[en] The objective of a quantitative analytical method is to be able to quantify accurately as possible each unknown that the laboratory will have to determine according to the analytical procedure. The analytical procedure refers to the way of performing the analysis. It should describe in detail the steps necessary to perform each analytical test. This may included but is not limited to samples, reference standards and reagents preparation: weighing, quantitative transfer and dispensing an aliquot. The choice of the laboratory material and also the way to use it have a dramatic influence on the accuracy of an analytical method.