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Thread: Calibration Curves

  1. #1 Calibration Curves 
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    I have been carrying out quite a lot of UV/Vis (and also fluorescence) spectroscopy recently and have been wondering about the calibration curves I have obtained.

    My question is basically whether the intercept should be forced to zero when calculating the equation for the straight line from the calibration curve, and does any rule that may exist vary when you have a point at 0,0? Or, is the decision based on the goodness of the fit (and maybe personal preference)?


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  3. #2  
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    Did you set your baseline to zero?

    If say water was your background and you were testing the absorbance of permanganate and you set water as zero absorbance, then yes your trendline should be forced through 0.


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  4. #3  
    Forum Sophomore Matt Lacey's Avatar
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    Personally I wouldn't force the curve through zero... keep the data as it is and put error bars on your curve. I imagine you're after the molar extinction coefficient of whatever it is you're studying so this way you'll get a better estimation & error.
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  5. #4 line of best fit 
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    Are you assuming that the calibration curve is a straight line? Perhaps it is a curve. I think the most importance thing regardless of what you decide is to be consistent in your approach through out your analysis. If you are using standard addition for calibration checks this will help.

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