I am currently doing research on total flavonoid content. I use Quercetin as standard for my calibration curve. The regression coefficient is 0.99. I use different solvent extracts as my samples. Apparently my extracts show higher absorbance value than my calibration curve. My question, does the equation generated from the calibration curve still valid to calculate the concentration of my extracts? Alternatively should I dilute the extracts until the absorbance values are within the calibration curve. Thank you.
Hi,
If you are using the AlCl3-NaNO2 method for total flavonoid content, I recommend you use Catechin instead of Quercetin. This will give you higher absorbance values. Regarding your second question, you should proceed to dilute your samples in order to interpolate your results in the calibration curve. Extrapolation of results is not correct, since the linearity of the assay is limited to a certain range of concentrations.
Best regards,
Hi,
If you are using the AlCl3-NaNO2 method for total flavonoid content, I recommend you use Catechin instead of Quercetin. This will give you higher absorbance values. Regarding your second question, you should proceed to dilute your samples in order to interpolate your results in the calibration curve. Extrapolation of results is not correct, since the linearity of the assay is limited to a certain range of concentrations.
Best regards,
You should dilute your plant extracts to get the absorbance within the range of standard cure. Then only you will conclude the quercetin equivalent of your plant extract.
Hi, I agree with the comments above. Before you did routine analysis for your work, please do not forget to do validation method first
Hi, I agree with the comments above. If you are not particular about Quercetin, you might also want to change your standard. Gallic acid has a wide absorbance range. Otherwise, dilute your samples.
Regards
Yes, you should dilute your sample. The value of concentration determined in diluted sample (amplified with dilution factor) is always higher than the concentration determined without dilution. Usually the absorbance value should be lower than 1.5.
Why if the flavonoid content is calculated according to the regression equation obtained from standard calibration curve, instead of making dilutions?
F.Romain Fouelefack. Extrapolating the results to obtain the TFC is not the right approach in this case as the assay is mostly concentration dependant and based on the standard used. Therefore, to get accurate results the best approach is to interpolate the absorbances of the samples to the standard used
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