实验室工作标准的中间控制

工作标准在任何实验室都发挥着关键作用。只有当它们与参考标准材料相关时，任何分析的结果都是有意义的。在理想情况下，每次进行分析时都应该使用认证的参考资料，但这不是实际命题，因为认证参考资料的成本非常高，因此唯一可用的选择是利用工作标准。

什么是工作标准？

工作标准是最高纯度的材料grade available whose composition is known in relation to a certified reference material having established traceability to a recognized global standard body. As a working standard is to be used over a prolonged time period it is necessary to evaluate its composition periodically to verify that it does not vary beyond acceptable limits. This also necessitates care in handling and preservation under prescribed storage conditions. Before its expiry date another working standard is prepared and its composition is compared to the existing standard .In this manner a record of traceability is maintained with the original certified reference material through an unbroken chain of traceability.

Stages of Procurement, handling and intermediate checking of Working Standards

Sourcing

可以在内部准备工作标准，或者可以从声名的供应商或其他实验室采购。分析证书应伴随物质从外部来源采购。

Storage

On receipt proper arrangements must be made for its storage, ie, temperature, humidity and exposure to light. Care needs to be taken after every use to properly close and seal the container and ensure that same storage conditions are maintained. It is also helpful if a log record is maintained on its consumption.

Quality Checking

The material should be analyzed on receipt or in – house preparation. The standard is analyzed by at least 3验证分析师for its assay, and other parameters such as loss on drying, moisture content, melting point, sulphated ash, etc. The average of results obtained is stored for future reference. Thereafter the vial or bottle is affixed a label assigning unique number, date of analysis, storage conditions and the use by date.

工作标准有效性

工作标准只能在标签上提到的日期使用。在此日期之前，应提供新标准。如果标准在其到期前消耗，则应提前提供新的更换。每次介绍新标准时，应保持工作标准清单。

保质期研究

使用的有效性是基于保质期研究。通常，稳定产品的有效性设定为3,6或12个月，但对于不稳定的材料，保质期通常在30 +/- 2℃和65 +/- 5％RH中进行。根据保质期研究，可以决定实用程序。

中间检查

作为一般规则，应在6个月后检查包括干燥和水分含量损失的工作标准的检测，以获得1年或3个月的其他工作标准。如果观察到任何意外变化或外观改变，即使在日期使用前也应丢弃标准。作为一个有用的指导，该表表提供了对工作标准的不同测试的最大偏差验收标准。

测试参数	验收标准
通过HPLC测定	+/- 0.5％
Chemical Assay	+/- 1.0 %
Microbiological Assay	+/- 2.0％
水	+/- 0.5％
l	+/- 0.5％