Application of stir bar sorptive extraction in combination with column liquid chromatography for the determination of polycyclic aromatic hydrocarbons in water samples

Porous aromatic framework coated stir bar sorptive extraction coupled with gas chromatography for the analysis of 16 polycyclic aromatic hydrocarbons in atmospheric particles and environmental water samples

In this work, porous aromatic frameworks (PAFs) with different pore size were evaluated for simultaneous adsorption of 16 polycyclic aromatic hydrocarbons (PAHs) with large difference in polarity and molecular size. Two other porous organic polymers containing electron pushing/withdrawing group were investigated along for a comparison, and PAF-120 with the pore size of appr. 2.1 nm exhibited the highest extraction efficiency. Based on water contact angle and molecular dynamics simulation, the adsorption of 16 PAHs on PAF-120 was attributed to hydrophobic interaction, π-π interaction and molecular sieving effect. PAF-120/PDMS coated stir bar was then prepared by physical adhesion, and a method of stir bar sorptive extraction-gas chromatography-flame ionization detector was established for trace PAHs analysis in environmental samples. Under the optimal experimental conditions, the limits of detection (S/N = 3) for 16 PAHs were found to be in the range of 42-375 ng/L, with the relative standard deviations of 4.1-14.6% (n = 7). The enrichment factors varied from 31 (Indeno[1,2,3-cd]pyrene) to 80-fold (anthracene), with the maximal enrichment factor of 100-fold. The proposed method was applied to the analysis of PAHs in local environmental water and atmospheric particle samples. None of the 16 PAHs were detected in the collected water samples. While for the collected atmospheric particles, 12 PAHs were detected in fine particulate matter (PM_2.5) within the range of 0.6-2.8 ng/m³. For inhalable particulate matter (PM₁₀) and total suspended particulate matter (TSP), 16 PAHs were all detected in the range of 0.6-3.8 ng/m³ and 0.6-5.9 ng/m³, respectively. Quantitative recoveries were obtained in recovery test, demonstrating the accuracy and application potential of the proposed method.

Iron oxide xerogels for improved water quality monitoring of arsenic(III) in resource-limited environments via solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT)

Arsenic is a widespread trace groundwater contaminant that presents a range of health risks and has an acceptable level of only 10 μg L-1 in drinking water. However, in many countries arsenic quantification in water is limited to centralized laboratories because it requires the use of elemental analysis techniques with high capital cost. As a result, routine water samples are frequently not tested for trace contaminants such as arsenic. In order to facilitate improved arsenic monitoring, we present the use of iron oxide xerogels for adsorption of arsenic(iii) from water samples at neutral pH, dry storage for over 120 days, and desorption of stored arsenic at elevated pH. Iron oxide xerogels offer high surface area (340 m2 g-1) and an As(iii) adsorption capacity of 165 mg g-1. Using an extraction solution of 100 mM sodium hydroxide and 1 mM sodium phosphate, As(iii) is reliably eluted from iron oxide xerogels for initial As(iii) concentrations from 10 μg L-1 to 1000 μg L-1, with a calculated detection limit of less than 4 μg L-1 and less than 17% difference in recovered As(iii) between test solutions with low and high interfering ion concentrations. By demonstrating the ability for iron oxide xerogels to reliably adsorb, store, and release arsenic, we enable the development of protocols for solid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT), where arsenic would be adsorbed from water samples onto xerogel-based sorbents and shipped to centralized laboratories for recovery and quantification.

Modern technologies for extraction of aroma compounds from fruit peels: a review

Fruit peel is an agricultural by-product and potential source to extract natural aroma compounds with low cost. In the past few decades, the extraction of plant aroma volatiles experienced a transition from traditional to modern technologies. This review summarizes the main aroma compounds in different fruit peels, evaluates modern extraction techniques applicable for these aroma compounds in terms of mechanism, procedure, merits and demerits, and practice. Additionally, the applications of fruit peel aroma extract in food, pharmaceutical and cosmetic industries are also discussed. This review provides comprehensive information for extraction and application of aroma compounds from fruit peels, which could facilitate the valorization of the agricultural by-products and reduce environmental impacts.

Trace detection of polycyclic aromatic hydrocarbons in environmental waters by SERS

Polycyclic aromatic hydrocarbons (PAHs) are among the most hazardous pollutants and have attracted significant attention in the last decades. Up to now, rapid and on-site trace detection of PAHs remains a challenging issue. Here, taking advantage of the high sensitivity and reliable qualification of Surface-enhanced Raman Spectroscopy (SERS), we firstly carried out trace analyses of 16 typical PAHs in water at concentrations as low as 100-0.1 μg/L, depending on the number of aromatic rings of the molecule. Furthermore, owing to the simplicity of the liquid-liquid extraction (LLE) step, the sensitivity was further improved 2-3 orders of magnitude, and the lowest detectable concentrations were 100, 50, and 5 ng/L for anthracene, pyrene, and benzo[a]pyrene (the three PAHs typically found in heavily polluted waters), respectively. The LLE-SERS approach was successfully applied to the qualitative and quantitative analyses of different (ocean and coast) water samples being spiked by these three PAHs, which showed great promise as a trace detection tool of PAHs under water environments having different contaminant matrices.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study, graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe₃O₄@SiO₂@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The resulting microspheres (Fe₃O₄@SiO₂@GO-PEA) were characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), CHNS elemental analysis, and vibrating sample magnetometry (VSM) techniques. The adsorbent possesses the magnetic properties of Fe₃O₄ nanoparticles that allow them easily to be separated by an external magnetic field. They also have the high specific surface area of graphene oxide which improves adsorption capacity. Desorption conditions, extraction time, amount of adsorbent, salt concentration, and pH were investigated and optimized. Following desorption, the PAHs were quantified by gas chromatography with flame ionization detection (GC-FID). The limits of detection (at an S/N ratio of 3) were achieved from 0.005 to 0.1μg/L with regression coefficients (R²) higher than 0.9954. The relative standard deviations (RSDs) were below 5.8% (intraday) and 6.2% (inter-day), respectively. The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7% and 106.7% (with RSDs of 1.6% to 8.4%, for n=3). The results indicated that the Fe₃O₄@SiO₂@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.

Plastic pellets sorptive extraction: Low-cost, rapid and efficient extraction of polycyclic aromatic hydrocarbons from environmental waters

For the first time, plastic pellets, a low-cost and easy to reach industrial raw material, are reported as an efficient sorbent material for the laboratory extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental waters. The proposed methodology, termed plastic pellets sorptive extraction (P2SE), consisted of a two-step procedure whereby target analytes were initially adsorbed onto the surface of three low-density polyethylene (LDPE) pellets and then desorbed using microliters of an organic solvent. Interphase mass transfer was greatly accelerated by means of vortex agitation. Organic extracts were analyzed by means of liquid chromatography-fluorescence detection. Different experimental parameters were controlled and the optimum conditions found were: three LDPE pellets (∼80 mg) added to 20 mL aqueous sample (20% w:v NaCl) followed by vortex agitation at 3000 rpm; for desorption, the three LDPE pellets were immersed in 100 μL of acetonitrile and the mixture was shaken at 3000 rpm for 5 min using the vortex agitator. The calculated calibration curves gave high levels of linearity yielding coefficients of determination (r(2)) greater than 0.9913. The precision of the proposed method was found to be good and the limits of the detection were calculated in the low ng L(-1) level. Matrix effects were determined by applying the proposed method to spiked river water, treated municipal wastewater and seawater samples. To compensate for the low recoveries of the more hydrophobic PAHs in spiked effluent wastewater and seawater samples the standard addition methodology was applied. The proposed method was applied to the determination of target pollutants in real seawater samples using the standard addition method. Overall, the performance of the proposed P2SE method suggests that the use of inexpensive and easy to reach sorbent materials for extracting analytes in the laboratory merits more intensive investigation.

Agarose- and alginate-based biopolymers for sample preparation: Excellent green extraction tools for this century

Recently, there has been considerable interest in the use of miniaturized sample preparation techniques before the chromatographic monitoring of the analytes in unknown complex compositions. The use of biopolymer-based sorbents in solid-phase microextraction techniques has achieved a good reputation. A great variety of polysaccharides can be extracted from marine plants or microorganisms. Seaweeds are the major sources of polysaccharides such as alginate, agar, agarose, as well as carrageenans. Agarose and alginate (green biopolymers) have been manipulated for different microextraction approaches. The present review is focused on the classification of biopolymer and their applications in multidisciplinary research. Besides, efforts have been made to discuss the state-of-the-art of the new microextraction techniques that utilize commercial biopolymer interfaces such as agarose in liquid-phase microextraction and solid-phase microextraction.

Innovative sampling and extraction methods for the determination of nonsteroidal anti-inflammatory drugs in water

Two different innovative approaches were used for the determination of nonsteroidal anti-inflammatory drugs (NSAIDs) in water: stir bar sorptive extraction (SBSE) and passive sampling, followed by electrospray ionization liquid chromatography-tandem mass spectrometry. SBSE was developed by comparing EG-Silicone and PDMS stir bars and optimizing main parameters to attain high preconcentration. Quantitative analysis was carried out by mass spectrometry in negative ionization mode and multiple reaction monitoring. The SBSE-LC-MS/MS method provided satisfactory figures of merit with LOD (7.5-71 ng L(-1)) and LOQ (22.5-213 ng L(-1)). The developed method was successfully applied to real samples collected from river water and wastewater effluents. The obtained results showed the presence of all analytes at trace levels, in a wide range of concentrations. The passive sampling approach was carried out by using Polar Organic Chemical Integrative Sampler (POCIS); samplers were deployed for 15 days in river and tap water, allowing to detect analytes at ultra-trace levels. Time-Weighted Average concentration of NSAIDs in river water was estimated in the range 0.33-0.46 ng L(-1), using the sampling rates previously obtained by means of a simple calibration system.

Development of a new sorptive extraction method based on simultaneous direct and headspace sampling modes for the screening of polycyclic aromatic hydrocarbons in water samples

A new straightforward and inexpensive sample screening method for both EPA and EU priority polycyclic aromatic hydrocarbons (PAHs) in water has been developed. The method is based on combined direct immersion and headspace (DIHS) sorptive extraction, using low-cost disposable material, coupled to ultraperformance liquid chromatography with fluorescence and UV detection (UPLC-FD-UV). Extraction parameters, such as the sampling mode, extraction time and ionic strength were investigated in detail and optimized. Under optimized conditions, water samples (16 mL) were concentrated in silicone disks by headspace (HS) and direct immersion (DI) modes simultaneously, at room temperature for 9h for the majority of the 24 studied compounds. Ultrasound-assisted desorption of extracted analytes in acetonitrile was carried out also at room temperature. The optimized chromatographic method provided a good linearity (R≥0.9991) and a broad linear range for all studied PAHs. The proposed analytical procedure exhibited a good precision level with relative standard deviations below 15% for all analytes. Quantification limits between 0.7 and 2.3 µg L(-1) and 0.16 and 3.90 ng L(-1) were obtained for compounds analyzed by UV (acenaphtylene, cyclopenta[c,d]pyrene and benzo[j]fluoranthene) and fluorescence, respectively. Finally, the proposed method was applied to the determination of PAHs in different real tap, river and wastewater samples.

Stir bar sorptive extraction: recent applications, limitations and future trends

Stir bar sorptive extraction (SBSE) has generated growing interest due to its high effectiveness for the extraction of non-polar and medium-polarity compounds from liquid samples or liquid extracts. In particular, in recent years, a large amount of new analytical applications of SBSE has been proposed for the extraction of natural compounds, pollutants and other organic compounds in foods, biological samples, environmental matrices and pharmaceutical products. The present review summarizes and discusses the theory behind SBSE and the most recent developments concerning its effectiveness. In addition, the main results of recent analytical approaches and their applications, published in the last three years, are described. The advantages, limitations and disadvantages of SBSE are described and an overview of future trends and novel extraction sorbents and supports is given.

Novel sorption-based methodologies for static microextraction analysis: A review on SBSE and related techniques

Stir bar sorptive extraction (SBSE) became a well-established analytical technique in the last years, for which hundreds of applications in almost all types of scientific fields can be found in the literature. In spite of the great enrichment capacity and outstanding performance to operate at the ultra-trace level, this remarkable static sorption-based method is already not quite effective for some complex systems, in particular to monitor the large group of polar organic compounds. This review aims to cover the state-of-the-art in SBSE, as well as supplying a discussion of the analytical potential of the novel adsorptive microextraction techniques, as complementary enrichment approaches, by explaining the main principles and providing technical know-how for the beginners.

Considerations on the application of miniaturized sample preparation approaches for the analysis of organic compounds in environmental matrices

The miniaturization and improvement of sample preparation is a challenge that has been fulfilled up to a point in many fields of analytical chemistry. Particularly, the hyphenation of microextraction with advanced analytical techniques has allowed the monitoring of target analytes in a vast variety of environmental samples. Several benefits can be obtained when miniaturized techniques such as solid-phase microextraction (SPME) or liquid-phase microextraction (LPME) are applied, specifically, their easiness, rapidity and capability to separate and pre-concentrate target analytes with a negligible consumption of organic solvents. In spite of the great acceptance that these green sample preparation techniques have in environmental research, their full implementation has not been achieved or even attempted in some relevant environmental matrices. In this work, a critical review of the applications of LPME and SPME techniques to isolate and pre-concentrate traces of organic pollutants is provided. In addition, the influence of the environmental matrix on the effectiveness of LPME and SPME for isolating the target organic pollutants is addressed. Finally, unsolved issues that may hinder the application of these techniques for the extraction of dissolved organic matter from environmental samples and some suggestions for developing novel and less selective enrichment and isolation procedures for natural organic matter on the basis of SPME and LPME are included.

Miniaturization of Analytical Methods

This chapter highlights miniaturization in sample preparation as a valuable alternative for green analytical chemistry. The current state of the art is discussed on the basis of examples selected from representative application areas, including biomedical, environmental and food analysis, and involving conventional instrumental techniques for final determination of the target compounds. The emphasis is on those techniques and approaches that have already demonstrated their practicality by the analysis of real-life samples, and in particular on those dealing with the accurate determination of minor organic components. The potential of recent developments in this field for sample treatment simplification and complete hyphenation of analytical processes are discussed and the most pressing remaining limitations evaluated.

An overview of sample preparation and extraction of synthetic pyrethroids from water, sediment and soil

The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors' knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed.