I have been working on heavy metal sequestration via adsorption mechanism. In order to calculate further statistical values, Ci (initial concentration) value is required. I use AAS to detect the absorbance values of adsorbent treated aqueous samples. As AAS equipment could only detect values up to 5 ppm concentration. I diluted all higher concentrations (ppm) to 5 ppm value. As we took only two standard values first at 1 ppm and second at 2 ppm to proceed. As I earlier mentioned I diluted all Higer concentrations to 5 ppm. As I only get two standard values, I followed a mathematical relation (Ref: Bracketing technique 1.4: Introduction to Atomic Absorption Spectroscopy - Chemistry Libre Texts) to draw a calibration curve from 1 ppm up to 100 ppm. JPEG of mathematical relation and calibration curve is attached. I just wanted to conform
- Is this method right for drawing a calibration curve
- What are pros and Cons of this method
- Can I trust the Ci value by following above mentioned, for further statistical evaluation like Co, % removal, Qi etc.
Hello Salah,
Thank you for sharing your question with the RG community. Unfortunately, I cannot yet understand your methodology. The bracketing technique is an interpolation technique. This means that if your standards have 1 ppm and 2 ppm, the concentration of your sample for measurement must be between these values. If I got you right, your samples are at 5 ppm and therefore outside the bracket. The bracketing technique does not aim to create a calibration curve up to high concentration ranges.
I wish you much success for your research.
Thanks, Florian Morsbach , for considering my question.
Yeah, you are right.
- AAS equipment only able to detect values ranging from 1 ppm to 5 ppm in my institute.
- I had higher concentration values but I diluted them by adding distilled water to 5 ppm so they would be detectable by AAS.
- I use these 1 ppm and 5 ppm concentration (in equation) to assume the higher concentration e.g. 10, 20, ... 100 ppm in order to draw a calibration curve.
I am afraid that there is a misunderstanding here. The bracketing technique has nothing to do with the creation of a calibration curve. The reason that your AAS instrument only measures in the range from 1 ppm to 5 ppm is because the linear range of the calibration curve ends at some point above 5 ppm. It makes no sense to construct a "virtual" calibration curve up to 100 ppm because there is no real equivalent.This means for your specific case: A sample with a measured absorbance of 2 does not really correspond to a concentration of 60 ppm, because this absorbance is very likely no longer in linear range. I still don't understand how exactly you used the equation from the text you attached.
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