ICP-OES analysis of Lithium in honey, royal jelly, bee bread, propolis, and bees following microwave-assisted sample preparation

Lithium is a natural, ubiquitously-occurring alkali metal found in varying amounts in foods like honey. Recently, lithium chloride (LiCl) was described to be effective against varroosis, a parasitic disease leading to loss of honey bee colonies with limited therapy options. However, LiCl treatment is not currently authorized for use in honey bee colonies. Such treatment might result in elevated lithium amounts in honey. To address this, a robust method for quantifying lithium in honey was validated using a microwave-assisted digestion technique combined with Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), achieving detection levels as low as 0.151 mg/kg. The method was applied to 65 commercially available, randomly chosen honey samples, all of which had lithium levels below the limit of quantitation (LOQ). Furthermore, the method was successfully adapted for use with more complex bee matrices, including royal jelly, bee bread, propolis, and whole bees.