USP Requirements for Volumetric Instruments: How to Work with Different Standards in the Lab

摘要

As mentioned at the start of this report, the diversity of commonalities and differences hampers an easy and appropriate work with glass volumetric instruments for end-users in European laboratories, if they have to follow the requirements of the USP/ASTM. Some manufacturers have modified their production lines to be able to offer volumetric instruments that fulfill both the class A error limits required by USP/ASTM, and the construction specifications of the respective DIN EN ISO standards. Usually changes are made to the certificates which refer to the USP/ASTM standards and, therefore, to the class A error limits demanded by USP/ASTM. Moreover, the DIN EN ISO standards are also printed on these certificates as the construction specifications and maximal permissible errors are met as well. It is possible to confirm smaller values for the maximal permissible errors, because standards prescribe only the maximal permissible error. Hence, in the particular cases of 1 ml graduated pipet and the 0.5 ml transfer pipet, whose class AS ISO error limits are smaller than the class A USP/ASTM error limits, the smaller one can be chosen. To differentiate between volumetric instruments in accordance with class A error limits required by USP and highest quality grade (class A or AS) following ISO, manufacturers print USP on the volumetric instrument (Fig. 3) and deliver either batch or individual certificates with USP and/or ASTM references. For applications supervised by US authorities like the FDA these USP volumetric instruments should be chosen instead of the ISO volumetric instruments. The calibration could be done in accordance with the established working plans as the DIN EN ISO 4787 shall be used for volumetric instruments whether according to USP/ASTM or ISO standards.