Neonicotinoids generally contain three chemical structures: N-cyanoamidines, N-nitroguanidines, and nitromethylenes(Jeschke et al., 2011). They are often applied as seed treatments, soil application, and foliar spraying to translocate to all plant organs and thus avoid insect damage(Jeschke et al., 2011; Elbert et al., 2008; Bonmatin et al., 2015). Since their invention in the mid-1990s, neonicotinoids have quickly become widely used, accounting for 25% of the world's pesticide market(Bass et al., 2015). Even though neonicotinoids provide positive results from a pest control perspective, their residues' adverse ecological, environmental, and public health effects in pollen, nectar, crops, fruits, and vegetables should also be reviewed. Recent studies have indicated that neonicotinoids can affect the acetylcholine levels of honey bees, resulting in paralysis, loss of orientation and flight ability, and possibly even death(Chensheng et al., 2012; Blacquiere et al., 2012). Due to their systemic mode of action, approximately 73% of pollen and honey collected from beehives contained at least one neonicotinoid(Lu et al., 2015). Furthermore, neonicotinoids are highly stable in water and soil and cannot be washed off before consumption, potentially endangering human health(Bonmatin et al., 2015; Goulson, 2013; Cimino et al., 2017; Mei Chen et al., 2014). A lack of toxicological data makes it difficult to fully assess how neonicotinoids affect human health. Still, mammalian studies have shown that neonicotinoids can severely damage the central nervous system and adversely affect reproduction(Mei Chen et al., 2014; Abou-Donia et al., 2008; Gibbons et al., 2015; Gu et al., 2013; Kimura-Kuroda et al., 2012; Simon-Delso et al., 2015; Tomizawa, 2004). It is worth noting that some neonicotinoid metabolites are even more toxic than their parent compounds(Mei Chen et al., 2014; Simon-Delso et al., 2015; Tomizawa, 2004; Goulson et al., 2015). With the widespread use of toxic neonicotinoids and their cumulative effects, their deleterious effects on infant brain development deserve special attention(Han et al., 2018). An FDA dietary study clearly stated that considerable levels of neonicotinoids were detected about 6–31% frequency among commercial infant foods(FDA, 2015). Therefore, it is critical to establish reliable analytical methods to detect neonicotinoids and their metabolites in commercialized infant food.
Several analytical methodologies are commonly employed to detect neonicotinoid residues in food. These include high-performance liquid chromatography with ultraviolet detection (HPLC-UV)(Mahdavi et al., 2020; Farajzadeh et al., 2016; Vichapong et al., 2016; Farajzadeh et al., 2015), high-performance liquid chromatography-mass spectrometry (HPLC-MS)(Lachat and Glauser, 2018; Suganthi et al., 2018; Valverde et al., 2018; Tian et al., 2020), ion chromatography (IC)(Muhammad et al., 2018), gas chromatography (GC)(Ko et al., 2014), capillary electrophoresis (CE)(Sánchez-Hernández et al., 2014; Zhang et al., 2012; Guan-Hua Chen et al., 2012), and non-chromatographic methods(Oliveira et al., 2018; Watanabe et al., 2018; Jiménez-López et al., 2018; Guo et al., 2016; Wijaya et al., 2014). Overall, among these methods, HPLC-MS is the most commonly used, based on its reliability, sensitivity, and selectivity. While instrument performance is positively correlated with the accuracy of results, sample pre-treatment techniques have a much more major impact. It is no exaggeration to say that the performance of the analytical instrument will be determined by whether or not it can be fully utilized. Traditional sample pre-treatment methods, such as liquid-liquid extraction (LLE)(Banerjee et al., 2007), solid-phase extraction (SPE)(Di Muccio et al., 2006; Seccia et al., 2008; Watanabe et al., 2007), etc., are considered less environmentally friendly due to their high consumption of organic solvents and lengthy operations, and gradually being replaced by the QuEChERS (Quick, Easy, Cheap, Efficient, Rugged and Safe) method(Barbieri et al., 2019; Yao et al., 2019; Moreno-González et al., 2018).
Although numerous studies have been conducted on neonicotinoid residues in adult foods, little attention has been paid to infant foods. This article aimed to develop a simple, rapid, and efficient QuEChERS method combined with HPLC-MS/MS to detect neonicotinoids as well as their metabolites in infant foods. As far as we know, the present study is the first to simultaneous determination of 20 neonicotinoid insecticides and their metabolites in infant foods. Various conditions for sample pre-treatment, chromatographic separations, and mass spectrometric detection were investigated and optimized. This established method was further validated and applied to real samples.