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Sampling Techniques to Ensure Quality Results
David Springer – ACLCA Adelaide June 2013
Tonight
• Measurement Uncertainty
• Poor Sampling Examples
• NEPM Preservations/Holding Times
• NEPM – TRH v’s TPH
• NEPM – F1/F2
• NEPM – BaP TEQ
• NEPM – WA Asbestos
• NEPM – B7
• Transport of Samples – Ice
• Acknowledgement – Thanks to ALS for assisting with some information
Measurement Uncertainty (MU)
• ‘A parameter associated with the result of a measurement that characterises the dispersion of the values that could reasonably be attributed to the measurand’
• (international vocabulary of basic & general terms in metrology)
Simple Definition of MU
• Basically – how sure is the lab of the result?
• It is a range containing the ‘true value’ with a stated level of confidence
– eg: Lead in soil has a MU of 10%. We test a soil & report to you 20 mg/kg.
– We are 95% confident that the concentration of Lead is somewhere between 18mg/kg & 22mg/kg
How to Calculate – various ways
• Precision and Bias
• Last resort – professional judgement
Analyte MU %
Alkalinity 21
Chloride 15
Sulfate 17
Nitrate 14
Nitrite 13
TSS 16
pH 3
Aluminium 18
Cobalt 21
Mercury 16
MU continued
• Depends on matrix and PQL
– eg: OC to 0.001ppm = 80%, to 0.1ppm = 15%
• Small uncertainty – reliable
• Large uncertainty – caution may be appropriate
• Biggest contributor to MU is sampling!
Conundrum
• Lab reports 1 mg/L for Lead
• Guideline value is 1mg/L
• Lab MU is 10% (ie: 0.9 – 1.1 mg/L)
• Is your result over the limit?
Our results are only as good as your Sampling.
• If you don’t get the sampling right, the testing may be a waste of money and your interpretations will be flawed.
How much do we actually take?
• 250g soil jar
• 10g PAH
• 5g BTEX
• 3g Metals
• 40g Asbestos
Foundry Soil
Lead – not too bad
0
500
1000
1500
2000
2500
3000
3500
0 10 20 30 40 50 60
mg
/kg
samples
Pb mg/kg
Series1
Copper - OK
0
100
200
300
400
500
600
700
0 10 20 30 40 50 60
mg
/kg
samples
Cu mg/kg
Series1
Chromium – non homogenous
0
50
100
150
200
250
300
0 10 20 30 40 50 60
mg
/kg
sample
Cr mg/kg
Series1
Pb in top 60mg/kg, Pb in bottom <1mg/kg
Not the best
Water - Field Duplicates
Water Field Duplicates
Duplicates? – Apparently Yes!
Acidification of Metals
0
20
40
60
80
100
120
0 1 3 5 7
pp
b in
so
lutio
n
Elapsed Time (hrs)
The Effect of Time on the Co-precipitation of Metals in a Neutralised Solution Containing 10 ppm Iron and 100ppb of Each Analyte.
Zn
Co
Ni
Cu
Cd
Pb
Filter v no filter - Fe Dropped out of solution
Always take a good QC sample
BaP (PAH) Duplicate - <0.1mg/kg top, 5mg/kg bottom
Hg Hotspots – Lab Duplicate was 4 & 40 mg/kg
NEPM Changes
Analyte Container Holding Time Old NEPM
Holding Time NEW NEPM
Cyanide P, PTFE, G 7 days 14 days
Fluoride P, G 7 days 28 days
Metals P (old) P/G (new) 6 months 6 months
Mercury P (also Cr6) P 28 days 28 days (7 days Hex)
VOC (except below) G 14 days 14 days
Vinyl chloride, styrene, 2-chloroethyl vinyl ester
G 14 days 7 days
TPH v TRH
• 2 new methods – TRH and TRH (silica)
• No longer referred to as TPH
• All labs will now extract/analyse/calculate/report the same way
• Advantages of New Fractions
• More info to make reasonable risk assessments
• Gains of New Method
• Standardisation of banding amongst labs = more consistent data
• Tightening of performance requirements
• The Term TRH is equivalent to the historically reported TPH
Banding
Volatile (vTRH) Semi Volatile (svTRH)
Was C6-C9 Was C10-C36
Now C6-C10 Now >C10-C40
Petrol, light fuel, petroleum based solvents
Diesel, other petroleum fuels, mineral oils and petroleum based solvents
Semi Volatile Fractions
• Interferences
• TRH includes any organic compounds that are soluble in the relevant solvent(s) and elute under a linear GC program method conditions.
• Can include vegetable & animal oils, fats, plasticisers and solvents i.e. Biogenic plus any Petrogenic hydrocarbons
• The use of silica gel to adsorb polar compounds may reduce potential false positives from Biogenic material thus yielding a result more reflective of any petroleum contamination (where applicable).
Fractions
>C10 – C16
>C16 – C34
>C34 – C40
What is Silica Gel Cleanup
• After a sample is extracted in solvent the solvent extract is poured through a column containing silica gel (or can be mixed in the extraction vessel directly). The solvent extract runs down through the column slowly, over the surface of the silica gel particles. The silica gel retains the more polar compounds that were co-extracted from the sample, allowing the less polar petroleum based compounds to flow through ready for GC-FID analysis.
• Note, Silica Gel analysis is only applicable to semi-volatile fractions.
Diesel spiked Woodchips - TRH
C10-C14 : 410ppm
C15-C28: 1500ppm
C29-C36 : 600ppm
Diesel spiked Woodchips - TRH – Silica Gel cleaned
C10-C14 : 380ppm
C15-C28 : 910ppm
C29-C36: 140ppm
The last 2 fractions yield a lower result after the silica gel cleanup, emphasizing the importance of determining TRH – Silica Gel where Biogenic material can lead to false positives.
The term ‘TRH-Silica’ is used as the separation of petrogenic and biogenic is not absolute!
Banding – Old v New NEPM
Old TPH Band Reporting
C10-C14: C>9-C14 : 180ppm
C15-C28: C>14-C28 : 280ppm
C29-C36: C>28-C36 : <PQL
New TRH Band Reporting
>C10-C16: 270ppm
>C16-C34: 190ppm
>C34-C40 : <PQL
The banding is now defined specifically in NEPM B3 with respect to certain n-alkane markers and must be adhered to!
F1, F2
In order to compare to HSLs, F1 and F2 are defined as:-
• F1 = C6-C10 less BTEX (as BTEX HSLs characterised)
• F2 = >C10 – C16 less Naphthalene (as Naphthalene HSL characterised)
From NEPM B1
(CCME)
F1, F2 continued
• F2 = >C10 – C16 less Naphthalene
• Napthalene for this subtraction will be taken from the BTEX analysis (due to BTEX generally being run with TRH). Most labs will do this, though NEPM does not say!
• Otherwise, a separate PAH run (and charge) would possibly occur.
• Always subtraction from BTEX run, even if PAH’s are done – keep consistent.
• Napthalene by P&T (BTEX) v’s Napthalene by GC-MS
• Soils – different extraction (methanol v DCM-Acetone), different instrumentation
• Waters – different preservatives, different instrumentation
WA Asbestos
• WA method = 10x more conservative than the Netherlands to account for dryer Australian soils
• WA = 0.001% asbestos in soil for FA (Fibrous Asbestos) & AF (Asbestos Fines)
• However, 0.01% remains the standard LOR for AS4964 method
• The examination of 500ml may improve the likelihood of identifying asbestos
• Any reporting of <0.01% MUST be NON NATA – Further info TBA
WA Asbestos
• A positive result would normally be considered by DOH to exceed the 0.001% w/w investigation criteria applied to fine asbestos material, especially given that a 0.01% LOD usually applies.
• However, a single such exceedance may not necessarily result in the sample source being deemed contaminated.
• A weight of evidence approach should be used by the consultant, auditor and regulator in assessing the significance of an exceedance, which should take account of the history of the site and frequency and occurrence of other positive and negative results.
Schedule B7 – Free Cyanide
• HIL has been derived for Free Cyanide
• However, the measurement of Free CN is difficult
• So, Schedule B3 recommends WAD CN as a conservative measure of Free CN.
Schedule B7 (Table 1A(1) HIL) - Mirex
• Phased out of Australia in 2007
• Prior to 2007, only used in NT for Giant Termite Control in Mango Trees
• Never Detected before in Australian Food (FASANZ 2001)
• No Background concentration data available in Australia
Schedule B7 - (Table 1A(1) HIL) - Toxaphene
• Mainly available 1940’s to 1980’s
• Still used in some parts of Africa and Asia
• Mainly used in Cotton, Grains, Fruits/Veg, Nuts, Cattle
• NEVER USED in AUSTRALIA !
Benzo (a) Pyrene TEQ
• B(1) includes HIL’s for BaP as Toxic Equivalents (TEQ)
• This is the comparison of 8 carcinogenic PAH’s relative to BaP
• Labs will do this calculation for you
Sample Transport
• Old NEPM – Ice or 4 degree refrigerated transport
• New NEPM – Preferably ice bricks or refrigerated container
• ELIG preferred option has always been –
• Cool samples in either fridge or ice
• Then - transport to lab with ice bricks or double-bagged ice (not free flowing ice)
• Free flowing ice can easily melt, and potentially contaminate your samples.
Potential Cross Contamination
Potential Cross Contamination?
Hydrocarbon Contamination?
Cairns to Sydney does need Bubble Wrap!
Floating in Ice Mud
Ice water penetration - contamination
Esky Ice water
esky water
• Al = 200,000 ppb
• As = 35 ppb
• Cd = 7 ppb
• Co = 930 ppb
• Cu = 3700 ppb
• Fe = 600,000 ppb
• Pb = 120 ppb
• Mn = 55,000 ppb
• Ni = 450 ppb
• U = 24 ppb
esky water + sampling rubbish
• Al = 6000 ppb
• Cu = 15 ppb
• Fe = 7500 ppb
• Pb = 40 ppb
• Mn = 60 ppb
• Zn = 80 ppb
• Ba = 120 ppb
• Sn = 20 ppb
• V = 10 ppb
Metals (total) in melted esky ice
Sydney Sydney Country NSW Sydney West NSW
Aluminium (ppb) 1,300 200,000 5,700 22,000 140
Arsenic (ppb) 2 35 2 20 1
Cadmium (ppb) <0.1 7 0.2 0.9 0.1
Chromium (ppb) 1 120 6 44 5
Cobalt (ppb) 5 930 1 28 <1
Iron (ppb) 1,500 600,000 7,500 24,000 380
Lead (ppb) 1 120 35 49 3
Zinc (ppb) 23 660 77 350 31
Manganese (ppb) 130 55,000 56 540 14
Duct Tape Sealed Bottles
Duct Tape Sealed Bottles
• The melted ice water was analysed for VOC’s:
• Toluene = 520 ppb
• (detection limit is 1 ppb)
Red Texta Stained Ice Water (from label ID’s)
Texta Water – VOC Analysis
• Benzene = 20 ppb
• Toluene = 190 ppb
• Ethyl Benzene = 2 ppb
• Xylenes = 4 ppb
• (Detection limit is 1µg/L = 1ppb)
Esky ice with a sheen?
Esky ice with a sheen - results
• Benzene = 2,100ug/L
• Xylenes – 4,300 ug/L
• Napthalene = 240 ug/L
• C10-C14 TRH = 7,000 ug/L
• C15-C28 TRH = 6,600 ug/L
What’s the Solution?
• Cool samples in ice/fridge – then transport with ice bricks
• Use ice, but double bag it. Don’t leave it free flowing.
What the Lab needs from you
• Clearly written and correct COC’s
• (PB won our 2012 $500 prize for consistently good
COC’s). Over 50% of all COC’s have issues
• Correct sampling – right bottles, metals filtered if needed (and ticked)
• Samples packed to avoid breakages
• Samples packed to avoid cross contamination
• Any doubts – just ask the lab. We don’t mind.
Asbestos or Soil?
Well, I guess we do ask for a separate bag!
No Ice Bricks? At least they made the effort!
Started a trend?
Again?
Ice Brick Fail !
Bacon Brick? – Fail. (the note says `sorry about the bacon J’)
As an Industry – lets get rid of Bad Ice
And only use Good Ice
Photo: Tom Raftery