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7th FSCC Interlaboratory Comparison
2012 - 2013
Nathalie Cools
Combined Expert Panel Meeting,
9 – 12 April 2013, Ljubljana, Slovenia
Presentation outline• Main conclusions
• Introduction• Background
• Time schedule
• Participation degree
• Financial overview
• Materials and methods• Samples and homogeneity test
• Evaluation by the median value and tolerable limits
• Dealing with values below LOQ
• Results• Overview successes/failures by i) variables ii) labs
• Comparison with RT6
• Results of selected set of variables
• Discussion• Improvements made?
• What are the problem variables?
• Lessons learned?
• Potential for improvement?
• Recommendations2
General conclusions 7th FSCC ring test
• RT7(2012) only 60% of participation degree compared to the past
because of budgetary reasons
• To cover costs at least 32 labs are needed. RT7 only 30 labs.
• The comparability of the ring test results did not improve compared to
RT6.
• A number of problems which were already identified in the past persist:
• A number of labs that do not use reference methods
• Too high LOQ values
• Reporting of 0 values
• Labs with poor results:
• New labs to the interlaboratory comparison programme
• BUT also labs that already participated in many FSCC ring tests
• Or labs that participated in helping programme of WG on QAQC
in the labs
3
Background
• 7th FSCC RT 2012:
Originally planned in EC Life+ EnForMon project in 2012
8th FSCC RT foreseen in EnForMon in 2015
EnForMon not granted so RT funded by registration fees of labs (650
€/lab)
Evaluation method: based on the median value (cfr. foliar & water ring
tests) and its tolerable ranges (same as 6th FSCC RT)
• Agreed at previous FSEPM:
1 sample with CaCO3 content between 10 – 20%
=> sample B CaCO3 content of 6.3 %
1 mineral topsoil sample with OC of few percentages
=> sample B OC content of 5.2 %
Time schedule
5
Task Deadline
Informing the participating labs by email & ICP Forests website
June, 15th 2012
Online registration of the participants September,7th 2012
Distribution of test samples & invoice for registration fee
September, 14th 2012
Payment of registration fee Before data submission
Data submission by the labs October - December 2012
Deadline of data submission December 31st , 2012
First results January 2013
Re-qualification process starts February 2013
Discussion of the results Ljubljana, April 2013Re-qualification process finishes October 1st, 2013
6
Response: participating laboratories
N° of labs
N°countries
Registered by 7th of September 2012 31 19
Late registration (1 FI, 1 DE) 2 2
Cancellations before sending of sample (LV, CY)
2 2
Cancellations after receiving the samples (DE)
1
Payments 30
Results in the evaluation of the median value 30 17Compared to previous FSCC RTs:
•Very lower degree of participation (previously always ≥ 50 labs)
•Results all submitted in time
Reasons for no participation
Labs did not participate because:
•Restricted lab budget (Norway, Cyprus, Portugal)•No national budget for monitoring (Latvia, Hungarian Forest Research Institute)•Lack of co-funding at international level (Hungary)•No possibility to apply the required reference methods (Croatia). If soil samples are to be analysed, it will be contracted to other labs (Greece).•One lab cancelled because of movement/reorganisation of the lab (Germany).•No sufficient qualified staff to conduct analysis (Turkey)
7
Financial overview
Conclusions:
•We needed registration fees of 32 lab to cover costs but only 30 participated
•Personnel costs covers preparation, evaluation and communication with the labs
•No personnel cost included for requalification, preparation of presentations, no travel costs to meetings
8
IncomeRegistration fees (30 * 650 euro) 19500 €
Expenses
Homogeneity tests 9100 €
Web interface & evaluation of median by BFW, Austria
1900 €
Packing material for the samples 330 €
Distribution of the samples by air mail 1200 €
Personnel cost of scientist (17 days * 320 €) 5440 €
Personnel cost of technician (10 days * 243.8 €) 2438 €
Balance -908€
9
Samples
Sample Matrix Location Texture
Depth/ horizon
Tree species Soil type
A Min. Germany SiL 10 – 30 cm Spruce Podsolige Parabraunerde‘Podzolic Luvisol’
B Min. Austria SiC Calcareous
C Min. Belgium S Ap Scots pine Albic Hypoluvic Arenosol
D Peat Ireland Peat
E Forest floor
Belgium OL & OF Oak Dredged land-fill
CE
10
Homogeneity tests
• Of each ring test sample (A, B, C, D and E)
• 8 subsamples (1 subsamples = 300g)
• 4 measurements on each subsamples
• Aqua regia extractable elements
• Total N, Total C (either TOC or LOI)
• Variation between subsamples and within subsamples was
compared
• Total Modified N (g kg-1):
Sample
MeanSt.dev
.Min Max
CV (%)
% within subsampl
e
% between subsample
s
A 0.95 0.02 0.93 0.99 4.4 99 1
B 3.66 0.08 3.57 3.74 4.6 100 0
C 0.90 0.07 0.79 0.98 10.7 67 33
D 10.4 0.26 10.1 10.8 3.3 58 42
E 14.1 0.24 13.8 14.5 3.8 100 0
11
Dealing with values < LOQ
• Important for exchangeable elements, CaCO3, Cd, Hg,…
• If value < LOQlab => labs report “< LOQlab”
• The LOQlab was checked against:
• max. allowable LOQ (LOQmax)
• If LOQlab > LOQmax => reject results
• If LOQlab < LOQmax => result accepted if LOQlab within tolerable
range of median value
• If median value ≤ LOQgen
⇒ the variable could not be quantified reliably
⇒ no tolerable range could be calculated
⇒ results were accepted
N° labs with results in 7th FSCC RT
12
⇒ If response is less, usually optional variables.⇒ Of the mandatory variables, acid oxalate extractable Fe and Al is still the least popular.
Variable N° labs N° failedClay 26 1Sand 26 3Silt 26 2
pH-CaCl2 30 1
pH-H2O 26 1
CaCO3 27 8OC, TotN 29 3Exchangeable elementsAcidity, Na 29 5Al 29 2Ca 30 10Fe 29 2K 29 3Mg 30 7Mn 29 0Free H+ 27 5Total elementsAl, Mg 8 0Ca 8 2Fe 9 0K, Mn, Na 9 1
Variable N° labs N°failedAqua regia extractablemacronutrients (mandatory in mineral soil)P 26 2Ca 28 1K 27 4Mg 28 4Mn 28 2Heavy metals (mandatory in min and org samples)Cu 28 6Pb 26 1Cd 26 4Zn 28 3Metals - micronutrients (optional)Al 24 1Fe 25 3Cr 24 3Ni 25 1S 22 2Hg 13 1Na 22 3Acid oxalate extractable Al and FeAl 23 2Fe 24 4
N° labs with successful/failed results in 7th FSCC RT
13
14
N° labs with successful/failed results in 7th FSCC RT
M (mineral) M (mineral and organic) Optional Aqua regia extractable Reactive
Number of successful/failed variables for each lab
15
Results RT7 2012
! Evaluation method changed (General cleaned mean compared to Median)
•Tolerable limits remained the same
•pH, OC, Tot N: +/- similar
•Clay: lower % of labs excluded
•Sand and silt: +/- similar
•CaCO3: more failures 16
pH-CaCl2
• Quantifiable in all samples
• Tol. Range: +/- 5 %
Conclusions
•1 lab did not measure pH-CaCl2 on both organic samples (although M)
•1 lab failed on 3 of 5 samples, so has to requalify for pH-CaCl2•Note: Sample E: pH-CaCl2= 5.5 & CaCO3 analyses necessary > 5.5 17
Sample N° labs reported N° labs successful
% labs failed CV (%)
A 30 29 3.3 1.7B 30 28 6.7 1.4C 30 28 6.7 2.5D 29 28 3.5 1.3E 29 29 0 1.6
pH-H2O
Quantifiable in all samples
Tol. Range: +/- 5 %
Optional parameter: not reported by 4 – 6 labs
1 lab failed on 4 out of 5 samples and has to requalify
18
Sample N° labs reported N° labs successful
% labs failed CV (%)
A 26 24 7.7 1.9B 26 22 15.4 2.9C 26 25 3.8 2.4D 25 21 16.0 3.6E 24 23 4.2 2.1
Carbonates• Quantifiable in sample B and E
(LOQgen = 3 g.kg-1)
• 70% labs successful on ≥ 1 sample
• Tol. range:
19
Sample
N° labs reported
N° labs successful
N° labs LOQ > 5
% labs failed
A 7 6 1 15
B 27 14 1 48
C 7 6 1 15
D 7 6 1 15
E 14 12 2 15Conclusions:
• 3 labs did not conduct mandatory analysis and 16 did not analyse the
org. sample with pH-CaCl2 = 5.5
• 2 labs with LOQ above LOQmax
• 5 labs between 5 – 15 % recovery: reported in % instead of g.kg-1?
• Other conversion errors e.g. C-CaCO3?
Conc. low
Tol. limit
Conc. high
Tol. limit
CaCO3
≤ 50 130 > 50 40
Particle size distribution
Conc. low
Tol. limit
Conc. high
Tol. limit
Silt ≤ 10.0 50 > 10.0 35
Sand ≤ 20.0 45 > 20.0 30
Clay ≤ 30.0 45 > 30.0 25
20
Max. LOQ = 1 %, all LOQs above
N° labs reported
N° labs successful
% labs failed CV (%)
A Silt 26 25 3.8 10.0B Silt 26 21 19.2 26.6C Silt 26 23 11.5 29.7A Sand 26 22 15.4 11.9B Sand 26 22 15.4 16.1C Sand 26 26 0 3.3A Clay 26 23 11.5 18.7B Clay 26 23 11.5 31.1C Clay 26 18 30.8 40.9
Methodological differences in texture analysis
Removal of compounds Determination
21
10 labs did not remove the OC/carbonates
3 labs were obviously not using the reference method
4 labs might have used hydrometer or pipette (gravimetry)
4 labs did not report the detection method
Organic carbon
22
Sample
N° labs reported
N° labs successful
% labs failed CV (%)
A 29 27 6.9 7.6
B 29 22 24 12.0
C 29 21 28 15.2
D 29 25 14 8.0
E 29 27 6.9 6.5
Conc. low
Tol. limit
Conc. high
Tol. limit
OC ≤ 25 20 > 25 15
Sample A and C in low concentration range but more failures in Sample C
=> Due to sandy nature of sample C ‘juxtaposition’
Though also high number of failures on sample B
One lab failed on 4 of 5 samples => requalification needed
• Quantifiable in all samples
• No labs LOQ > LOQmax = 2
• Tol. range:
Total N
• All quantifiable; 2 in low range
and 3 in high range
• Tol. ranges:
• More failures for organic compared to mineral samples
⇒Tolerable limit for high conc. range (so for the organic samples) is
ambitious but should be feasible23
Sample
N° labs reported
N° labs successful
% labs failed CV (%)
A 30 28 6.7 13.8
B 30 26 13.3 6.2
C 30 28 6.7 17.7
D 30 24 20 9.1
E 30 26 13.3 5.2
Tol range
Conc. low
Tol. limit
Conc. high
Tol. limit
N ≤ 1.5 30 > 1.5 10
Exchangeable elements
• RT7 not better than RT6
• Exch. Mn: 3 of 5 samples ≤ LOQgeneral so no reliable median value could be
calculated
24
Exchangeable cations
• Based on pH values, Carbonate content, texture, matrix
� Expect that exchangeable acidity, free H+ and acid cations will be
low in sample B = calcareous sample
� But what do we expect in Sample E = forest floor sample?
• Are we able to measure these characteristics according to
our needs?
• Is what we measure ecological relevant and necessary?
25
Exchangeable acidity
26
Present in quantifiable amounts in 4
samples (LOQ = 0.1 cmol(+).kg-1)
83 % labs successful on at least 3 of
5 samples
Sample
N° labs reported
N° labs successful
N° labs LOQ > 0.25
% labs failed
CV (%)
A 29 26 10 12
B 27 21 1 22 95
C 29 25 16 25
D 29 18 38 25
E 28 10 1 64 87
Conclusions: Conclusions: Conclusions: Conclusions:
•Most labs face problems in forest floor sample
•High CV in calcareous samples B and E
Tol. range
Conc. low
Tol. Limit (%)
Conc. high
Tol. Limit (%)
Acidity
≤ 1.0 90 > 1.0 35
Free H+
• sample B close to LOQ =0.1 cmol(+).kg-1
• 81 % labs successful on at least 3 of 5
samples
• Tol. range +/- 100 %
Conclusions
•3 – 5 labs did not report free H+
•Report of conc. < LOQ: provide your LOQ in stead of reporting nothing or ‘0’
•Extremely high CVs! 27
Sample N° labs reported
N° labs successful
N° labs < LOQ
N° labs LOQ > 0.25
% labs failed
CV (%)
A 27 20 2 1 26 153
B 21 15 11 1 29 122
C 27 23 15 55
D 27 22 19 76
E 25 21 16 97
Reported methods for Exchangeable Acidity
and free H+ in RT7• 29 labs reported exchangeable acidity and 27 Free H+
• Unclear reporting of methods. It should be:
• Pretreatment = single BaCl2 extraction
• Determination:
• Either potentiometric titration (ISO 14254, 1994 though single extraction)
• Either German method by ‘calculation’ (König et al. 2005)
28
Not accepted! Not accepted!The same?
Or could it also refer to the titration?
Exchangeable AlQuantifiable in 3 of 5 samples
93 % labs successful on at least
3 of 5 samples
Conclusions:
•Report of conc. < LOQ: provide your LOQ in stead of reporting nothing or 0
values
•Very high CV in calcareous sample and forest floor sample: close to LOQ 29
Sample
N° labs reported
N° labs successful
N° labs below LOQ
N° labs LOQ > 0.1
% labs failed
CV (%)
A 29 27 2 7.0 20.6
B 27 22 11 1 18.5 93.9
C 29 27 7.0 12.2
D 29 27 3 1 7.0 38.9
E 28 20 12 1 29 109.6
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
Al ≤ 0.5 105 > 0.5 30
Exchangeable Fe• Not quantifiable in 2 samples (LOQ =
0.02 cmol(+).kg-1)
• 93 % labs successful on at least 3 of
5 samples
• Extremely large CV in calcareous sample and forest floor
30
Sample
N° labs reported
N° labs successful
N° labs < LOQ
N° labs LOQ >
0.1
% labs failed
CV (%)
A 29 26 2 10 29
B 26 25 15 9.6 151
C 29 27 7 21
D 29 20 1 31 45
E 28 24 13 1 14 122
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
Fe ≤ 0.02 140 > 0.02 50
Exchangeable Mn• Not quantifiable in mineral samples
when reporting up to two decimals (LOQ = 0.02 cmol(+).kg-1)
• 100 % labs successful on at least 3 of 5 samples
Conclusions:Conclusions:Conclusions:Conclusions:
•High CV in mineral samples (close to or below LOQ)
•High number of failures in organic samples
•Additional problem: only requested to report up to two decimals
•Recommendation: increase reporting requirement to 3 decimal places31
Sample
N° labs reported
N° labs successful
N° labs below LOQ
% labs failed
CV (%)
A 29 29 9 0 44
B 29 29 7 0 83
C 27 27 12 0 92
D 29 22 2 24 30
E 29 20 2 31 33
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
Mn ≤ 0.03 45 > 0.03 25
Exchangeable Ca• Quantifiable in all samples; close to LOQ
= 0.03 cmol(+).kg-1 in sample A
• 67 % labs successful on at least 3 of 5
samples
• High number of labs excluded in organic samples (high CVs)
• Tol. ranges too narrow for the organic matrix?
• Method suitable for organic samples? E.g. recommended sample weight
now equal for min. as for org. samples (2.5 g). In literature only 0.5 g for org.32
Sample
N° labs reported
N° labs successful
N° labs < LOQ
% labs failed
CV (%)
A 30 22 4 27 46
B 30 22 27 29
C 30 27 10 30
D 30 16 47 35
E 30 16 47 41
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
Ca ≤ 1.5 65 > 1.5 20
Exchangeable K• Quantifiable in all samples
• Close to LOQ = 0.03 in sample A & C
• 90 % labs successful on at least 3 of 5
samples
• High number of labs excluded in organic samples (CV = 31 - 35 %)
• Tol. ranges too narrow for organic samples?
• Method suitable for organic samples? E.g. recommended sample weight
now equal for min. as for org. samples (2.5 g). In literature only 0.5 g for org.33
Sample
N° labs reported
N° labs successfu
l
N° labs < LOQ
N° labs LOQ >
0.1
% labs failed
CV (%)
A 29 25 4 1 14 23
B 29 27 7 13
C 29 26 4 1 10 13
D 29 20 1 31 31
E 29 23 21 35
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
K ≤ 0.10 45 > 0.10 30
Exchangeable Mg• Quantifiable in all samples
• Close to LOQ = 0.03 in sample A
• 77 % labs successful (on at least 3 of 5 samples)
• High number of labs excluded in organic samples (CV = 30 – 31 %)
• Tol. ranges too narrow for high range in organic samples
• Method suitable for organic samples? E.g. recommended sample weight
now equal for min. as for org. samples (2.5 g). In literature only 0.5 g for org.34
Sample N° labs reported
N° labs successful
N° labs < LOQ
N° labs LOQ > 0.1
% labs failed
CV (%)
A 30 23 3 1 23 32
B 30 24 20 11
C 30 27 10 20
D 30 20 33 31
E 30 20 33 30
Tol. range
Conc. low
Tol. limit
Conc. high
Tol. limit
Mg ≤ 0.25 50 > 0.25 20
Exchangeable Na
• Quantifiable in Org. sample but close or ≤ LOQ = 0.03 in min. samples
• 83 % labs successful on at least 3 of 5 samples
• Tol. Range: +/- 80 %
Conclusions:
•CVs remain all high
•1 lab with too high LOQ for both organic and mineral samples
•Other labs failed because of too high recovery (> 200 %) 35
Sample
N° labs reported
N° labs successful
N° labs below LOQ
N° labs LOQ > 0.1
% labs failed
CV (%)
A 29 23 5 1 21 52.4
B 29 24 3 1 17 47.6
C 29 24 4 1 17 48.5
D 29 27 1 1 6.9 31.4
E 29 25 1 1 14 36.9
Exchangeable basic cations Ca, Mg, K and Na
• Quantifiable in all samples though Na close to LOQ in
samples A and C
• CV’s range from 13 till 52% in order K < Mg < Ca < Na
• CV’s (except for Na) higher in organic samples compared to
mineral
• %of failed labs (except for Na) higher in organic sample
compared to mineral
• Tolerable limits (20% for K and Mg and 30% for Ca) might
be too severe for the high concentration ranges in the
organic samples
• 1 lab reported LOQlab > LOQgen
36
Aqua regia extractable elements• Most elements: improvement compared to RT6
• K, Mg and Cd: results are worse compared to RT6
37Mandatory in organic MandatoryOptional
Aqua regia extractable macronutrients
• Sample C: poor sandy soil
with few nutrients but still
above LOQ
• Often higher CVs when
concentration was low
• Phosphorus: 6 labs failed
on peat sample (D)
38A B C D E
Con
cent
ratio
n (g
.kg-
1 )
Aqua regia extractable heavy metals Cu, Cd, Pb, Zn
• Results are of better quality than RT6
• Except Cd:
• 3 sample below LOQgen (0.5 ppm)
• 2 samples slightly above LOQgen
• So due to nature of samples
• Sample A: highest CV of all aqua regia extractable elements
39
A B C D E
Aqua regia optional variables
40
A B C DE
Total and reactive elements
• Total elements: difficult to compare with previous ring tests due to low
number of labs that reported results
41
Reactive Al & Fe
Quantifiable in all samples
• 1 lab failed for all samples (both Al & Fe)
• Many labs too high recovery in sample B (calcareous) 42
Conc. low
Tol. limit
Conc. high
Tol. limit
Al ≤ 750 30 > 750 15
Fe ≤ 1000 30 1000 15
Sample
N° labs reported
N° labs successful
N° labs LOQ >
100
% labs failed
CV (%)
Al Fe Al Fe Al Fe Al Fe Al Fe
A 22 23 20 20 9.1 15 6.3 9.7
B 23 24 15 13 35 46 15 34
C 23 24 19 19 17 21 12 10
D 18 19 17 16 5.6 16 9.8 8.9
E 18 19 16 16 1 11 16 11 9.9
Discussion: Improvements made?
43
• In RT7 there are less ‘successful’ labs (no failed variables) compared to RT6
• % of labs with ≤ 10 % failed variables and classes > 20% increased and % labs
between 10 – 20 % decreased
• Overall 11.4 % of the lab/variable combinations failed in RT7 compared to
11.2% in RT6
• So no improvement compared to previous ring test
Distribution of labs according to percentage of failed variables in 2009 vs. 2012
Evolution of CVs between 1993 - 2012
0 100 200 300 400
Evolution of coefficients of variation (%)
2
3
4
5
6
7
FS
CC
Inte
rlabo
rato
ry C
ompa
rison
44
Tim
e
Requalification
• Requalification between Feb and Sept 2013
• In total 113 failed lab-parameter combinations
• By 05-04-2013 only received answers for 10 failed combinations
45
Lab ID N° failed variables in 7 th FSCC ring
test
N° variables in questionnaire
N° variables requalified
S04 2 3 2
S08 4 4 Asked for additional sample material
S13 1 4 1
F17 3 3 3
F12 0 By email feedback on 2 variables
Recommendations to improve results• Carbonates
• Report in correct units g.kg-1
• Make sure carbonates are reported (not the Carbon)!
• Analyse carbonates when pH-CaCl2 > 5.5
• Otherwise report < LOQ (but never 0 values)
• If not analysed: leave data field empty
• Particle size distribution
• Use reference method = pipette
• Do the pretreatment properly: remove OC, carbonates, salts
• Correct for inorganic carbon in calcareous samples
• Exchangeable elements
• Use single BaCl2 extraction
• Can the method be improved, especially in organic samples?
e.g. lower sample weight in organic samples (0.5 g in stead of 2.5 g)
• Do not report Free H+, exch. Acidity, acid exch. cations (Al, Fe, Mn) on calcareous samples (report < LOQ value)
• Organic carbon in non-homogeneous natural samples (e.g. sandy Sample C)
• Increase homogeneity by further grinding
• Increase sample weight if instrument allows
• Increase number of replicates to obtain more reliable estimate
46
Recommendations to improve results
• Aqua regia (HCl/HNO3) extractable elements:
• Still some labs used different extracts
• Reference = reflux no microwave digestion
• Labs with too high LOQ need to look for reasons for this high LOQ to lower it.
• Please take care of reporting the applied methods properly. FSCC can help by providing the correct codes for the reference methods described in the manual.
• FSCC is aware that success/failure or progress/poor results can be due to the nature of the sample. In this regard, a ring tests with less samples is not an option.
• One lab recommended to provide more sample material.
• For sake of comparability, FSCC prefers not to changes the tolerable limits for the moment. Further we do not see the need as % of failed labs did not improve.
• The exchangeable Mn needs to be reported with 3 decimals (cmol+.kg-1) in order calculate reliable median value
47
How to report results of FSCC Interlaboratory
comparison in LQA form?
Column Description Format Ref_Tab
Item #
74 Participated at Ring Test (yes = 1, no = 0) I 1 (180)76 – 78 ICP Forests Ring Test Number C 3 (180)80 – 82 ID of laboratory (e.g. H45, B78, etc.) C 3 (180)84 – 86 Percentage [%] of the results of the ring
tests within tolerable limits for each ring testI 3 (180)
88 Requalification information (yes = 1, no = 0) I 1 (180)90 – 92 Percentage [%] of the results of the ring
tests within tolerable limits for each ring test in requalification
I 3 (180)
Part of LQA form contains information from the qualification report
48
NC1
Folie 48
NC1 Should become an integer "I1"COOLS, Nathalie; 08.04.2013
