Due to their high biological activity, beekeeping products such as honey, bee pollen, royal jelly, and bee bread are in high demand in the food, pharmaceutical, and cosmetic industries. Therefore, monitoring pesticide residues not only in crops directly exposed to them but also in beekeeping products is of vital importance.
This dissertation presents the results of an assessment of the suitability of a method for detecting residues of multi-component pesticide mixtures in honey using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-MS/MS). The main stages of pesticide extraction from the tested samples using QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) sample preparation are described, followed by the simultaneous quantitative determination of up to 200 analytes in a single sample without the use of internal standards.
The conducted research revealed that the highest bee colony mortality across various regions of Ukraine in 2021–2022 was caused by individual pesticides from different chemical groups, namely thiamethoxam, acetamiprid, and clothianidin, as well as by combined exposure to multiple pesticides.
During the analysis of honey samples collected from apiaries where mass bee colony deaths were recorded, residues of insecticides, primarily neonicotinoids, were most frequently detected, as well as fungicides, predominantly triazoles, strobilurins, and benzimidazoles. Contamination of honey with neonicotinoids was detected in 163 cases, accounting for 58.8 % of the total number of samples. Residues of triazoles were found in 82 cases, representing 29.6 % of the total. The detection frequency of strobilurins in honey reached 18 cases, or 6.5 % of the samples tested. Benzimidazole residues were the least frequently found among the analyzed samples, 14 cases, or 5.1 %.
The determination of pesticide residues in the bodies of dead bees using liquid chromatography-mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS/MS) revealed the presence of both individual pesticides from various chemical groups and mixtures of these compounds in different combinations and concentrations, complicating the objective assessment of their synergistic toxicity.
Residues of insecticides from the neonicotinoid group, as well as fungicides from the triazole, benzimidazole, and strobilurin groups, did not undergo degradation in honey during 12 months of storage at 4 °C. Under storage conditions at 20 °C, the degradation of neonicotinoids imidacloprid, clothianidin, and thiamethoxam over 12 months was not confirmed. However, increased degradation of thiacloprid and acetamiprid was observed only at high initial concentrations. Under these conditions, the reduction in thiacloprid content in honey reached 21.2 %, and acetamiprid – 20.7 % compared to the initial data.
Residues of triazoles – tebuconazole, cyproconazole, and epoxiconazole – showed no change during 12 months of honey storage at 20 °C. However, the concentration of flutriafol decreased by 36.3 %.
Storage of honey at 20 °C did not affect the degradation of the strobilurins pyraclostrobin and azoxystrobin over the 12 months, though it led to a reduction in the residual content of picoxystrobin: by 24.5 % at the 9th month and by 38.0 % at the 12th month compared to the initial concentration.
An increase in honey storage temperature to 20 °C enhanced the degradation rate of benzimidazoles, particularly carbendazim, which decreased by 80.0 % by the 9th month and fully degraded by the 12th month. The degradation dynamics of thiophanate-methyl showed a higher degradation rate in honey at 20 °C: 28.0 % by the 6th month, 46.0 % by the 9th month, and 55.4 % by the 12th month compared to the initial values.
The studies conducted have proven the necessity of using the method of controlling residues of multicomponent pesticide mixtures in bee products and environmental objects using liquid triple quadrupole tandem chromatography-mass spectrometry (LC-MS/MS) with QuEChERS sample preparation. The causes and sources of mass poisoning of bee colonies in apiaries in various regions of Ukraine have been identified. The high persistence of most pesticides, especially insecticides and fungicides, in honey during storage for 12 months at different temperatures has been proven, which requires the development of alternative plant protection products based on biopathogens.
