Recent Advances in Environmental Analysis

Facile synthesis of amino-functionalized magnetic materials for efficient enrichment of anionic metabolites from biological samples

The analysis of biological samples is often affected by the background matrix. Proper sample preparation is a critical step in the analytical procedure for complex samples. In this study, a simple and efficient enrichment strategy based on Amino-functionalized Polymer-Magnetic MicroParticles (NH₂-PMMPs) with coral-like porous structures was developed to enable the detection of 320 anionic metabolites, providing detailed coverage of phosphorylation metabolism. Among them, 102 polar phosphate metabolites including nucleotides, cyclic nucleotides, sugar nucleotides, phosphate sugars, and phosphates, were enriched and identified from serum, tissues, and cells. Furthermore, the detection of 34 previously unknown polar phosphate metabolites in serum samples demonstrates the advantages of this efficient enrichment method for mass spectrometric analysis. The limit of detections (LODs) were between 0.02 and 4 nmol/L for most anionic metabolites and its high sensitivity enabled the detection of 36 polar anion metabolites from 10 cell equivalent samples. This study has provided a promising tool for the efficient enrichment and analysis of anionic metabolites in biological samples with high sensitivity and broad coverage, facilitating the knowledge of the phosphorylation processes of life.

Highly porous gold supraparticles as surface-enhanced Raman spectroscopy (SERS) substrates for sensitive detection of environmental contaminants

Surface-enhanced Raman spectroscopy (SERS) has great potential as an analytical technique for environmental analyses. In this study, we fabricated highly porous gold (Au) supraparticles (i.e., ∼100 μm diameter agglomerates of primary nano-sized particles) and evaluated their applicability as SERS substrates for the sensitive detection of environmental contaminants. Facile supraparticle fabrication was achieved by evaporating a droplet containing an Au and polystyrene (PS) nanoparticle mixture on a superamphiphobic nanofilament substrate. Porous Au supraparticles were obtained through the removal of the PS phase by calcination at 500 °C. The porosity of the Au supraparticles was readily adjusted by varying the volumetric ratios of Au and PS nanoparticles. Six environmental contaminants (malachite green isothiocyanate, rhodamine B, benzenethiol, atrazine, adenine, and gene segment) were successfully adsorbed to the porous Au supraparticles, and their distinct SERS spectra were obtained. The observed linear dependence of the characteristic Raman peak intensity for each environmental contaminant on its aqueous concentration reveals the quantitative SERS detection capability by porous Au supraparticles. The limit of detection (LOD) for the six environmental contaminants ranged from ∼10 nM to ∼10 μM, which depends on analyte affinity to the porous Au supraparticles and analyte intrinsic Raman cross-sections. The porous Au supraparticles enabled multiplex SERS detection and maintained comparable SERS detection sensitivity in wastewater influent. Overall, we envision that the Au supraparticles can potentially serve as practical and sensitive SERS devices for environmental analysis applications.

On the use of metal-organic frameworks for the extraction of organic compounds from environmental samples

The determination of trace metals and organic contaminants in environmental samples, such as water, air, soil, and sediment, is until today a challenging process for the analytical chemistry. Metal-organic frameworks (MOFs) are novel porous nanomaterials that are composed of metal ions and an organic connector. These materials are gaining more and more attention due to their superior characteristics, such as high surface area, tunable pore size, mechanical and thermal stability, luminosity, and charge transfer ability between metals and ligands. Among the various applications of MOFs are gas storage, separation, catalysis, and drug delivery. Recently, MOFs have been successfully introduced in the field of sample preparation for analytical chemistry and they have been used for sample pretreatment of various matrices. This review focuses on the applications of MOFs as novel adsorbents for the extraction of organic compounds from environmental samples.

Inorganic oxidizer detection from propellants, pyrotechnics, and homemade explosive powders using gradient elution moving boundary electrophoresis

Advancement in rapid targeted chemical analysis of homemade and improvised explosive devices is critical for the identification of explosives-based hazards and threats. Gradient elution moving boundary electrophoresis (GEMBE), a robust electrokinetic separation technique, was employed for the separation and detection of common inorganic oxidizers from frequently encountered fuel-oxidizer mixtures. The GEMBE system incorporated sample and run buffer reservoirs, a short capillary (5 cm), an applied electric field, and a pressure-driven counterflow. GEMBE provided a separation format that allowed for continuous injection of sample, selectivity of analytes, and no sample cleanup or filtration prior to analysis. Nitrate, chlorate, and perchlorate oxidizers were successfully detected from low explosive propellants (e.g., black powders and black powder substitutes), pyrotechnics (e.g., flash powder), and tertiary explosive mixtures (e.g., ammonium nitrate- and potassium chlorate-based fuel-oxidizer mixtures). Separation of these mixtures exhibited detection without interference from a plethora of additional organic and inorganic fuels, enabled single particle analysis, and demonstrated semiquantitative capabilities. The bulk counterflow successfully excluded difficult components from fouling the capillary, yielding estimated limits of detection down to approximately 10 μmol/L. Finally, nitrate was separated and detected from postblast debris collected and directly analyzed from two nitrate-based charges.

Molecularly Imprinted Polymers for the Selective Extraction of Bisphenol A and Progesterone from Aqueous Media

This paper describes the development of a novel sorbent for selective extraction of endocrine disruptors (EDs) from aqueous media. The main goal was to obtain sufficient molecularly imprinted polymers (MIPs) for selective detection, preconcentration, and extraction of EDs such as bisphenol A (BPA) and progesterone (PG). Series of MIPs and their analogues, non-molecularly imprinted polymers (NIPs), were synthesised following a non-covalent imprinting strategy based on radical polymerisation. Sets of synthesis were performed in order to optimise variables of the polymerisation including solvent, cross-linker, and template ratio. The retention capacity of MIPs was determined using HPLC in the range of 33.3% to 96.6% and 32.5% to 96% for BPA and PG, respectively. The adsorption mechanism was studied by isothermal and kinetic assays. The kinetic analysis showed a high retention capacity within 15 min of contact. The polymer yield was obtained in the range of 30% to 100%. Additionally, there was no significant cross-reactivity observed upon testing MIPs with structural analogues and other endocrine disruptors instead of target molecules. The results also revealed the high importance of different concentrations of cross-linker and solvent during the polymerisation. Firstly, the pre-organisation of complementary functional groups, which were present in the polymerisation mixture, and secondly, selective cavity formation for target molecules.

β-Cyclodextrin coated SiO2@Au@Ag core–shell nanoparticles for SERS detection of PCBs

A new type of surface-enhanced Raman scattering (SERS) substrate consisting of β-cyclodextrin (β-CD) coated SiO₂@Au@Ag nanoparticles (SiO₂@Au@Ag@CD NPs) has been achieved.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Preparation of magnetic multi-functional molecularly imprinted polymer beads for determining environmental estrogens in water samples

Magnetic multi-functional molecularly imprinted polymer (mag-MFMIP) beads were prepared for determining environmental estrogens in water samples. This novel material adopted a superparamagnetic microparticle as the supporter and used 17β-estradiol (E2) as the imprinting template, aiming for recognizing many kinds of environmental estrogens simultaneously. Characterization analysis and binding experiments revealed that mag-MFMIP beads had outstanding magnetic property, large adsorption capacity and high competitive selectivity to most of the commonly seen environmental estrogens. When mag-MFMIP beads were used as dispersed solid-phase extraction (SPE) adsorbents in water samples, the recoveries of estriol (E3), bisphenol A (BPA), E2 and ethynylestradiol (EE) were 72.2 - 92.1%, 89.3 - 96.0%, 93.3 - 102% and 89.7 - 95.9%, respectively with relative standard deviation (RSD) lower than 7.0%. These results indicated that mag-MFMIP beads had the potential to be the common adsorbents for many kinds of environmental estrogens, representing a novel application of MIPs in the field of environmental chemistry.

Sorption behavior of charged and neutral polar organic compounds on solid phase extraction materials: which functional group governs sorption?

Numerous polar anthropogenic organic chemicals have been found in the aqueous environment. Solid phase extraction (SPE) has been applied for the isolation of these from aqueous matrices, employing various materials. Nevertheless, little is known about the influence of functional groups on the sorption of the solutes onto these materials. Therefore, the sorption interactions of (charged) polar organic solutes to neutral (HLB), cation-exchanging (MCX, WCX), and anion-exchanging (MAX, WAX) OASIS polymers have been studied. For neutral solutes HLB has the highest capacity and affinity. Van der Waals interaction, rather than hydrogen bonding, appears to be the predominant factor determining sorption. For charged molecules, MCX and MAX show by far the highest affinity and capacity. Adsorption is already efficient at low concentrations and the maximum sorption capacity equals the amount of charged functional groups on the material. The results from this study allow semiquantitative predictions if a solute will adsorb on one of the OASIS materials and which functional groups govern adsorption.

Enantiomeric fraction as an indicator of pharmaceutical biotransformation during wastewater treatment and in the environment--a review

Enantioselective analysis of some pharmaceuticals during wastewater treatment has the potential to reveal significant insights regarding the effectiveness of biotransformation processes. Furthermore, enantioselective analysis of chiral pharmaceuticals in the aquatic environment may provide a useful historical record revealing the dominant source of (treated or untreated) wastewater contamination. This review of the recent scientific literature has identified only a handful of studies that have directly investigated these promising applications. However, a range of enantioselective analytical techniques are likely to be adaptable from those which have been developed within the pharmaceutical industry. These include direct enantioseparations of enantiomers on chiral stationary phases as well as indirect separations by achiral stationary phases after chiral derivatization to form pairs of physically distinguishable diastereomers. Further investigations of the patterns of enantiomeric fractionation of pharmaceuticals in wastewater and environmental samples will provide an increasingly solid understanding of the relationship between biotransformation processes and the often overlooked parameter of enantiomeric fraction.

Preparation of dummy template imprinted polymers at surface of silica microparticles for the selective extraction of trace bisphenol A from water samples

Molecularly imprinted polymers for bisphenol A (BPA) were prepared by using surface molecular imprinting technique. Analogues of BPA, namely 4,4'-dihydroxybiphenyl and 3,3',5,5'-tetrabromobisphenol A, were used as the dummy templates instead of BPA, to avoid the leakage of a trace amount of the target analyte (BPA). The resulting dummy molecularly imprinted polymers (DMIPs) showed the large sorption capacity, high recognition ability and fast binding kinetics for BPA. The maximal sorption capacity was up to 958 micromol g(-1), and it only took 40 min for DMIPs to achieve the sorption equilibrium. The DMIPs were successfully applied to the solid-phase extraction coupled with HPLC/UV for the determination of BPA in water samples. The calibration graph of the analytical method was linear with a correlation coefficient more than 0.999 in the concentration range of 0.0760-0.912 ng mL(-1) of BPA. The limit of detection was 15.2 pg mL(-1) (S/N=3). Recoveries were in the range of 92.9-102% with relative standard deviation (RSD) less than 11%. The trace amounts of BPA in tap water, drinking water, rain and leachate of one-off tableware were determined by the method built, and the satisfactory results were obtained.

Environmental and food analysis by desorption atmospheric pressure photoionization-mass spectrometry

Desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) is a versatile surface analysis technique for a wide range of analytes, especially for neutral and non-polar analytes. Here, a set of analytes typically found in environmental or food samples was analyzed by DAPPI-MS. The set included five polyaromatic hydrocarbons (PAHs), one N-PAH, one brominated flame retardant, and nine pesticides, which were studied with three different spray solvents: acetone and toluene in positive ion mode, and anisole in negative ion mode. The analytes showed [M + H](+), M(+*), and [M-H](-) ions as well as fragmentation and substitution products. Detection limits for the studied compounds ranged from 30 pg to 1 ng (from 0.14 to 5.6 pmol). To demonstrate the feasibility of the use of DAPPI-MS two authentic samples - a circuit board and orange peel - and a spiked soil sample were analyzed. Tetrabromobisphenol A, imazalil, and PAHs were observed from the three above-mentioned samples, respectively. The method is best suited for rapid screening analysis of environmental or food samples.