The Increment Preparation Errors and the Notion of Sample Integrity

All of the nonselective operations performed on a lot of material, or on the successive samples are referred to as “preparation stages.” These preparation stages are necessary to convey the increments and samples to a predetermined location and to modify them into an appropriate form for the ultimate analytical stage. A large number of articles and books written on sampling confuse selective operations (i.e., sampling in a proper sense) with nonselective operations (i.e., preparation stages). It should be emphasized that unless this differentiation is clearly made, and accepted, it is impossible to conduct a logical analysis of all the errors involved in the Overall Estimation Error OEE . Preparation errors are strictly inherent to those who design, build, operate, clean and maintain sampling systems. They are the result of ignorance, carelessness, clumsiness, unintentional mistakes, and sometimes fraud and sabotage. We are going to review the following categories: Contamination errors, Loss errors, Errors generated by a change in chemical composition, Errors generated by a change in physical composition, Errors generated by unintentional mistakes, and Errors resulting from fraud and sabotage.