COA Explained

COA Explained

Certificates of Analysis are essential to provide all the required information about a particular material, giving the end user confidence that the reference material is fit for purpose.

The guide below is intended to provide an overview of the main content of our certificates of analysis. If you have specific queries relating to a certain certificate or product please email us at and we will be delighted to help.

All our reference materials are accompanied by comprehensive certificates of analysis. These provide a full description of the material to which they relate, and summarise the analysis undertaken during the characterisation process. Our certificates of analysis are prepared in accordance with ISO Guide 31, which specifies the requirements for the description of reference materials and the contents of certificates and labels. Current examples of our certificates of analysis for all products ranges are openly available via the website on the relevant product pages.

Certificate of analysis guide


Long term storage unless otherwise stated, storing reference materials in pure organic solvent at temperatures below those specified is not detrimental. Some analytes may come out of solution at lower temperatures and so the reference material should be warmed to room temperature and mixed prior to use. Products in aqueous solvent should not be stored at temperatures below 0°C unless explicitly stated.


Uncertainty of analysis is in accordance with the guide to the Expression of Uncertainty in Measurement (GUM). Our certificate of analysis list the expanded concentration uncertainty at the about 95% level of confidence using a coverage factor of k=2. They incorporate uncertainty of the purity, material density and balance and weighing technique. Our concentration uncertainties are valid in the range between 19°C and 25°C.


Expiry Date (Retest date)- We run "accelerated stability studies" backed up with additional stability testing at regular time points after initial production - "real time stability tests". From the data obtained during these investigations, we determine the ideal long-term storage conditions of our reference materials. Additionally the stability of every lot is regularly investigated through a routine quality control testing program. These results can be used to reassign expiry dates and on occasion may lead to changes in the storage temperature.


The concentration is based on gravimetric material weighings - using weights traceable to SI units - and material purity factor (assay of the neat material). The concentration listed is 'as is' for neat materials or 'free base/acid' for salt forms, meaning no further correction is required.