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(a) Orciprenaline tablets (containing orciprenaline sulphate) are a moderately selective B2 adrenergic receptor agonist formulation that stimulates receptors of the smooth muscle in the lungs, uterus, and vasculature supplying skeletal muscle for the treatment of asthma. To determine the uniformity of content for orciprenaline sulphate tablet the following assay was conducted: Weigh and powder 20 tablets, shake a quantity of the powder containing 80 mg of orciprenaline sulphate with 50 mL of 0.01 M HCl. Filter and add sufficient 0.01 M HCI to the filtrate to produce 100 mL. Dilute 10 mL to 100 mL with 0.01 M HCl and measure the absorbance of the solution at the maximum 276 nm. Calculate the content of orciprenaline sulphate taking 72.3 as the value of A (1%, 1 cm) at 276 nm. The following information is given: . . Weight of each tablet is 2.5534 g Weight of the tablet powder assayed = 0.5266 g Absorbance reading = 0.5878 Molecular weights (g/mole): C = 12; H = 1; 0 =16; N = 14; S = 32. . =
Orciprenaline sulphate structure: OH H но, HO—5—OH OH 2 (i) Draw the part of molecule responsible for the absorption of light in this assay.
(ii) What assumptions are made in this assay?
(iii) Draw the structure that is unstable with high temperature and/or humidity conditions. Explain the reasons.