Extraction properties of new polymeric sorbents in SPE/GC analysis of phenol and hydroquinone from water samples

Extraction Properties of New Polymeric Sorbents Applied to Wine

Polymeric sorbents are frequently used in wine, either as solid phase extraction materials for isolation of analytes or as sorptive materials for removal of undesirable compounds (amelioration). Six new polymeric sorbents were produced thermally or in a microwave from various ratios of methacrylic acid, acrylic acid, and 4-vinylbenzoic acid as hydrophilic monomers, together with ethylene glycol dimethacrylate as cross-linker, using different porogen solvents. The relationship between physicochemical properties (pore size, surface area, and polarity) of the sorbents and their sorption properties for compounds in wine was investigated and compared to four commercially available sorbents. With some similarities to their commercial counterparts depending on hydrophobic and hydrophilic characteristics, the six new sorbents showed specificity toward different groups of compounds (e.g., volatiles and phenolics) and could be applied for targeted purposes. The results provide insight into the selection and utilization of new polymeric materials for extraction of components from wine.

Comparison of Three Solid Phase Materials for the Extraction of Carboxylic Acids from River Water Followed by 2D GC × GC-TOFMS Determination

The extraction and determination of aliphatic and aromatic carboxylic acids as well as their influence on the aromaticity and molecularity relationship of natural organic matter (NOM) in water are reported in this study. Three solid phase extraction (SPE) sorbents were used and their extraction efficiencies evaluated after chromatographic determinations (using gas chromatography with a time of flight mass spectrometer (GC × GC-TOFMS) and liquid chromatography with organic carbon detector (LC-OCD)). More than 42 carboxylic acids were identified in raw water from the Vaal River, which feeds the Lethabo Power Generation Station, South Africa, with cooling water. The aromatic carboxylic acid efficiency (28%) was achieved by using Strata™ X SPE while the highest aliphatic carboxylic acid efficiency (92.08%) was achieved by silica SPE. The hydrophobic nature of NOM in water depends on the nature of organic compounds in water, whether aromatic or aliphatic. The LC-OCD was used to assess the hydrophobicity levels of NOM as a function of these carboxylic acids in cooling water. The LC-OCD results showed that the aromatic nature of NOM in SPE filtered water followed the order Silica>Strata X>C-18. From the results, the hydrophobicity degree of the samples depended on the type and number of carboxylic acids that were removed by the SPE cartridges.

Removal of naphthalene from aqueous systems by poly(divinylbenzene) and poly(methyl methacrylate-divinylbenzene) resins

Treatment of the oily wastewater from crude oil extraction is a growing challenge due to rising concern for the environment. Polyaromatic hydrocarbons (PAHs) deserve special attention because of their high toxicity. There is a need to develop processes able to minimize the discharge of these compounds and analytic techniques to monitor the levels of PAHs in aqueous media. In this study poly(methyl methacrylate-divinylbenzene) (MMA-DVB) and poly(divinylbenzene) (DVB) were assessed with respect to their capacity to retain naphthalene (NAF) in continuous flow and batch processes (adsorption equilibrium and kinetics). The analytic techniques applied were gas chromatography and spectrofluorimetry, which was adapted for quantification of NAF. The batch adsorption studies showed that DVB is more efficient in adsorption than MMA-DVB, and the Freundlich model and pseudo-second-order model better fitted the equilibrium data and adsorption kinetics, respectively. The elution results showed that both resins are highly efficient in removing NAF, with DVB outperforming MMA-DVB. However, MMA is cheaper raw material, making MMA-DVB more competitive for treatment of oily wastewater. The resins were regenerated by eluting about 7.2 and 2.5 L of methanol:water (70:30 v/v), respectively for DVB and MMA-DVB. Regarding to the useful life after regeneration, the resins presented a reduction about 30%, relating to zero concentration of NAF.

Simultaneous Determination of Plasma Deferasirox and Deferasirox-Iron Complex Using an HPLC-UV System and Pharmacokinetics of Deferasirox in Patients With β-Thalassemia Major: Once-daily Versus Twice-daily Administration

PURPOSE

Deferasirox (DEFR), when administered BID, improves iron overload and decreases DEFR-related adverse effects in patients with β-thalassemia major. However, the pharmacokinetic (PK) disposition of DEFR and the iron-DEFR complex (Fe-[DEFR]2) in this dosing strategy is unclear.

METHODS

Chromatographic analysis was performed using a solvent delivery system coupled to an HPLC-UV detector to determine the steady-state concentrations of DEFR (CDEFR) and Fe-(DEFR)2 (CFe-[DEFR]2) in β-thalassemia major patients (n = 8) following either once-daily or BID dosing, during which the PK parameters of the 2 dosing schedules were compared.

FINDINGS

An HPLC-UV system for the analysis of blood samples following solid-phase extraction was validated. Patients who received 40 mg/kg of DEFR had higher mean CDEFR and CFe-[DEFR]2 values at all sampling times. However, concentrations of iron-DEFR complex were similar in patients who received 30 or 40 mg/kg of DEFR in the once-daily group at the 6- to 24-hour sampling times. There was no significant difference in any of the PK parameters; however, DEFR administration BID increased the mean trough levels of DEFR (183.8 [157.5] μmol/L) compared with once daily (87.7 [56.8] μmol/L), whereas all the patients had increased peak levels per individual DEFR dose when they were switched from once daily to BID (139.0 [59.8] μmol/L vs 289.2 [145.8] μmol/L, respectively).

IMPLICATIONS

Splitting the dose increased the peak levels of DEFR per unit dose in all patients and tends to increase drug exposures, but there were no significant differences in DEFR PK parameter estimates. Switching from once daily to BID may be considered for patients with an inadequate response to chelation therapy to achieve optimal drug levels. Further research is needed with a larger sample size to determine the clinical importance of the significant results due to the interindividual variability of DEFR.

Influence of the filler on thermal properties of porous VP-TRIM copolymers

In this paper, the synthesis and characterization of thermal properties of porous copolymers 1-vinyl-2-pyrrolidone with trimethylolpropane trimethacrylate are presented. They were obtained by suspension polymerization as a pure polymers or composite materials with different inorganic fillers. The influence of the type of filler on the textural and thermal properties was investigated in details. It was found that the value of the porous surface area of composites is much lower than in the case of pure copolymers. Thermal properties of the obtained materials were investigated by the means of thermogravimetry and differential scanning calorimetry.

Optimization of SPE/GC/HPLC Analytical Procedure for Determination of Phenol, Quinones, and Carboxylic Acids in Water Samples

Chromatographic techniques are among the most useful analytical methods. Gas and liquid chromatography were used in the analysis of some organic compounds: phenol, hydroquinone, benzoquinone, and maleic and fumaric acids. The analytical way for the determination of these compounds in water samples was investigated. Solid-phase extraction (SPE) technique was used on the sample preparation step, different divinylbenzene-based sorbents were applied. Calibration curves of given compounds were linear over the ranges: 50–500 μg/mL for phenol and its acetic derivatives, 50–1500 μg/mL for benzoquinone in GC analysis, and 50–250 μg/mL for phenol, 40–1000 μg/mL for hydroquinone, and 4–4500 μg/mL for carboxylic acids in HPLC analysis. The LOD and LOQ of proposed analytical procedure were in the ranges of LOD: 0.042–23.83 μg/mL; LOQ: 0.138–78.64 μg/mL.

Determination of endocrine disrupting chemicals in surface water and industrial wastewater from Beijing, China

An analytical method was developed for determination of some endocrine-disrupting chemicals in water samples from Beijing, China. Fifty two surface water and 50 industrial wastewater samples were analyzed. The residue was detected in 26 industrial wastewater and 19 surface water samples. Atrazine was detected in 8 samples at different levels ranging from 0.12 to 5.16 microg L(-1), and phenolic compounds were detected in 19 samples ranging from 0.8 to 26.1 microg L(-1). The results show that the main pollutants of surface water samples were atrazine and octylphenol. In industrial wastewater samples, bisphenol A and octylphenol were most commonly found.

Solid-phase microextraction and gas chromatography–mass spectrometry for analysis of phenols and nitrophenols in rainwater, as their t-butyldimethylsilyl derivatives

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry has been used for analysis of four phenols and sixteen nitrophenols in rainwater samples. Analytes were extracted from the water in the immersion mode and derivatised for 5 min during direct desorption in the GC injector. Before desorption, 2 microL N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MDBSTFA) was introduced into the injector, which was maintained at 280 degrees C. Different conditions affecting extraction efficiency were studied, including temperature, type of microextraction fibre, and effect of pH and ionic strength. Five different fibre coatings were tested: 85-mum polyacrylate (PA), 100-microm polydimethylsiloxane (PDMS), 65-mum Carbowax-divinylbenzene (CW-DVB), 75-microm Carboxen-polydimethylsiloxane (CAR-PDMS), and 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB). The best conditions were use of PA fibres for 40 min at ambient temperature (75 g NaCl per 100 mL, pH 3.0). MDBSTFA was used as derivatising agent because it enables analysis of phenols derivatives with high confidence in identification, because in electron-impact mode TBDMS-phenol derivatives produce the specific M-57 ion. Quantification was achieved by using 4-nitrophenol-d4, at 1 mg L(-1), as internal standard. Linearity was good, with correlation coefficients in the range 0.9888 (o-cresol) to 0.9987 (dinitro-o-cresol, DNOC). Detection limits varied between 0.208 and 99.3 microg L(-1) and quantification limits between 0.693 and 331 microg L(-1). Uncertainties varied between 8.7% (phenol) and 17.9% (4-methyl-2-nitrophenol). The method was successfully applied to the analysis of rainwater collected at urban and rural sites in Alsace (East of France). Because of derivatisation in the injector and the associated high temperature, the lifetime of the fibre is severely reduced.