A pharmaceutical technician has been asked to assay a sealed packet of

chlorphenamine maleate tablets recently manufactured by a local pharmaceutical

company. The assay method to be employed is described below. According to the

labelling of the tablet packaging, each tablet should contain 4 mg of the drug.

HOOC

Chlorphenamine

maleate

a.

COOH

Weigh 20 tablets and determine the average tablet weight. Grind the tablets to a fine

powder and weigh an amount of tablet powder containing approximately 20 mg of

chlorphenamine maleate. Transfer the tablet powder to a 250 mL volumetric flask and

add 25 mL of 0.1M HCI. Shake the flask contents for 5 minutes then make up to

volume using deionised water. Filter a small portion (-50 mL) of the tablet stock

solution using a dry filter funnel and paper. Pipette a 10 mL portion of the filtrate into

a 25 mL volumetric flask and make up to volume using deionised water. Transfer a 20

mL portion of the dilute sample solution into a 50 mL separating funnel and add 0.5 mL

of 3M NaOH. Extract the contents of the funnel with three 10 mL portions of

dichloromethane (DCM). To the combined DCM solution (-30 mL) obtained at the end

of this procedure; perform a back-extraction procedure using three 20 mL portions of

1.0M HCI solution. The final combined portions of 1.0M HCl solution (-60 mL) are then

finally transferred into a 100 mL volumetric flask and made up to the mark using 1.0M

HCI. Measure the absorbance of this aqueous sample solution at a wavelength of 265

nm in a 1 cm cell. The A1 cm value of the drug at the above wavelength is 210.

Using the below analytical data and the information above, answer the following TWO

(2) question parts a and b. FOR EACH QUESTION PART, PLEASE SHOW ALL

STEPS OF YOUR CALCULATION.

Mass of 20 drug tablets = 4.5037 g

Mass of powder used for 250 mL stock solution - 1.1278 g

Absorbance of the dilute drug solution = 0.136

Calculate the amount of drug in mg per average tablet.