This study evaluated different methods of extraction based on quick, easy, cheap, effective, rugged and safe (QuEChERS) method for analysis of the antibiotics ceftiofur, cloxacillin and enrofloxacin in milk using ultra-performance liquid chromatography-tandem mass spectrometry. The QuEChERS acetate method has been shown to be inefficient for extracting such antibiotics. The optimized QuEChERS method presented excellent recoveries, from 95 to 99%. A complete factorial design was used to evaluate the effects of variables of the clean-up step: anhydrous octadecylsilane (C18), primary secondary amine (PSA) and sodium acetate (NaAc). Linearity (R 2) above 0.96 was achieved for all compounds. Accuracy and precision were assessed by recovery. Accuracy was 91-99%. Intraday precision with relative standard deviations (RSD) lower than 12.3% and interday precision lower than 12.4% were obtained. Limits of detection (LOD) and quantification (LOQ) were obtained between 1.4-6.8 and 1.5-8.7 µg L-1 , respectively. The applicability was evaluated using 91 real milk samples.

Antioxidants are used to increase the shelf life of food and oils. The most common extraction method of antioxidants from natural sources is the use of organic solvents, like methanol and ethanol. Evaporation of all the organic solvent is necessary to prevent health diseases. In this study, we present a new "organic solvent-free" method to extract antioxidants, which uses canola oil as extraction solvent to incorporate natural antioxidants from oregano and ginger without the use of organic solvent. The oil solvent extraction capacity was assessed by assays of oxygen radical absorbance capacity method for hydrophilic (721.9 ± 10.5 and 89.0 ± 2.5 µmol TE g -1 to canola oil with oregano and ginger, respectively) and lipophilic (118.8 ± 7.4 and 48.2 ± 9.7 µmol TE g -1 to canola oil with oregano and ginger, respectively) compounds, oxidation test (Oxitest ® ) (1,434 and 1,018 minutes to canola oil with oregano and ginger, respectively) and thiobarbituric acid reactive substances (0.01 ± 0.02 and 0.11 ± 0.06 mg MA g -1 to canola oil with oregano and ginger, respectively). Results provide evidence of the efficiency of canola oil as antioxidants extractor. Nine antioxidant compounds from canola oil incorporated with antioxidants compounds were identified using high performance liquid chromatography tandem mass spectrometry.Keywords: antioxidant capacity, high-performance liquid chromatography-electrospray ionization mass spectrometry, green chemistry, solvent free IntroductionThe use of antioxidants is the simplest method to reduce fat oxidation in food and oils. 1 In most cases, synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tert-butylhydroquinone (TBHQ) are used as additives. However, there is evidence that synthetic antioxidants have harmful effects on human health. 2,3 Because of this, research for suitable natural sources of antioxidants for use in the food and oil industries have been performed. 4 Natural antioxidants from plants have many advantages when compared to synthetic antioxidants. 1 Overall, natural antioxidants have functional and sensory properties, are considered safe, and have greater acceptability by the consumers. 1 On the other hand, different organic solvents such as methanol, ethanol and acetone are used to extract antioxidants from fruits, vegetables and other types of foods. These solvents have hazardous and toxic properties and can cause adverse health effects. 5 This study aimed to develop a new "organic solventfree" method to extract antioxidants from oregano and ginger using canola oil. The antioxidant capacity from the canola oil with spices was evaluated by oxygen radical absorbance capacity method (ORAC), using the fluorescein (FL) decay curve (ORAC FL ) of hydrophilic compounds (H-ORAC FL ) and lipophilic compounds (L-ORAC FL ). The lipid oxidation of the samples was measured by two different methods: a new method known as Oxitest, and by thiobarbituric acid reactive substances (TBARS) assay. Antioxidants compounds...