Synthesis of nitrogen-rich magnetic hypercrosslinked polymer as robust adsorbent for the detection of neonicotinoids in honey, tomatoes, lettuce and Chinese cabbage

Covalent organic framework-sodium alginate-Ca2+-polyacrylic acid composite beads for convenient dispersive solid-phase extraction of neonicotinoid insecticides in fruit and vegetables

Neonicotinoids, the fastest-growing class of insecticides, have posed a multi-media residue problem with adverse effects on environment, biodiversity and human health. Herein, covalent organic framework-sodium alginate-Ca2+-polyacrylic acid composite beads (CACPs), facilely prepared at room temperature, were used in convenient dispersive solid-phase extraction (dSPE) and combined with high-performance liquid chromatography (HPLC) for the detection of five neonicotinoid insecticides (thiamethoxam, acetamiprid, dinotefuran, clothianidin, imidacloprid). CACPs can be completely separated within 1 min without centrifugation. After seven adsorption/desorption cycles, it maintained high extraction efficiencies (>90%). The developed method exhibited a wide linear range (0.01 ∼ 10 μg mL-1), low limits of detection (LODs, 0.0028 ∼ 0.0031 mg kg-1), and good repeatability (RSD ≤ 8.11%, n = 3). Moreover, it was applied to the determination of five neonicotinoids in fruit and vegetables (peach, pear, lettuce, cucumber, tomato), and recoveries ranged from 73.6% to 116.2%.

Amino-functional magnetic covalent organic framework as an effective adsorbent for the determination of neonicotinoids in food samples

Recently, covalent organic frameworks have gained popularity in sample pretreatment. However, the application of covalent organic frameworks in the enrichment of hydrophilic compounds remains a challenge. Thus, a functionalized magnetic covalent organic framework equipped with amino groups was constructed using a bottom-up functionalization strategy. Considering the advantages of this novel adsorbent such as high porosity, large adsorption capacity, and hydrophilic surface, a sensitive magnetic solid-phase extraction coupled with high-performance liquid chromatography-tandem mass spectrometry method was established for the effective determination of neonicotinoids. This method exhibited good linearities with correlation coefficients ranging from 0.9983 to 0.9995, low detection limits in the range 0.003-0.009 ng g-1 and 0.001-0.013 ng mL-1, and limits of quantification in the range 0.010-0.031 ng g-1 and 0.004-0.044 ng mL-1. Furthermore, satisfactory repeatability with relative standard deviations ≤ 6.7% and spiked recoveries between 82.3 and 99.8% were obtained. This work not only provided a promising adsorbent for the sensitive determination of trace-level neonicotinoids but also represented a unique insight for effective enrichment of super hydrophilic hazards.

A chitin-based magnetic hyper-cross-linked polymer for highly efficient enrichment of neonicotinoids in lemon juice and tomatoes

A chitin-based magnetic hyper-cross-linked polymer (labeled as Ch-MHCP) has been successfully synthesized and utilized for highly-effective solid-phase extraction of neonicotinoid insecticides (NEOs). The extraction capability of Ch-MHCP for four common NEOs is higher than that of four commercial sorbents including octadecyl-silane C18, oasis hydrophilic/lipophilic balanced sorbent, oasis mixed anion sorbent and poly-phenylacetic mixed anion sorbent. The large number of hydroxyl and amide groups as well as benzene rings in Ch-MHCP allow the H-bond and π-π* interaction to be the principal adsorption mechanism of Ch-MHCP for NEOs. Besides, polar interaction was also involved in the adsorption process. In combination of Ch-MHCP based extraction technique with high-performance liquid chromatography, a novel analytical method for sensitive detection of NEOs in lemon juice and tomatoes has been established. At optimal conditions, wide linear ranges were obtained to be 0.20-100 ng mL-1 for lemon juice and 0.80-1000 ng g-1 for tomatoes. The detection limits were 0.06-0.12 ng mL-1 for lemon juice and 0.24-0.60 ng g-1 for tomatoes. This work not only provides a powerful tool for simultaneously detecting four NEOs in lemon juice and tomatoes, but also offers a new insight into the preparation of bio-based magnetic sorbents for adsorption/removal of pollutants.

Rapid determination and health risk assessment of neonicotinoids in source water and tap water of the tropical Hainan Island, China

Neonicotinoids (NEOs) pesticides are widely used around the world, especially in the tropics with greater frequency and intensity. However, little is known about NEOs residue in drinking water of tropics. In this study, a highly efficient method using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for determining eight NEOs in source water and tap water of Hainan Island, China. The method adopted a high-throughput direct aqueous injection without sample concentration steps, with a rapid analyzing period of 5.0 min, method detection limits (MDLs) in the range of 0.84-1.82 ng/L and the average recoveries ranged from 83% to 116%. NEOs were detected in all source water samples and at an upper level as compared with other parts of China. The most frequently detected NEO was imidacloprid with a detection frequency of 94%, followed by clothianidin (88%) and thiamethoxam (78%), with maximum concentrations of 86.4, 164, and 188 ng/L, respectively. Moreover, seasonal and spatial variations had remarkable impacts on NEO contamination in source water. Drinking water treatment processes removed approximately 20% of NEOs from surface water. However, 90% of tap water samples contained at least one NEO, With 3 samples' concentration of single NEO exceeding the acceptable value recommended by the European Union (100 ng/L). Therefore, the risk of human exposure through drinking water was evaluated for 4 age group and 2 genders. Young children aged 9 months to 3 years old were found to have the highest risk, with the median exposure up to 4 times greater than teenagers and adults. Next, water intake is likely only a small part of the daily intake of these individuals, thus the potential health problems caused by NEOs present in the tap water of Hainan should not be ignored.

Design of hydroxyl-functionalized nanoporous organic polymer with tunable hydrophilic-hydrophobic surface for solid phase extraction of neonicotinoid insecticides

As being widely used insecticides, neonicotinoid residues are toxic and harmful to human health and aquatic ecosystems. Thus, the sensitive monitoring of neonicotinoids in water and food samples is highly desirable to reduce their risks to humans. Herein, four novel hydroxyl-functionalized nanoporous organic frameworks (OH-NOP1, OH-NOP2, OH-NOP3 and OH-NOP4) with tunable hydrophilic-hydrophobic surface have been designed and fabricated for the first time by employing luteolin as monomer and 4,4'-bis(chloromethyl)-1,1'-biphenyl as crosslinker at the molar ratio of 3:1, 1:1, 1:3 and 1:6, respectively. When the molar ratio of luteolin to crosslinker was 1:3, OH-NOP3 was obtained and it presented the highest affinity with excellent adsorption performance towards the studied neonicotinoids. The adsorption mechanism was proposed to be the strong hydrogen bond, polar interaction, Lewis acid-base interaction and pore adsorption between OH-NOP3 and neonicotinoids. Then, utilizing OH-NOP3 as sorbent for solid phase extraction cartridges, an effective method for extraction and preconcentration of neonicotinoids followed by high performance liquid chromatography analysis has been developed for quantitative detection of neonicotinoids from water and edible fungi. The method provided good linearity over the range of 0.06-100.0 ng mL^-1 for lake water, 1.5-100.0 ng g^-1 for pleurotus eryngii and sea-shroom. Low detection limit (at the signal to noise ratio of 3) was achieved in the range of 0.02-0.08 ng mL^-1 for water, 0.50-0.60 ng g^-1 for pleurotus eryngii and 0.50-0.80 ng g^-1 for sea-shroom, while the limit of quantification was 0.06-0.25 ng mL^-1, 1.50-1.80 ng g^-1 and 1.50-2.50 ng g^-1, respectively. Satisfactory method recoveries (85.1-112%) were obtained, with relative standard deviations below 8.2%. This study offered a new strategy for designing efficient sorbents to adsorb or remove organic pollutants based on the structure and properties of substrates.