The last 10 years have seen more innovation in laboratory techniques than perhaps we have ever seen before. Instrumentation once only found in research and development laboratories is now commonly found in routine testing laboratories.
With manufacturers continually developing faster and more automated instrumentation, laboratories are often looking to innovate in more alternative ways, often revisiting first principles to yield different strategies for both age old and new analytical challenges.
Geotechnical testing methods are only just starting to take advantage of some of the automations and instrumental advantages that have been a routine facet of chemical testing for many years. This is largely due to the established mechanical methods that date back decades that have become both the accepted norm and also incorporated into accepted standards (BS1377, etc.), and whilst these documented methods are updated, they rarely consider the use of computerised equipment. Typically methods that required manual handling of the samples when they were first developed still require people to carry out the analysis in a very similar manner.
However, a typical problem in carrying out geotechnical testing is the presence of contaminants which render the material unsafe to handle; the most common and problematic being asbestos. Where a laboratory wishes to proceed with the testing of such samples, it requires them to revise their sample handling processes in order for the samples to be processed and tested. Such a sample is called a “Red” sample, a term which stems from the British Drilling Association to categorise sites known to be contaminated with traces of asbestos, hydrocarbons and heavy metals.
A geotechnical sample may be received up to 80 kilograms in mass which is quite different from samples for chemical analysis which may be as small as only a few grams; and most, if not all, of the sample is subjected to manual or physical processes such as sieving, compression, agitation – all of which have the potential to generate airborne fibres. Airborne fibres are those which are potentially respirable and therefore present the greatest risk to the staff involved in working with such samples.
In order to allow for testing of these “Red” samples a lab must be able to provide a safe working environment, often referred to as a “Red Lab”. Typically housed in a separate unit, the Red Lab is an enclosed facility equipped with extensive HEPA filtered air extraction and an upgraded PPE (Personal Protective Equipment) requirement, with “air-locked” areas allowing access for staff and the ability to change in and out of PPE safely. In such a facility a wide range of tests can be carried out safely on samples which are contaminated with asbestos.
Our understanding of contaminants and how they behave in the environment is increasing all the time, and linked to this is our knowledge of how different chemical species and compounds of the same element present quite different toxicological risks. The field of speciation analysis is fast moving with ever more challenging regulatory requirements – and not just from an environmental perspective – speciation of chromium in toys and foodstuffs is a particularly hot topic.
Typically the most commonly requested speciation analysis tests within any environmental laboratory are for chromium (split into trivalent and hexavalent forms) and mercury (split into its various elemental, organic and inorganic forms). It is widely known that Chromium VI is highly toxic; whereas chromium III is essential for life. Mercury is toxic in all forms, but some forms are more bioavailable and are therefore considered to be more toxic.
The analysis of chromium is fairly straight forward utilising acid digestion and Inductively Coupled Plasma (ICP), usually in conjunction with a range of other metal compounds. The most routine for chromium (VI) utilises 1,5-diphenylcarbazide which reacts with Cr(VI) present in a solution (water or soil extract) to form a highly coloured solution. The intensity of the colour is measured by visible spectroscopy at a wavelength of 540 nm. Many laboratories are equipped with a continuous flow analyser which carries out this analysis as an automated process, and allows the detection and quantitation of hexavalent chromium alongside other routine analytes such as cyanide compounds.
The speciation analysis of mercury is complex and relates to its various chemical forms and not just oxidation states. The need for this kind of analysis arises due to the different toxicities of the different forms. Inorganic mercury salts are soluble in water and this allows them to be readily absorbed into the body through the gastrointestinal tract. Once absorbed they can cause severe kidney damage, but they cannot cross the blood-brain barrier easily and as a result exposure to inorganic mercury tends to cause little neurological damage unless there is prolonged or heavy exposure. Conversely, organo (methyl) mercury is a form of toxic mercury which bioaccumulates through the food chain and the primary exposure route for humans is through the consumption of fish. Organic methyl mercury can cross the bloodbrain barrier and is a neurotoxin. Elemental mercury (Hg0, liquid mercury) is a different form of mercury with a different pathway into the human body – typically through vapour inhalation into the lungs.
“a more elegant and innovative solution is to use basic chemical fractionation which avoids the need for any complex hyphenated techniques”
When speciation is required then there are a few options available, but all rely on the same basic principles. Firstly the mercury species in the soil sample need to be extracted using a suitable solvent, then the mercury species separated, and then finally detected. The solvent mixes used may vary depending on the separation technique and detector employed; however, they will typically comprise some acid (either nitric or hydrochloric) and a water miscible organic solvent such as ethanol. Once the mercury in the soil sample has been extracted in to a sample aliquot, this is then analysed by one of a variety of complex hyphenated analytical techniques.
A more elegant and innovative solution is to use basic chemical fractionation which avoids the need for any complex hyphenated techniques and also breaks down the mercury compounds into groups which have a similar toxicological risk.
The first fraction extracts simple inorganic mercury compounds such as HgCl2 and the second more complex inorganic mercury compounds such as HgSO4 and HgO. The third fraction extracts the organo-mercury species including methyl mercury. The fourth fraction extracts strongly complexed mercury and also elemental mercury (Hg0) and the final fifth fraction pulls out the firmly mineral bound mercury compounds (i.e. those which are less bioavailable). This test is more cost effective than complex hyphenated techniques and only requires a simple sensitive mercury analyser such as a cold vapour instrument which is universally found in laboratories analysing low levels of mercury in environmental samples.
Regulatory driven innovation
The Water Framework Directive 2000/60/EC is an EU directive which committed European Union member states to achieve good qualitative and quantitative status of all water bodies by 2015. This has since been reviewed and updated and as a result a range of parameters have been assigned contamination levels which should be met – these are known as Environmental Quality Standards (EQS). These EQS have generated both international and national critical concentration levels assessing contaminants in surface waters and ground waters. This contaminant list and the levels of interest represent significant challenges even for modern analytical labs to achieve.
The original EQS (2008) supporting documentation does give some guidance on standard analytical methods that may be employed for the analysis of pollutants; however, even at this time it was acknowledged that standard methods may not meet the required levels and since 2013 most of the EQS levels have been revised to lower values. EQS levels are largely derived from ecological and human toxicology data and as such are not necessarily representative of what existing laboratory techniques are able to deliver, hence the setting of an EQS is a key driver in the innovation cycle for new and improved techniques. Additionally, within the remit of the directive, new pollutants are often identified, thereby a new EQS is set and the cycle continues.
“an example of how labs have innovated to generate analytical methods capable of detecting EQS level contaminants is a lab method for Perfluorooctane sulfonic acid (PFOS) which has an EQS target of 1.3 x 10-4 μg/l (or 0.00013 μg/l)”
An example of how labs have innovated to generate analytical methods capable of detecting EQS level contaminants is a lab method for Perfluorooctane sulfonic acid (PFOS) which has an EQS target of 1.3 x 10-4 μg/l (or 0.00013 μg/l) – standard lab techniques have detection levels in the region of 0.01 μg/l. This requirement for a detection level at around 100 times lower than a standard limit of detection causes a number of challenges, not least of which is the background present in the lab, from ultra pure lab water and from any component used in the instrumentation. However with high levels of technical expertise the instrumentation can be optimised and through using rigorous and thorough quality checks during extraction processes, this low detection level can be met with confidence.
With the European Water Framework directive being revised every two years and each member state setting a programme of chemical investigation, this legislation is constantly evolving and it can only be hoped that analytical techniques and capabilities are able to keep up with the rate of change.
Industry led innovation
Often it is the case that the customers using environmental labs for a range of testing pose questions which they are not aware the lab may have the tools or innovative methods to answer; an excellent example of this is the area of asbestos testing in soils.
Presently much of the analysis of asbestos in soils is to undertake an identification and potentially a quantification to determine the amount of asbestos within the soil; and potentially how much of that Asbestos is loose fibres which present a higher risk to human health and how much is bound up in asbestos containing materials and as such may be considered to present a lower risk to human health. Established guidelines refer to a single research paper which established that a soil containing 0.001 % asbestos could release fibres greater than the control limit at the time of 0.01 fibres/ml. However, with more innovative techniques, it may be possible to carry out further testing of the sample to perhaps generate a more meaningful assessment of risk. The primary concern for human health is the presence of respirable fibres, and whilst these can be identified as part of the fibre counting (Phase Contrast Optical Microscopy) element of a quantification analysis, it gives no indication of the likelihood of release to air under site conditions. Using existing formulae it is possible to determine potential air fibre concentrations, but these look at a worst case scenario based on the number of fibres that fit the definition, again without factoring the likelihood of release.
One recent approach to filling in this gap has been to look at Activity Based Sampling (ABS). Put simply, one would simulate normal on site activities under controlled conditions and then measure the actual fibre release using some form of air sampling equipment and then fibre counting techniques using PCOM. The USEPA approached this using personal air sampling kit carried by site workers (suitably attired to protect against inhalation) as they performed various activities either common to the site or its intended function. In the UK, an approach was taken where an area of the site was enclosed in an air tight tent while the surface was agitated using various pieces of equipment. The dust that was released to the air would be extracted by pump through a filter, and that filter reviewed by PCOM for respirable fibres. Given a known volume of air extracted a fibres/ml in air concentration can be calculated.
It may not always be possible or appropriate to perform site based monitoring, and the laboratory world has responded by looking at differing options for lab based methods which can help provide the same levels of data for risk assessment. Varying approaches have been taken across the UK, US and Australia (amongst others), with the basic principle being of a fine soil sample being agitated in some manner under a controlled flow of air with fibres collected via filtration and fibres identified using PCOM – the intention is to generate a fibre concentration in air (fibres/ml) of the respirable asbestos fibres at a specific level of dust generation.
Using an existing British Standard BS EN 15051-2 (Workplace exposure – Measurement of the dustiness of bulk materials – Rotating drum method) an innovative method for the determination of respirable fibres released from soil samples has been developed. The method itself uses a rotating drum to perform the process of sample agitation under a continual flow of air. A series of foam and membrane filters are used to collect the dust fractions generated, allowing the gravimetric determination of the total dust generated, and then using PLM/PCM (Polarising Light Microscopy/Phase Contrast Microscopy) quantification of the number of respirable fibres released. Each fibre is measured (both length and width) with the aspect ratio calculated to ensure it meets the criteria for respirable status. From the empirical data, the concentration of dust generated in mg/m3 and also the fibre concentration in air in fibres/cm3 can be calculated.
These are just four brief examples of lab innovations led either by industry, or by laboratories themselves taking advantage of the advancements in technical knowledge, instrumentation and method developments to push the boundaries of what we thought possible and answer questions of ever increasing complexity. It’s not always however in pursuit of the lowest detection limit or newest emerging contaminant; high levels of focus are also put into developing and modernising existing techniques to increase automation, reduce required sample volumes, improve efficiency and delivery as well as increasing consistency and accuracy. The last 10 years have seen considerable progress in lab innovations, and the future is indeed bright for those laboratories which embrace research and development as part of their continuous improvement programme.