In Guangdong Province of China, the climate is very wet, so there are many different fungi living in aquatic feeds, which produce mycotoxins. These compounds contaminate agricultural products worldwide and present a great threat to human health. It is necessary to determine their contamination level in aquatic feeds. A high performance liquid chromatography (HPLC) tandem mass spectrometry (MS/MS) method was developed for the quantitative analysis of aflatoxin B₁, aflatoxin M₁, T-2 toxin, HT-2 toxin, deoxynivalenol, ochratoxin, and zearalenone in fish and shrimp feed. Samples were extracted with acetonitrile–water (3+1, v/v), and degreased with acetonitrile-saturated hexane. The extract was cleaned up with a multitoxin column. The target compounds were separated on a C₁₈ chromatographic column and analyzed simultaneously by electrospray ionization mass spectrometry in both positive and negative ion mode. Detected compounds were quantified using the matrix-matched external standard method. Under the optimized conditions, good linearities for the analytes in the corresponding concentration range were obtained, with correlation coefficients (r²) higher than 0.9948. LODs ranged from 1.83 to 12.63 μg/kg, and LOQs ranged from 5.49 to 37.89 μg/kg. Average recoveries for the target mycotoxins at three spiked levels ranged from 80.5 to 116.5% with RSD ranging from 2.4 to 10.4%. Twenty-three real aquafeed samples were determined by this method, and seven kinds of toxins were detected. The results show that the developed method can be successfully applied for the simultaneous determination of mycotoxins in aquatic feeds. Multitoxin purification columns proved to be a powerful technique for determining seven mycotoxins simultaneously. This method ensured simple sample pretreatment and less operation time. The established method was successfully applied to the analysis of seven mycotoxins species in aquatic feeds.

Scientific, accurate, and rapid detection of the composition and content of tea polyphenols is an important basis for their rational use and giving full play to their physiological effect. The spectrophotometric assays for total polyphenols have poor selectivity. Therefore, there is a need to develop a simple and reliable method for the determination of the total polyphenolic level in tea products. The aim of this research was to develop a flow injection chemiluminescence (FI-CL) method based on the Ag(III)-luminol system for the total polyphenol content analysis of tea and substitute tea. Through Box–Behnken experimental design, we selected the optimum determination condition. The Ag(III) concentration was 5 × 10^–5 mol/L, and the luminol concentration was 3 × 10^–7 mol/L (including 0.15 mol/L NaOH). The peristaltic pump is 25 r/min, and the photomultiplier voltage is 600 v. Sample extracts were diluted 100 000 times for the FI-CL assay. Under optimal conditions, CL intensities were proportional to total polyphenol content (in terms of gallic acid concentrations) in the range of 0.1∼100 μg/L. The LOD and LOQ were 0.03 μg/L and 0.1 μg/L. The recovery values were in the range of 86.3–111.0% with a RSD of 1.04∼2.62%. The polyphenolic content of 12 teas and 6 substitute teas was determined, and the results of the developed method and Folin–Ciocalteu method were highly correlated (r = 0.9493 for tea and r = 0.8533 for substitute tea). The proposed method is better than the Folin–Ciocalteu method in terms of selectivity, sensitivity, and accuracy. It is suitable for the determination of polyphenol content not only in tea, but also in substitute tea. We developed a new flow-injection analysis method for polyphenolic content determination based on the Ag(III)-luminol chemiluminescence system. It is simple, rapid, sensitive, and accurate. It is suitable for the determination of polyphenols content not only in tea, but also in substitute tea.