Dear friends,
Today I have got Atomic absorption data of my plant sample in which I have got one sample showing 497.1 microgram/L means in PPB and the Blank reading is 16 PPB
Now I would like to know the calculation formula of AAS data. The sample was solid material which was around 70 mg weighted and it was acid digested followed by made upto 50 ml final volume.
Blank was also processed same except material
Kindly refer me the exact formula to calculate the metal in plant sample with subtracting the blank.
The blank you measured is only for the substraction of impurities, which could have been added by dissolving your plant in acid (also the water or generating a higher baseline etc. --> systematic faults). If you have the pure data of your AAS determination then you will have to substract this from your result before you calculate your analyte concentration back to your sample weight. So youhave:
497.1 - 16 = 491.7 µg/L divided by 20 (50 mL fit 20 times into 1 L) -> so you have 24.585 µg in 50mL --> so you have 24.585 µg absolute per 70 mg solid sample. Just divide by the solid sample weight andthen you have around 355 ng/mg = ppm.
All that you make for your calculation by AAS method, you must take instruction manual for operating by instrument and to make calibration curves for each elements that you need for measurements.
More of AAS instrument, calculated automatically your concentration in the samples by compare with standards concentration.
For more information you must read about AAS method.
Dear Amber,
since you already have your concentration you only need to know if the blank concentration is automatically substracted from the sample concentration (as it is in most cases). If not your concentration in the plant (µg/g) = (Measured concentration - blank concentration (µg/l) * 0.05 l)/ 0.07g -->µg/g
I think this link is useful,
http://www.instanano.com/characterization/theoretical/concentration-calculation-from-uv-vis-absorbance/
AAS uses linear equation when calculating conce: y = mx + b.
Concentration of sample is Y
Absorbance due to background/blank is b, this can be got from y intercept in the graph
Slope of the gradient is x
Kindly note that AAS software plot a graph of absorbance vz. concentration of standards.
To find absorbance due to sample signal (a) you subtract signal due to blank(b);
i.e a-b and to get y=(a-b)/x
You must factor in dilution, for your case(70/50)=1.4
Thus the metal in plant will be=Y*1.4
Dear Gupta,
Send me AAS print out showing absorbance of standards, samples and calibration curves;[email protected]
Metal weight mg/kg = (ppb concentration from AAS * 50)/plant sample weight
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