Liquid chromatography - high resolution mass spectrometry (LC-HRMS) developed to screen some residues in rice. Pesticides, aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2 and quaternary ammonium surfactants were detected by the optimized method. Rice samples were extracted and cleaned by QuEChERS then analyzed by QExactive system with HESI ionization source for both negative and positive modes. The C18 reversed phase column was used and the mobile phase consists of water and Methanol containing 0.1% formic acid and 10 mM ammonium formate. The method was applied successfully to analyze 60 rice samples collected in Hanoi city. The results showed that 5 pesticides in 30 rice samples from 10.3 to 160 µg/kg.  

Liquid chromatography tandem mass spectrophotometry (LC-MS/MS) has been developed for simultaneous determination of four antibiotics which have coccidiicidal effects including monensin, dimetridazole, sulfadimethoxin, and sulfadimidine in feed samples. The research conducted by using mobile phase A (0.1% formic acid solution; 10 mM ammonium formate) and phase B (MeOH; 0.1% formic acid; 10 mM ammonium formate) with C18 reversed-phase chromatography column (2.1 × 1.5 mm, ID 3.5 μm) simultaneously and successfully identified these four antibiotics in a short time about 10 minutes. The method detection limits and quantification limits for all analytes were 15.0 and 45.0 µg/kg, respectively. The calibration curve of the method was in the range of 45 - 1,500 µg/L. The method was validated for high accuracy, efficiency and applied to analyze the feed samples on the Hanoi market.

Trong nghiên cứu này, phương pháp sắc ký khí khối phổ kết hợp với việc dẫn xuất hóa đã được thẩm định và áp dụng để phân tích đồng thời 6 chất nhóm phytosterol trong dầu thực vật . Mẫu được thủy phân trong tủ ấm 70°C trong 60 phút, rồi được chiết với toluen. Các chất nhóm phytosterol được dẫn xuất với trimethysilyl ether trước khi phân tích trên hệ thống sắc ký khí khối phổ. Giới hạn phát hiện và giới hạn định lượng của phương pháp lần lượt là 5 và 15 mg/kg. Độ thu hồi của cả 6 chất nhóm phytosterol trong khoảng từ 93,5 đến 101%.

In this study, a method for determination of six phytosterols by gas chromatography-mass spectrometry with derivatization in vegetable oils was validated. The samples were hydrolyzed in an alkaline media at 70°C for 60 min. Then, the samples were performed liquid-liquid extraction with toluene. The phytosterols are derivatized to trimethylsilyl ethers and then analyzed by gas chromatography-mass spectrometry. The limit of detection and limit of quantification was 5 and 15 mg/kg, respectively. Recoveries of six phytosterols were between 93.5% and 101%.

In this study, a method for simultaneous determination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in paper-based food packaging was validated. The paper samples were extracted with ethanol/water (1 : 1, v/v) mixture at 70°C for 2 h by using an incubator shaker. The extracts were passed through 0.2 μm filters before LC-MS/MS analysis. The method detection limit and method quantification limit of both PFOA and PFOS were 0.1 and 0.3 ng/g, respectively. Correlation coefficients > 0.99 were obtained over concentration ranges from 0.3 to 10 ng/mL. The method recovery ranged from 100 - 106% with good repeatability (RSD < 5%). The method was applied to analyze 23 paper samples, however, PFOA and PFOS were not detected in any of these samples.