ToF-SIMS quantification of bromine based insecticide in mosquito netting

Abstract

Insecticides are used to combat diseases such as malaria by incorporation in or topical application on mosquito netting. Determination of the insecticide available on the surface of the treated material has been difficult to achieve. A recent study of the chlorine based insecticide permethrin in mosquito netting has shown that time-of-flight secondary ion mass spectrometry (ToF-SIMS) was able to detect and, with the development of ion implanted standards, to quantify permethrin on the fiber surface and subsurface. The ion implantation method has been used extensively for SIMS quantification. A similar approach to analysis and quantification has now been achieved for the brominated insecticide deltamethrin, which is used at significantly lower concentrations than permethrin. ToF-SIMS analysis of deltamethrin indicated a dominant bromine ion in the negative ion mass spectrum. 79Br was implanted into high density polyethylene (HDPE), which is the netting material, into acetone washed netting fibers, and into silicon to verify implant dose. ToF-SIMS depth profiles of the implanted HDPE showed a detection limit of 5.2 × 1017 atoms/cm3, which corresponds to a detection limit of 0.046% by weight for deltamethrin. The implanted fiber showed an implant profile superimposed on the bromine contributed from the deltamethrin. The insecticide concentration below the fiber surface at two different locations was measured at 0.17 and 0.23 wt. %, which is in excellent agreement with the insecticide specification of 0.18 wt. % ±25%. Analysis of unimplanted netting fibers showed localized high concentrations of insecticide. The results obtained provide quantitative analysis of the insecticide on the surface and bulk of the netting and are significant to evaluate net performance.