Before you plan analysis of a sample in your laboratory you should be aware of the essential details of the sample like its homogeneity, its physical state, available quantity and its stability.
It is also essential to know the requirements of analysis such as:
- Components to be detected and quantified
- Expected concentration levels
- Nature of sample matrix. In other words the nature of interferences that can be present that can complicate determination of required components
- Required degree of accuracy and precision
- Appropriate analytical technique for the analysis
- Material and apparatus required for the analysis
- Availability of required resources
- Cost of analysis
The above considerations require a judicious selection of the method. Let us see what could be those useful reference sources that you can access. You can consider yourself fortunate if your laboratory has already a validated method available which can be adopted without applying a second thought. However, this may not be the case every time and you would feel the need to search a suitable method due to the following constraints:
- The sample matrix is different from routine samples and requires different set of extraction procedures or can introduce different interferences
- Non-availability of required reagents or glassware
- Non-functional or un-calibrated instruments
In such situations you will have to look for other alternative methods so you will have to search for the method through the available options such as:
- Standard textbooks
- Reference analytical journals
- Pub Med
- Google search
The more you search chances are that you may get confused further. Let us assume that after going through the references you have zeroed down on a particular method. Now comes the important stage of validating the method before it is put into routine use. You have to keep in mind the fact that the analytical results reported by you can have far reaching consequences concerning safety of use of the products, efficacy of drugs, toxic limits for environmental samples, or verdict on legal matters. As a responsible analyst you have to make sure that the data reported by you is reliable and would be accepted universally. Such objectives can be achieved only through following the rigorous validation process.
Validation becomes necessary:
- Before adopting the method in routine use
- Whenever there is a requirement of analysis of components in different sample matrix
- Sample analysis requires different analytical procedures
Revalidation would be necessary even when the analysis instrument has undergone major repairs or major accessories are added to existing facilities.
Analytical method validation involves validation of procedures against parameters which are clearly defined in several texts covering method validation in detail. The parameters covered in method validation include:
- Limit of quantification
Only after the selected method meets the prescribed criteria should it be put into regular use as this is the accepted approach to generate reliable results which cannot be challenged under similar set of conditions in other laboratories.