Tolerance (chemistry)
For raw material testing, in-process control and the analytical release of chemicals produced (pure substances or mixtures of substances) in the chemical industry, tolerance is the difference between a maximum permissible value and a minimum value for a quantified test criterion and a specified test method . The actual values (actually measured values) for this test criterion may lie between the maximum value and the minimum value, whereby the maximum and minimum values may or may not be included, depending on the definition. For example, if the tolerance is ≥ 99.0% content to ≤ 101.0% content, the maximum and minimum values are included. However, if the tolerance is> 99.0% content to <101.0% content, the maximum and minimum values are not included.
In addition, there are one-sided “open” tolerance ranges in chemistry. Then it is specified, for example, that the purity of a substance must be at least 97% (≥ 97%) or more than 97% (> 97%). Analogously, it can be established, for example, that the melting point of a solid is at least 154 ° C (≥ 154 ° C ) or the ash content is below 0.10% (<0.10%).
Compliance with the tolerance (target values) is a criterion for ensuring that a process runs under controlled conditions. For many chemicals, compliance with the tolerance for the specified test criteria is a contractually agreed quality certificate between the manufacturer and the customer. The test criteria can include a large number of physical-chemical or also microbiological and other test criteria , for example viscosity , refractive index , boiling curve, cold resistance, density , ash content, nitrogen content, pH value , humidity , etc.
For many drugs and pharmaceutical excipients , permissible tolerances for quantifiable test criteria are mandatory in pharmacopoeias ; the test method for each test criterion is also specified there in detail. Pharmaceutical manufacturers ( pharmaceutical industry , pharmacies ) may only use substances that meet the prescribed specifications. Example of a tolerance requirement for the drug nicotinamide from the European Pharmacopoeia: "Nicotinamide contains at least 99.0 and at most 101.0 percent 3-pyridinecarboxamide, calculated on the dried substance ."
Individual evidence
- ↑ European Pharmacopoeia, Deutscher Apotheker Verlag Stuttgart, 6th edition, 2008, pp. 2339-2340, ISBN 978-3-7692-3962-1 .