe sample, there is 0.4 mg of iron (0.04 mg/mL * 10 mL) and this corresponds to 400 ppm (40 ppm/0.04 mg * 0.4 mg).

For your calibration curve, you can use these values to plot your points and determine the equation of the line. Keep in mind that the dilution factor will also need to be taken into account when calculating the concentration of iron in your samples. So for example, if you diluted your 10 mL standard Fe sample to 100 mL, the concentration of iron in that sample would be 40 ppm * (10 mL/100 mL) = 4 ppm.

I hope this helps clarify any confusion you had. Good luck with your lab!

Related to Calculating Iron (Fe) PPM from mL Lab Sample

1. What is the formula for calculating Iron (Fe) PPM from mL Lab Sample?

The formula for calculating Iron (Fe) PPM from mL Lab Sample is: (Fe concentration in mg/L) x (1000 mL/L) x (mL sample) = Iron PPM in sample.

2. What is the purpose of calculating Iron (Fe) PPM from mL Lab Sample?

The purpose of calculating Iron (Fe) PPM from mL Lab Sample is to determine the concentration of Iron in a given sample. This information is crucial in understanding the quality and composition of the sample, and can be used for various applications in research, industry, and environmental analysis.

3. How do you obtain the Fe concentration in mg/L for the calculation?

The Fe concentration in mg/L can be obtained by conducting a chemical analysis of the sample using techniques such as spectrophotometry, atomic absorption spectroscopy, or colorimetry. These methods involve measuring the absorbance or intensity of a specific wavelength of light emitted or absorbed by Iron in the sample, and converting it to the concentration value.

4. What factors can affect the accuracy of the Iron (Fe) PPM calculation?

There are several factors that can affect the accuracy of the Iron (Fe) PPM calculation, such as human error, calibration of instruments, sample contamination, and sample dilution. It is important to carefully follow the correct procedures and techniques, and regularly calibrate the instruments to ensure accurate results.

5. Can the Iron (Fe) PPM calculation be used for all types of samples?

The Iron (Fe) PPM calculation can be used for most types of samples, including water, soil, plants, and food products. However, the method of sample preparation and the specific techniques used for analysis may vary depending on the type of sample. It is important to consult the appropriate guidelines and protocols for accurate and reliable results.

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