Determination of Rhodamine B in Food Using Ionic Liquid–Coated Multiwalled Carbon Nanotube–Based Ultrasound-Assisted Dispersive Solid-Phase Microextraction Followed by High-Performance Liquid Chromatography

Urea-linked covalent organic framework functionalized polytetrafluoroethylene film for selective and rapid thin film microextraction of rhodamine B

Incorporation of highly selective and stable adsorbent with facile extraction technology is desired in practical analysis. Here we show the rational preparation of a urea-linked covalent organic framework functionalized polytetrafluoroethylene film (COF-117-PTFE) with ordered porous structure, rich functional groups, and large surface area-to-volume ratio as the effective adsorbent for convenient, selective and rapid thin film microextraction (TFME) of rhodamine B (RB). The COF-117-PTFE based TFME coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) successfully realized the determination of RB with the limit of detection of 0.007 μg L^-1, the linear range of 0.1 - 100 μg L^-1. The relative standard deviation (RSD) of intraday (n = 5) and interday (n = 5) for the determination of 10 μg L^-1 RB were 2.3% and 6.8%, respectively. The absolute recoveries were 80.3%, 71.2% and 67.9% in river water, chili powder and Sichuan pepper powder, respectively. The recoveries for RB spiking in complicated real samples (dry chili, chili powder, dry Sichuan pepper, Sichuan pepper powder and river water) ranged from 90.4% to 107.5%. The developed COF-117-PTFE based TFME-HPLC-FLD method is promising in practical application. This work reveals the high potential of functionalized COF film as the adsorbent for effective extraction of trace contaminants in complicated samples.

Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Simultaneous determination of multiple phytohormones in tomato by ionic liquid-functionalized carbon fibers-based solid-phase microextraction coupled with liquid chromatography-mass spectrometry

Phytohormones are interrelated by synergistic or antagonistic crosstalk and play important roles in the regulation of plant growth and development. In order to understand the interaction between phytohormones in the plant physiological network, it is necessary to determine trace levels of multiple phytohormones simultaneously in a complex matrix. Here, we synthesized ionic liquids containing different functional groups and modified the surface of carbon fibers with them. Based on these carbon fibers-ionic liquid (CFs-IL) materials, a solid phase microextraction method was developed to enable the simultaneous extraction of phytohormones. The adsorption specificity of multiple phytohormones was studied by identifying the hydrophobic, electrostatic, and π-π interactions, as well as hydrogen bonds, which favor simultaneous extraction of the relevant acidic, alkaline and neutral phytohormones by improving compatibility. The proposed method, coupled with liquid chromatography-tandem mass spectrometry, was applied to the simultaneous determination of 13 acidic, alkaline and neutral phytohormones in tomato. The limits of quantification were found to be in the range of 0.32-54.05 ng mL^-1 and 4.6-185.8 pg mL^-1, respectively, when measured by QQQ and Q-TOF. All of the relative recoveries were in the range of 94.40-113.37% with RSDs ≤15.36% (n = 3) for spiked tomato samples. This method is expected to be widely applied to multiple phytohormones analysis for in-depth researches concerning the physiological networks of plants.