Self-test 11.5
\( 1.0512 \mathrm{~g} \) of ampicillin was dissolved in \( 5 \mathrm{ml} \) of \( 1 \mathrm{M} \mathrm{NaOH} \) and the solution was extracted into \( 1 \mathrm{ml} \) of cyclohexane containing \( 50 \mu \mathrm{g} / \mathrm{ml} \) of naphthalene. A \( 1 \mathrm{ml} \) of a calibration sample containing approximately \( 20 \mu \mathrm{g} / \mathrm{ml} \) of \( \mathrm{N}, \mathrm{N} \) dimethylaniline dissolved in \( 1 \mathrm{M} \mathrm{HCL} \) was mixed with \( 4 \mathrm{ml} \) of \( 1 \mathrm{M} \mathrm{NaOH} \) and extracted into \( 1 \mathrm{ml} \) of cyclohexane containing \( 50 \mu \mathrm{g} / \mathrm{ml} \) of naphthalene. The following data were obtained. Calculate the content of \( \mathrm{N}, \mathrm{N} \) dimethylaniline in the sample in ppm:
Weight of \( \mathrm{N}, \mathrm{N} \) dimethylaniline used to prepare calibration stock solution \( =50.3 \mathrm{mg} \) Volume of calibration stock solution \( =50 \mathrm{ml} \)
Dilution of calibration stock solution \( =5 \mathrm{ml} \) to \( 250 \mathrm{ml} \)
Peak area for dimethyl aniline obtained from calibration solution \( =3521 \)
Peak area obtained for naphthalene IS in calibration stock solution \( =23616 \)
Peak area for dimethyl aniline obtained from sample solution \( =543 \)
Peak area obtained for naphthalene IS in sample solution \( =24773 \).
