Analysis of Atomic Absorption Spectroscopy results

• Organoid
In summary, the machine's results provide us with an average concentration and standard deviation for the three tests run, but the diluted solutions give different results. The equation connecting the variables AA and C doesn't seem to work correctly.
Organoid

Homework Statement

Hello,

This week I ran an AA Spectroscopy experiment in my university, in which we had to analyze the percentage of Copper in a metal coin, and the containment of Iron in morning cereal.

We used 2 standard solutions of 1 and 10 ppm (containing both Copper and Iron), and exprimented a few diluted solutions of the extracted Copper and Iron from the substances.

The results we received were an average value and standard deviation of the 3 tests run by the machine.

Homework Equations

My question is: what do the concentration results that the machine provides us with mean? i.e. if 1 and 10 ppm standards had an average of 0.525 and 1.426 respectively, and the diluted solutions (x10, x100, x1000) had an average of 10.72, 4.094 and 2.644 respectively, how can I analyze these results to calculate the original conc. in the original substance?

The Attempt at a Solution

I've generated a standard curve using the standards' results and reveied a linear-fit equation of the graph with a matching slope.
I know that the equation connecting those variables is AA = K x C, (where AA=absorbance, k is the trend line's slope and C is the conc.) but when I tried to apply my results of the diluted solutions to that equation, and by multiplying by the dilution factor, they don't make sense. Each solution gives different concentration of the original solution.

Am I analyzing my results using the standard curve wrong?

I'd appretiate any help, thank you.

Organoid said:
I know that the equation connecting those variables is AA = K x C, (where AA=absorbance, k is the trend line's slope and C is the conc.)

i think you try to relate concentration of the material with dilution so that the AA value can be correlated -perhaps you know k value from the graphs.

drvrm said:
i think you try to relate concentration of the material with dilution so that the AA value can be correlated -perhaps you know k value from the graphs.
I do know the k value from the graphs, but I actually don't have any correlation between the results - if I calculate backwards to get to the initial conc. I get totally different results from each dilution. it doesn't make sense

Organoid said:
the diluted solutions (x10, x100, x1000) had an average of 10.72, 4.094 and 2.644 respectively
If these numbers are correct, then you definitely don't have a linear relationship between AA and C.

I guess you can't redo the experiment, but it is not good at all that the AA of the standard are not in the same range as the AA of the sample.

DrClaude said:
If these numbers are correct, then you definitely don't have a linear relationship between AA and C.

I guess you can't redo the experiment, but it is not good at all that the AA of the standard are not in the same range as the AA of the sample.
I think that we couldn't predict such high conc. of the original substances. Either way, I could use extrapolation to calculate the initial conc., but if these are the results we recieved, how can I still utilize them?

Organoid said:
but if these are the results we recieved, how can I still utilize them?
try to see some work being done on the net

for example ;
http://www.ausetute.com.au/aas.html

drvrm said:
try to see some work being done on the net

for example ;
http://www.ausetute.com.au/aas.html
I'm already familiar with this procedure, I wish I only had tested one solution but I had a series of dilutions so it makes it much more complicated since there is actually no correlation between the absorbance and the dilute. By my last phrase I mean that if I dilute by x10, I don't get a linear fit between the absorbance of the dilution and the original solution I used to make the x10 dilution for.

1. What is Atomic Absorption Spectroscopy (AAS)?

Atomic Absorption Spectroscopy is a scientific technique used to determine the concentration of a specific element in a sample. It works by using light of a specific wavelength to excite the atoms in the sample, causing them to emit light at that same wavelength. The amount of light absorbed by the atoms is then measured, and the concentration of the element can be calculated.

2. What types of samples can be analyzed using AAS?

AAS can be used to analyze a wide range of samples, including liquids, solids, and gases. It is commonly used in environmental, pharmaceutical, and industrial laboratories to measure the concentration of elements in various substances.

3. How is the concentration of an element determined using AAS?

The concentration of an element is determined by comparing the absorbance of the sample to a calibration curve. This curve is created by measuring the absorbance of known concentrations of the element, and a mathematical equation is used to determine the concentration of the unknown sample based on its absorbance value.

4. What factors can affect AAS results?

Several factors can affect AAS results, including the type of sample being analyzed, the concentration of other elements in the sample, the temperature of the sample, and the quality of the instrument being used. Proper sample preparation and calibration are also crucial for obtaining accurate results.

5. How can the accuracy and precision of AAS results be improved?

The accuracy and precision of AAS results can be improved by using high-quality instruments, properly preparing samples, and following strict quality control measures. Regular maintenance and calibration of the instrument is also essential to ensure accurate results. Additionally, running multiple replicates of the same sample and using statistical analysis can help to improve precision.

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