7 th FSCC Interlaboratory Comparison Nathalie Cools Combined Expert Panel Meeting, 9 12 April 2013, Ljubljana, Slovenia

Transcription

1 7 th FSCC Interlaboratory Comparison Nathalie Cools Combined Expert Panel Meeting, 9 12 April 2013, Ljubljana, Slovenia 1

2 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? Recommendations 2

3 General conclusions 7 th 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

4 7 th FSCC RT 2012: Background Originally planned in EC Life+ EnForMon project in th 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 6 th FSCC RT) Agreed at previous FSEPM: 1 sample with CaCO 3 content between 10 20% => sample B CaCO 3 content of 6.3 % 1 mineral topsoil sample with OC of few percentages => sample B OC content of 5.2 %

5 Time schedule Task Informing the participating labs by & ICP Forests website Deadline June, 15 th 2012 Online registration of the participants September,7 th 2012 Distribution of test samples & invoice for registration fee Payment of registration fee September, 14 th 2012 Before data submission Data submission by the labs October - December 2012 Deadline of data submission December 31 st, 2012 First results January 2013 Re-qualification process starts February 2013 Discussion of the results Ljubljana, April 2013 Re-qualification process finishes October 1 st,

6 Response: participating laboratories N of labs N countries Registered by 7 th of September Late registration (1 FI, 1 DE) 2 2 Cancellations before sending of sample (LV, CY) Cancellations after receiving the samples (DE) Payments Results in the evaluation of the median value Compared to previous FSCC RTs: Very lower degree of participation (previously always 50 labs) Results all submitted in time 1 6

7 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

8 Financial overview Income Registration fees (30 * 650 euro) 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 * ) 2438 Balance -908 Conclusions: We needed registration fees of 32 lab to cover costs but only 30participated 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

9 Sample Matrix Location Textur e Samples Depth/ horizon Tree species Soil type A Min. Germany SiL 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 E C 9

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 ): Sampl e Mean St.dev. Min Max CV (%) % within subsampl e % between subsample s A B C D E

11 Dealing with values < LOQ Important for exchangeable elements, CaCO 3, Cd, Hg, If value < LOQ lab => labs report < LOQ lab The LOQ lab was checked against: max. allowable LOQ (LOQ max ) If LOQ lab > LOQ max => reject results If LOQ lab < LOQ max => result accepted if LOQ lab within tolerable range of median value If median value LOQ gen the variable could not be quantified reliably no tolerable range could be calculated results were accepted 11

12 N labs with results in 7 th FSCC RT Variable N failed Clay 26 1 Sand 26 3 Silt 26 2 ph-cacl ph-h 2 O 26 1 CaCO OC, TotN 29 3 Exchangeable elements Acidity, Na 29 5 Al 29 2 Ca Fe 29 2 K 29 3 Mg 30 7 Mn 29 0 Free H Total elements Al, Mg 8 0 Ca 8 2 Fe 9 0 K, Mn, Na 9 1 If response is less, usually optional variables. Variable N failed Aqua regia extractable macronutrients (mandatory in mineral soil) P 26 2 Ca 28 1 K 27 4 Mg 28 4 Mn 28 2 Heavy metals (mandatory in min and org samples) Cu 28 6 Pb 26 1 Cd 26 4 Zn 28 3 Metals - micronutrients (optional) Al 24 1 Fe 25 3 Cr 24 3 Ni 25 1 S 22 2 Hg 13 1 Na 22 3 Acid oxalate extractable Al and Fe Al 23 2 Fe 24 4 Of the mandatory variables, acid oxalate extractable Fe and Al is still the least popular 12

13 N labs with successful/failed results in 7 th FSCC RT 13

14 N labs with successful/failed results in 7 th FSCC RT M (mineral) M (mineral and organic) Optional Aqua regia extractable Reactive 14

15 Number of successful/failed variables for each lab 15

16 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 CaCO 3 : more failures 16

17 ph-cacl 2 Quantifiable in all samples Range: +/-5 % Sample reported successful % labs failed CV (%) A B C D E Conclusions 1 lab did not measure ph-cacl 2 on both organic samples (although M) 1 lab failed on 3 of 5 samples, so has to requalify for ph-cacl 2 Note: Sample E: ph-cacl 2 = 5.5 & CaCO 3 analyses necessary >

18 ph-h 2 O Quantifiable in all samples Range: +/-5 % Sample reported successful % labs failed CV (%) A B C D E Optional parameter: not reported by 4 6 labs 1 lab failed on 4 out of 5 samples and has to requalify 18

19 Carbonates Quantifiable in sample B and E (LOQ gen = 3 g.kg -1 ) 70% labs successful on 1 sample range: CaCO 3 Sampl e Conc. low limit reported Conc. high limit > successful LOQ > 5 % labs failed A B C D Conclusions: E labs did not conduct mandatory analysis and 16did not analyse the org. sample with ph-cacl 2 = labs with LOQ above LOQ max 5 labs between 5 15% recovery: reported in % instead of g.kg -1? Other conversion errors e.g. C-CaCO 3? 19

20 Particle size distribution Conc. low limit Conc. high limit Silt > Sand > Clay > Max. LOQ = 1 %, all LOQs above reported successful % labs failed CV (%) A Silt B Silt C Silt A Sand B Sand C Sand A Clay B Clay C Clay

21 Methodological differences in texture analysis Removal of compounds Determination 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 21

22 Organic carbon Quantifiable in all samples N o labs LOQ > LOQ max = 2 range: Sampl e Conc. low limit reported Conc. high limit OC > successful % labs failed CV (%) A B C D E 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 22

23 Total N All quantifiable; 2 in low range and 3 in high range ranges: Tol rang e Sampl e Conc. low limit reported Conc. high limit N > successful More failures for organic compared to mineral samples % labs failed CV (%) A B C D E Tolerable limit for high conc. range (so for the organic samples) is ambitious but should be feasible 23

24 RT7 not better than RT6 Exchangeable elements Exch. Mn: 3 of 5 samples LOQ general so no reliable median value could be calculated 24

25 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

26 Exchangeable acidity Present in quantifiable amounts in 4 samples (LOQ = 0.1 cmol (+).kg -1 ) 83 % labs successful on at least 3 of 5 samples range Acidit Sampl y e Conc. low Limit (%) reported Conc. high successful Limit (%) > LOQ > 0.25 % labs failed CV (%) A B C D E Conclusions: Most labs face problems in forest floor sample High CV in calcareous samples B and E 26

27 Free H + sample B close to LOQ =0.1 cmol (+).kg % labs successful on at least 3 of 5 samples range +/-100 % Sample Conclusions reported successful 3 5 labs did not report free H + < LOQ LOQ > 0.25 % labs failed CV (%) A B C D E Report of conc. < LOQ: provide your LOQ in stead of reporting nothing or 0 Extremely high CVs! 27

28 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 BaCl 2 extraction Determination: Either potentiometric titration (ISO 14254, 1994 though single extraction) Either German method by calculation (König et al. 2005) Not accepted! Not accepted! The same? 28 Or could it also refer to the titration?

29 Exchangeable Al Quantifiable in 3 of 5 samples 93 % labs successful on at least 3 of 5 samples range Samp le Conc. low Conclusions: limit reported Conc. high limit Al > successful below LOQ LOQ > 0.1 % labs failed CV (%) A B C D E 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

30 Exchangeable Fe Not quantifiable in 2 samples (LOQ = 0.02 cmol (+).kg -1 ) 93 % labs successful on at least 3 of 5 samples rang e Sampl e Conc. low limit reported Conc. high limit Fe > successful < LOQ LOQ > 0.1 Extremely large CV in calcareous sample and forest floor % labs failed CV (%) A B C D E

31 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 rang e Sampl e Conc. low limit reported Conc. high limit Mn > successful below LOQ % labs failed CV (%) A B C D E 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 places 31

32 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 rang e Sampl e Conc. low limit reported Conc. high limit Ca > successful < LOQ High number of labs excluded in organic samples (high CVs) ranges too narrow for the organic matrix? % labs failed CV (%) A B C D E 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

33 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 rang e Sampl e Conc. low limit reported Conc. high limit K > successfu l < LOQ High number of labs excluded in organic samples (CV = %) ranges too narrow for organic samples? LOQ > 0.1 % labs failed CV (%) A B C D E 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

34 Exchangeable Mg Quantifiable in all samples Close to LOQ = 0.03 in sample A 77 % labs successful (on at least 3 of 5 samples) rang e Sample Conc. low limit reported Conc. high limit Mg > successful < LOQ LOQ > 0.1 High number of labs excluded in organic samples (CV = %) ranges too narrow for high range in organic samples % labs failed CV (%) A B C D E 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

35 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 Range: +/-80 % Sampl e reported successful below LOQ LOQ > 0.1 % labs failed CV (%) A B C D E 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

36 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 LOQ lab > LOQ gen 36

37 Aqua regia extractable elements Most elements: improvement compared to RT6 K, Mg and Cd: results are worse compared to RT6 Mandatory in organic Optional Mandatory 37

38 Aqua regia extractable macronutrients Concentration (g.kg -1 ) 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) A B C E D 38

39 Aqua regia extractable heavy metals Cu, Cd, Pb, Zn Results are of better quality than RT6 Except Cd: 3 sample below LOQ gen (0.5 ppm) 2 samples slightly above LOQ gen So due to nature of samples Sample A: highest CV of all aqua regia extractable elements A B C D E 39

40 Aqua regia optional variables A B C D E 40

41 Total and reactive elements Total elements: difficult to compare with previous ring tests due to low number of labs that reported results 41

42 Reactive Al & Fe Quantifiable in all samples Conc. low limit Conc. high limit Al > Fe Sampl e reported successful LOQ > 100 % labs failed CV (%) Al Fe Al Fe Al Fe Al Fe Al Fe A B C D E lab failed for all samples (both Al & Fe) Many labs too high recovery in sample B (calcareous) 42

43 Discussion: Improvements made? Distribution of labs according to percentage of failed variables in 2009 vs 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 % 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 43

44 Evolution of CVs between Time FSCC Interlaboratory Comparison Evolution of coefficients of variation (%) 44

45 Requalification Requalification between Feb and Sept 2013 In total 113 failed lab-parameter combinations By only received answers for 10 failed combinations Lab ID N failed variables in 7 th FSCC ring test N variables in questionnaire N variables requalified S S Asked for additional sample material S F F12 0 By feedback on 2 variables 45

46 Recommendations to improve results Carbonates Report in correct units g.kg -1 Make sure carbonates are reported (not the Carbon)! Analyse carbonates when ph-cacl 2 > 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 BaCl 2 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

47 Recommendations to improve results Aqua regia (HCl/HNO 3 ) 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. FSCCcan 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

48 How to report results of FSCC Interlaboratory comparison in LQA form? Part of LQA form contains information from the qualification report Column Description Format Ref_Ta Item # b 74 Participated at Ring Test (yes = 1, no = 0) I 1 (180) ICP Forests Ring Test Number C 3 (180) ID of laboratory (e.g. H45, B78, etc.) C 3 (180) Percentage [%] of the results of the ring I 3 (180) tests within tolerable limits for each ring test NC1 88 Requalification information (yes = 1, no = 0) I 1 (180) Percentage [%] of the results of the ring tests within tolerable limits for each ring test in requalification I 3 (180) 48

49 Folie 48 NC1 Should become an integer "I1" COOLS, Nathalie;