Development And Validation of An Eco-Friendly and High-Throughput HPLC Method To Quantify Pyrethroid and Pyriproxyfen in Long-Lasting Insecticide-Treated Nets

Long-lasting insecticide-treated nets (LLINs) are essential to preventing malaria transmission. The LLINs should last for at least three years, even after repeated washings. Currently, tracking insecticides in LLINs is cumbersome, costly, and requires specialized equipment and hazardous solvents. We therefore developed a low-resource, high-throughput method for detecting insecticides in LLINs. In order to extract insecticides from polyethylene, LLIN samples were heated for 45 minutes at 85 o C in 1-propanol-heptane containing dicyclohexylphthalate as an internal standard. Sample size was reduced to ~0.2 g for reduced extraction volume, which is 90% less than what was recommended. We optimized HPLC chromatographic conditions to assess pyrethroid and pyriproxyfen content in polyethylene-based LLINs. The method is capable of quantifying levels ≥ 0.0015% permethrin, 0.00045% alpha-cypermethrin and 0.00025% pyriproxyfen (w/w) in polyethylene, allowing tracking the insecticides before and after LLINs use. A variety of LLINs can be evaluated with this method, including those with 1% pyriproxyfen (pyriproxyfen-LLIN) or 2% permethrin (Olyset ® Net), 1% pyriproxyfen and 2% permethrin (Olyset ® Duo), or 0.55% pyriproxyfen combined with 0.55% alpha-cypermethrin (Royal Gaurd ® ). Analysis of 120 samples (40 nets) per run can be done with high precision and accuracy, reducing labour time and costs whilst reducing the environmental impact of organic solvents.