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## Main Question or Discussion Point

Hello,

I am wondering how to make a standard additions curve for this experiment. In this experiment, we used cyclic voltammetry to determine the original concentration of an elixir. We diluted the elixir to 0.75mM based on a claimed concentration of acetaminophen (instructed) and an elixir density of 1.1g/mL. We used 10mL of this dilution and measured the peak anodic current after each 20uL addition of 10mM standard solution of acetaminophen.

I know that I have to plot the points and create a linear regression that I will then use to solve for the x-intercept (concentration of acetaminophen present). Current is on the y-axis, but how do I calculate the x values of my points?

I know of two options that I could use for this particular experiment:

1. Use concentration

2. Use volume

I do not quite know how to do #1...I tried to multiply the original elixir molarity by 10mL to obtain moles of elixir and divide by 10mL + incremented volume (e.g. 1x = 75uL, 2x = 150uL, etc.), but since the additions were small, my molarity barely changed. I don't think this is right..?

#2 was fairly easy because I just used the incremented volumes. However, the x-intercept of this equation tells me simply the original volume of acetaminophen present. How do I find the starting concentration from this?

I have considered:

1. Multiplying the original elixir molarity by volume (0.75mM*10mL - with correct units, of course) and then dividing by the x-intercept value to obtain molarity. Does this work since I started with moles of elixir?

2. Dividing the x-intercept by 10mL (original volume) to get the ratio, which may give me the relative moles of acetaminophen? Then divide these moles by 10mL to obtain molarity (with correct units, of course). This was hinted to be the correct method by the professor, but I am not sure if it is valid.

Could someone please go through and explain both methods to me? I would like to know for this homework as well as for future reference in case I need to do this later on. Thank you in advance!

I am wondering how to make a standard additions curve for this experiment. In this experiment, we used cyclic voltammetry to determine the original concentration of an elixir. We diluted the elixir to 0.75mM based on a claimed concentration of acetaminophen (instructed) and an elixir density of 1.1g/mL. We used 10mL of this dilution and measured the peak anodic current after each 20uL addition of 10mM standard solution of acetaminophen.

I know that I have to plot the points and create a linear regression that I will then use to solve for the x-intercept (concentration of acetaminophen present). Current is on the y-axis, but how do I calculate the x values of my points?

I know of two options that I could use for this particular experiment:

1. Use concentration

2. Use volume

I do not quite know how to do #1...I tried to multiply the original elixir molarity by 10mL to obtain moles of elixir and divide by 10mL + incremented volume (e.g. 1x = 75uL, 2x = 150uL, etc.), but since the additions were small, my molarity barely changed. I don't think this is right..?

#2 was fairly easy because I just used the incremented volumes. However, the x-intercept of this equation tells me simply the original volume of acetaminophen present. How do I find the starting concentration from this?

I have considered:

1. Multiplying the original elixir molarity by volume (0.75mM*10mL - with correct units, of course) and then dividing by the x-intercept value to obtain molarity. Does this work since I started with moles of elixir?

2. Dividing the x-intercept by 10mL (original volume) to get the ratio, which may give me the relative moles of acetaminophen? Then divide these moles by 10mL to obtain molarity (with correct units, of course). This was hinted to be the correct method by the professor, but I am not sure if it is valid.

Could someone please go through and explain both methods to me? I would like to know for this homework as well as for future reference in case I need to do this later on. Thank you in advance!