A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex for the extraction of preservatives and antioxidant.

A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) was prepared for use in micro-solid phase extraction sorbent of preservative agents and antioxidants from cosmetic products. The extracted analytes were quantified by GC-MS. Under the optimized conditions, the calibration plots are linear in the concentration ranges between 5.0 µg·L-1 to 1.0 mg·L-1 for benzoic acid, of 10.0 µg·L-1 to 1.0 mg·L-1 for 2-methyl-3-isothiazolinone (MI), and between 1.0 µg·L-1 and 1.0 mg·L-1 for both 3-tert-butyl-4-hydroxyanisole (BHA) and 2,6-di-tert-butyl-p-hydroxytoluene (BHT). The LODs are 1.0 µg·L-1 for benzoic acid, 5.0 µg·L-1 for MI and 0.5 µg·L-1 for both BHA and BHT. The stir-foam can be easily prepared, is inexpensive and well reproducible (RSDs <3%, for n = 6). It can be re-used for up to 12 times after which extraction efficiency has dropped to 90%. The method was successfully applied to the determination of preservatives and antioxidants in cosmetic samples. Recoveries from spiked samples ranged between 94.5 ± 2.1% and 99.8 ± 1.8%. Graphical abstract A stir foam was prepared from graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) and is shown to be a most viable sorbent for the microextraction of trace amounts of preservative agents and antioxidants from cosmetic products.

Online microchannel preconcentrator for carbofuran detection.

A simple and rapid online microchannel preconcentrator coupled with an amperometric detection for the analysis of carbofuran using polyethylene glycol coated onto magnetic particle (PEG-magnetic particles) sorbents was developed. This simple-to-prepare microchannel preconcentrator used an external magnet to retain the PEG-magnetic particle sorbents inside the microchannel. Under optimum conditions, the system provided two linear ranges, from 0.01 to 10.0 mg L(-1) and from 10.0 to 130.0 mg L(-1) with a limit of detection of 8.7 ± 0.1 µg L(-1). The microchannel preconcentrator provided very good stability; it can be used for up to 326 consecutive injections of 5.0 mg L(-1) carbofuran with a relative standard deviation of less than 3%. The developed system provided a good microchannel-to-microchannel and a good electrode-to-electrode reproducibility (n = 6, %RSD < 1). It also provided an excellent selectivity when it was tested with two other carbamate pesticides, carbaryl and methomyl, with a 43 and 256 times higher detection sensitivity for carbofuran, respectively. The developed system was successfully applied to detect carbofuran in surface water samples obtained near vegetable plantation areas. The concentrations of carbofuran in these samples were found to be in the range of non-detectable to 0.047 ± 0.001 mg L(-1). The developed system is easy to operate and easy to couple with other analytical instruments and it could be easily adapted for the analysis of other polar organic contaminants.

A preconcentrator-separator two-in-one online system for polycyclic aromatic hydrocarbons analysis.

A novel preconcentrator-separator two-in-one online system has been developed for the online analysis of trace amounts of four polycyclic aromatic hydrocarbons (PAHs) in tea samples. A micro-preconcentrator unit of zeolite imidazolate framework-8-poly(vinyl alcohol) cryogel (ZIF-8-PVA cryogel) and a micro-separation unit of multiwalled carbon nanotubes-poly(vinyl alcohol) cryogel (MWCNTs-PVA cryogel) were fabricated onto an acrylic plate. The eluent from this two-in-one system flowed directly to an on-column UV-visible detector. Under optimum conditions, the system provided a wide linear range from 0.10µgL-1 to 2.00mgL-1 for benzo(a)anthracene (BaA) and chrysene (Chry), 0.15µgL-1 to 3.00mgL-1 for benzo(a)pyrene (BaP) and 0.20µgL-1 to 5.00mgL-1 for benzo(b)fluoranthene (BbF). The limits of detection were 0.05µgL-1 of both BaA and Chry, 0.10µgL-1 of BaP and 0.20µgL-1 of BbF. This two-in-one system was cost-effective, easy to prepare, had excellent stability for up to 417 consecutive injection cycles and provided a good system-to-system reproducibility (n=6) with a relative standard deviation of less than 4%. The system was successfully applied to detect PAHs in tea samples. The concentrations of BaA, Chry, BaP and BbF in seven tea samples were found in the range of non-detectable 2.73±0.07mgL-1 with good recoveries of 83±6 to 108±4%. In addition, it can be easily applied for the detection of other aromatic compounds in contaminated water samples.