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Highlights: [•] A magnetic solid phase extraction method based on Fe3O4–SiO2–phenyl was developed. [•] This technique is based on the dispersion of a magnetic adsorbent in liquid samples. [•] Method developed was employed for the extraction of nine sulphonamides from milk. [•] The novel method was validated according European Decision 2002/657/EC. [•] Method demonstrated to be an efficient strategy for sulphonamides determination. [Copyright &y& Elsevier]

Abstract: A magnetic solid phase extraction method coupled to capillary electrophoresis is proposed for the determination of tetracycline, oxytetracycline, chlortetracycline and doxycycline in milk samples. Five different magnetic phenyl silica adsorbents covered with magnetite were synthesized by varying the molar ratio of phenyltrimethylsilane and tetramethylorthosilicate; these adsorbents were evaluated in terms of their pH and degree of hydrophobicity for tetracycline retention. The optimal, selected combination of conditions was a pH of 10.0 and a magnetic sorbent ratio of 4:1; under these conditions, the retention capacity ranged from 99.7% to 101.2% for the four tetracyclines analyzed. The elution conditions and initial sample volume of the proposed extraction method were also optimized, and the best results were obtained with 1×10−3 M acetic acid in methanol as eluent and a 200ml of sample volume. Under optimal conditions, average recoveries ranged from 94.2% to 99.8% and the limits of detection ranged from 2 to 9μgl−1 for the four tetracyclines. After the proposed method was optimized and validated, 25 milk samples of different brands were analyzed, oxytetracycline residues were detected in five samples, in concentrations ranging from 98 to 213μgl−1. Subsequent analysis of positive samples by SPE–CE and magnetic solid phase extraction–HPLC revealed than no significant differences were found from results obtained by the proposed methodology. Thus, the developed magnetic extraction is a robust pre-concentration technique that can be coupled to other analytical methods for the quantitative determination of tetracyclines. [Copyright &y& Elsevier]

Solid-phase extraction in combination with large-volume sample stacking-capillary electrophoresis (SPE-LVSS-CE) was applied to measure chlortetracycline, doxycycline, oxytetracycline, and tetracycline in milk samples. Under optimal conditions, the proposed method had a linear range of 29 to 200 µg·L−1, with limits of detection ranging from 18.6 to 23.8 µg·L−1 with inter- and intraday repeatabilities < 10% (as a relative standard deviation) in all cases. The enrichment factors obtained were from 50.33 to 70.85 for all the TCs compared with a conventional capillary zone electrophoresis (CZE). This method is adequate to analyze tetracyclines below the most restrictive established maximum residue limits. The proposed method was employed in the analysis of 15 milk samples from different brands. Two of the tested samples were positive for the presence of oxytetracycline with concentrations of 95 and 126 µg·L−1. SPE-LVSS-CE is a robust, easy, and efficient strategy for online preconcentration of tetracycline residues in complex matrices. [ABSTRACT FROM AUTHOR]

To achieve analytical success, it is necessary to develop thorough clean-up procedures to extract analytes from the matrix. Dispersive solid phase extraction (DSPE) has been used as a pretreatment technique for the analysis of several compounds. This technique is based on the dispersion of a solid sorbent in liquid samples in the extraction isolation and clean-up of different analytes from complex matrices. DSPE has found a wide range of applications in several fields, and it is considered to be a selective, robust, and versatile technique. The applications of dispersive techniques in the analysis of veterinary drugs in different matrices involve magnetic sorbents, molecularly imprinted polymers, carbon-based nanomaterials, and the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method. Techniques based on DSPE permit minimization of additional steps such as precipitation, centrifugation, and filtration, which decreases the manipulation of the sample. In this review, we describe the main procedures used for synthesis, characterization, and application of this pretreatment technique and how it has been applied to food analysis. [ABSTRACT FROM AUTHOR]

Magnetic solid phase extraction has been used as pretreatment technique for the analysis of several compounds because of its advantages when it is compared with classic methods. This methodology is based on the use of magnetic solids as adsorbents for preconcentration of different analytes from complex matrices. Magnetic solid phase extraction minimizes the use of additional steps such as precipitation, centrifugation, and filtration which decreases the manipulation of the sample. In this review, we describe the main procedures used for synthesis, characterization, and application of this pretreatment technique which were applied in food analysis. [ABSTRACT FROM AUTHOR]

A method is presented for magnetic solid phase extraction of tartrazine from nonalcoholic beverages. The method involves the extraction and clean-up by activated carbon covered with magnetite dispersed in the sample, followed by the magnetic isolation and desorption of the analyte by basified methanol. The tartrazine eluted from the magnetic support was determined by spectrophotometry. Under optimal conditions, the linear range of the calibration curve ranges from 3 to 30 mg L−1, with a limit of detection of 1 mg L−1. The method was validated by comparing the results with those obtained by HPLC. A precision of <5.0% was obtained in all cases and no significant differences were observed (P<0.05). [ABSTRACT FROM AUTHOR]

method is presented for magnetic solid phase extraction (MSPE) of tetracyclines in milk samples. The method involves the extraction and clean-up by silica based magnetic support dispersion on non-pretreated milk samples, followed by the magnetic isolation and desorption of the analytes by acidified methanol. The tetracyclines eluted from the magnetic support were determined simultaneously by flow injection analysis with spectrophotometric detection. Under optimal conditions, the linear range of the calibration curve ranges from 0.03 to 0.60 mg L, with a limit of detection of 10 μg L. Recoveries were determined for milk spiked at levels from 0.15 to 0.60 mg L. Average recoveries ranged from 91.0 to 97.0%, with a precision of <5.0% in all cases. The method was validated by comparing the results with those obtained by MSPE-HPLC and SPE-HPLC. No significant differences were observed ( p < 0.05) [ABSTRACT FROM AUTHOR]

N-carbamylglutamate (NCG), a synthetic analogue of N-acetylglutamate, is an activator of blood ammonia conversion and endogenous arginine synthesis. Here, we established an accurate quantitative determination of NCG in feeds, animal tissues, and body fluids using the high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The sample pretreatment procedures included extraction with 0.5% of formic acid in water/methanol (80/20, v/v), and purification using an anionic solid phase extraction cartridge. Satisfactory separation of NCG was achieved in 20 min with the application of an Atlantis T3 column, and a confirmative detection of NCG was ensured by multiple reaction monitoring of positive ions. NCG spiked in feeds, tissues, and body fluids were evaluated in regard to linearity, sensitivity, recovery, and repeatability. Recoveries for different sample matrices were in the range of 88.12% to 110.21% with relative standard deviations (RSDs) less than 8.8%. Limits of quantification were within the range of 0.012 to 0.073 mg kg−1 and 0.047 to 0.077 μg mL−1 for solid and liquid samples, respectively. This study will provide a solid foundation for the evaluation of availability and metabolic mechanism of NCG in animals. [ABSTRACT FROM AUTHOR]

Review: 75 refs. [ABSTRACT FROM AUTHOR]