I understand the use of the internal standard methodology, however I am unsure which values I should use in the equation as although I have been given the internal standard solution I also have been given the second standard solution of both codeine and morphine?
The question is asking to find the content of morphine in the sample tablet (200mg) via the use of an internal standard solution of codeine (50mg) which was made up to 50mL ([codeine] = 1gL^-1). This was given as well as another standard solution of codeine (50mg) and morphine (50mg) made up to 50mL ([codeine] = 1gL^-1).
The equation I have been given is Drfx = (Ax / Ais) X (Cis / Cx)
x = unknown, is = internal standard, A = peak area, C = concentration
First we need to calculate the detector response factor (Drf) of the standard solution - but which standard solution?
Assuming that the standard solution conc. of both morphine and codeine are 1gL^-1, this gives a Drf for the standard solution of 0.722.
Using the calculated Drf value, the Drf equation can be rearranged to find the conc. of codeine in the sample tablet.
However my question is which values need to be used for the Ax and Ais - do they need to be both morphine or just the two values from the sample peak areas? * Values can be found in photo
Any help is appreciated