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SlideShare utilise les cookies pour améliorer les fonctionnalités et les performances, et également pour vous montrer des publicités pertinentes. Si vous continuez à naviguer sur ce site, vous acceptez l’utilisation de cookies. Consultez notre Politique de confidentialité et nos Conditions d’utilisation pour en savoir plus.
The Laboratory Process
• Taking a representative sample is usually outside
the control of the lab.
• What is important
– Using the correct container for the analysis
– Filling them correctly
– getting them to the lab in a timely fashion
• If not the samples could be deviating and a
comment would go on the report to state the
integrity of the sample could be compromised
• These are supplied by the laboratory and are
dependant on the type of analysis required.
– Plastic tub for Inorganic contaminants
– Glass jar for Organic contaminants
– Small glass jar with no headspace for volatile
What could possibly go wrong?
• Its all down to communication
• Or lack of it
• You know what you want
• Labs think we know what you want
On Receipt at the Lab
• Samples are checked against a chain of custody to
highlight any discrepancies, ambiguities, breakages
or deviating samples.
• Once this process has been completed and any
issues resolved, then the samples are ready for
registration onto The Laboratory Information
Management System (LIMS)
• Is there sufficient instruction with the samples
• Could the instructions be ambiguous
• Is there sufficient detail
Things we are asked
• Can you tell me if this soil is contaminated?
• Can you tell me what it is?
• Can you tell me what’s in it?
• Being non specific can cause problems!
Registering samples at the lab
• Correct registration is very important since it determines
the analysis carried out and how it gets reported
– Have we got the correct det? – is total or dissolved det reqd
– Have we chosen the det with the correct unit - %, mg/kg,
µg/kg, g/l, mg/l, µg/l, ng/l
– Have we chosen the correct Form of Expression –
Ammoniacal nitrogen as N, as NH3, as NH4
– Have we included all the necessary information – sample
dates, depths, BH numbers, sample descriptions, TRTs,
dependant options, monohydric phenol or speciated.
• If not you could end up with something you didn’t want
• Not all labs prepare samples the same way
– Some remove stones and analyse the remainder
– Some crush the whole sample and analyse it all
• A new ‘Blue Book’ written by the SCA is being
published by the EA which approves both
• IMPORTANT –you need to know which method
your lab employs
Preparation of soils samples
• Depending on what analysis is asked for
• Analysis is typically carried out on an air dried (30°C)
and ground sample where more representative sub
sample can be taken.
• However, some analyses, such as volatile organics are
carried out on an as received (AR) sample. Volatile
parameters would be lost if the sample was dried &
ground. This results in it being more difficult to take a
representative sub sample.
Procedure for preparation of soil
• Whole sample hand mixed and quartered, one
quarter for air dried analysis and one for as received
• Air dried portion
• Dried at 30°C and moisture content recorded
• Stone content (>10mm) not recorded unless
• Whole dried sub-sample crushed to pass through a
• As received wet portion
• Representative sub-samples are taken for each analysis
• Labs tend not to analyse soil as such but extract
the contaminant of interest and analyse the
• Inorganic contaminants are digested in polar
solvents such as acids, whereas organic
contaminants are extracted into organic solvents
• Analysis tends to be split into 3 types
HPLC TLC GC
Flame - Heavy
Furnace - Low
Hydride - As,
ICP - MSOES
ICP + USN - Low
Photometry -Na, K
Quality in the Laboratory
• ISO 17025
– Proficiency Testing Schemes
• Quality Control
– Reference materials
When we say its 10mg/kg is it
• The answer is not really!
• All chemical analysis has a % uncertainty of
measurement which depends on the analyte
and the method employed.
• Typically it can range from 10% to 30%
(uncertainty in sampling is usually far greater)
• What this means is that the result reported is
within a range.
A few misconceptions
• The lower the limit of detection, the more
accurate the analysis
oNo the opposite is the case
• Results from different labs should always give the
oNo it depends on the methods used
• Total results mean total
oFor organics, total means the total of the compounds
• Sampling is as important as analysis
• Differences in how a sample is prepared can
have a large influence on the final analytical
• The more information accompanying a
sample, the quicker the analysis becomes.
So what do consultants think of labs?
– Labs try to be as flexible as possible but there are
• We cannot do a five day test in 3 days (no matter how
much money is offered)
• If you only have 1g of sample then we cannot do a full
suite of analysis (we are not CSI)
• Despite appearances we are human and occasionally
we do make mistakes!
So what do labs think of consultants?
• Do labs think consultants expect too much?
I can assure you this is not what labs
think of consultants