Use of Poly(vinyl alcohol)-Malic Acid (CLHPMA) Hydrogels and Chitosan Coated Calcium Alginate (CCCA) Microparticles as Potential Sorbent Phases for the Extraction and Quantitative Determination of Pesticides from Aqueous Solutions.

Pesticides are used worldwide to increase crop yields in agriculture. However, their toxicity and accumulation capacity can make them toxic to the environment, animals and humans. In the case of workers chronically exposed to these substances, they must be sampled continuously, so urine is an excellent option. In this sense, this study proposes to use poly(vinyl alcohol)-malic acid hydrogels, and chitosan-coated calcium alginate as new sorbent phases to be used in pesticide determination processes in urine. To better understand the behavior of these materials in the capture and desorption process, molecular dynamics simulations (MDS) were used, and desorption experiments were performed, using mechanical agitation, ultrasound, and pH variation in the desorption process, in order to optimize the parameters to obtain better recoveries. Under the optimal experimental conditions, the maximum recoveries were of the order of 11% (CFN), 3% (KCF), 53% (DMT), 18% (MTD) and 35% (MTL). Although the recoveries were not exhaustive, they are a first approximation for the use of these new sorbent phases in the determination of this type of compound in aqueous solutions and urine.

Exploiting agarose gel modified with glucose-fructose syrup as a green sorbent in rotating-disk sorptive extraction technique for the determination of trace malondialdehyde in biological and food samples.

This research reports for the first time on the application of agarose gel impregnated with high fructose corn syrup (AG/HFCS) as a biodegradable and eco-friendly extraction phase in rotating-disk sorptive extraction (RDSE). The gel disk is driven by a rotary rod attached to an electric stirrer during extraction. Malondialdehyde (MDA) was chosen as a model analyte, and was extracted from biological and food samples using the proposed technique after derivatization with 2-thiobarbituric acid (TBA). Due to the hydrophilic nature of the sorbent phase, MDA was concentrated efficiently. After extraction, MDA was quantified directly in the gel disk by solid phase visible spectrophotometry and smartphone-based Red-Green-Blue (RGB) detection. The procedure used no organic solvents, showed clear advantages in terms of simplicity and short analysis time (5 min), and showed potential as a green analytical method. The extraction procedure was studied and optimized to maximize the partition of MDA into the gel. Under optimized conditions, the method provided linear dynamic ranges of 5.5-1000 ng mL-1 for biological samples and 62.5-12500 ng g-1 for food samples with correlation coefficients (R2) higher than 0.9975, relative recoveries between 88.3 and 103.3% along with relative standard deviation (RSD) values less than 3.5%. Accordingly, the proposed method can be employed by analytical laboratories for the rapid determination of MDA in complex matrix of body fluids and food samples under the principles of green chemistry.

A miniaturized sorbent phase-based extraction device in the form of syringe filter holder using molecularly imprinted polymer as sorbent and its application to extract benzophenones.

The molecularly imprinted polymer using 2,4-dihydroxybenzophenone as the template (DHBP-MIP) was synthesized via sacrificial support method. The DHBP-MIP was demonstrated to possess good adsorption capacity and selectivity towards benzophenones. Moreover, a miniaturized sorbent phase-based extraction device in the form of syringe filter holder using DHBP-MIP as the sorbent was proposed, and named as µ-SPE-SFH-MIP device. The µ-SPE-SFH-MIP device consisted of a reusable syringe filter holder, flexible amount of sorbent and a sub-microporous membrane, which could be conveniently connected to different driving forces, like syringe pump, solid-phase extraction device and peristaltic pump. It was successfully applied to extract five benzophenones from swimming pool water and human urine samples, combined with high performance liquid chromatograph-UV analysis, with detection limits of 0.12-0.68 µg L-1 and 0.21-1.05 µg L-1, respectively. The accuracy and precision of the analytes were in the range of 89.27%-113.35% for swimming pool water samples and 90.65%-108.00% for urine samples, with all the relative standard deviation values below 7.89%. The µ-SPE-SFH-MIP device was portable, cost-effective operational convenient and suitable for the small-size samples; moreover, with the MIP as the sorbent, it afforded additional high selectivity and sensitivity.

A hybrid material as a sorbent phase for the disposable pipette extraction technique enhances efficiency in the determination of phenolic endocrine-disrupting compounds.

In this study, the hybrid material 3-n-propyl(3-methylpyridinium) silsesquioxane chloride (Si3Py+Cl-) was synthesized and investigated as a novel sorbent phase for the disposable pipette extraction (DPX) technique coupled to high-performance liquid chromatography-florescence detection. This sorbent phase was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Aqueous samples containing the phenolic endocrine-disrupting compounds bisphenol A (BPA), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (4-t-OP), 4-octylphenol (4-OP) and 4-nonylphenol (4-NP) were subjected to DPX procedures and a series of optimizations was performed to determine the ideal extraction conditions using this approach. The proposed sorbent phase exhibited higher extraction efficiency than DPX-RP (reversed phase tips containing styrene-divinylbenzene), commonly used for the determination of the phenolic endocrine- disrupting-compounds under study. Satisfactory analytical performance was achieved with linear ranges from 2 to 100µgL-1 for 4-t-OP and 1-100µgL-1 for the other analytes. Limits of detection of 0.60µgL-1 for 4-t-OP and 0.30µgL-1 for other analytes, RSDs ranging from 1 to 20% and relative recoveries of 83-116% were obtained. Based on these satisfactory results, this sorbent phase represents a valuable alternative for the extraction of compounds with polar moieties in their structure.

In vitro biotransformation rates in fish liver S9: effect of dosing techniques.

In vitro biotransformation assays are currently being explored to improve estimates of bioconcentration factors of potentially bioaccumulative organic chemicals in fish. The present study compares thin-film and solvent-delivery dosing techniques as well as single versus multiple chemical dosing for measuring biotransformation rates of selected polycyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) liver S9. The findings show that biotransformation rates of very hydrophobic substances can be accurately measured in thin-film sorbent-dosing assays from concentration-time profiles in the incubation medium but not from those in the sorbent phase because of low chemical film-to-incubation-medium mass-transfer rates at the incubation temperature of 13.5 °C required for trout liver assays. Biotransformation rates determined by thin-film dosing were greater than those determined by solvent-delivery dosing for chrysene (octanol-water partition coefficient [KOW ] =10(5.60) ) and benzo[a]pyrene (KOW =10(6.04) ), whereas there were no statistical differences in pyrene (KOW =10(5.18) ) biotransformation rates between the 2 methods. In sorbent delivery-based assays, simultaneous multiple-chemical dosing produced biotransformation rates that were not statistically different from those measured in single-chemical dosing experiments for pyrene and benzo[a]pyrene but not for chrysene. In solvent-delivery experiments, multiple-chemical dosing produced biotransformation rates that were much smaller than those in single-chemical dosing experiments for all test chemicals. While thin-film sorbent-phase and solvent delivery-based dosing methods are both suitable methods for measuring biotransformation rates of substances of intermediate hydrophobicity, thin-film sorbent-phase dosing may be more suitable for superhydrophobic chemicals.