09 February
31 December 2015

Study of the chemical and physico-chemical characteristics of pesticides

Study of the chemical and physico-chemical characteristics of pesticides


Since the 1990s, compliance with European Directive 91/414/EEC concerning the placing of plant protection products on the market and the requirement to operate under a Quality System such as the OECD Good Laboratory Practice (GLP), requires the use of objective and independent laboratories. These institutions must be up to date with legislative and scientific changes and able to preparing the dossiers required by the regulatory authorities in Europe, the United States and many other countries strongly influenced by the European Directive. In view of its participation in drawing up the European Directive, its contribution to standardisation of analytical methods (CIPAC), its activity within the FAO and the WHO with regard to specifications (product quality) and also the establishment of the OECD GLP Quality System in 1994, the Unit is of course approached by pesticide manufacturers involved in patented or generic molecules and formulations. It is now one of the leading laboratories in this field.


With this industry-supported project, it is possible to provide industry and the regulatory authorities in particular with the chemical and physico-chemical data legally required for the registration of products placed on the market and the protection of the environment and public health. This project guarantees strict confidentiality of the data supplied by the industry, whilst ensuring the transparency required for approval of the products. The aim of the tests is to guarantee the quality of products placed on the market and thus the protection of agriculture and users as well as public health and the environment.

Description of tasks

The Plant Protection Products and Biocides Physico-Chemistry and Residues Unit uses standard methods to determine the active substance contents of technical (TC) and formulated products and manufacturing impurities or validates the analytical methods for new formulations, mainly by gas and liquid chromatography. The Unit evaluates the physico-chemical characteristics of formulations based on published or accepted CIPAC methods and the recommendations of the European Directive. The principal techniques are: appearance, water content, flash point, acidity, alkalinity, pH, viscosity, surface tension, density, wettability, foaming, suspension stability, emulsion stability, spontaneity of dispersion, dilution stability, wet and dry sieve tests, particle size (sieving or laser diffraction), pourability, rinsability, physical and/or chemical compatibility, long term stability (6 months, 1, 2 years or longer) at room temperature, accelerated storage (14 days/54°C, 8 weeks/40°C, 12 weeks/35°C, 18 weeks/30°C), stability in the cold and thermal cycles. A detailed list of the methods is included in the Annex to this sheet.

Results obtained

Since recognition in 1994 of compliance with Good Laboratory Practice (GLP), the majority of manufacturers of pesticides and their formulation called upon our experience in preparing physico-chemical dossiers for approval of their products. The Unit processes more than 200 completed dossiers annually. Demand is constantly growing, especially for the validation of methods for analysing known active substances in new types of formulation and the analysis of formulations containing several active substances. In fact the latter type of formulation hardly ever undergoes international evaluation due to its complexity (origin of the active substances, adjuvants and co-formulants), with regard to both chemical and physico-chemical characteristics.


The Plant Protection Products and Biocides Physico-Chemistry and Residues Unit  is responsible for developing and implementing analytical methods (Ing. B. de Ryckel, Ing. V. Lecocq, Lic. M. Baes and Ing. C. Cornet). It establishes study protocols in compliance with GLP and finalises dossiers in reports complying with the requirements of Quality and international regulations. Lic. V. Hérion and V. De Cock are responsible for the Quality Assurance of the studies.


Dr. M. Zaim: WHO Pesticide Evaluation Scheme (WHOPES) – WHO/HQ – Geneva - Switzerland - (zaimm@who.int) Pesticide manufacturers, including well known multinationals as well as local or international manufacturers of generic substances. The Public Health SPF, Food Chain and Environment Safety – Brussels TNO Prins Mauritz Laboratory, Rijswijk, Netherlands. Defitraces, Brindas, France. Huntingdon Life Science, Eye, Suffolk, England The OECD has entrusted the Quality Assurance Office of the Scientific Institute of Public Health with the certification of compliance with GLP.


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  • WHO - World Health Organization