External Standard , Internal Standard, and Standard Addition | Chemistry with Dr. G

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[@siyabongamnyoni1699]

Thank you for highlighting the differences between the quantifying techniques, Dr. G. Looking forward to more videos 👏👍

[@ChemistrywithDrG]

Glad it was helpful!

[@yukinaminato]

Thank you so much, sir! This video is really helpful.

[@ChemistrywithDrG]

Glad it was helpful! Thank you for letting me know.

[@dhuhabariysa6869]

this was very helpful, thank you!

[@ChemistrywithDrG]

Glad it was helpful!

[@yunengliao6190]

Good! thank you for sharing!

[@ChemistrywithDrG]

Glad it was helpful

[@didiez8678]

So helpful, thank you so much !

[@ChemistrywithDrG]

Glad it was helpful!

[@normanbates6638]

Great video, thanks!

[@ChemistrywithDrG]

Great. Glad you liked it.

[@devpatel2309]

thank you , keep it up

[@ChemistrywithDrG]

Glad to hear it is helpful.

[@ivanbombana7282]

Good morning. What should I do to understand if I have matrix effect?

[@ChemistrywithDrG]

You could think about measuring an external standard with a known concentration with the instrument. Then dope in the same standard analyte amount into the sample and see if you get the same signal increase in the doped standard as in the external standard. For example, an external standard with a concentration of 0.2 M gave a signal of 0.5. The sample gives a signal of 0.3 for the analyte. If the sample doped with 0.2 M gives a signal of 0.8 (the sum of the sample and the external sample signal) then there is no matrix effect. However if it differs from this then you know there is a matrix effect.

[@user-rq6dx5ro3w]

Thank you sir, for your nice explanation. i have one question regarding standard addition. If the unknown concentration shows a negative signal(i.e S1(absorbance)= -0.1245) of arsenic due to matrix(salt) effect in an atomic absorption spectrometer then how i will calculate it from standard addition method? waiting for your kind response.

[@ChemistrywithDrG]

This seems like that you would want to reconsider your blank that you used for the calibration of the instrument. Also, the arsenic concentration might be too low and below the LOD

[@ChemistrywithDrG]

The concentration might be too low and below the LOD. Also, you would want to check the blank you use for calibration as they may contribute to the negative signal.

[@PritomAhad]

So with internal standard, am i still getting a conc v signal graph nd using it to find conc of unknown?

[@ChemistrywithDrG]

You will be using a comparison. You will have a standard solution that has a known amount of the analyte you are interested in quantifying (for example caffeine) and a known internal standard concentration added (for example benzoic acid) and get a signal for both caffeine (analyte) and benzoic acid (internal standard). Then you will add the same amount of benzoic acid to your unknown solution as an internal standard. Get the signal for both caffeine and benzoic acid, then compare the signals for caffeine and benzoic acid from the standard solution to the unknown solution.

[@za7607]

Great thank you! I have a question. how should I specify the maximum and minimum range for calibration carve while I have no idea about the concentration in my sample?

[@ChemistrywithDrG]

Great question. If you are unaware of the concentration of your sample, you will want to do some research about the instrument you are using. What is the linear range possible with the instrument? What is the LOD or LOQ? Then, do a first test of your sample with a dilution, to make sure that the pure sample will not overload your detector or your analytical system. If it is low, then analyze the sample at higher and higher concentrations, until you get a significant signal.

[@za7607]

@@ChemistrywithDrG thank you for replying 🙂 so helpful !

[@ChemistrywithDrG]

@@za7607 Glad it was helpful!