USP天平最小称样量确认

768305022

USP32–NF27 <41>里面我怎么没有看到关于最小称样量的要求  包括用多大的砝码做10次 有的人说1%-5% 有人说5%-100%
还有0.41d的描述 我也没有找到，请大家帮我看看  谢谢  

小胡同学

在NF39啊，大哥<41>Balance里边，全文就三段话

ygl820

á41&#241; BALANCES
This chapter states the requirements for balances used for materials that must be accurately weighed (see General Notices,
8.20 About). Unless otherwise specified, when substances must be “accurately weighed”, the weighing shall be performed
using a balance that is calibrated over the operating range and meets the requirements defined for repeatability and accuracy.
For balances used for other applications, the balance repeatability and accuracy should be commensurate with the requirements
for its use.
For a discussion of the theoretical basis of these requirements, see Weighing on an Analytical Balance á1251&#241;, which may be a
helpful—but not mandatory—resource.
Change to read:
REPEATABILITY
Repeatability is assessed by weighing one test weight NLT 10 times. [NOTE—The test weight must be within the balance’s
operating range, but the weight need not be calibrated. Because the standard deviation is virtually independent of sample mass
within the balance’s capacity, use of a small test weight, which may be difficult to handle, is not required.]
Repeatability is satisfactory if ▲twice▲ (USP 1-Aug-2019) the standard deviation of the weighed value, ▲▲s▲ (ERR 1-Aug-2019)
,▲ (USP 1-Aug-2019)divided by the desired smallest net weight (i.e., smallest net weight that the users plan to use on that balance),
does not exceed 0.10%. ▲The repeatability measurement establishes the smallest net amount of material that may be weighed
on the balance in conformance with the 0.10% limit. The minimum weight, Mmin, is described by the inequality Mmin ≥
2000▲s▲ (ERR 1-Aug-2019). For example, if ▲s is found to be 0.00015, then Mmin
must be ≥ 0.30000 g or
300.00 mg.▲ (ERR 1-Aug-2019)▲ (USP 1-Aug-2019) If the standard deviation, s, obtained is less than 0.41d, where d is the scale ▲interval
of the balance, then the inequality becomes Mmin ≥ 2000 (0.41d). For example, for a 4-place analytical balance, d is 0.0001 so
that Mmin
must be ≥ 0.0820 g or 82 mg.▲ (USP 1-Aug-2019)
ACCURACY
The accuracy of a balance is satisfactory if its weighing value, when tested with a suitable weight(s), is within 0.10% of the
test weight value.
A test weight is suitable if it has a mass between 5% and 100% of the balance’s capacity. The test weight’s maximum
permissible error (mpe), or alternatively its calibration uncertainty, shall be NMT one-third of the applied test limit of the
accuracy test.
[NOTE—Applicable standards are the following: American Society for Testing and Materials (ASTM) E617 (available from
http://www.astm.org) and International Organization of Legal Metrology (OIML) R 111 (available from http://www.oiml.org).]