Advanced testing methods ensure high standard maintained

Extraction

Chemical analysis by HPLC This test method is used to analyse the content of Deltamethrin in a given net sample. First the sample is submerged in a solution of a mixture of solvents. This is called the extraction process, because it extracts the Deltamethrin out of the net sample and into the liquid, called the extract. The extract, now containing the Deltamethrin from the net sample, is injected into an HPLC (High Performance Liquid Chromatograph).

HPLC

The principle of HPLC is that it has a long column, through which there is a constant flow of a solvent. This is called the mobile phase. The extract is injected into the mobile phase, and as it is moved through the column by the mobile phase. The individual chemical substances in the extract are separated because of their different retention time in the column. At the end of the column there is a detector that detects and records the time and the amount of the Deltamethrin. (Hereby the amount of Deltamethrin in the original sample can be calculated).

Bioassay

This is a test method whereby the insecticidal efficacy of the net is tested. The test method is developed and approved by WHO. 50 mosquitoes per net sample are introduced into four PVC test cones. These test cones are open at the wide end, and this is where the net is placed. As the mosquitoes do not like to rest on the PVC material, they are forced to sit on the net. After three minutes in the cone the mosquitoes are removed and transferred to a plastic cup.

Efficacy evaluation

The mosquitoes remain in the plastic cup, initially for 60 minutes, after which the amount of "knocked down mosquitoes" is evaluated (how many are lying inactive at the bottom of the cup). The result of this evaluation is called KD60 and is expressed as the percentage of mosquitoes being knocked down 60 minutes after exposure to the net. Subsequently, the mosquitoes remain in the cups for another 23 hours (24 hours in total after the exposure), after which it is counted how many mosquitoes are dead or have lost more than two legs or a wing. This figure is called Functional Mortality (FM). WHO specifies that a net is efficient if it has a KD60 of more than 95% and a FM of more than 80%.