Seven parabens are widely used in soy sauce, vinegar, jam, oyster sauce, stuffing, and other foods. The long-term intake of large amounts of parabens and similar substances may be harmful to the human body. Therefore, the addition of paraben preservatives to food should be strictly controlled. The current detection method is applicable to single target compound and several food categories, and the experimental pretreatment method involves extraction with anhydrous ethyl ether, which is a toxic reagent. Moreover, interferences in the analysis of parabens via gas chromatography limit the versatility and accuracy of the detection method. Herein, a novel method based on solid-phase extraction (SPE) coupled with high performance liquid chromatography (HPLC) was developed for the determination of seven paraben preservatives (methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, isobutyl p-hydroxybenzoate, and heptyl p-hydroxybenzoate) in oyster sauce, shrimp sauce, and fish sauce. Compared with the conventional method, the proposed work enables the determination of more compounds, thereby expanding its scope of application to different food types. This strategy also optimizes the pretreatment method and device parameters. The samples were extracted with methanol and 20% methanol aqueous solution by ultrasonication, respectively, and then centrifuged. The experimental pretreatment method was enriched, and sample clean-up was conducted using a MAX SPE column. The seven parabens were separated using a Chromcore 120 C18 column (150 mm×4.6 mm, 3.0 μm). Gradient elution was performed with acetonitrile-5 mmol/L ammonium acetate aqueous solution as the mobile phase (initial mobile phase volume ratio, 30∶70). The flow rate was 0.7 mL/min, and the column temperature was 35 ℃. A diode array detector with a detection wavelength of 254 nm was also used. The seven paraben preservatives showed good linearity in the range of 0.5-50.0 mg/L, with correlation coefficients greater than 0.9999. The limits of detection (LODs) and quantification (LOQs) for the seven paraben preservatives were 0.2-0.4 mg/kg and 0.5-1.3 mg/kg, respectively. A spiked recovery test was conducted using oyster sauce, shrimp sauce, and fish sauce at three spiked levels of 2, 40, and 200 mg/kg. Good recoveries for the seven paraben preservatives were obtained and the recoveries of the analytes in oyster sauce, shrimp sauce, and fish sauce were 91.0%-102%, 95.5%-106%, and 95.0%-105%, respectively, with relative standard deviations of ≤6.97%. Compared with the liquid-liquid extraction method, the proposed method demonstrated better purification effects. The recoveries of the seven paraben preservatives extracted using this method were also much higher than those obtained from liquid-liquid extraction. We determined the contents of these preservatives in 135 food products using the method established in this study and detected methyl p-hydroxybenzoate and ethyl p-hydroxybenzoate in soy sauce, vinegar, and pickles. Thus, the established method can be used for the effective determination of seven parabens in aquatic seasoning such as oyster sauce, shrimp sauce, and fish sauce.
建立了固相萃取-高效液相色谱法同时测定蚝油、虾油、鱼露中的7种对羟基苯甲酸酯类防腐剂(对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯、对羟基苯甲酸异丙酯、对羟基苯甲酸异丁酯、对羟基苯甲酸庚酯)。样品分别用甲醇和20%甲醇水溶液超声提取,离心后经MAX固相萃取小柱富集、净化。使用Chromcore 120 C18色谱柱(150 mm×4.6 mm, 3.0 μm)分离,以乙腈-5 mmol/L乙酸铵水溶液为流动相(初始流动相体积比30∶70),梯度洗脱,流速0.7 mL/min,以二极管阵列检测器检测,检测波长254 nm,柱温35 ℃。7种对羟基苯甲酸酯类防腐剂在0.5~50.0 mg/L内具有良好的线性关系,相关系数均大于0.9999,检出限为0.2~0.4 mg/kg,定量限为0.5~1.3 mg/kg。选用蚝油、虾油、鱼露3种样品在3个加标水平下做加标回收试验,7种防腐剂在3种样品中的回收率较好,分别为91.0%~102%、95.5%~106%、95.0%~105%,相对标准偏差≤6.97%。利用该研究建立的检测方法对135个实际样品进行风险筛查,发现某酱油、醋、酱腌菜等存在对羟基苯甲酸甲酯、对羟基苯甲酸乙酯等。该方法操作简单,结果准确,重复性好,干扰少,灵敏度高,可作为测定水产调味品蚝油、虾油、鱼露中7种对羟基苯甲酸酯的有效检测方法。
Keywords: fish sauce; high performance liquid chromatography (HPLC); oyster sauce; parabens; shrimp sauce; solid-phase extraction (SPE).