Solid-phase microextraction using octadecyl-bonded silica immobilized on the surface of a rotating disk: Determination of hexachlorobenzene in water

Green method to determine triazine pesticides in water using Rotating Disk Sorptive Extraction (RDSE)

The following work presents the development of the solid phase extraction technique with rotary disk (RDSE) in which the analysis for seven triazines in surface waters was first implemented. All the variables involved in extraction have been studied and optimized using a solid phase of octadecyl (C18) deposited on surface of the disk. Triazines were analyzed quantitatively by gas chromatography with simple quadruple mass detector, recoveries obtained for seven triazines were between 80% and 120%, accuracy expressed as RSD was between 3.21% and 6.34%, and detection limit of the method was between 0.020-0.056 μgL^-1 according to each analyte, which indicates a good reproducibility and precision of the method. Finally, the method was applied to analyze the objective compounds in water samples obtained in the Bolo River (Palmira-Colombia), in which triazines were not detected.

A rotating disk sorptive extraction based on hydrophilic deep eutectic solvent formation

An elegant preconcentration method assumed sorption of polar analytes from complex non-polar matrices on a rotating disk based on hydrophilic deep eutectic solvent formation is presented for the first time. The surface of poly(vinylidene fluoride-co-tetrafluoroethylene) rotating disk was coated with choline chloride acted as a precursor of deep eutectic solvent (hydrogen bond acceptor). The rotating disk was immersed in vegetable oil sample and phenolic compounds (hydrogen bond donors) were efficient separated on the disk during its rotation due to deep eutectic solvent formation. Ability of hydrophilic deep eutectic solvent decomposition in aqueous phase was used for fast analytes elution from the disk surface (2 min). Finally, the obtained aqueous solution of phenolic compounds and choline chloride was analyzed by high-performance liquid chromatography with fluorescence detection. Under optimal conditions, the limits of detection for gallic acid, protocatechuic acid, tyrosol, vanillic acid, p-coumarinic acid, syringaldehyde and thymol were in the range of 10-60 μg L^-1. The developed approach allowed to significantly reduce sorption and elution time in comparison with previously reported rotating disk sorptive extraction approaches. The extraction mechanism based on deep eutectic solvent formation provided selective separation of target analytes with absolute extraction recovery in the range of 66-87%.

Cork sheet as a sorptive phase to extract hormones from water by rotating-disk sorptive extraction (RDSE)

This work reports for the first time the use of laminar cork as a sorptive phase in a microextraction technique, rotating-disk sorptive extraction (RDSE). Typical hormones (estrone, estradiol, estriol and ethinyl estradiol) were selected as analyte models and extracted from wastewater samples on laminar cork with statistically equivalent extraction efficiency to that provided by Oasis HLB. The cork characterization was performed by confocal fluorescence microscopy (CLSM), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), allowing the identification of lignin, suberin and polysaccharides (cellulose and hemicellulose) as the main components of the cork. The best conditions for extraction were as follows: rotation velocity of the disk, 2000 rpm; extraction time, 45 min; and sample volume, 20 mL. The analytical features of the developed method show that calibration curves for all analytes have R² values higher than 0.99. The absolute recoveries were higher than 63%, and the precision, expressed as relative standard deviation, ranged from 2 to 16%. The LOD and LOQ ranges were 3-19 and 10-62 ng L^-1, respectively. The proposed method was applied to the analysis of wastewater, and the concentrations of hormones in a wastewater treatment plant in Santiago, Chile, ranged from <LOQ to 48 ng L^-1.

Direct photoimmobilization of extraction disks on "green state" 3D printed devices

Post-curing is essential to improve the mechanical properties of 3D printed parts fabricated by stereolithography (SLA), since right after 3D printing they remain in a "green state". It means that the 3D printed parts have reached their final shape, but the polymerization reaction has not been yet completed. Herein, we take advantage of the tacky partially polymerized surface of "green state" SLA 3D printed parts to immobilize extraction disks and miniature magnets, which after UV post-curing, become permanently attached to the 3D printed part resulting in a rotating-disk sorptive extraction device (RDSE). The developed "stick & cure" procedure is reagent-free and does not require any additional preparation time, specialized skills, or instrumentation. As proof of concept, 3D printed RDSE devices with immobilized chelating disks have been applied to the simultaneous extraction of 14 trace metals prior to ICP-OES determination, featuring LODs between 0.03 and 1.27 μg L^-1, and an excellent device-to-device reproducibility (n = 5, RSD = 2.7-8.3%). The developed method was validated using certified wastewater and soil reference samples, and satisfactory spiking recoveries were obtained in the analysis of highly polluted solid waste treatment plant leachates (89-110%). In addition, exploiting the versatility of 3D printing, nine RDSE devices with different shapes were fabricated. Their performance was evaluated and compared for the fast extraction of the highly toxic Cr (VI) as its 1,5-diphenylcarbazide complex in reversed-phase mode, showing different extraction performance on depending on the shape of the 3D printed RDSE device.

Ionic liquids intercalated in montmorillonite as the sorptive phase for the extraction of low-polarity organic compounds from water by rotating-disk sorptive extraction

Montmorillonite (MMT) clays were modified by the intercalation into their galleries of ionic liquids (IL) based on imidazolium quaternary ammonium salts. This new eco-materials exhibited good features for use as a sorptive phase in the extraction of low-polarity analytes from aqueous samples. Spectroscopic analyses of the modified clays were conducted and revealed an increase in the basal spacing and a shifting of the reflection plane towards lower values as a consequence of the effective intercalation of organic cations into the MMT structure. The novel sorbent developed herein was assayed as the sorptive phase in rotating-disk sorptive extraction (RDSE), using polychlorinated biphenyls (PCBs), representative of low-polarity pollutants, as model analytes. The final determination was made by gas chromatography with electron capture detection. Among the synthetized sorptive phases, the selected system for analytical purposes consisted of MMT modified with the 1-hexadecyl-3-methylimidazolium bromide (HDMIM-Br) IL. Satisfactory analytical features were achieved using a sample volume of 5 mL: the relative recoveries from a wastewater sample were higher than 80%, the detection limits were between 3 ng L^-1 and 43 ng L^-1, the precision (within-run precision) expressed as the relative standard deviation ranged from 2% to 24%, and the enrichment factors ranged between 18 and 28. Using RDSE, the extraction efficiency achieved for the selected MMT-HDMIM-Br phase was compared with other commercial solid phases/supports, such as polypropylene, polypropylene with 1-octanol (as a supported liquid membrane), octadecyl (C18) and octyl (C8), and showed the highest response for all the studied analytes. Under the optimized extraction conditions, this new device was applied in the analysis of the influent of a wastewater treatment plant in Santiago (Chile), demonstrating its applicability through the good recoveries and precision achieved with real samples.