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Asymmetrical flow field‐flow fractionation is a rising useful technique to separate and characterize macromolecules. Elution behaviors of allergen protein ovalbumin and immunoglobulin E were studied here. Effects of flow rates, kinds of carrier solutions, and injection amounts were investigated in the desire to experiment and verify the effect of every factor and to validate asymmetrical flow field‐flow fractionation theory. Results suggested that cross‐flow is the most important factor among all the factors that have been studied. Too‐low focus flow (0.5 ml/min) and outflow (0.4 ml/min) are harmful for protein separation and characterization. Smaller size ovalbumin (with a monomer is 11.4 nm) is more prone to be influenced compared with the bigger analyte immunoglobulin E (with a monomer diameter is 32.1 nm) by flow rates. The adopted types of carrier fluids did not change the retention behavior of the two proteins. Still, protein aggregation and membrane adsorption should be paid more attention to under different carrier fluids.

Glucocorticoids (GCs) widely exist in animal food including aquatic food. This study aimed to survey the occurrences of cortisone and cortisol in aquatic food and the estimated daily intake (EDI) of cortisone and cortisol due to different habits of aquatic food consumption. The mean levels of cortisone and cortisol in freshwater fish purchased from market were 14.59 μg/kg and 69.15 μg/kg, respectively, which were markedly higher than the levels in marine fish. A test using Zebrafish was performed to compare the concentration of GCs by different killing methods. The results suggested that physically traumatic killing methods are one of the reasons why the levels of GCs in freshwater fish were higher than those in marine fish. The concentrations of cortisone and cortisol in composite aquatic food samples from 12 provincial districts of the fourth China Total Diet Study (TDS) were 0.72~15.75 μg/kg and 4.90~66.13 μg/kg, respectively, which were positively correlated with the distance from the coastline. Further, the correlation coefficient between the levels of cortisone and cortisol in aquatic food and the percentages of freshwater fish consumption were 0.758 (p < 0.01) and 0.908 (p < 0.01), respectively. There was a significant positive correlation between the levels of cortisone and cortisol in aquatic food in the fourth TDS and the percentages of freshwater fish consumption. The calculated average EDIs of cortisone and cortisol from aquatic food in the fourth TDS were 0.16 μg/d and 0.72 μg/d, respectively.