Do Mosquito Bites Annoy You? Investigating Neat Repellent Using 1H NMR Data

While mosquitos remain active year-round in tropical regions, their peak season occurs during the summer in other areas. The warmer temperatures expedite their life cycle, accelerating processes such as egg hatching, larval development, and pupation, ultimately resulting in a large population of adult mosquitos. Like most insects, mosquitos are ectothermic, which means that their body temperature is regulated by the environment around them. Consequently, the warm temperatures enhance their metabolism, increasing their activity and mobility.

Do only female mosquitos bite? YES! Female mosquitos rely on the proteins found in humans and other animal blood to develop and nourish their eggs. They use specialized mouthparts called proboscis to pierce the host’s skin and extract blood. Conversely, male mosquitos obtain the energy they need from feeding on plant nectar and other sugary substances. Although males do not possess a strong proboscis to pierce skin, they have bushy antennae that allow them to detect the pheromones released by female mosquitos.

Beyond the intriguing aspects of mosquitoes, safeguarding against biting insects is important due to the potential for itchiness, irritation, and diseases transmission, including malaria, dengue fever, Zika virus, or West Nile virus. To address this, personal insect repellent or bug spray is widely used. The Environmental Protection Agency (EPA) mandates the registration of skin-applied repellents before they can be sold, ensuring the efficacy of active ingredients in repellents to prevent insect bites and their safety when used as directed. According to the California Department of Public Health, EPA-registered repellents containing DEET (N,N-diethyl-m-toluamide), Picaridin, IR3535, Oil of lemon eucalyptus (OLE) or Para-menthane-diol are considered safe for use. ¹

Let’s explore a commercial repellent through ¹H NMR (Figure 1). The ¹H NMR spectrum illustrates that this repellent primarily comprises ethanol, water and DEET in its formulation.

Figure 1: ¹H NMR spectrum acquired at 100 MHz of a neat sample of repellent. The DEET molecule is displayed, and its protons are assigned in the spectrum.

NMR is a powerful technique for structure elucidation. However, its capabilities extend beyond that; NMR can be used to determine the relative quantity of compounds in a mixture or their absolute quantity with the use of an internal calibrant. Within a few minutes, an unknown repellent sample was analyzed, revealing its main components.

For more information about our 100 or 60 MHz benchtop NMR spectrometer, or options for advanced experiments or pulse programming capabilities through SPINit, please contact sales@nanalysis.com or fill out this form.

¹ https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/EPA-Registered-Repellent-Ingredients.aspx, accessed on July 18th, 2023.