Question 7.11: Define and briefly describe the five steps of the analytical...

First step: Identification of the information requirements, which rests on effective communication between the client and the analytical chemist in order to define the characteristics of the information needed. Example: the client asks the analytical chemist to determine whether a salmon batch is fit for marketing based on its pinkish colour.

Second step: Specifying the analytical information required. Conversion of the socio-economic information requested in the first step into analytical information. Example: the analytical chemist associates the pinkish colour of salmon to the concentration of astaxanthin.

Third step: Planning the analytical strategy. Development of the methodology to be applied (an appropriate analytical process). Example: The analytical chemist develops a method by which samples are subjected to solid–liquid extraction, elution with acetone and liquid–liquid extraction with hexane in order to isolate astaxanthin free of interferences from other substances. The pinkish colour is determined by using a photometer to measure the absorbance at 470 nm of the hexane extract.

Fourth step: Monitoring the results, which involves assessing them against internal and external references. If the results are correct, the analytical process will have been solved; otherwise, a fifth step will be needed. Example: The experimental result is compared with a tabulated reference and the analyte percent recovery as determined by adding a known amount of astaxanthin as internal standard to a sample.

Fifth step: Corrective actions. Identifying errors in the previous steps and correcting them. After each corrective action, the process returns to step 4 until the analytical problem is solved. Example: if the results are not acceptable, the solvent used in either or both extractions may have to be changed with a similar one where astaxanthin is more readily soluble.