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A solid-phase extraction (SPE) method was established for fipronil and its metabolite residues (fipronil desulfinyl, fipronil sulphone and fipronil sulphide) in eggs with a covalent triazine framework (CTF) porous material as the adsorbent followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) detection. Multiple probes and quantum chemistry theory calculations were conducted to describe the versatile adsorption property directly and quantifiably. The conjugated structure of CTF and N-containing triazine generated π-π interactions and hydrogen bonds between the CTF and the targets, which led to high extraction efficiency and recoveries. The solid-phase extraction parameters, including amount of the adsorbent, type of eluent, amount of eluent and loading rate were investigated. Under the optimal experimental conditions, the recoveries of the analytes were between 85.5% and 103.2%, and the RSD (n = 5) was between 1.8% and 3.6%. The LODs and LOQs were 0.13–0.2 ng g−1 and 0.5–0.8 ng g−1, respectively. The sorbent can effectively reduce the interference of the matrix and meet the detection requirements of fipronil and its metabolites in eggs. These results imply that the CTF as adsorbents have great potential in the analysis of trace targets in samples with complex matrices. [ABSTRACT FROM AUTHOR]

A methodology is presented for the sensitive determination of nitromidazole residues in egg by means of micellar electrokinetic capillary chromatography in combination with cation selective exhaustive injection and ultraviolet detection. Six compounds have been considered and the separation has been achieved in less than 12 min in a 61.5-cm effective length capillary with 50-μm internal diameter. Phosphate buffer 44 mM pH 2.5, containing 8% tetrahydrofurane and 123 mM sodium dodecyl sulfate was employed as running buffer. Solid phase extraction has been employed for sample clean-up. The methodology has been successfully validated in hen eggs, obtaining method detection limits in the range of 2.1–5.0 ng/g. Precision was studied in terms of repeatability and intermediate precision, with relative standard deviations lower than 18.0%. Recoveries were calculated in quail eggs and a commercial pasteurized egg white product, reaching over 70% for most of the considered 5-nitroimidazoles. [ABSTRACT FROM AUTHOR]

Abstract: A simple and effective method based on magnetic separation has been developed for the extraction of sulfonamides (SAs) from egg samples using magnetic multiwalled carbon nanotubes (MMWCNTs) as an adsorbent. The MMWCNTs were simply prepared by depositing Fe3O4 onto MWCNTs that had been previously oxidised. The extraction procedure was carried out in a single step by blending and subsequently stirring the mixture of MMWCNTs and aqueous egg samples. The SAs were first extracted as described above, adsorbed onto the MMWCNTs directly and finally analysed by liquid chromatography–tandem mass spectrometry. The limits of detection obtained are in the range of 1.4–2.8ngg−1. The proposed method was successfully applied in determining SAs in the eggs obtained from laying hens fed with SA standards, and compared to eggs purchased from local markets. The results demonstrate that SAs were detectable in the incurred egg samples. [Copyright &y& Elsevier]

A monolithic molecularly imprinted polymer for enrofloxacin was synthesized by in situ copolymerization of methylacrylic acid and methyl methacrylate in a traditional stainless-steel chromatographic column for the rapid separation and determination of enrofloxacin and ciprofloxacin in eggs. By optimizing the polymerization condition, the monolithic MIP showed highly specific recognition for enrofloxacin over its active metabolite ciprofloxacin. The influence of components of monomers on hydrophobicity, contractibility, selectivity, and binding capacity of polymer were investigated. As shown by SEM, the mesopores and macropores were formed in the monolith column; this allowed the mobile phase to flow through the column with low backpressure. Furthermore, some chromatographic conditions such as mobile phase composition and flow rate on the retention times were investigated. The binding capacity was evaluated by static adsorption and Scatchard analysis, which showed that the dissociation constant and the maximum binding capacity were 117.7 mg/L and 27.27 mg/g for high affinity binding site, and 297 mg/L and 187.4 mg/g for lower affinity binding site, respectively. The mean recoveries of enrofloxacin and ciprofloxacin from egg samples were 103.3-115% and 89.3-95.1%, respectively. The research has shown that copolymerization provides more adjustable conditions for making molecularly imprinted monolithic columns with different morphologies and higher selectivity. [ABSTRACT FROM AUTHOR]

Abstract: In the work, magnetic strong cation exchange (MSCX) resins were prepared using hydrophobic Fe3O4 magnetite as the magnetically susceptible component, styrene and divinylbenzene as polymeric matrix components, acetyl sulfonate as the sulfonation agent. The resins were successfully applied to the extraction of melamine (MEL) from egg samples. The extraction procedure was carried out in a single step by blending and stirring the sample, extraction solvent and the magnetic resins. The MEL was extracted from the sample matrix then adsorbed onto the resins directly through ion-exchange interaction. When the extraction was completed, the resins with adsorbed analyte were easily separated from the sample matrix by applying an appropriate magnetic field. Main factors affecting the extraction of MEL such as the amount of MSCX resins, extraction time, washing and eluting conditions were optimized. The MEL eluted from the resins was determined by liquid chromatography–tandem mass spectrometry. The linearity of quantification obtained by analyzing matrix-matched standards is in the range of 10–1000ngg−1. The limit of detection and quantification obtained are 2.6 and 8.8ngg−1, respectively. The relative standard deviations of intra- and inter-day ranging from 1.6% to 6.5% and from 2.1% to 7.2% are obtained. The recoveries of MEL are in the range of 77.2–99.3%. The proposed method was successfully applied to determine MEL in eggs obtained from different local markets. MEL was detectable with the contents of 43.5 and 234.1ngg−1 in two samples. [Copyright &y& Elsevier]

The screening of antimicrobial residues in eggs is an especially important subject. Three different commercial kits for the screening of sulphonamides and other antimicrobials in eggs were validated in accordance with Decision 2002/657/EC: one enzyme-linked immunoabsorbant assay (ELISA) kit multi-sulphonamides (from RAISIO Diagnostics) and two microbiological tests (a Premi® test from DSM and an Explorer® kit from Zeu-Inmunotec). The false-positive rates were lower than 2% for all kits. The detection capabilities (CCβ) have to be as low as possible for banned substances and lower than the maximum residue limit (MRL) when MRLs have been set. The sensitivity of the Premi® test was better than that of the Explorer® test, probably because of the dilution of the eggs before the Explorer® test was used. The CCβ values towards most of the tested sulphonamides were satisfactory with the Premi® test (≤ 100 µg kg-1). Performance in a proficiency test for the detection of sulphonamides in eggs with the Premi® test confirmed these results. The detection capabilities of tetracycline and doxycycline were at the level of the MRL or twice the MRL maximum. The detection capabilities for chlortetracycline and oxytetracycline were higher (four to six times the MRL). The detection capabilities for amoxicillin, neomycin, tylosin and erythromycin were lower than their respective MRLs. Detection capabilities for sulphonamides were much lower for the ELISA kit than for microbiological tests. The ELISA kit could be recommended for the targeted screening of sulphonamides in eggs. On the other hand, the Explorer® and Premi® tests could be used as wide screening tests allowing the detection of most of the antimicrobial families. [ABSTRACT FROM AUTHOR]

• ISPE, a new form of SPE method, is developed combing advantages of PT-SPE and DSPE. • IL-TGO was used to extract fipronil and showed high adsorption capacity. • IL-TGO-ISPE method reduce the time of sample preparation and the usage of adsorbent. • A fast, economic and accurate method was developed for detection of fipronil in eggs. A rapid and economic integrated solid-phase extraction (ISPE) method with ionic liquid-thiol-graphene oxide composite (IL-TGO) as a new adsorbent was established for the extraction of fipronil in chicken eggs. In this study, ISPE, a new form of solid-phase extraction, which combined the advantages of pipette-tip solid phase extraction (PT-SPE) and dispersive solid-phase extraction (DSPE), achieving rapid extraction of analyte with only a small amount of adsorbent. The three-dimensional porous IL-TGO was a new ideal adsorbent for fipronil due to the multiple adsorption interactions (π-π interaction, hydrophobic interaction and hydrogen bond), large adsorption capacity and fast adsorption rate. For this ISPE procedure, the analyte was adsorbed by IL-TGO through the pipette tip mode and then eluted through dispersive mode. Under the optimized condition, the proposed method performed following merits: good linearity (r = 0.9999), precision (RSD ≤ 6.3%), high recoveries (83.7% to 97.7%), rapid extraction (16 min), low consumption of adsorbent (3.00 mg of IL-TGO). The excellent recyclability of the ISPE device and the reusability of IL-TGO were observed and high recovery of fipronil (> 90%) was obtained after fifteen cycles. This work might provide promising strategy for the sensitive extraction and analysis of trace levels of fipronil from egg products. [ABSTRACT FROM AUTHOR]

In this work, an automated 2D-LC approach for protein isolation from egg samples on preparative scale is proposed. The method is based on the use of a C18 guard column installed in a switching valve to focus the proteins coming from the first dimension column, before their elution in the second column. For the first dimension separation, a size-exclusion column, packed with 3 μm ultrapure silica particles was used. An RP column based on core-shell technology was used for the second dimension separation. A standard mixture of BSA, β-lactoglobulin, and glucose oxidase, chosen as a protein model system, was used to optimize the chromatographic separation conditions. The fully automated workflow allowed to isolate, in a single-chromatographic analysis, a protein amount of 50 μg for each peak fraction, with a total time of 15 min for the first separation and additional 30 min of the second separation for each trapped protein. The final aim was the development of proper analytical tools for protein isolation from foodstuffs to be used for the molecular identification by MS, as well as for biotherapeutic uses, allergy testing, and large-scale investigations in biological systems., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)