Question

The structures of naproxen (pKa = 4.2) and codeine (pKa = 8.2) are given below. A liquid-liquid extraction of a mixture of naproxen sodium and codeine hydrochloride that would partition naproxen into the aqueous layer and codeine into the organic layer would require an aqueous layer pH of

A. 10.2

B. 2.2

C. 6.2

D. 4.2

7. Which of the following is not an acceptable confirmatory test under SWGDRUG guidelines?

A. Fourier transform infrared spectroscopy (FTIR)

B. Enzyme-linked immunosorbent assay (ELISA)

C. Mass spectrometry (MS)

D. Nuclear magnetic resonance spectroscopy (NMR)

. Which of the following techniques is considered to be a non-destructive technique?

A. Gas chromatography-mass spectrometry (GC-MS)

B. qualitative color tests

C. Fourier transform infrared spectroscopy (FTIR)

D. Enzyme multiplied immunoassay technique (EMIT)

Answer 1

6) Naproxen pKa is 4.2 hence above pH 4.2 it will be in dissociated form. And Codeine will be free base above pH 8.2, hence at pH 6.2 Naproxen will be in dissociated form and it will be in aqueous layer, leaving codeine hydrochloride in organic layer as this pH is not sufficient for its dissociation.

Answer is option C. 6.2

7) FTIR is not an acceptable confirmatory test under SWGDRUG guidelines.

8) GC-MS detects compounds based on fragmention patteren, hence it is distructive technique.

Qualitative color test involves chemical transformations and hence it is distructive technique.

EMIT as well involved chemical transformation and hence it is also a distructive technique.

Only FTIR is non-distructive technique as sample is scanned without doing any chemical transforamtion. There are other spectroscopic techniques which are non-districtive along with FTIR.

Hence answer is FTIR.