The minimum weight of every balance should be periodically assessed for conformance.Īpplying a safety factor minimizes the risk of out-of-calibration, out-of-specification (OOS), or out-of-tolerance (OOT) results. Every balance has an individual minimum weight, depending on the type and performance of the load cell, the location, and the environmental conditions. This requirement is clearly applied to the sample weight, not including the tare vessel. Crucially, weighing net samples sufficiently above the minimum weight is recommended to take balance performance fluctuations into account. For example, performance verification should be carried out using a risk-based approach. These major revisions focus on balance qualification and operation. For more information on balance testing, the USP video tutorial can be viewed at: Advisory Chapter provides additional clarification and extends the scope to any balance used for an analytical procedure. With higher weights (i.e., above 5%), repeatability will increase, leading to higher minimum weight values. In this lower range, the repeatability is virtually independent of the test weight. In contrast, repeatability testing and minimum-weight determination should be carried out using a small weight below 5% of the balance capacity. In the lower weighing range, repeatability is the dominant source of error. Hence, accuracy testing below 5% is no longer allowed. Accuracy, defined by USP as the systematic error, must be determined at higher loads close to the balance capacity (i.e., largest systematic error), as it cannot be detected reliably below 5%.
These requirements apply for balances used to weigh analytes for quantitative measures.įor accuracy testing, using a test weight of 5–100% of the balance capacity is now applicable.
It also details a relatively demanding balance assessment, describing accuracy and repeatability tests with new acceptance limits. The revised chapter now states that accurate weighing must be performed using a calibrated balance. The new requirements of General Chapter are mandatory.
0 kommentar(er)
