Evaluation of low-cost disposable polymeric materials for sorptive extraction of organic pollutants in water samples

The capabilities of four commercially available and low cost polymeric materials for the extraction of polar and non-polar contaminants (logK(ow)=-0.07-6.88, from caffeine to octocrylene, respectively) from water samples was compared. Tested sorbents were polyethersulphone, polypropylene and Kevlar, compared to polydimethylsiloxane as reference material. Parameters that affect the extraction process such as pH and ionic strength of the sample, extraction time and desorption conditions were thoroughly investigated. A set of experimental partition coefficients (K(pw)), at two different experimental conditions, was estimated for the best suited materials and compared with the theoretical octanol-water (K(ow)) partition coefficients of the analytes. Polyethersulphone displayed the largest extraction yields for both polar and non-polar analytes, with higher K(pw) and lower matrix effects than polydimethylsiloxane and polypropylene. Thus, a sorptive microextraction method, followed by large volume injection (LVI) gas chromatography-tandem mass spectrometry (GC-MS/MS), was proposed using the former sorbent (2 mg) for the simultaneous determination of model compounds in water samples. Good linearity (>0.99) was obtained for most of the analytes, except in the case of 4-nonylphenol (0.9466). Precision (n=4) at 50 and 500 ng L(-1) levels was in the 2-24% and limits of detection (LODs) were in the 0.6-25 ng L(-1) range for all the analytes studied.

Evaluation of the occurrence and biodegradation of parabens and halogenated by-products in wastewater by accurate-mass liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-QTOF-MS)

An assessment of the sewage occurrence and biodegradability of seven parabens and three halogenated derivatives of methyl paraben (MeP) is presented. Several wastewater samples were collected at three different wastewater treatment plants (WWTPs) during April and May 2010, concentrated by solid-phase extraction (SPE) and analysed by liquid chromatography-electrospray-quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). The performance of the QTOF system proved to be comparable to triple-quadrupole instruments in terms of quantitative capabilities, with good linearity (R(2) > 0.99 in the 5-500 ng mL(-1) range), repeatability (RSD < 5.6%) and LODs (0.3-4.0 ng L(-1) after SPE). MeP and n-propyl paraben (n-PrP) were the most frequently detected and the most abundant analytes in raw wastewater (0.3-10 μg L(-1)), in accordance with the data displayed in the bibliography and reflecting their wider use in cosmetic formulations. Samples were also evaluated in search for potential halogenated by-products of parabens, formed as a result of their reaction with residual chlorine contained in tap water. Monochloro- and dichloro-methyl paraben (ClMeP and Cl(2)MeP) were found and quantified in raw wastewater at levels between 0.01 and 0.1 μg L(-1). Halogenated derivatives of n-PrP could not be quantified due to the lack of standards; nevertheless, the monochlorinated species (ClPrP) was identified in several samples from its accurate precursor and product ions mass/charge ratios (m/z). Removal efficiencies of parabens and MeP chlorinated by-products in WWTPs exceeded 90%, with the lowest percentages corresponding to the latter species. This trend was confirmed by an activated sludge biodegradation batch test, where non-halogenated parabens had half-lives lower than 4 days, whereas halogenated derivatives of MeP turned out to be more persistent, with up to 10 days of half-life in the case of dihalogenated derivatives. A further stability test performed with raw wastewater also showed that parabens degrade rapidly in real sewage, with half-lives lower than 10 h for n-butyl-paraben, while dihalogenated species again turned out to be more stable, with half-lives longer than a week.

Optimization of a dispersive liquid-liquid microextraction method for the analysis of benzotriazoles and benzothiazoles in water samples

A simple and rapid dispersive liquid-liquid microextraction method has been developed for the determination of 11 benzotriazoles and benzothiazoles in water samples. Tri-n-butylphosphate (TBP) was used as extractant, thus avoiding the use of toxic water-immiscible chlorinated solvents. The influence of several variables (e.g., type and volume of dispersant and extraction solvents, sample pH, ionic strength, etc.) on the performance of the sample preparation step was systematically evaluated. Analytical determinations were carried out by high-performance liquid chromatography with fluorescence and UV detection and liquid chromatography-electrospray ionization-tandem mass spectrometry. The optimized method exhibited a good precision level with relative standard deviation values between 3.7% and 8.4%. Extraction yields ranging from 67% to 97% were obtained for all of these considered compounds. Finally, the proposed method was successfully applied to the analysis of benzotriazoles and benzothiazoles in real water samples (tap, river, industrial waters, and treated and raw wastewaters).

Comparison of molecularly imprinted, mixed-mode and hydrophilic balance sorbents performance in the solid-phase extraction of amphetamine drugs from wastewater samples for liquid chromatography-tandem mass spectrometry determination

Recent studies have shown that amphetamines and other drugs of abuse residues occur in wastewater. Consequently, several methods have been developed for their determination by solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, a major drawback of these methods is the lack of selectivity during SPE that results in reduced sensitivity, due to matrix effects, and in some cases in low precision and poor accuracy. In order to tackle this problem, three different SPE alternatives have been evaluated in this work for the determination of five amphetamines: common hydrophilic balance (Oasis HLB), mixed-mode (Oasis MCX) and molecularly imprinted polymers (MIPs) sorbents. Among them, Oasis HLB showed the worst performance, as three amphetamines (MDA, MDMA and MDEA) could not be determined because of interfering signals in the LC-MS/MS chromatogram, and amphetamine recoveries could not be corrected by the use of the deuterated analogue internal standard. Oasis MCX permitted the determination of all target analytes, but with still strong signal suppression: ca. 70% signal drop with wastewater samples, which could in this case be corrected by the internal standards providing acceptable trueness (overall recoveries: 101-137%), precision (RSD: 2.0-12%) and limits of detection (LOD: 1.5-4.4 ng/L). Alternatively, MIPs rendered cleaner extracts with less matrix effects (ca. 30% signal drop), and thus lower LODs (0.5-2.7 ng/L) and even better trueness (91-114% overall recovery) and precision (1.5-4.4%RSD). The final application of the method with MIP cartridges showed the presence of MDA and MDMA in the seven analysed wastewaters at the 4-20 ng/L level.

Comparison of molecularly imprinted, mixed-mode and hydrophilic balance sorbents performance in the solid-phase extraction of amphetamine drugs from wastewater samples for liquid chromatography-tandem mass spectrometry determination

Recent studies have shown that amphetamines and other drugs of abuse residues occur in wastewater. Consequently, several methods have been developed for their determination by solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, a major drawback of these methods is the lack of selectivity during SPE that results in reduced sensitivity, due to matrix effects, and in some cases in low precision and poor accuracy. In order to tackle this problem, three different SPE alternatives have been evaluated in this work for the determination of five amphetamines: common hydrophilic balance (Oasis HLB), mixed-mode (Oasis MCX) and molecularly imprinted polymers (MIPs) sorbents. Among them, Oasis HLB showed the worst performance, as three amphetamines (MDA, MDMA and MDEA) could not be determined because of interfering signals in the LC-MS/MS chromatogram, and amphetamine recoveries could not be corrected by the use of the deuterated analogue internal standard. Oasis MCX permitted the determination of all target analytes, but with still strong signal suppression: ca. 70% signal drop with wastewater samples, which could in this case be corrected by the internal standards providing acceptable trueness (overall recoveries: 101-137%), precision (RSD: 2.0-12%) and limits of detection (LOD: 1.5-4.4 ng/L). Alternatively, MIPs rendered cleaner extracts with less matrix effects (ca. 30% signal drop), and thus lower LODs (0.5-2.7 ng/L) and even better trueness (91-114% overall recovery) and precision (1.5-4.4%RSD). The final application of the method with MIP cartridges showed the presence of MDA and MDMA in the seven analysed wastewaters at the 4-20 ng/L level.

Development of an ionic liquid based dispersive liquid-liquid microextraction method for the analysis of polycyclic aromatic hydrocarbons in water samples

A simple, rapid and efficient method, ionic liquid based dispersive liquid-liquid microextraction (IL-DLLME), has been developed for the first time for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in water samples. The chemical affinity between the ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate) and the analytes permits the extraction of the PAHs from the sample matrix also allowing their preconcentration. Thus, this technique combines extraction and concentration of the analytes into one step and avoids using toxic chlorinated solvents. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, type and volume of disperser solvent, extraction time, dispersion stage, centrifuging time and ionic strength, were optimised. Analysis of extracts was performed by high performance liquid chromatography (HPLC) coupled with fluorescence detection (Flu). The optimised method exhibited a good precision level with relative standard deviation values between 1.2% and 5.7%. Quantification limits obtained for all of these considered compounds (between 0.1 and 7 ng L(-1)) were well below the limits recommended in the EU. The extraction yields for the different compounds obtained by IL-DLLME, ranged from 90.3% to 103.8%. Furthermore, high enrichment factors (301-346) were also achieved. The extraction efficiency of the optimised method is compared with that achieved by liquid-liquid extraction. Finally, the proposed method was successfully applied to the analysis of PAHs in real water samples (tap, bottled, fountain, well, river, rainwater, treated and raw wastewater).