Solid Sampling Electrothermal Vaporization Inductively Coupled Plasma Optical Emission Spectrometry for the Analysis of Insects

Alternative protein sources such as insects are of interest because of their many nutritional and ecological benefits compared to traditional animal-based proteins. As they may contain potentially toxic elements in addition to essential elements, their analysis is important to ensure their safety for human consumption. To avoid time-consuming acid digestion, which may lead to contamination or loss of analytes, the direct analysis of insects via solid sampling electrothermal vaporization coupled with inductively coupled plasma optical emission spectrometry (SS-ETV-ICPOES) was explored for the first time. Different approaches for the analysis of black soldier fly meal were evaluated, using CF4, polytetrafluoroethylene (PTFE) powder pre-mixed with the sample, or PTFE pre-mixed with the sample and H-2 in the carrier gas as chemical modifier. Addition of N-2 as a sheathing gas around the ETV effluent to increase plasma robustness was also studied. The best results were obtained with the Ar-N-2 mixed-gas plasma, PTFE powder pre-mixed with samples, and H-2 in the carrier gas, allowing the accurate determination of Cd, Co, Fe, K, P, S, and Zn in black fly soldier meal in 100 s by external calibration with a dogfish muscle certified reference material (CRM) and internal standardization with Ar 404.442 nm to compensate for sample loading effects on the plasma. Application of this method to other insects resulted in accurate results for Co, Fe, and S in cricket flour as well as Co, Fe, P, S, and Zn in mealworm powder. Thus, SS-ETV-ICPOES shows promise as a screening method for insect analysis.