INTRODUCTION
Reference substances of known content are often essential for the quantitative determination of pesticide active ingredients in different types of sample and at various concentration levels. They are available from various sources. It is important that the active ingredient content is declared and certified (Note 1).
1. SUPPLY OF REFERENCE SUBSTANCES
There are two sources for the supply of certified reference substances:
- the manufacturer of the active ingredient in question;
- standards institutions or companies selling reference substances.1.1 Supply by the manufacturer
The manufacturer of a pesticide technical grade active ingredient, or its formulations, is obliged to supply a certified reference substance in the following cases:
1.1.1 Trade relations between customer and manufacturer
The customer, or an independent laboratory, might want to check the active ingredient content of material delivered by the manufacturer. This is to be done on the basis of the specification and using the analytical method stated therein. The manufacturer's certified reference substances should be made available to the customer so as to avoid any discrepancy in the analytical results, which could otherwise be derived from differences in the purity of the reference substances used by the two parties.
1.1.2 Relations between manufacturer and registration authorities
Each company (not only the inventor company) applying for the registration of a pesticide (new a.i. or formulation) must supply its own certified reference substance, if required by the registration authorities.
1.2 Supply by reference substances producers or suppliers
There are various standards institutions (Note 2) and commercial companies which offer reference substances. They should normally be approached if reference substances are required in situations different from those mentioned above. On request manufacturers may, at their discretion, also supply reference substances in such cases.
2. CERTIFICATION
A certificate of identity and determined content, together with the corresponding measurement uncertainty and a reference to the method(s) of analysis used, must always accompany each sample of a certified reference substance. Descriptions such as "greater than..%" are unacceptable. The recommended storage conditions and an expiry date shall be stated.
Note 1 For more detailed information, see CIPAC Handbook D, pages 186-196.
Note 2 e.g. LGC, Queen’s Road, Teddington, Middlesex, TW11 0LY, U.K.
