No abstract

Fabric-phase sorptive extraction has already been recognized as a simple and green alternative to the conventional sorbent-based sorptive microextraction techniques, using hybrid organic-inorganic sorbent coatings chemically bonded to a flexible fabric surface. Herein, we have investigated the synergistic combination of the advanced material properties offered by sol-gel graphene sorbent and the simplicity of Fabric phase sorptive extraction approach in selectively extracting bisphenol A and residual monomers including bisphenol A glycerolatedimethacrylate, urethane dimethacrylate, and triethylene glycol dimethacrylate derived dental restorative materials from cow and human breast milk samples. Different coatings were evaluated. Final method development employed sol-gel graphene coated media. The main experimental parameters influencing extraction of the compounds, such as sorbent chemistry used, sample loading conditions, elution solvent, sorption stirring time, elution time, impact of protein precipitation, amount of sample, and matrix effect, were investigated and optimized. Absolute recovery values from standard solutions were 50% for bisphenol A, 78% for T triethylene glycol dimethacrylate, 110% for urethane dimethacrylate, and 103% for bisphenol A glycerolatedimethacrylate, while respective absolute recovery values from milk were 30, 52, 104, and 42%. Method validation was performed according to European Decision 657/2002/EC in terms of selectivity, sensitivity, linearity, accuracy, and precision.

QuEChERS (quick, easy, cheap, effective, rugged and safe) dispersive extraction was applied for the extraction of tetracyclines (oxytetracycline, tetracycline, chlorotetracycline and doxycycline) from milk. Target analytes were determined by an accurate and sensitive chromatographic analytical method, which was validated in terms of 2002/6572/EC decision. The analytes were separated on an Orbit 100C 4 (5 µm, 250 × 4.0 mm) analytical column under a gradient mobile phase composed of a mixture of 0.01 M oxalic acid, 10 −4 M Na 2 EDTA and acetonitrile. For the extraction of isolated compounds from sorbent, a methanol and 0.01 M oxalic acid mixture (1:1 v/v) was used, leading to relative recovery rates from 83.07% to 106.3% at concentration levels in the range 100-200 µg/kg. The within-laboratory reproducibility, expressed as a relative standard deviation, was <15.5%. Decision limits ranged between 100.3 µg/kg and 105.6 µg/kg and the detection capability varied between 100.6 µg/kg and 109.7 µg/kg. Ruggedness was evaluated by following the Youden approach, in terms of milk mass, sorbent mass, centrifugation time, vortex time, type and volume of organic solvents and evaporation temperature.Separations 2019, 6, 21 2 of 9 solid-phase extraction (D-SPE) clean-up step. This process was firstly developed for the extraction of pesticides from different matrices, such as soil [10], sugarcane juice [11], honey [12], wheat grains, flour and bran [13], but also for the extraction of drugs and phenols from soil [14-16] and veterinary drug residues from foods of animal origin [17][18][19].Although a number of methods [20,21] can be found in the literature employing mass spectrometric detection for confirmation purposes, this instrumentation is not always available in analytical laboratories. The aim of this study was to develop a simple and quick HPLC-DAD method for the determination of four tetracyclines (oxytetracycline, tetracycline, chlorotetracycline and doxycycline) in milk using QuEChERS dispersive extraction. The method was validated according to the European Union Decision 2002/657/EC with regards to selectivity, linearity, accuracy, precision, sensitivity and ruggedness by applying the Youden approach [22].