A common analytical method for determining the active ingredients of insecticides and piperonyl butoxide in filter papers from laboratory impregnation and field trials. Report of a study

Overview

For quality control of filter paper impregnation or field applications, the content of various insecticide active ingredients and/or piperonyl butoxide (PBO; a synergist) must be determined for scientific studies, such as:

• laboratory studies in which filter papers are treated with various concentrations of insecticides or PBO to test their bioefficacy;
• studies of dose–response relations;
• product evaluation trials, in which filter papers are placed on indoor surfaces of experimental huts for quality control of spraying with insecticides;
• in large-scale field trials of indoor residual spraying (IRS), in which filter papers are placed on indoor surfaces of houses and sprayed with insecticides; and
• laboratory studies in which filter papers are impregnated with well-defined target discriminating concentrations of insecticides to evaluate resistance (or susceptibility) in mosquito, sand fly and triatomine vectors.

Currently, chemical testing laboratories use individual methods to determine the content of insecticide active ingredient or PBO in filter papers. These methods involve different extraction solvents, internal standards, laboratory glassware, extraction equipment and conditions, chromatographic columns and conditions as well as different calibration procedures. In view of the absence of a common standard operating procedure (SOP) for analysis of insecticide active ingredients and PBO on filter papers, WHO has developed and validated a common analytical method in collaboration with the Walloon Agricultural Research Centre (CRA-W), Gembloux, Belgium.

This document describes the materials, analytical method and method validation. The analytical method will be useful to:

• research institutions and laboratories that conduct testing and field trials of insecticides sprayed indoors to determine their efficacy in the laboratory and in the field;
• research laboratories that determine the actual insecticide content of filter papers treated for determining lethal and discriminating concentrations as part of dose-response studies;
• pesticide quality control laboratories; and
• research and development laboratories, including those of the pesticide industry.

Use of this common analytical method could be extended to other insecticides and pesticides after proper validation and performance verification.