主题：【讨论】欧洲药典中关于称量的规定

原文由 hyheying 发表:
欧洲药典附录1.2中有一段关于称量的规定，具体内容是这样的：
Quantities. In tests with numerical limits and assays, the
quantity stated to be taken for examination is approximate.
The amount actually used, which may deviate by not more than 10 per cent from that stated, is accurately weighed or measured and the result is calculated from this exact quantity. In tests where the limit is not numerical, but usually depends upon comparison with the behaviour of a reference in the same conditions, the stated quantity is taken for examination. Reagents are used in the prescribed amounts. Quantities are weighed or measured with an accuracy
commensurate with the indicated degree of precision. For weighings, the precision corresponds to plus or minus 5 units after the last figure stated (for example, 0.25 g is to be interpreted as 0.245 g to 0.255 g). For the measurement of volumes, if the figure after the decimal point is a zero or ends in a zero (for example, 10.0 ml or 0.50 ml), the volume is measured using a pipette, a volumetric flask or a burette, as appropriate; otherwise, a graduated measuring cylinder or a graduated pipette may be used. Volumes stated in microlitres are measured using a micropipette or microsyringe.
前面提到，对于数值限度及含量测定时，应称准至规定值的±10%；后面又提到，称量的精密度应符合规定值最后一位数字之后±5个单位。我对这两个规定的实用性感觉很模糊，不知到各位是怎么理解的？

原文由 hyheying 发表:
感谢redanqi版主的回复，不过我还是不太明白。我想知道的是，假如药典规定一种物质需称取0.300g，另一种需称取0.3g，那么这两种情况下称量范围分别为多少才符合规定呢？

原文由 hyheying 发表:
感谢redanqi版主的回复，不过我还是不太明白。我想知道的是，假如药典规定一种物质需称取0.300g，另一种需称取0.3g，那么这两种情况下称量范围分别为多少才符合规定呢？

原文由 hyheying 发表:
关于精密度，中国药典是这样规定的：
试验中供试品与试药等“称重”或“量取”的量，均以阿拉伯数字表示，其精确度可根据数值的有效数位来确定，如称取“0.1g”，系指称取重量可为0.06-0.14g；称取“2g”，系指称取重量可为1.5-2.5g；称取“2.0g”，系指称取重量可为1.95-2.05g；称取“2.00g”，系指称取重量可为1.995-2.005g。
“精密称定”系指称取重量应准确至所取重量的千分之一；“称定”系指称取重量应准确至所取重量的百分之一；“精密量取”系指量取体积的准确度应符合国家标准中对该体积移液管的精密度要求；“量取”系指可用量筒或按照量取体积的有效数位选用量具。取用量为“约”若干时，系指取用量不得超过规定量的±10%。
综上所述，欧洲药典与中国药典具体的区别是什么呢？

原文由 qingtian1210 发表:
我随意翻了一下美国药典和欧洲，觉得在称量这块和中国要求是一样的，只不过国外是四舍五入的要求
  CP                  EP                  USP
  约（100%+-10%）    about              about
称取0.3g          直接表述出该质量      同EP


称取0.300g，在国内指0.2995~0.3005g，国外也一样
称取0.3g，国内指0.26~0.34g，国外指0.25~0.35g