Essential precautions required for validation of analytical methods

Every method requires critically controlled conditions for its validation

Validation of analytical method plays a crucial role before it is put to routine use. It is therefore important that required precautions be taken during the validation process itself as otherwise it is as good as adopting an un-validated method.

The article underlines such parameters and suggests measures that should be taken during the validation process. In other words authentication becomes important at all stages and contributes towards the complete validation process.

Instrument

The instrument on which validation is required needs to be calibrated in advance and its calibration should be valid on the day of its use for the validation purpose. The same applies to other instruments which may be required such as pH meter, UV- visible spectrophotometer, thermometers, etc.

Glassware

All required glassware should be scrupulously clean and dry. Volumetric apparatus like burettes, pipettes, volumetric flasks need to be calibrated and it is equally important to maintain a constant environmental condition in laboratory such as temperature and humidity.

Freedom from contamination

Freedom from contamination is important for any laboratory. Its sources can be other test samples, laboratory environment, sample handling tools, laboratory visitors or from analysts themselves. It becomes all the more necessary to restrict visitor entry and ensure that the chemists wear protective clothing while conducting method validation studies

Standards

Standards used for validation purpose should be procured from reliable sources and accompanied with the certificate of analysis. It is also important that they should bear traceability to standard regulatory bodies

Reagents

The required reagents should be of highest purity grades. Reagent blanks should be free of any analyte of interest. The same holds for acids, water and other solvents used in sample preparation, calibration standards dilutions, digestion media and mobile phase preparations. Laboratory water used for validation activities should meet the purity criteria.

Sample Blanks

Sample blanks should also be carefully selected so that they are free from presence of analyte of interest

Calibration standards

Great care should be exercised in preparing calibration standards as dilution errors at this stage can multiply during subsequent serial dilutions. The spiking range should cover at least 80 – 120 percent of the expected concentration range of the analyte

Weighing

Proper weighing technique and periodic calibration of the weighing balance cannot be underestimated. The method validation exercise would be in vain if errors get introduced due to weighing errors at time of preparation of samples, standards or reagents.

Method validation is a critical operation which requires all the precautions outlined above so that the selected method will meet the desired requirements of the analysis.