A method using high performance liquid chromatography with diode array detector and fluorescence detector (HPLC-DAD-FLD) was established to simultaneously analyze seven water-soluble vitamins in starch-fortified foods. The sample was hydrolyzed by amylase at 60 ℃ for 45 min and ultrasonically extracted after pH adjustment. Chromatographic separation was carried out by gradient elution using 5 mmol/L sodium dodecyl sulfate solution containing 0.1% phosphoric acid adjusted to pH 3.0 with triethylamine as mobile phase A and acetonitrile as mobile B. Vitamin B₁, niacin and nicotinamide were detected at maximum UV absorption wavelengths. Good linearity was observed for all analytes with correlation coefficients (r²) of 0.9996–0.9999. The recoveries for spiked samples were 90.5%–102.5%, the limits of detection (LODs) were 0.01-0.08 mg/100 g, and the limits of quantitation were 0.025–0.26 mg/100 g. The developed method is rapid, efficient and suitable for the simultaneous determination of the seven vitamins in bulk starch-fortified foods.

Using a Kjeldahl distillation apparatus, a method for the simultaneous determination of formaldehyde and sodium diacetate in aquatic products by dual-gradient liquid chromatography (DGLC) with online derivatization was established. Formaldehyde and sodium diacetate in samples were collected by steam distillation using the kjeldahl apparatus after adding phosphoric acid. The distillates were detectd by DGLC. In the left pump system, the content of sodium diacetate in aquatic products was directly detected. In the right pump system, 10 μL of acetonitrile-acetic acid solution containing 2,4-dinitrophenylhydrazine was used as the derivatization agent, and the sample volume was 10 μL. The content of formaldehyde in the distillate was detected after on-line derivatization for 4 min. The linear ranges of formaldehyde and sodium diacetate were 0.5–20.0 and 10–200 mg/L, respectively, with correlation coefficients greater than 0.999. The detection limits of formaldehyde and sodium diacetate were 0.5 and 10 mg/kg, respectively. For the intrabatch repeatability, the recoveries of formaldehyde and sodium diacetate were 81.4%–88.3% and 91.4%–102.9%, respectively, with relative standard deviations (RSDs) of 1.73%–2.68% and 3.08%–4.16%, respectively. For the interbatch repeatability, the recoveries of formaldehyde and sodium diacetate were 80.6%–87.9% and 90.8%–105.1%, respectively, with RSDs of 2.07%–2.72% and 3.44%–4.64%, respectively. The method is rapid and efficient, and is suitable for the simultaneous determination of formaldehyde and sodium diacetate in bulk samples of of aquatic products.

A novel adsorption material for dispersive solid phase extraction (DSPE) was prepared using amino-functionalized zirconium-based metal-organic framework (UiO-66-NH₂) as the core and molecularly imprinted polymer as the shell. Subsequently, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the material. Key experiential parameters such as solvent, adsorbent concentration, adsorption time, desorption solvent and time were systematically investigated. Furthermore, a highly sensitive method for the determination of fluoroquinolone residues in aquatic products was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with DSPE. The extract was blown to near dryness under nitrogen and re-dissolved with 10% methanol-ammonia solution (pH 8.0). Subsequently, 30 mg of the adsorbent was added for adsorption for 8 minutes. Next, the fluoroquinolones sorbed were ultrasonically desorbed with 10% acetic acid-methanol solution for 4 minutes, blown to near dryness under nitrogen and re-dissolved before analysis by LC-MS/MS. Good linearity was observed all 10 fluoroquinolones in the concentration range of 0.1–200 μg/L, with recovery rates of 84.5%–105.9%. Compared with the national standard method, the established method had higher accuracy, lower limit of detection (LOD) and limit of quantification (LOQ), simpler and more efficient operation. The new material had good selectivity and reusability, effectively reducing the cost of detection. This study helps expand the application scope of metal-organic framework-based molecularly imprinted polymers in food safety detection.

A novel metal-organic framework (MOF) material, UiO-66-NH₂, was synthesized using a solvothermal method. Subsequently, a high performance liquid chromatography (HPLC) method with solid phase extraction using UiO-66-NH₂ was established for the simultaneous detection of five fluoroquinolone (FQ) residues in aquatic products. The sample was extracted with acetonitrile in 1.0% formic acid, degreased with n-hexane, and concentrated by rotary evaporation. The extract was then redissolved in aqueous ammonia solution at pH 8.0. The FQs were enriched and purified with a solid phase extraction (SPE) column filled with 30 mg of UiO-66-NH₂ using 6 mL of 20% acetic acid-methanol solution as the eluent. The collected eluate was blown to dryness under nitrogen, redissolved and detected by HPLC with a fluorescence detector. Under the established experimental conditions, good linear relationships were achieved for the five FQs in the concentration range of 0.005–0.50 mg/L, with determination coefficients (R²) of 0.9999–1.0. The recovery rates ranged from 81.4% to 104.8% with relative standard deviation (RSD) of 1.29%–4.93%, and the limits of detection (LOD) were in the range of 0.21–2.05 μg/kg. The prepared SPE column could be reused up to five times, which was environmentally friendly and costeffective. The established method had good accuracy, precision, reproducibility, and selectivity, and was suitable for the simultaneous detection of various trace FQ residues in aquatic products.