Applications of fluorescence spectrophotometry in pharmaceutical analysis

After the fluorescence of the sample extract in methanol has been determined, 

1 M sodium hydroxide solution is added to the sample solution and the fluorescence is determined again. The addition of sodium hydroxide removes the fluorescence by ionising the phenol group of the ethinyloestradiol and thus any residual fluorescence which is due to excipients can be subtracted from the reading. In the BP assay the ethinyloestradiol content of the tablet extract is determined by comparison with the fluorescence of a solution containing a known amount of ethinyloestradiol standard analysed using the same conditions. 

A methanolic extract from ethinyloestradiol tablets is measured using fluorescence spectrophotometry. A standard containing the pure drug is also measured under the same conditions. Calculate the content per tablet of the dmg from the following data  

Fluorescence reading of sample after addition of 0.1 M NaOH = 3.5. 

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