Method validation studies help estimate the level of uncertainty associated with weighing experiments that are conducted, in an analytical balance for example. These methods are based either on data obtained after following protocols for validation in labs and medical establishments or during various development methods. The practices and procedure that lab personnel use while handling analytical weighing equipment can contribute significantly to weighing errors and weighing uncertainty. Method validation studies help not only correct but also remove these significant factors that influence the overall precision of the weighing balance.

The combined data contains measurements that have significant effects, overall performance figures and scores that provide supportive evidence of insignificance. Validation studies that are carried out for the qualitative analysis of analytical weighing determine the parameters of precision, bias, linearity, detection limit, selectivity or specificity, ruggedness or robustness, etc. Precision studies can be done using data from either a single lab or can be based on the data collected from inter laboratory studies. The data is obtained by measuring the reproducible standard deviation, intermediate precision and repeatability.

Individual variances are obtained on weighing a test sample and these precision studies help determine the overall level of uncertainty associated with the balance. Bias is another important component of uncertainty; it should either be negligible in the lab or absent using corrective techniques. When an overall bias from an appropriate value is known, the traceability can be determined. Relevant materials for reference must be used for calculating the bias. Linearity of the analytical balance is calculated through the process of non-linearity and inspection. The balance’s linearity response to both standard reference values and test samples are determined. It helps establish whether the balance is suitable enough to weigh test samples across a wide range of weights.

The detection limit is an important concept that is central to validation studies. It is primarily employed to determine the lower extreme of the weighing range during the operation of the balance. Though this component of the study is not directly applicable to determine the level of uncertainty, it requires special consideration and careful treatment. Selectivity and specificity studies mainly address the potential interferences that contribute to the uncertainty of the balance and are also used to demonstrate the insignificance of practical effects on the weighing system. These interferences are added to the blank test samples and fortified samples to test the balance’s response to them. Ruggedness and robustness studies are an example of detailed multi-factorial studies where one or more parameters are altered to investigate the weighing precision of analytical balances. Ruggedness tests are performed to understand which particular parameter has the maximum and most significant influence on the performance of the balance and the levels of uncertainty associated with the weighing process.

Method validation studies for determining analytical balance precision need to be representative. Only realistic studies that clearly list out the exact number of factors and the range of effects along with the types of samples used during the weighing procedure using the technique of random selection prove useful.

Author Bio: Dr. Bob Sandor is a Director at Tovatech, a leading North American supplier of analytical balances. When not busy running his company, he explores his fascination with the many aspects of various scientific & industrial devices. For more details on the above you can reach him through the analytical balance section of his website.

Category: Education
Keywords: analytical balance precision,method validation studies,analytical balance