Pesticide residue analysis in cereal-based baby foods using multi-walled carbon nanotubes dispersive solid-phase extraction

Simultaneous determination of spiropidion and its five major metabolites in sweet orange fruit and various processing by-products using ultra-high performance liquid chromatography-tandem mass spectrometry

The present work reported the application of an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous analysis of spiropidion and its five major metabolites in sweet orange fruit and by-products throughout the whole industrial juicing process of the orange fruit. The reversed-dispersive solid phase extraction (r-DSPE) with multi-walled carbon nanotubes (MWCNTs) was employed for the extraction and purification. The established method was validated and satisfactory parameters (linearity, trueness, precision, sensitivity, matrix effect and stability) were obtained. And then, the field trial of spiropidion on sweet oranges has been conducted and the effect of commercial juicing processing on the residue of spiropidion and its metabolites was further investigated. The various processing factors (PFs) for washing, juicing, sterilization, concentrating and essential oil collecting were also determined. The final results indicated that washing processing reduced residues by 18.4%; the juicing step allowed a significant decrease of the spiropidion residue by 34.2-70.8%, with PFs value in the range of 0.290-0.658. However, high level of residual spiropidion (ranging from 4.016 to 4.205 mg/kg) was detected in orange essential oil, with PFs value of 17.157. All the above results demonstrated the efficiency of the established method in the routine control analysis of spiropidion residues in sweet orange fruits and their by-products, and will facilitate the further intensive research on its spatial distribution, transfer and degradation during the different processing procedures of the sweet orange fruits.

Development of a novel nano-based detection card by electrospinning for rapid and sensitive analysis of pesticide residues

BACKGROUND

Increasing food safety awareness of consumers promotes the development of rapid and sensitive detection techniques for pesticide residues. In this study, a new type of rapid detection card for organophosphorus and carbamate pesticide residues was developed by electrospinning. The card involved enzyme fiber mat (EFM) and substrate fiber mat (SFM) which were prepared by mixing poly(vinyl alcohol) with acetylcholinesterase (AChE) and indolyl acetate (IA), respectively.

RESULTS

The mean diameter of fibers was 240 ± 53 nm for EFM and 387 ± 84 nm for SFM. Results of Fourier transform infrared and X-ray photoelectron spectroscopies confirmed that AChE and IA were successfully encapsulated into the fibers. The minimum concentrations of AChE and IA for effective detection were 1 and 3 mg mL^-1 , respectively, and the optimal detection time was 15 min. The limits of detection for this card were 0.5 mg L^-1 for omethoate, 1.5 mg L^-1 for malathion, 0.1 mg L^-1 for carbaryl and 0.02 mg L^-1 for carbofuran. The detection card exhibited good storage stability and its activity could be maintained when stored at room temperature for at least 4 months. Additionally, the EFM can be reused three times.

CONCLUSIONS

The detection card obtained here was superior to a commercial card in detecting pesticide residues in real food samples. Hence, this electrospun detection card has potential for simple, rapid and sensitive analysis of pesticide residues. © 2020 Society of Chemical Industry.

Differential metabolic signatures in naturally and lactic acid bacteria (LAB) fermented ting (a Southern African food) with different tannin content, as revealed by gas chromatography mass spectrometry (GC-MS)-based metabolomics

Fermented whole grain (WG) sorghum food products including WG-ting can be obtained from different sample sources and fermentation conditions, leading subsequently to variations in the molecular composition of the products. There is however, a lack of detailed understanding and description of differential molecular profiles of these food products. Thus, the current study is a nontargeted gas chromatography-mass spectrometry (GC-MS)-based metabolomics approach to descriptively elucidate metabolic profiles of two WG-sorghum types [high tannin (HT) and low tannin (LT)] and their derived WG-ting products obtained via fermentation. Metabolites were extracted with 80% aqueous methanol and analyzed on a gas chromatography high resolution time of flight mass spectrometry (GC-HRTOF-MS) system. Chemometric methods such as principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA) were applied to mine the generated data. Our results showed that tannin contents influenced the composition of the raw sorghum and derived WG-ting samples. Metabolite signatures that differentiated raw HT- and LT-sorghum included cyclic compounds, pesticides, 2,4-di-tert-butylphenol, fatty acid esters, and sugar derivatives. Furthermore, fermentation of the HT- and LT-sorghum into WG-ting led to an increase in the levels of fatty acids, fatty acid esters and some other compounds which are vital from a dietary and health context. Equally observed were reduction of some phenols, cyclic compounds, a pesticide and ketone. Thus, the results demonstrated that the inherent metabolic composition of raw sorghum would lead to differential metabolic changes in the fermented products such as WG-ting, with subsequent dietary and health implications. Fermenting ting with Lactobacillus fermentum FUA 3321 was most desirable as relevant metabolites were observed in both HT- and LT-ting samples. Furthermore, the study highlights the applicability of GC-MS metabolomics in understanding WG-ting fermentation.

Recent advances in applications of nanomaterials for sample preparation

Sample preparation is a key step for qualitative and quantitative analysis of trace analytes in complicated matrix. Along with the rapid development of nanotechnology in material science, numerous nanomaterials have been developed with particularly useful applications in analytical chemistry. Benefitting from their high specific areas, increased surface activities, and unprecedented physical/chemical properties, the potentials of nanomaterials for rapid and efficient sample preparation have been exploited extensively. In this review, recent progress of novel nanomaterials applied in sample preparation has been summarized and discussed. Both nanoparticles and nanoporous materials are evaluated for their unusual performance in sample preparation. Various compositions and functionalizations extended the applications of nanomaterials in sample preparations, and distinct size and shape selectivity was generated from the diversified pore structures of nanoporous materials. Such great variety make nanomaterials a kind of versatile tools in sample preparation for almost all categories of analytes.

Carbon nanotube-based QuEChERS extraction and enhanced product ion scan-assisted confirmation of multi-pesticide residue in dried tangerine peel

Carbon nanotubes-based QuEChERS extraction and enhanced product ion scan-assisted confirmation was developed for multi-pesticide residue analysis in dried tangerine peels.