New Developments in the Analysis of Complex Environmental Matrices

Jun 03, 2015
Volume 11, Issue 11

New Developments in the Analysis of Complex Environmental Matrices was held on 6 February 2015 at the Royal Society of Chemistry (RSC), Burlington House, London, UK, and was organized by the Environmental Chemistry Group and the Separation Science Group. The meeting covered developments in instrumentation for the analysis of numerous pollutants in solid, liquid, or gaseous matrices. Talks addressed sample clean-up, liquid and gas chromatographic separation (LC and GC) with mass spectrometric (MS) detection, and nuclear magnetic resonance (NMR). Both laboratory and field techniques were covered.

Dr Mohamed Abdallah (University of Birmingham, Birmingham, UK) kicked off the morning by describing the use of mass spectrometry (MS) to study human metabolism products of organophosphates and brominated flame-retardants. Indoor dust has been identified as the major pathway of human exposure. Mixtures of brominated and organophosphate flame retardants were added to human hepatocytes cells as a dust sample and as a synthetic mixture containing similar concentrations of the retardants. The dosage was designed to be equivalent to 12 mg dust based on a 12.3 kg child ingesting 200 mg dust/day. After 24 h incubation, the metabolites were analyzed by ultrahigh-performance liquid chromatography coupled to electrospray ionization ion trap mass spectrometry (UHPLC–ESI–MS). Metabolite identification was by MS full scan, and confirmation by MS–MS. Phase I and phase II metabolism was identified, with all ion fragmentation spectra being useful for identification of conjugates and the metabolic pathways involved.  

Dr Jake Bundy (Imperial College, London, UK) asked the question “Is it possible to study environmental effects by metabolomic analysis of a single species under a variety of environmental stressors?” Earthworms were studied in the laboratory and at UK sites where soil properties and metallic contamination were known. 1H/13C heteronuclear nuclear magnetic resonance (NMR) experiments were undertaken on tissue extracts, restricting data acquired to the “interesting” betaine region to cut down the acquisition time. Although it was proving possible to link some laboratory stresses to field effects, there was large between-site and in-site variation and the model was not predictive. Part of the problem was the number of genotypes of earthworm, two species having being found in the UK and probably several more across Europe. Metabolites were identified that could distinguish the different genotypes.

Anthony Gravell (Natural Resources Wales, Llanelli Laboratory, Wales) discussed the use of passive samplers to monitor polar pollutants in surface waters. Devices can be deployed in rivers for several weeks to give time-weighted average concentrations. Herbicides that were monitored were highly water soluble and almost completely ionized at environmental pHs. They also needed to be extracted by ion‑exchange rather than conventional adsorption. Passive samplers using anion exchange disks were investigated in the laboratory and in the field. Measurements were taken in the linear uptake phase (before equilibrium) where the concentration of the pollutant was proportional to the mass on the disk, the sampling rate, and the exposure time. Typical field concentrations were in the low ng/L range. Limits of detection were consistently below those found by analysis of spot water samples.

Paralytic shellfish poisoning algal toxins cause severe illness in humans at 5.6–2058 μg/kg Saxitoxin (STX) equivalent. Dr Andrew Turner (CEFAS Weymouth Laboratory, Weymouth, UK) introduced alternative methods to the official reference mouse bio-assay method. Post-column oxidation liquid chromatography with fluorescence detection (LC–FLD) needs two columns or systems to run each sample, has very short column lifetimes, and is prone to matrix effects giving false +/– results. Another approach uses hydrophilic interaction liquid chromatography coupled to tandem MS (HILIC–MS–MS), but has problems with sensitivity and run-time, huge matrix effects, and in‑source fragmentation implications. The current work at CEFAS investigated these problems. Comparative testing of different columns showed using a triple quadrople mass spectrometer gave substantially better sensitivity, which enabled low limits of detection/quantification. Fast ultrahigh‑performance liquid chromatography proved ideal for rapid cycle times. Fragmentation mitigation included using –ve mode rather than +ve ionization for some transitions and optimization of the HILIC separation. Matrix effects could not be reduced by simple dilution techniques. Carbon solid-phase extraction removed 90–100% Na, Mg, K, and Ca though some sodium formate remained. With these improvements the method was fully validated for 12 species of interest and showed good equivalence with the LC–FLD methods.

Polyisobutenes (PIBs) are a group of oligomeric to polymeric, liquid to solid hydrocarbons, and are used in numerous industrial applications, such as viscosity modifiers and “tackifier” additives in lubricating oils, in cosmetics, and in chewing gum. Modern (highly reactive [HR]) PIBs can be made by well-controlled reactions, which produce alkenes with a larger proportion of oligomers with terminal double bonds. The multiple uses of PIBs requires movement by road, rail, and ship around the world. Several marine pollution events involving PIBs or their derivatives have occurred, presumably from discharges from shipping. In January and April 2013, discharges of what was identified in the speaker’s laboratories as HR–PIBs and confirmed by a laboratory in Germany, apparently polluted seabirds in the English Channel. Techniques used included NMR, infrared (IR), and high temperature gas chromatography (GC) coupled to MS. Thousands of birds died and a media storm resulted. Professor Steve Rowland (University of Plymouth, Plymouth, UK) described the background, analytical data, reviewed possible origins, and discussed the possible subsequent fate of the HR–PIB spills. The findings helped multiple wildlife agencies in the UK to press for a change in the classification of PIBs; this was actioned within months.

The keynote lecture was given by Professor Damià Barceló (CSIC, Barcelona, Spain) and covered LC–MS–MS strategies for analysis of water soil and sediment samples. Endocrine disruptors and related compounds in river waters (ng/L to μg/L) and sediment samples (ng/g) were determined by a dual column LC switching system in which 2–5 mL samples were loaded onto a pre‑concentration column and then eluted onto the analytical column with MS–MS analysis. The degradation products of tetracyclines in contaminated waters were investigated using on-line turbulent flow chromatography. This was coupled to a LC–ESI–ion trap MS system. This approach uses large particle columns (30 μm or greater) and eliminates large molecules (for example, peptides), smaller molecules being retained on the column with separation being achieved by difference in diffusion rates according to compound size. MS was by full scan electrospray ionization (ESI), positive and negative ionization, and by ion trap with MS2 fragmentation of the five most intense peaks from the full scan. Iodinated X-ray contrast media compounds are detected in wastewaters at μg/L concentrations and in surface waters up to 0.1 μg/L. The small number of commercially available standard compounds can readily be photolyzed to produce over 100 transformation products. These were studied in laboratory samples after simulated environmental degradation then in surface water samples. Once detected then prioritized, a number were isolated by semi-preparative LC with confirmation of their structures by 13C/1H–NMR spectroscopy. Initial screening was by high resolution MS, but, once confirmed, standard isolated low resolution MS could be used. Seen as emerging pollutants, fullerenes have non‑anthropogenic sources as well as industrial combustion related emissions and emissions from manufactured products. After extraction and chromatographic separation, analysis was performed by atmospheric pressure photo ionization (APPI)–MS, which was found to be approximately 100× more sensitive than MS–ESI with adducts being virtually non-existent in the spectra. Extraction from water was by liquid–liquid extraction and from sediments by ultrasonic extraction. The chromatographic column was pyrenylpropyl-bonded silica (buckyprep column) with toluene as the mobile phase. Concentrations of C60 and C70 were in the high pg–μg/L range in wastewater effluents with concentrations approximately a factor of 10 lower in river water. There was no clear relationship between the river water and discharge concentrations; however, there are other possible sources, with C60 and C90 being detected at low pg/g levels in 91% of the urban soils studied.z

Drinking water quality was covered by Gavin Mills (Severn Trent Water Ltd, UK). He reviewed methods for the analysis of halogenated and other compounds produced by disinfection necessary to comply with drinking water supply quality standards. Trihalomethanes (THMs) have a PCV (prescribed concentration or value) of 100 μg/L total THMs. Analysis is by headspace GC–MS on de-chlorinated samples with sodium chloride added as a matrix modifier. Bromate, produced by ozone treatment of raw water containing bromide (PCV = 10 μg/L), can be analyzed by ion-exchange chromatography, post‑column derivatization, and UV detection. N-Nitrosodimethylamine is produced by ozonolysis of water containing specific pesticides (action levels 1, 10, and 200 ng/L). GC triple quadrupole (QQQ) was performed to reduce interferences. Analysis of halophenols by GC–QQQ allowed reduced sample volumes and automation.

Professor Elizabeth Hill (University of Sussex, Sussex, UK) discussed screening processes for compounds, which, when combined with oestrogens, contribute to the feminization of fish. Analysis was by GC–MS and liquid chromatography–time-of-flight‑MS (LC–TOF-MS) combined with bio-assay. Samples downstream of sewage effluent were sequestered by silicone strips or LDPE flat tubing for components with log KOW > 4. Polar organic samplers were filled with different multi-functional sorbents for either pharmaceuticals or pesticides, compounds in both groups having log KOW < 4. The extracts were fractionated by reversed-phase HPLC and then tested for anti-androgenic activity. Further studies identified anti-androgens in clams exposed to wastewater effluent and in coastal sediments around the English Channel. Bio‑assay-directed analyses can be a critical tool to identify causative agents for toxicity.

In the final presentation, Dr Andrew Hobson (Quantitech Ltd, Milton Keynes, UK) outlined two new commercial field MS instruments for rapid on-site analysis of contaminants. The GC ion trap instrument, typically used for trihalomethane analysis in water and odours in air, incorporated a capillary column, heating wire, and temperature sensor wrapped together. The GC photoionization instrument incorporated a pre-concentration stage where compounds sparged from a sample are absorbed on an application specific sol gel. Heating releases the concentrate onto a 2.5 m, 0.8 μm GC column. Typical applications include analysis of 10 volatile organic compounds in six minutes using a 40–100 °C temperature gradient. The portable nature of this instrument means that it can be left in situ for long-term analysis of contaminants.

The meeting closed with general agreement of a thoroughly worthwhile day with many new methods introduced for the analysis of complex matrices using minimal sample clean-up. A similar event is likely to be held early in 2017.

Roger Reeve is a senior lecturer in inorganic and analytical chemistry in Sunderland Pharmacy School, University of Sunderland, Sunderland, UK. ([email protected])
Graham Mills is a professor of environmental chemistry in the School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK. ([email protected])
Ian Forber is the deputy technical manager at Alcontrol Laboratories, Hawarden, UK. ([email protected])

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