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Pharmacopeial tests and assays require balances that vary in capacity, sensitivity, and reproducibility. Unless otherwise specified, when substances are to be “accurately weighed” for Assay, the weighing to be performed with a weighing device whose measurement uncertainty (random plus systematic error) does not exceed 0.1% of the reading. Measurement uncertainty is satisfactory if three times the standard deviation of not less than ten replicate weighings divided by the amount weighed, does not exceed 0.001. Unless otherwise specified, for titrimetric limits tests, the weighing shall be performed to provide the number of significant figures in the weight of the analyte that corresponds to the number of significant figures in the concentration of the titrant.
药典测试和检测所需的天平要求多种负荷、灵敏度和可重现性。除另有规定,否则当物质被要求在含量测定中“精确称定”时,用来称重的设备在测量中的不确定性(随机加系统误差)不超过读数的0.1%。如果不少于十次重复称重的标准差乘以三除以称得的重量,结果不超过0.001,则测量的不确定性令人满意。除另有规定,对于滴定法限定检测,需进行称重以提供与滴定液浓度有效数字位数相对应的待分析物重量的有效数字位数。