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专业: 中药质量评价

[求助] 看不懂的系统适用性案例-EP8.0 头孢他啶已有2人参与

EP8.0 头孢他啶原料药质量标准中杂质F（即吡啶）的含量测定方法如下：
Impurity F. Liquid chromatography (2.2.29). Prepare the solutions immediately before use.
Phosphate buffer solution. Prepare a 10 per cent V/V solution of phosphate buffer solution pH 7.0 R4.
Test solution. Dissolve 0.500 g of the substance to be examined in phosphate buffer solution and dilute to 100.0 mL with the same solution.（供试品浓度为5mg/ml）
Reference solution (a). Dissolve 1.00 g of pyridine R in water R and dilute to 100.0 mL with the same solvent. Dilute 5.0 mL of the solution to 200.0 mL with water R. Dilute 1.0 mL of this solution to 100.0 mL with phosphate buffer solution.（对照品浓度为2.5ug/ml，限度为500ppm）
Reference solution (b). Dilute 1 mL of the test solution to 200 mL with phosphate buffer solution. To 1 mL of this solution add 20 mL of reference solution (a) and dilute to 200 mL with phosphate buffer solution.（原料药浓度为0.125ug/ml（相当于供试品浓度的0.0025%），吡啶浓度为0.25ug/ml（相当于限度浓度的10%）。为什么溶液B中原料药的浓度不是供试品一样，即供试品为5mg/ml，吡啶为2.5ug/ml？这样设计是出于什么考虑？）
Column:
– size: l = 0.25 m, Ø = 4.6 mm;
– stationary phase: octadecylsilyl silica gel for
chromatography R (5 μm).
Mobile phase: mix 8 volumes of a 28.8 g/L solution of ammonium dihydrogen phosphate R previously adjusted to
pH 7.0 with ammonia R, 24 volumes of acetonitrile R and 68 volumes of water R.
Flow rate: 1.0 mL/min.
Detection: spectrophotometer at 255 nm.
Injection: 20 μL.
Run time: 10 min.
System suitability: reference solution (b):
– resolution: minimum 7.0 between the peaks due to
ceftazidime and impurity F.
Limit:
– impurity F: not more than the area of the principal peak
in the chromatogram obtained with reference solution (a)
(500 ppm).

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