Environmental Laboratory Testing Contaminated land analysis in the 21st century: A European perspective [Jun 2006]
'In the present advanced state of chemistry, very expensive and complicated instruments are becoming indispensably necessary for ascertaining the analysis ... of bodies with the requisite precision as to quantity and proportion.' Antoine Laurent Lavoisier (1743-1794) in 'Elements of Chemistry in a New Systematic Order.'
Environmental Laboratory Testing Contaminated land analysis in the 21st century: A European perspective
'In the present advanced state of chemistry, very expensive and complicated instruments are becoming indispensably necessary for ascertaining the analysis ... of bodies with the requisite precision as to quantity and proportion.' Antoine Laurent Lavoisier (1743-1794) in 'Elements of Chemistry in a New Systematic Order.'
The French chemist's words are as relevant today as they were when he wrote them, if not more so. But over 200 years since Lavoisier ultimately lost his head to the guillotine, chemical analysis, and particularly chemical analysis of the environment, now owes more to Bill Gates than Bunsen burners. A visitor to a modern environmental laboratory may well be disappointed to see not the rather clichéd hubble-bubbling of burners and flasks but rows and rows of grey or white boxes with PCs next to them.
A contemporary of Lavoisier's, William Blake (1757-1827) bemoaned the environmental and sociological effects of unbridled industrialisation in his anthemic Jerusalem ('dark satanic mills'), and in England, various Acts of Parliament such as the first Alkali Act of 1863 and the Clean Air Act of 1956 (in response to the Great London Smog of December 1952) eventually ensued. Yet it is arguable that the full global effects of mankind's effects on the environment were first brought home thanks to an inconspicuous device now called the Electron Capture Detector (ECD). Invented by the maverick scientist James Lovelock in the 1960s, this detector, when coupled with the rapidly improving technique of gas chromatography, was able to detect residues of man-made chemicals (particularly the insecticide DDT) in living tissue at levels far below anything previously attainable. Lovelock's invention tellingly demonstrated that pollution does not respect frontiers. In 1962, Rachel Carson's seminal book on the effect of the pesticide DDT on America's birdlife, Silent Spring became the wake-up call for the environment.
This article touches on one aspect of the environment, namely land, or the application of modern chemical analysis techniques to soil samples. Despite the relative vintage of the opening quotation, chemical analysis of contaminated or potentially contaminated land has moved on from its early beginnings in the 1970s of the high profile Love Canal contamination case in the USA and in 1980 Lekkerkerk in the Netherlands.
Regulators have become more prescriptive and clients more discerning and more demanding. Results are required more rapidly, to higher levels of accuracy and precision, and to increasingly lower levels of reporting. As a result of improving knowledge in the toxicology and carcinogenicity of chemical compounds, more speciation knowledge is required.
Chromatography: the work-horse of the modern analytical laboratory
Take chromatography as one example. 100 years ago, the Russian botanist Mikhail Tswett developed the technique of chromatography for the separation of plant pigments-hence the name, chroma referring to the Greek for colour.
Chromatography has come a long way since then and identifies far more than just colours. Although more manual techniques of paper chromatography and thin layer chromatography are still used to some extent, the application of modern electronics, computer power and instrument design has revolutionised this aspect of chemical analysis. Chromatographs in their various guises now form the work horses of modern chemical analysis laboratories. Whichever particular variation is selected, the principle is the same: separation of the compounds in the sample via an appropriate chromatographic column, followed by detection with a detector selective for the compounds of interest.
Ion chromatography measures anions (negatively charged ions such as bromide, chloride, fluoride, nitrate, nitrite, and sulfate) and cations (positively charged ions such as ammonium).
But it is perhaps in the field of organic chemistry rather than inorganic chemistry, that the full power of chromatography has been exploited most successfully.
In a letter to the Swedish chemist Jöns Jacob Berzelius (1770-1848) as long ago as 1835, German chemist Friedrich Wöhler (1800-1882) bemoaned the ever-growing numbers of organic compounds that were being discovered and synthesised:
"Organic chemistry is enough to drive one mad. It gives one the impression of a primeval, tropical forest full of the most remarkable things, a monstrous and boundless thicket, with no way of escape, into which one may well dread to enter."
Almost 200 years later, millions more organic compounds have been discovered and synthesised. Fortunately, elucidation of molecular structures and a more systematic classification has allowed chemists to see the wood for the trees, but such a Pandora's Box of potential chemical pollutants demands determined detective work and a powerful arsenal of analytical instrumentation.
For higher molecular weight compounds, polar compounds or compounds not amenable to volatilisation, HPLC (High Performance Liquid Chromatography) is a common technique. Also known simply as Liquid Chromatography, techniques such as LC-MS (i.e. Liquid Chromatography coupled with Mass Spectrometry) and indeed LC-MS/MS are tackling topical issues such as the measurement of Endocrine Disrupting Chemicals at very low (sub-ppb, parts per billion) levels.
For lower molecular weight or less thermally labile compounds, or compounds capable of derivitisation into a suitable form, gas chromatography is a particularly powerful technique. In addition to the ECD already mentioned, a range of other detectors are available to target different molecular species. Gas Chromatography coupled with Mass Spectrometry (GC-MS, an example of a so-called hyphenated technique) improves on the process, taking the compounds that elute from the chromatographic column and positively identifying the species from their mass spectra (as in the example in Figure 1) when compared with a computer library of tens of thousands of possible compounds. This belt-and-braces approach minimises the possibility of incorrect identification of co-eluting peaks which could otherwise occur when compound identification depends on run-time alone.
For instance, whereas a decade ago clients and regulators in the UK accepted analysis for Total PAHs by relatively unsophisticated screening techniques, hyphenated techniques such as GC-MS are now required to provide concentrations of the individual species (again see Figure 1).
Chromatographic run times have been reduced and sample preparation methods improved. Chemometric techniques (such as chromatographic deconvolution software) and more rapid data capture ensure that the maximum amount of analytical information is extracted from a particular analysis. Chemometrics therefore to some extent ameliorate the potential loss of chromatographic resolution when run times are reduced.
GC-FID (Gas Chromatography-Flame Ionisation Detection) is typically employed for routine analysis of soils for petroleum hydrocarbons. Whereas perfectly adequate for many routine petroleum hydrocarbon analyses, GC with a non-selective FID that responds to all substances containing organic carbon will not always provide the speciation necessary for forensic analysis. In such cases GC-MS or the more sophisticated GC-TOFMS (Gas Chromatography with Time of Flight Mass Spectrometry) may be used.
GC-TOFMS
Expert interpretation of GC-TOFMS data, employing comparative tools such as CORAT (Compound Ratio Analysis Technique) of selected species such as biomarkers allows correlation of a hydrocarbon spill with its source.
There is still a place for what traditionally has been known as 'wet chemistry' but for a process that previously required a lot of manipulation and manual dexterity on the part of the analyst, automation improves repeatability, increases productivity (which benefits the client both in turnaround and cost), improves Health and Safety and leaves the analyst to concentrate on less routine areas such as method development and client liaison.
Regulation
Following an initial mushrooming of laboratories to cope with the emerging contaminated land market, the last decade has witnessed a consolidation of testing laboratories both in the UK and Europe, not only as a result of fierce competition and acquisition strategies, and increasingly sophisticated and expensive instrumentation, but also due to regulatory drivers such as the UK Environment Agency's MCERTS for Chemical Testing of Soil. In addition to ISO 17025 accreditation of methods of analysis which is now seen as a minimum requirement across Europe, this scheme provides additional assurance to users of analytical data that their data is robust and fit for purpose.
Unlike the approach taken by some other countries (such as the Netherlands) which have actually prescribed specific methods of analysis, MCERTS for Chemical Testing of Soil instead prescribes a rigorous validation protocol for a laboratory's methods, and does not dictate which method to use. Although such a non-partisan approach should be less likely to lead to fossilisation of methods of analysis and promote innovation, the downside is that clients of UK laboratories may still find a plethora of analytical methods available for any one test. In such cases it is important that both client and laboratory understand the advantages and disadvantages of the test(s) provided. Nonetheless, achievement of MCERTS accreditation for any test represents a significant financial investment by the laboratory and will be proportionately more difficult for smaller operations or new entrants to the market to achieve.
Garbage in, garbage out
This is not a reference to analysis of waste (although Waste Acceptance Criteria testing of soils prior to potential disposal in landfills is a growing area for contaminated land testing laboratories). Rather a reference to the obvious fact that however good a laboratory is, the analytical results produced are only as good as the sample received. Errors introduced through soil sampling tend to be far greater than the relatively well-defined uncertainties in the laboratory analysis.
In the UK, and at time of going to press, the Environment Agency has yet to provide definitive MCERTS-type guidance for soil sampling (as opposed to testing). Yet a soil sub-sample ultimately presented to an analyst for testing, after sieving, drying, and grinding typically comprises less than one millionth of a per cent of the volume of soil on site that sample is meant to represent.
In the rest of Europe, other countries have managed to address this thorny issue, perhaps none more than Belgium. Focussing on the complete environmental chain, Belgium currently has the strictest rules for Contaminated Land Investigation with regulations covering soil sampling and consultancies in addition to the normal laboratory testing. The governmental control body OVAM controls the implementation of these methods by audits, site visits and round robin tests. Every year the test must be passed in order to be able to work in the field of environmental investigation. If an organisation fails the test, it is not allowed to work in the sector for a minimum period of 3 months until the test is passed.
The Netherlands is currently in the implementation phase of very strict methods for sampling, laboratory testing and consulting in the environmental sector. This will be achieved through certification. In the Netherlands you also need additional certificates over and above the ISO 17025 in order to test for different areas.
This also applies to Germany where certificates specific for a particular Bundesland are required in addition to ISO 17025. So if you want to work throughout Germany you need a lot of specific certificates.
Lost in transit
Assuming however, that the soil sample is indeed representative of the whole, errors can still occur even before the sample has reached the analyst, particularly due to loss of more labile or volatile species during transit and storage.
Cross-contamination may also occur due to sloppy sampling practices or use of an incorrect container (for instance, analysis of a soil submitted in the default plastic pot for Semi-Volatile Organic Compounds will probably provide false positives for phthalates, used as plasticisers).
At ALcontrol Laboratories, a Production Driven Analytical Platform (PDAP) approach has been adopted in some of its European Environmental laboratories, particularly in this area. Routine analytical procedures are broken down into their constituent steps and controlled via analysts' workstations via a Labflex software system: the analyst is provided instructions at each and every step and cannot proceed until previous tasks have been fulfilled. This provides greater transparency and traceability of the whole process.
Web-enabled analytical pre-scheduling by site samplers and barcoded sample containers ensure that samples can be automatically booked into the Laboratory Information Management System (LIMS) and subsequent analysis can proceed without delay. Barcoding of samples also facilitates rapid retrieval of samples from refrigerated storage. Interfacing analytical instrumentation with LIMS improves productivity and minimises transcription errors.
The future?
Environmental analysis depends on chemical innovation. As we learn more about the toxicology of compounds on the ecosystem, it is clear that more sophisticated chemical analysis is required by the risk assessors. More speciation information is required, not less. And for that more sophisticated instrumentation is required, particularly exploiting hyphenated techniques. As the world becomes more litigious and regulation more robust, there will be a greater demand for forensic type investigations, and a greater emphasis on data quality.
Yet with increasing sophistication, selectivity and sensitivity there lies a danger. That of finding the needle and missing the haystack. Synergistic effects of a combination of pollutants could well be missed by what is necessarily the reductionist technique of chemical analysis. Ecotoxicology combines the disciplines of chemistry and biology to give a more holistic overview.
And results are required more rapidly. Delayed results mean delayed development. Laboratories are responding as best they can, but field test kits and on-site instruments necessarily have their place, although there is still some way to go with laboratory test validation and correlation. Used as screening tools and backed-up by robust validation and laboratory data where appropriate, there is significant scope for innovation in this area.
Authors
Paul Board BSc (Hons) CSci CChem FRSC
UK Marketing Manager ALcontrol Laboratories
paul.board@alcontrol.co.uk
Jaap Willem Hutter MSc
Benelux Business Manager
ALcontrol Specials
j.hutter@alcontrol.nl
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