(c) a detection wavelength of about 282 run and (d) a fixed-volume loop injector Inject 20 ul of each solution The test is not valid

solutions For solution (1) dssolve 0.1 g in sufficient 0.1 M hydrochloric acid to produce 10 ml For solution (2) ofdissolve 5 mg of methyldopa RS and 5 mg of 3-O-methylcarbidopa RS in sufficient 0.1M hydrochloric acid To produce 100 ml For solution (3) dissolve 5 mg of carbidopa RS and 5 mg of methyldopa RS in sufficient 0.1M hydrochloric acid to produce 10 ml Tha chromatographic procedure may be carried out using (a) a stainless steel column (25 cm x 4.6 mm) packed with stationary phase LC2 (5 pm), (b) a mixture of 98 volumes of a 1 4% w/v solution of potassium dihydrogen phosphate and 2 volumes of methanol as the mobile phase with a flow rate of 1 ml per ninute. (c) a detection wavelength of about 282 run and (d) a fixed-volume loop injector Inject 20 ul of each solution The test is not valid unless the resoluiion facior between the peaks due fo methyldopa and carbidopa in the chromatogram obtained with solution (3) is greater than 4.0 In the chromatograrn obtained with solution (1), the areas of any peaks corresponding to methyldopa and 3-O-methylcarbidopa are not greater than the areas of the corresponding peaks obtained in the chromatogram with solution (2) Sulphated ash Not more Than 0.1%. Appendix 3.22 Loss on drying Between 6.9 and 7.9%, determined on 1 g by drying in an oven at 105°, Appendix 8.6.Assay Weigh accurately about 0.15 g and dissolve in 75 ml of anhydrous glacial acetic acid with the aid of gentle heat and carry out Method A for non-aqueous litration. Appendix 3.45, determining the end-point potentiometrlcally Perform a blank determination and make any necessary correction Each ml of 0.IM perchloric acid is equivalent to 0.02262 g of C1OH14N2O4 CARBIMAZOLE C7H1ON2O2S Mol. Wt. 18623 Carbimazole is ethyl 3-methyl-2-thioxo-4-irnidazollne-lcarboxylate Category Antithyroid Dose Controlling dose, 30 to 60 mg daily, in divlded doses, maintenance dose 5 to 20 mg daily Description White or creamy-white, crystalline powder, odour, characteristic Solubility Freely soluble in chloroform, soluble in acetone; sparingly soluble in ethanol (95%), slightly soluble In water and in ether Slorage Store in well-closed containers STANDARDSCarbimazole contains not less than 98.5 per cent and not more than 100.5 per cent of C7H10N2O2S. calculated with reference to the dried substance Identification: A The Infra-red absorption spectrum. Appendix 5.4. Is concordant with the reference spectrum of carbimazole or with the spectrurn obtained from carbimazoleRS. B: Heat 0.2 g with 5 ml of dilute hydrochloric acid on a water-bath for 1 hour Cool extract with three quantities, each of 5 ml, of chloroform, wash the combined chloroform extracts with 0 5 ml of water, filter through a dry filter paper and remove the chloroform. The residue, after crystallisation from ethanol (95%), melts at about 140'. Appendix 8.8.C To a small quantity add 1 drop ol dilute potassium lodobismuthate solution, a scarlet colour is produced Methimazole. Carry out the method for thin-layer chromalography, Appendix 46, using silica gel G as the coating substance and a mixture ol 80 volumes of chloroform and20 volumes of acetone as the mobile phase Apply separately to the plate 10 pi of each of two solutions In chloroform containing (1) 1 0% w/v of the substance being examined and (2) 0005% w/v ol methirnazoleRS and develop Immediately After removal ol the plate, allow It to dry in air and spray with dilute potassium