How to work out the concentration if the unknown sample falls out of the standard range?


Posted on : 06-03-2013 | By : My Study Coach | In : Improve Your Concentration
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I have had to use Flame AAS to determine the concentration of calcium and magnesium in some unknown samples

For example, if a couple of my absorbance values fall below the range of standards for calcium does this mean that there is no calcium in my samples or do I have to extend my graph to accomodate this?

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Comments (1)

Being outside your standards casts a lot of doubt on your results.

That said, it’s not so bad if your unknown has absorbance below your lowest standard; presumably you have a blank, so you can consider that as a standard with a concentration of zero. If your standard graph is still linear going down to the y-intercept, you can have pretty good confidence in your results.

If ever your absorbance is higher than that of your highest standard, however, you absolutely need to redesign the experiment. Use higher standards, dilute your unknown, whatever.

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