Chen Yang,Tianwei Lv,Hongyuan Yan,Gaochan Wu,Haonan Li
A new kind of glyoxal–urea–formaldehyde molecularly imprinted resin (GUF-MIR) was synthesized by a glyoxal–urea–formaldehyde (GUF) gel imprinting method with 4,4′-dichlorobenzhydrol as a dummy template. The obtained GUF-MIR was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) and applied as a selective adsorbent of miniaturized pipet tip solid-phase extraction (PT-SPE) for the separation and extraction of three organochlorine pesticides (dicofol (DCF), dichlorodiphenyl dichloroethane (DDD), and tetradifon) in spinach samples. The proposed pretreatment procedures of spinach samples involved only 5.0 mg of GUF-MIR, 0.7 mL of MeOH–H2O (1:1, v/v) (washing solvent), and 0.6 mL of cyclohexane–ethyl acetate (9:1, v/v) (elution solvent). In comparison with other adsorbents (such as silica gel, C18, NH2–silica gel, and neutral alumina (Al2O3–N)), GUF-MIR showed higher adsorption and purification capacity for DCF, DDD, and tetradifon in aqueous solution. The average recoveries at three spiked levels ranged from 89.1% to 101.9% with relative standard deviations (RSDs) ≤ 7.1% (n = 3). The presented GUF-MIR-PT-SPE method combines the advantages of molecularly imprinted polymers (MIPs), GUF, and PT-SPE and can be used in polar solutions with high affinity and selectivity to the analytes in complex samples.
Qian Hou,Tong Zhou,Xinjing Li,Cuimin Hua,Heping Cui,Foxin Zhang,Khizar Hayat,Xiaoming Zhang,Chi-Tang Ho
The browning degree in light-colored Maillard reaction products (L-MRPs), derived from the glycine-xylose system with cysteine (Cys) addition increased during storage. This secondary browning reaction might compromise their long-term stability. To elucidate the underlying mechanism, accelerated storage and model systems (glycine-xylose Amadori compound (GX-ARP) and GX-ARP/cystine) were employed. The findings demonstrated that cysteine undergoes oxidative conversion to cystine, triggering adverse changes including promoted degradation of GX-ARP and retro-aldolization of deoxyosones (DXs) into glyoxal (GO) and methylglyoxal (MGO), thereby accelerating secondary browning. Storage tests with different Cys levels indicated low concentrations insufficiently inhibited browning, while high levels exacerbated darkening from cystine accumulation, and 2 mmol/L Cys achieved optimal balance between browning inhibition and minimized side reactions. In conclusion, the conversion of Cys to cystine and its interference in the GX-ARP degradation pathway cause the instability of L-MRPs. This finding provides a novel theoretical basis for improving the color stability of L-MRPs.
Yehong Han,Zhiqiang Wang,Jun Jia,Ligai Bai,Haiyan Liu,Shigang Shen,Hongyuan Yan
A method based on solid-phase extraction (SPE) coupled with high-performance liquid chromatography (HPLC) was developed to determine the content of 4-chlorophenoxy acetic acid (PCPA), naphthylacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in green bell peppers. A molecularly imprinted 3-aminophenol-glyoxal-urea resin (MIAGUR) was first synthesized as a specific SPE adsorbent, which exhibited special selectivity and multiple adsorption interactions including hydrogen bonding and π-π interactions. The quantities of PCPA, NAA and 2,4-D in green bell peppers from 20 samples scattered throughout Baoding city (Hebei province, China) were determined using the proposed method. The results suggested that the use of PCPA, NAA and 2,4-D in green bell peppers from Baoding’s markets is almost in fair. Moreover, MIAGUR-SPE-HPLC is suitable for the specific simultaneous monitoring of PCPA, NAA, and 2,4-D in green bell peppers and has potential applications in determination of PCPA, NAA, and 2,4-D of other plant products.
危险品化学品经营许可证（带存储）