Analytical Methods Based on Liquid Chromatography and Capillary Electrophoresis to Determine Neonicotinoid Residues in Complex Matrices. A Comprehensive Review

Neonicotinoids (NNIs) are neuro-active and systemic insecticides widely used to protect crops from pest attack. During the last decades, there has been an increase concern about their uses and toxic effects, especially to beneficial and non-target insects such as pollinators. To assess potential health hazards and the environmental impacts derived from NNIs uses, a great variety of analytical procedures for the determination of their residues and their metabolites at trace level in environmental, biological and food samples have been reported. Due to the complexity of the samples, efficient sample pretreatment methods have been developed, which include mostly clean-up and preconcentration steps. On the other hand, among the analytical techniques used for their determination, high-performance liquid chromatography (HPLC) coupled to ultraviolet (UV) or mass spectrometry (MS) detection is the most widely used, although capillary electrophoresis (CE) has also been employed in the last years, considering some improvements in sensitivity when coupling with new MS detectors. In this review, we present a critical overview of analytical methods based on HPLC and CE reported in the last decade, discussing relevant and innovative sample treatments for the analysis of environmental, food and biological samples.

Development and Validation of a Gas Chromatography-Mass Spectrometry Method for Determining Acaricides in Bee Pollen

Pesticides can be found in beehives for several reasons, including contamination from surrounding crops or for their use by beekeepers, which poses a risk to bee ecosystems and consumers. Therefore, efficient and sensitive methods are needed for determining pesticide residues in bee products. In this study, a new analytical method has been developed and validated to determine seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, α-endosulfan, bromopropylate, coumaphos, and τ-fluvalinate) in bee pollen using gas chromatography coupled to mass spectrometry. After an optimization study, the best sample treatment was obtained when using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method employing an ethyl acetate and cyclohexane as the extractant mixture, and a mixture of salts for the clean-up step. A chromatographic analysis (<21 min) was performed in an Agilent DB-5MS column, and it was operated under programmed temperature conditions. The method was fully validated in terms of selectivity, limits of detection (0.2–3.1 µg kg−1) and quantification (0.6–9.7 µg kg−1), linearity, matrix effect (<20% in all cases), trueness (recoveries between 80% and 108%), and precision. Finally, the proposed method was applied to analyze commercial bee pollen samples, and some of the target pesticides (chlorfenvinphos, α-endosulfan, coumaphos, and τ-fluvalinate) were detected.

Characteristics of contaminants in the polish-origin bee products and cancer risk assessment

The aim of this study was to evaluate the concentration of 5-hydroxymethylfurfural (HMF), furfural, polycyclic aromatic hydrocarbons (PAHs), and pesticide residues, as well as assessment of cancer risk of the Polish-origin bee products. The bee product samples were prepared using a modified QuEChERS method, then PAHs and pesticides were analysed by gas chromatography-mass spectrometry (GC-MS), neonicotinoids by high-performance liquid chromatography with a diode array detector (HPLC-DAD), and HMF and furfural by spectrophotometry (HPLC-UV/Vis). The results showed that the highest furfural content was found in bee bread from the northeast part of Poland; moreover, samples obtained from the same region were also characterized with a higher level of HMF. The total sum of PAHs ranged from 324.0 to 866.4 μg/kg; the highest content of PAH4 (the sum of benzo[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene) was 21.0 μg/kg, but only benzo[a]anthracene and chrysene were detected in the samples. Imidacloprid and acetamiprid were found only in bee bread from the northeast part of Poland, while clothianidin was detected in honey samples. The acceptable cancer risk has been calculated for PAHs due to ingestion of honey, while increasing the risk of cancer was calculated for bee bread and bee pollen. Due to the high concentration of PAHs and excessively high recommended consumption dose, regular consumption of bee bread and pollen may pose a severe threat to human health and should be strictly limited.

Effects of Thiamethoxam-Dressed Oilseed Rape Seeds and Nosema ceranae on Colonies of Apis mellifera iberiensis, L. under Field Conditions of Central Spain. Is Hormesis Playing a Role?

Simple Summary

The collapse of the honey bee colonies is a complex phenomenon in which different factors may participate in an interrelated manner (e.g., pathogen interactions, exposure to chemicals, beekeeping practices, climatology, etc.). In light of the current debate regarding the interpretation of field and monitoring studies in prospective risk assessments, here we studied how exposure to thiamethoxam affects honey bee colonies in Central Spain when applied as a seed treatment to winter oilseed rape, according to the good agricultural practice in place prior to the EU restrictions. Under the experimental conditions, exposure to thiamethoxam, alone or in combination with other stressors, did not generate and maintain sufficient chronic stress as to provoke honey bee colony collapse. The stress derived from exposure to thiamethoxam and honey bee pathogens was compensated by adjustments in the colony’s dynamics, and by an increase in the worker bee population, a behavior known as hormesis. An analysis of the factors underlying this phenomenon should be incorporated into the prospective risk assessment of plant protection products in order to improve the future interpretation of field studies and management practices.

Abstract

To study the influence of thiamethoxam exposure on colony strength and pathogen prevalence, an apiary (5 colonies) was placed in front of a plot sown with winter oilseed rape (wOSR), just before the flowering phase. Before sowing, the seeds were treated with an equivalent application of 18 g thiamethoxam/ha. For comparison, a second apiary (5 colonies) was located in front of a separate 750 m plot sown with untreated wOSR. Dead foragers at the entrance of hives were assessed every 2–3 days throughout the exposure period, while the colony strength (number of combs covered with adult honey bees and brood) and pathogens were monitored each month until the following spring. Foraging on the wOSR crop was confirmed by melissopalynology determination of the corbicular pollen collected periodically, while the chemical analysis showed that exposure to thiamethoxam was mainly through nectar. There was an increase in the accumulation of dead bees in the apiary exposed to thiamethoxam relating with the control, which was coped with an increment of bee brood surface and adult bee population. However, we did not find statistically significant differences between apiaries (α = 0.05) in terms of the evolution of pathogens. We discuss these results under hormesis perspective.

A global study of pesticides in bees: QuEChERS as a sample preparation methodology for their analysis - Critical review and perspective

To this day, it remains unknown what the cause of decline of honey bee populations is and how to prevent this phenomenon efficiently. Poisonings with pesticides are assumed to be among the main causes for the decline of the honey bee population. Despite the significant progress observed in analytics over recent years, research aimed at improving methods applied in diagnostics of bee poisoning is still in progress. This is no easy task, since determination of the content of trace amounts (often equal to sublethal doses) of a wide range of compounds with diverse physico-chemical properties in honey bee samples with a complex matrix composition poses a serious challenge to modern analytics. This overview is the first to include a comprehensive critical assessment of analytical methods proposed for quantification of pesticides in honey bees over the last decade. Since the QuEChERS method is currently of great significance to ensuring accurate and reliable results of pesticide quantification in honey bees, the present overview focuses on the major aspects of this method, which will provide a comprehensive reference for scientists. The review focuses on the limitations of methods and on potential future prospects. It also contains information on the detection of pesticides in honey bees between 2010 and 2020 and characterizes the pesticide classes which are most toxic to these insects. This is extremely important, not just in the context of understanding the potential adverse impact of pesticides, manifesting as losses in bee colonies; it is also intended to facilitate decision-making in future research related to this difficult yet very important subject.

A Case Report of Chronic Stress in Honey Bee Colonies Induced by Pathogens and Acaricide Residues

In this case report, we analyze the possible causes of the poor health status of a professional Apis mellifera iberiensis apiary located in Gajanejos (Guadalajara, Spain). Several factors that potentially favor colony collapse were identified, including Nosema ceranae infection, alone or in combination with other factors (e.g., BQCV and DWV infection), and the accumulation of acaricides commonly used to control Varroa destructor in the beebread (coumaphos and tau-fluvalinate). Based on the levels of residues, the average toxic unit estimated for the apiary suggests a possible increase in vulnerability to infection by N. ceranae due to the presence of high levels of acaricides and the unusual climatic conditions of the year of the collapse event. These data highlight the importance of evaluating these factors in future monitoring programs, as well as the need to adopt adequate preventive measures as part of national and international welfare programs aimed at guaranteeing the health and fitness of bees.

Electrochemical sensor based on multi-walled carbon nanotubes for imidacloprid determination

A simple and robust sensor (fMWCNT-Nafion®0.5%/GCE) for determination of imidacloprid (IMI), a widely used neonicotinoid, was developed using a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (fMWCNT) and Nafion®. The obtained data suggest that IMI reduction is an irreversible process, due to the reduction of the nitro group to hydroxylamine derivatives, with the participation of two protons and four electrons, and a charge transfer coefficient of 0.141. The optimized square-wave voltammetric conditions were: McIlvaine buffer at pH 6.0, 0.5% of Nafion® in the fMWCNT suspension, -0.6 V and 180 s as accumulation potential and time, respectively. A linearity in the range of 2.00 × 10-7 to 1.77 × 10-6 mol L-1 IMI, with the values of limit of detection and limit of quantification were equal to 3.74 × 10-8 mol L-1 and 1.25 × 10-7 mol L-1, respectively. Repeatability and reproducibility displayed relative standard deviations lower than 5%. Recovery tests performed in tap water, melon, and shrimp yielded mean values of 94 ± 6%, 97 ± 10% and 93 ± 10%, respectively. Moreover, several inorganic and organic compounds did not significantly interfere (0.6 to 4.5%) on the IMI signal, proving the selectivity and applicability of the developed sensor for IMI detection in complex samples.

Magnetic molecularly imprinted polymer nanoparticles for the extraction and clean-up of thiamethoxam and thiacloprid in light and dark honey

In this work, new selective and sensitive dual-template molecularly imprinted polymer nanoparticles (MIPs) were synthesized and characterized. Sorbent MIPs were investigated for simultaneous extraction and clean-up of thiamethoxam and thiacloprid from light and dark honey samples. In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry triple-quadrupole (UHPLC-MS/MS) (QQQ) was used to detect and quantify the pesticides. The kinetic model with adsorption kinetics of sorbent was investigated. The optimal adsorption conditions were 80 mg of polymer MIPs, a 30-min extraction time, and a pH of 7. The detection limit (LOD) and the quantification limit (LOQ) varied from 0.045 to 0.070 µg kg^-1 and from 0.07 to 0.10 µg kg^-1, respectively. The intra-day and inter-day precision (RSD, %) ranged from 1.3 to 2.0% and from 8.2 to 12.0%, respectively. The recovery of thiamethoxam and thiacloprid ranged from 96.8 to 106.5% and 95.3 to 104.4%, respectively, in light and dark honey samples.

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

With the exponential number of published data on neonicotinoids and fipronil during the last decade, an updated review of literature has been conducted in three parts. The present part focuses on gaps of knowledge that have been addressed after publication of the Worldwide Integrated Assessment (WIA) on systemic insecticides in 2015. More specifically, new data on the mode of action and metabolism of neonicotinoids and fipronil, and their toxicity to invertebrates and vertebrates, were obtained. We included the newly detected synergistic effects and/or interactions of these systemic insecticides with other insecticides, fungicides, herbicides, adjuvants, honeybee viruses, and parasites of honeybees. New studies have also investigated the contamination of all environmental compartments (air and dust, soil, water, sediments, and plants) as well as bees and apicultural products, food and beverages, and the exposure of invertebrates and vertebrates to such contaminants. Finally, we review new publications on remediation of neonicotinoids and fipronil, especially in water systems. Conclusions of the previous WIA in 2015 are reinforced; neonicotinoids and fipronil represent a major threat worldwide for biodiversity, ecosystems, and all the services the latter provide.

Overview of Analytical Methods for the Determination of Neonicotinoid Pesticides in Honeybee Products and Honeybee

Neonicotinoid pesticides are widely applied for controlling pests in a variety of agriculture crops. Due to the systemic distribution in plants, neonicotinoid pesticides have been found in nectar and pollen, which are the main source of food for the important pollinator honeybee. The risk of neonicotinoid residues in honeybee products and honeybee has caused great attention since their impacts on the environment, ecology, and food safety issues. These concerns require the accurate and sensitive determination of neonicotinoids and their metabolites in the honeybee products and honeybee. Since the trace residue level of neonicotinoid and the complexity of the samples, analysis of neonicotinoid targets in these important matrices is still a great challenge. The present review provides general overview of analytical methods for the determination of neonicotinoid pesticides and their metabolites in honeybee products and honeybee.

Quantitative Determination of Acetamiprid in Pollen Based on a Sensitive Enzyme-Linked Immunosorbent Assay

A sensitive biotinylated indirect competitive enzyme-linked immunosorbent assay (Bic-ELISA) was developed to detect acetamiprid pesticides in pollen, based on the heterogeneous coating antigen and biotinylated anti-acetamiprid monoclonal antibody. Under optimized experimental conditions, the detection limit for the Bic-ELISA was 0.17 ng/mL and the linear range was 0.25–25 ng/mL. The cross-reactivities could be regarded as negligible for the biotinylated antibodies with their analogues except for thiacloprid (1.66%). Analyte recoveries for extracts of spiked pollen (camellia pollen, lotus pollen, rape pollen) ranged from 81.1% to 108.0%, with intra-day relative standard deviations (RSDs) of 4.8% to 10.9%, and the average reproducibility was 85.4% to 110.9% with inter-assay and inter-assay RSDs of 6.1% to 11.7%. The results of Bic-ELISA methods for the Taobao’s website samples were largely consistent with HPLC-MS/MS. Therefore, the established Bic-ELISA methods would be conducive to the monitoring of acetamiprid in pollen.