Report Laboratories

Laboratories Working Group Report

10th Feb 2015 - by Ciaran Jennings

Tags: 341 526 BS 1377 BS/526/3 BSI CEN CEN TC consultation John Powell laboratories Labs UKAS WG6

John Powell, Chairman, Laboratories Working Group writes:

The meeting had 8 member attendees and 7 apologies.

BSI Committee B/526/3

Revision of BS5930: Section 8- Laboratory Testing on Samples

The public consultation is now complete with around 1000 comments being received (many just editorial) with only about half a dozen of these being for the Labs section. Publication is anticipated later this year.

Future of BS 1377 and CEN TC 341 WG6

WG6 had progressed well –

Parts 1 (Water Content) and 2 (Density Tests) – both were published worldwide on 31/12/2014, in the UK as BS EN ISO 17892-1 and BS EN ISO 17892-2.
The corresponding parts of BS1377: Part 2 (Clauses 3.2 and 7 respectively) will be withdrawn by 30/06/2015. UKAS has issued a memo relating to these two tests. Labs that are accredited to the BS equivalents can have these added to their accreditation schedules by signing a self-declaration, rather than by application, fee and audit.
Parts 3 (Density of Solid Particles) and 4 (Particle Size Distribution) – are under final review taking into account public comments. It is expected they will be submitted for final formal vote within a month or so, and will be published around mid-year
Parts 5 (incremental oedometer) and 6 (fall cone) – are in public review now (BSI website until 18 April). Please take opportunity to comment.
Parts 7 (Unconfined Compression test on Fine Grained Soil), 8 (Unconsolidated Undrained Triaxial Test) & 9 (Consolidated Triaxial Compression Test on Water Saturated Soils) – are close to submission for public consultation, these are expected to be out during the second half of this year.
Parts 10 (Direct Sheer Test) & 11 (Determination of Permeability by Constant and Falling Head) and Part 12 (Determination of Atterberg Limits) – remain under review in WG6.

The AGS lab group are to considering if there any tests they would like to be standardised and brought to European level (and other AGS members are welcome to do the same via the Labs group).

An Introduction to Geotechnical Laboratory Testing for Routine Construction Projects

In reviewing the guide reference is made to “Selection of Geotechnical Soil Laboratory Testing” and the AGS Power Point presentation on “Ground Investigation Testing”. It was agreed that these also needed a detailed review.

The document “Selection of Geotechnical Soil Laboratory Testing” would need to be reviewed by a separate sub group of consultants and others and this would require approval from the Executive. John Powell agreed to raise it at the next Executive meeting on the 19th February 2015.

All to 3 documents to be reviewed together to ensure consistency.

Membership Drive for Laboratory Testing Organisations Only

John Powell announced the Executive had approved the proposed Laboratories Seminar. It was decided the seminar would be held in October, depending on venue availability and would be aimed towards clients and consultants educating them on what Laboratories can provide and the importance of sampling.

Proficiency testing

John Masters would be running a scheme in 2015. Test to be notified.

UKAS

UKAS are reinstating the Construction Technical Committee and the AGS had been invited to contribute and has asked for volunteers. Kevyn Brooks advised he had been asked to be involved also and was happy to represent the AGS.

Article Laboratories

On Stony Ground

1st Aug 2011 - by Ann-Marie Casserly

Tags: analysis laboratories

How standardised is MCerts analysis in stony samples?

Despite articles such as that by Mark Perrin (Ground Engineering, April 2007), many engineers, consultants and regulators still appear to be largely ignorant of the differences in soil sample preparation methods between laboratories and the effect this can have on the results produced. Many assume that the MCerts accreditation commonly required by Local Authorities and the Environment Agency has ‘standardised’ laboratory analysis such that the reported contaminant concentration will be that of the soil tested without any significant variance. Unfortunately, whilst the MCerts scheme focuses on quality procedures to ensure repeatability within an individual laboratory, it does not standardise the test method itself, and thus variations between laboratories remain.

The MCerts scheme requires comparison trials between labs to be carried out on a standard homogeneous matrix, which generally produces a high degree of comparability between laboratories; unfortunately most soils that are sent for analysis tend not to be like this homogeneous matrix. Typically most analysis is carried out on samples of near surface made ground which is by its very nature largely heterogeneous, and usually with a high stone content. As an extract can not be produced from the stones, sample preparation including either grinding of the stones to a fine powder or excluding them such that the sub-sampling uncertainty can be reduced or eliminated. However, the methods adopted to achieve this are by no means standardised between laboratories.

How do laboratory methods vary?
All commercial laboratories with MCerts accreditation for PAHs and toxic metals were asked about their sample preparation methods. Responses were received from 18 of these laboratories with 17 being accredited for metals and 17 for PAH. A surprising number of laboratory managers were unsure of the sample preparation method and had to check their procedures before being able to reply; however the responses received are summarised below;

Metals	No of labs using this method	Percent of labs that responded
Dry and crush to less than 0.5mm	8	47%
Remove stones greater than 2mm diameter	2	12%
Remove Stones Greater than 10mm diameter	6	35%
Remove all ‘inert’ stones	1	6%

For metals the main difference appears to be whether the stones are removed or are crushed and when removed what size stones are removed. However, with PAH a greater range of sample preparation methods were apparent;

PAH	No of labs using this method	Percent of labs that responded
Test as received sample but avoiding stones	8	47%
Dry and crush to less than 0.5mm	4	24%
Remove Stones Greater than 2mm diameter	2	12%
Remove Stones Greater than 4.75mm diameter	1	6%
Remove Stones Greater than 10mm diameter	2	12%

Of those labs that dried the samples, two did so at 28 ^oC, five at 30 ^oC, one at 35 ^oC and one at 37 ^oC. Variation in the extraction solvent was also apparent as set out below.

Extraction solvent for PAH analysis	No of labs using this method	Percent of labs that responded
Dichloromethane (DCM)	13	76%
DCM & Hexane	1	6%
Hexane:Acetone	2	12%
Pentane	1	6%

This variation has been further complicated recently, as during the recent recession, the partial shut down of the car industry reduced the demand for foam rubber, a bi-product of the production of which is DCM. Therefore the price of DCM rose significantly and several laboratories switched from using pure DCM to a mix of DCM and hexane or acetone or even hexane:acetone:triethylamine. Once the car industry recovered and the price of DCM fell these laboratories reverted back to using pure DCM.

What are the effects of variation in preparation methods?

In a soil where the contaminant concentration is distributed evenly between the matrix and the stone content, removing or crushing the stones would clearly have no effect on analysis results. However, where the metallic contaminants are expected to be concentrated in the coarser particles, as in a slag or clinker, crushing of the stones will produce a higher contaminant concentration than would be produced in a laboratory that removes the stones. Similarly, as the bulk of the made ground which is present in garden areas that have been used for a considerable period will have been subject to bonfires and the active digging in of ash, part burnt fragments of coal or timber are common. Such relatively coarse fragments could be expected to be a source of PAH (including benzo(a)pyrene) and therefore a sample which was crushed prior to analysis could be expected to yield a higher concentration than one from which the larger particles had been removed. Conversely, where the burning of painted wood has resulted in elevated lead concentrations in a fine ash, or where soot has been dug into the soil, the presence of natural stones in the sample will act to ‘dilute’ the measured concentration if they are crushed during the analysis rather than removed.. However where the weight of the stones removed is back-calculated into the reported result this effect should be eliminated.

In addition to the effect of stone content, where a sample is dried the variation in drying time and temperature will surely have an effect upon the more volatile compounds such as naphthalene which could be lost to some extent, especially where the sample is dried overnight at 37oC. The reported naphthalene concentration of a dried and crushed sample would thus be expected to be lower than that of a sample tested in the as received condition.

The variation in extraction efficiency of the different solvents and solvent mixes would also be expected to induce variability.

So which is the right method?
Unfortunately, there is no right or wrong method of analysis, as the applicability of each method is dependent on the use to which the results are to be put, which is beyond the control of the laboratory. The onus therefore ,has to be placed upon the consultant scheduling the testing and interpreting the results to use an appropriate method.

For example; waste classification is based upon a hazard assessment and the analysis is required to be representative of the whole load being disposed of, and thus a dried and crushed approach may be applicable. However, for human health a risk based assessment is adopted and thus consideration needs to be given to the likely exposure pathways.

For Benzo(a)Pyrene some 56% of the total exposure for the residential land use arises from the ingestion of soil and indoor dust. As soil Pica has not been included as an exposure route in the CLEA model, the bulk of the ingestion of soil will be from accidental ingestion from hand to mouth contact and as such larger particles are unlikely to be involved. Similarly, dermal contact, which amounts to 36% of the total exposure for the residential land use is unlikely to be significantly affected by the larger particles which will have a far lower surface area to volume ratio. Therefore, for a Benzo(a)Pyrene risk assessment, an analysis of the fine particles following sieving and the exclusion of the stone content from the calculated results would appear to be far more appropriate. This would also be the case with the majority of the PAHs and toxic metals.

Conclusions
Engineers and consultants scheduling laboratory analyses need to be aware of the sample preparation method that is to be adopted by the laboratory and the effect that this will have on the results for the specific soil which is being tested. It would also be helpful if laboratories published a basic summary of the sample preparation method along with the results to aid those interpreting the results and to assist where comparisons between different sets of data on the same site are being carried out, be it by different laboratories or by the same laboratory over a prolonged period. Furthermore, when the chemical analyses indicate that the soil in a garden contains contaminant concentrations close to or a little in excess of the adopted threshold values, it would be worth considering the effect of the sample preparation method and whether retesting a sieved sample may produce a more appropriate concentration to compare with the adopted threshold, considering the assumed critical exposure pathways.

Mike Plimmer
GEA Associates

Article Contaminated Land Laboratories

UKWIR – GUIDANCE FOR THE SELECTION OF WATER SUPPLY PIPES TO BE USED IN BROWNFIELD SITES

1st May 2011 - by Ann-Marie Casserly

Tags: analysis brownfield contaminated investigation laboratories

Peter Boyd, AECOM Limited and Neil Parry, Geotechnical Engineering Limited

The UK Water Industry Research (UKWIR) has produced this document to replace the heavily criticised 2002 WRAS guidance on water supply pipe materials for contaminated land. Unfortunately there remain several similar problems with the new document. It has been produced by UKWIR with the footnote “Promoting Collaborative Research” but there does not appear to have been any collaboration or consultation with practitioners in the industry. As a result the document fails to reflect commonly accepted industry practice and terminology.

The basis of the document is highly conservative, for example making reference to identifying whether “any chemical may have ever been on a site” and that “samples should be collected at a frequency and depth that will identify any contamination”. Although it rightly advocates a risk based approach to sampling and assessment many of the recommendations ignore this premise and current guidance, with the end result likely to be overdesign and significantly increased costs for end users.

The document was recently revised, where some of the initial errors were corrected, unfortunately several errors remain and the opportunity to gain widespread acceptance was missed.

The responsibility for the selection of supply pipes is confused between the Developer, Self Lay Organisation (SLO) and Designer. The responsibility for the production of the crucial Site Assessment Report (SAR) is not clear between the “Developer” or the “Designer” without considering whether they have the necessary contaminated land expertise. Guidance such as the new Eurocodes define competence roles and from an industry perspective it’s yet another missed opportunity to give some further recognition to the SiLC qualification. It seems to be aimed at the layman but also advocates a very wide ranging and unusual range of laboratory implying the user has a detailed knowledge of soil sampling, preservation and laboratory testing. It is also unfortunate that 30 years after the first edition of BS5930 the document blurs the distinction between site investigation and ground investigation.

Desk Study
The document provides some good general guidance on establishing previous site use and the potential for contamination but insufficient information or reference is provided for a general user to adequately complete this. It suggests that the findings should be summarised on a map to show current and historic land use but show a level of detail at a scale which would not be possible in most practical instances. implying that the authors have not actually performed this exercise with real data or thought about the preparation of a robust conceptual model, which is the basis for most contaminated land assessment.

The document suggests that the Local Authority may request an SAR as part of the planning process. There is no recognition of the fact that such an assessment could and perhaps should be incorporated into the routine pre-development desk study, intrusive ground investigation and interpretative reporting process.

Investigation
When looking at investigation the application of photoionization detector (PID) screening is meaningless without further guidance. The “suitable survey pattern” is not defined and ignores the shortcomings of PID readings. The extent of suggested PID testing could also be onerous in most circumstance.

The soil sampling section refers to an unspecified “suitable survey pattern” which is easily confused with the PID screening. Although it recommends the use of BS10175 for more detailed information on the design of a sampling plan no specific information on sampling for proposed services is included. It makes reference to taking “a spadeful” and the use of a “plastic bag” for samples which may be inappropriate and ignore the complexities of sampling. Investigation and sampling are assumed to be undertaken via trial pits (likely to be machine dug to achieve the recommended depths) which would be difficult in an urban situation where numerous existing services are present and may not present the best method for obtaining the best samples, particularly for groundwater. It suggests that if groundwater is present within 1m (or 2m in summer) of the base of the intended trench then a water sample should be taken from “a suitably completed narrow borehole” but establishing groundwater depth may be difficult.

Chemical Analysis
One of the most onerous parts of the recommendations is the imposition of a mandatory analytical suite to be undertaken on all samples. Despite the fact that a desk study and ground investigation has been undertaken, including PID screening for VOCs, it appears that there is a limited choice for the user of the document in respect of what testing is required. The suite is far from routine with several determinands not generally carried out by any of the commercial laboratories in the UK on soils. To cover the lists as provided would probably cost in excess of £300 per sample. Notably only organic contaminants are considered with the absence of inorganics such as arsenic.

Confusion extends to the proposed testing suites. The extended VOC suite (by GCMS) contains many non VOCs such as Benzo(a)pyrene and propylene glycol, explosives such as nitroglycerine and nitrotoluene (which are analysed by HPLC), Nitrohydrochloric acid (Aqua Regia a mixture of HCL and nitric acid which again cannot be analysed as a VOC) and Naphtha which is petroleum terminology for an ill defined distillate. There are misspelled chemicals such as “Mesityl” oxide and duplicated compounds such as methyl chloroform (which is 1,1,1 TCE) and Monochlorobenzene which is Chlorobenzene.

Other suites contain similar errors. Petroleum ether is incorrectly listed under ethers. Under mineral oil the document contains a turpenoid, a plasticiser, a flavour, a fatty acid and fuming sulphuric acid with no mention of mineral oil C5-C10, C11-C20 and C21-C40 listed in the “mandatory analytical suite”. A random list of chemicals is listed under Conductivity, Redox and pH including a vitamin, food preservatives and a range of compounds that would either not be found or could not be determined by routine analyses.

The simplistic approach to the determination of redox and resistivity in disturbed samples also causes some concern. This should at least reference BS 1377 Part 3:1990 and mention the benefits of in-situ measurements. Other soil conditions, not necessarily associated with a brownfield site, may also need to be examined for classification, for example “Wetness Class” which, although are not directly related to contamination, are used in the examination of sites for existing or proposed ductile iron pipes.

In relation to chemical testing reference is made to detection limits – but no discussion on how these limits were arrived at is included. These are set at “at least 10 times lower that the screening values identified” which appears to be arbitrary.

Specification of Water Supply Pipes
The final part of the document, as expected, relates to the process of specification of pipes. It provides a comprehensive list of standards and guidance for each of the options including ductile iron, steel, polyethylene (PE), PE Barrier, PVC and copper. Further undefined terms which will have a major effect on the specification are included such as “light chemical contamination”

Unfortunately some of the chemistry in this part is also misleading. It gives a conversion from EC to resistivity, which is not applicable to soils as it does not take into account natural moisture content, compaction, voids or the benefit of in-situ measurements. Redox is used as a criteria without proper reference to BS1377 or acknowledging the problems likely to be encountered with disturbed samples.

Once all of the results of the extended testing have been received, individual chemicals are summed in groups, which appears to be highly questionable considering the differences between each of them. Further mistakes are noted on the Pipe Selection Table 3.1, below which is provided to make a final selection, notably with disagreements between these figures and those in F.4 (Derivation of ‘data-supported threshold values’ for PE and PVC). In this table there would be no requirement for any analysis if Barrier Pipe (PE-Al-PE) is used as it passes on all counts. It is felt that the selection of barrier pipe for all sites will be a frequently exercised option as this is suitable for all conditions, it would also negate the need for any of the desk study, analysis, site assessment and pipe selection process covered in the rest of the document. A statement that “barrier pipes should be used for all brownfield sites” would make the whole of this document redundant.

		Pipe material
		All threshold concentrations are in mg/kg
	Parameter group	PE	PVC	Barrier pipe (PE-Al-PE)	Wrapped Steel	Wrapped Ductile Iron	Copper
1	Extended VOC suite by purge and trap or head space and GC-MS with TIC	0.5	0.125	Pass	Pass	Pass	Pass
1a	+ BTEX + MTBE	0.1	0.03	Pass	Pass	Pass	Pass
2	SVOCs TIC by purge and trap or head space and GC-MS with TIC (aliphatic and aromatic C5 – C10)	2	1.4	Pass	Pass	Pass	Pass
2e	+ Phenols	2	0.4	Pass	Pass	Pass	Pass
2f	+ Cresols and chlorinated phenols	2	0.04	Pass	Pass	Pass	Pass
3	Mineral oil C11-C20	10	Pass	Pass	Pass	Pass	Pass
4	Mineral oil C21-C40	500	Pass	Pass	Pass	Pass	Pass
5	Corrosive (Conductivity, Redox and pH)	Pass	Pass	Pass	Corrosive if pH < 7 and conductivity > 400μS/cm	Corrosive if pH < 5 , Eh not neutral and conductivity > 400μS/cm	Corrosive if pH < 5 or > 8 and Eh positive
Specific suite identified as relevant following Site Investigation
2a	Ethers	0.5	1	Pass	Pass	Pass	Pass
2b	Nitrobenzene	0.5	0.4	Pass	Pass	Pass	Pass
2c	Ketones	0.5	0.02	Pass	Pass	Pass	Pass
2d	Aldehydes	0.5	0.02	Pass	Pass	Pass	Pass
6	Amines	Fail	Pass	Pass	Pass	Pass	Pass

Table 3.1: Pipe selection table

Conclusions

Although the document recommends a staged process of desk study, investigation, assessment and specification there are several areas where it is far from satisfactory. Lack of suitable detail, ignorance of current guidance and an unwieldy and expensive approach to chemical analysis has made the process of selecting suitable pipe materials almost impossible.

Given the potential complexity and cost of the investigation and analysis to fulfil the requirements of the document it is likely that developers and specifiers will often take the simpler approach of always using barrier pipes in brownfield sites when there is any possibility of contamination. This will be the case in most existing domestic plots and extensions (where the presence of a garage or garden shed would lead to the onerous investigation procedure) and may in turn lead to barrier pipes being unnecessarily specified. It is also possible that the replacement of lead water pipes will be prevented by the higher costs caused by following this guidance.

We would recommend that the document goes through a further period of consultation including commercial laboratories, consultants and industry groups (such as EIC, NHBC and AGS). The limitation of desk studies and PID screening should be added and more guidance and reference on the investigation, preparation of a conceptual model and provision of competent personnel given. A more flexible approach to analysis should be taken, relating the testing to the previous site usage. The selection process should also be made simpler, making the choice of other pipe materials more likely.

Article Contaminated Land Laboratories

MCERTS

26th May 2004 - by Ann-Marie Casserly

Tags: Chemical test data chemical testing laboratories MCERTS soils

The Environment Agency have advised that a policy titled ‘Chemical Test Data on Contaminated Soils – Qualification Requirements (307_03)’ has recently been published. The purpose of the policy is to implement the ‘MCERTS Performance Standard for Laboratories Undertaking Chemical Testing of Soils’, which was published in March 2003.

Chemical test data on soils is used by the Agency to support its regulatory activities under a number of regimes, such as Part IIA of Environmental Protection Act 1990, Pollution, Prevention and Control (England and Wales Regulations) 2000 and Waste Management Licensing Regulations 1994. The Performance Standard will be applicable to all laboratories and procurers of analytical services where results generated from the chemical testing of soil are presented to the Agency for regulatory purposes. After September 2004, the Agency expects that all soil testing results submitted will be from methods which have been accredited to BS EN ISO/IEC 17025:2000 for the MCERTS performance standard.

In the interim period, it is encouraged that all data provided to the Agency should be from a testing method accredited to BS EN ISO/IEC 17025:2000 and be accompanied by a brief method description, together with bias and precision estimates.

In addition to the policy, the Agency are producing a document for those who procure soil testing, for example consultants or local authorities, titled ‘Brief guide for procurers of analytical services’ which outlines what is expected of them and why it is required. All the documents mentioned above will be available from the Agency’s MCERTS website at www.mcerts.net.

Any technical queries relating to MCERTS should be addressed to Mike Healy, Technical Advisor, by email (Mike.Healy@environment-agency.gov.uk) and queries relating to the policy itself should be directed to Nicky Skidmore, Land Contamination Policy Advisor (Nicky, Skidmore@environment-agency.gov.uk).

Article Contaminated Land Laboratories

The Extension of MCERTS to Chemical Testing Of Soils – An Update

26th Jan 2004 - by Ann-Marie Casserly

Tags: Contaminated Land laboratories MCERTS quality control soil

In January 2003, issue number 45 of the AGS Newsletter contained an article by Bruno Guillaume, of Arup Geotechnics, who outlined the MCERTS performance standard for the chemical testing of soils. The following is an update, and a view from an analytical chemist`s perspective.

On the Environment Agency website reference has been made to the fact that the Agency is aware that it will take time for laboratories to gain approval through the appropriate accreditation process. An eighteen month period, starting from March 2003, has been given for laboratories to bring their soil testing methods up to the MCERTS standard.

During this period laboratories reporting data to the Agency have as a minimum to be accredited to the ISO 17025 standard for the soil test methods. It is also recommended that tests should have a brief method description together with estimates of bias and precision. From September 2004 only data from laboratories that have been accredited to ISO 17025 for MCERTS will be accepted.

Since the last article in the newsletter, Version 2 of the MCERTS standard has been published, and this was available from February 2003. The standard highlights particularly important areas, namely contract review, bias and precision targets, quality control( both internal and external), method validation, and uncertainty of measurement. Important differences from the first version are the exclusion of expected limits of detection for methods, and the inclusion of an improved protocol for validation.

The issues can be confusing but the standard simply aims to establish a level playing field in a competitive market, based on the Agency`s requirements, and to set a minimum acceptable performance. In short the data received by the laboratory`s customers must be accurate, reliable and comparable.

The analysis of soil is complex in terms of the chemistry involved. It aims to determine both macro and trace components in a matrix that is, quite often, dirty in both a physical and chemical context. There is a need to analyse for trace organic and metallic contaminants in soils that contain large quantities of other industrial materials, such as oil or tar, in a background that also contains high concentrations of naturally occurring, or artificially polluted, inorganic compounds.

We all use “parts per million” as routine terminology, but the significance is commonly ignored. 1 part per million is more easily visualised as 1 grain of salt in a swimming pool. When we talk of the concentrations of polynuclear aromatic hydrocarbons (PAH), an important environmental parameter, we often refer to micrograms per kilogram, which is three orders of magnitude lower.

The contaminated land testing industry has grown very quickly, and methodologies have been borrowed from other more well established areas of analytical chemistry, such as food or potable water. The only industry standard for analysis of soils in the UK are the robust and technically sound ” British Gas Methods “, but even these were not designed to tackle the lower end of detection, and do not take advantage of some of the more modern developments in analytical chemistry.

MCERTS effectively defines a standard for the performance of analytical methods, and includes the requirements of ISO 17025 in terms of certification of instrument performance, approved competency of personnel and the accreditation of laboratory procedures and organisation. It means that it is no longer sufficient that the laboratories follow a rigorous UKAS quality system in line with the international standard, but that the methodologies must also be demonstrated as fit for purpose.

The Environment Agency has not, in its standard, adopted the principle of prescriptive methods, as has been the example in the USA, through the so-called EPA procedures. This approach can commit the industry to inappropriate analytical techniques, a long time in their reform once committed to paper, and takes away the flexibility of developing new improvements for the industry as a whole.

It cannot be relied upon that environmental specialists, requiring the services of an analytical laboratory, will have the depth of technical to knowledge to understand the concepts of analytical bias or precision. MCERTS is designed to take away the need for such expertise.

Another variable that stops a customer from being able to compare “apples with apples” is the limit of detection (LOD) quoted. This can vary widely depending on how the laboratory defines it. A sound statistical principle is to use three times the standard deviation associated with a blank, or a sample with a very low concentration of the determinand of interest. This is all carried out interspersed with other standards and samples over eleven separate days. Other lesser definitions than this one seem to describe a “better” LOD, but mislead the customer into thinking they are getting an improved service, and can give false positive concentrations on soils where none of the contaminant actually exists.

All of these concerns are addressed by the MCERTS standard. Precision and bias must be of an acceptable standard, as must LOD. “Recoveries”, namely what happens when a soil is spiked with known amounts of the material of interest and is reanalysed, are examined in the standard to ensure acceptable performance. The validation must be carried out on three completely different soil types with two spiking levels, and include the use of certified reference materials wherever possible. Detailed methodologies, together with a prescribed uncertainty of measurement must also be given.

The Contract Review is the point at which the client`s needs must be understood, and the point at which the laboratory must document them. What does ” Total PAH” mean, or “Total TPH”, and what does the client consider to be the critical level of interest? This is an area quite often poorly addressed, and to which the standard lends some priority.

The laboratory`s quality control also comes under close scrutiny. At least 5% of the resources allocated to a test must be used to ensure validation. In addition the laboratory must participate in as many of the acknowledged external proficiency tests as is appropriate, such as Contest, Aquacheck, and the SPH test scheme. The results of these must be readily available for inspection by the client.

It is generally recognised amongst the community of analytical laboratories that there is a real challenge in order to be able to comply with the new version. The standards relating to bias and precision and, in particular, the guideline that “the limit of detection usually regarded as being fit for purpose is 10% of the concentration regarded as the critical level of interest” are extremely demanding. There are some method improvements required within the industry before these levels of performance can be achieved. Most laboratories, however, will feel a relief that any ambiguity is now removed, so that everyone can compete to provide a well defined product, and be able to market its expertise without confusion.

Whilst addressing the vagaries of analytical results the Environment Agency has also acknowledged the uncertainty associated with other areas, and is considering certification schemes to address field aspects, including sampling. Other subjects, for example the suitability of leachability tests, toxicity assessments and the bioavailability of metals need to be topics for guidance by the regulator.