Preparation of a Novel Resin Based Covalent Framework Material and Its Application in the Determination of Phenolic Endocrine Disruptors in Beverages by SPE-HPLC

A new type of economical covalent organic framework material(COF), namely resin based covalent organic framework material, was prepared by combining resin and covalent organic framework material by hydrothermal synthesis, which was based on the preparation of traditional COF material(TpBD COF). The properties of the material and covalent organic framework material were compared in the way of characterization, and the possible reaction mechanism was analyzed. The solid phase extraction separation (SPE) ability of this material for four kinds of phenolic endocrine disrupting compounds (bisphenol F, bisphenol A, octylphenol and nonylphenol) in beverage samples was investigated. The results showed that the prepared COF materials had abundant internal channels, ordered structure, large specific surface area (TpBD COF: 814.6 m2/g and resin based COF: 623.9 m2/g) and good thermal stability (pyrolysis temperature was 443 °C and 437 °C, respectively). Solid phase extraction experiments demonstrated that the two COF materials as adsorbent of solid phase extraction column had ideal adsorption separation effect and good anti-interference ability, and had strong anti-interference ability. The SPE effect was superior to the traditional solid phase extraction column. The precision RSD of this method was less than 3%. This SPE method had high recovery and could be reused (carbonated beverage: 98.18–102.18% and beverage: 98.52–101.79%), In addition, the recovery of the material did not change significantly in the 50 cycles of solid phase extraction, indicating that the material had good stability and could be reused, which could meet the requirements for the detection and analysis of trace pollutants in environmental samples. The resin based COF material prepared in this study could reduce the cost of monomer uses and provide a possibility for its industrial production. At the same time, as an efficient SPE adsorbent, it also provided a new research scheme for the enrichment of trace phenolic endocrine disruptors in beverage samples.

Determination of 24 Pesticides Residues in Leather Products by Solid-Phase Microextraction Coupled with Gas Chromatography–Mass Spectrometry

Considering the high content of oil and complex residual additives in leather samples, a new analytical method based on the solid-phase extraction technique and gas chromatography-selected ion monitoring mass spectrometry (GC-SIM-MS) was developed to determine 24 organic compounds involving the organochlorine pesticides (OCPs), organophosphorous pesticides (OPPs) and pyrethroids pesticides residues in leather. The extraction conditions (such as the extraction solution, purification procedure and solid-phase extraction column) were optimized using the positive leather samples based on the recovery rates of the pesticides. The best extraction solution, solid-phase extraction column and chromatography column were n-hexane and ethyl acetate (1+1, volume) mixed solution, Carb-PSA (1.0 g, 6mL) and DB-1701 (length: 30 m, inside diameter: 0.25 mm, film thickness: 0.25 μm). The optimized extraction time and temperature were 20 min and 25°C, respectively. The detection limits of 24 pesticide residues range from 0.05 to 0.10 mg/kg, and the recoveries range from 74% to 116%. The relative standard deviations (RSD, n=6) range from 5.42% to 12.00%. The developed method presented a simple, rapid, sensitive, and inexpensive method to detect 24 pesticides in skin and leather and was successfully applied to the detect them in leather products (cowhide, sheep leather and pig leather).

Preparation and characterization of molecularly imprinted solid-phase extraction column coupled with high-performance liquid chromatography for selective determination of melamine

We synthesized a selective molecularly imprinted solid-phase extraction (MIP-SPE) column and established an extraction and enrichment method using this MIP-SPE column. By coupling with HPLC, we developed a new method to detect trace amounts of melamine in eggs. The MIP-SPE column was synthesized by in situ thermal-initiated polymerization using melamine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and azodiisobutyronitrile as the initiator. HPLC was used to evaluate the identification and enrichment capability of the MIP-SPE column and for the measurement of melamine in the sample. The melamine concentration exhibited an excellent linear relationship in the range of 0.1–25.0 µg ml −1 ( r = 0.9983). The identification capability of the MIP-SPE column was apparently superior to that of the non-imprinted polymer solid-phase extraction column; an average enrichment factor of 46.8-fold (RSD = 3.5%) was obtained for 0.4 µg ml −1 melamine by the MIP-SPE column. When the MIP-SPE HPLC method was applied to the detection of melamine in eggs, an average recovery rate of 93.5–102.0% (RSD = 3.6–4.9%) and a limit of detection of 0.05 µg kg −1 were obtained. This method is simple, fast and cost-effective; thus, it can greatly simplify the pre-treatment of complex samples and can be used in the detection of residual melamine in eggs and other products.