EURL-HM-23 Proficiency Test Report : determination of total As, Cd, Pb, Hg and inorganic As in palm kernel expeller.
Date: 2016-12-21
Institutions: Joint Research Centre
Subjects: EU research policy, cadmium, directive (EU), lead, mercury, palm nut, research method, research report, semi-metal, testing, vegetable oil

EURL-HM-23 Proficiency Test 
Report 

Determination of total As, Cd, Pb, Hg, and 
inorganic As in palm kernel expeller 

Peter Dehouck, Ioannis Fiamegkos, Hakan 
Emteborg, Jean Charoud-Got, James Snell,  
Aneta Cizek-Stroh and Piotr Robouch 

2016 

EUR 28282 EN 

 
 
 
 
This publication is a Technical report by the Joint Research Centre (JRC), the European Commission’s science 
and knowledge service. It aims to provide evidence-based scientific support to the European policymaking 
process. The scientific output expressed does not imply a policy position of the European Commission. Neither 
the European Commission nor any person acting on behalf of the Commission is responsible for the use that 
might be made of this publication. 

Contact information  
Name: Piotr Robouch 
Address: Retieseweg 111 – 2440 Geel, Belgium 
Email: piotr.robouch@ec.europa.eu  

JRC Science Hub 
https://ec.europa.eu/jrc 

JRC103688 

EUR 28282 EN 

PDF 

ISBN 978-92-79-64421-4 

ISSN 1831-9424 

doi:10.2787/370477 

Luxembourg: Publications Office of the European Union, 2016 

© European Union, 2016 

The reuse of the document is authorised, provided the source is acknowledged and the original meaning or 
message of the texts are not distorted. The European Commission shall not be held liable for any consequences 
stemming from the reuse. 

How to cite: Pieter Dehouck, Ioannis Fiamegkos, Hakan Emteborg, Jean Charoud-Got, Jams Snell,  Aneta Cizek-
Stroh and Piotr Robouch; "EURL-HM-23 Proficiency Test Report", EUR 28282 EN, doi:10.2787/370477 

All images © European Union 2016, except:  
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EURL-HM-23 Proficiency test report  

Determination of total As, Cd, Pb, Hg 
and inorganic As in palm kernel expeller 

Pieter Dehouck, Ioannis Fiamegkos, Hakan Emteborg,  
Jean Charoud-Got, James Snell, Aneta Cizek-Stroh and  
Piotr Robouch  

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table of contents 

Executive summary ............................................................................................... 1 
Introduction .................................................................................................... 2 
1 
2  Scope............................................................................................................. 2 
3  Set up of the exercise ...................................................................................... 2 
3.1  Time frame ............................................................................................... 2 
3.2  Confidentiality ........................................................................................... 2 
3.3  Distribution ............................................................................................... 3 
Instructions to participants .......................................................................... 3 
3.4 
4  Test item ........................................................................................................ 3 
4.1  Preparation ............................................................................................... 3 
4.2  Homogeneity and stability ........................................................................... 4 
5  Assigned values and corresponding uncertainties ................................................. 4 
5.1  Assigned values ......................................................................................... 4 
5.2  Associated uncertainties .............................................................................. 6 
5.3  Standard deviation of the proficiency test assessment, σpt ............................... 7 
6  Evaluation of results ........................................................................................ 7 
6.1  Scores and evaluation criteria ...................................................................... 7 
6.2  General observations .................................................................................. 9 
Laboratory results and scorings ................................................................... 9 
6.3 
6.3.1  Performances ....................................................................................... 9 
6.3.2  Uncertainties...................................................................................... 10 
6.3.3  Compliance assessment ...................................................................... 11 
6.3.4  Additional information from the questionnaire ........................................ 12 
7  Conclusion .................................................................................................... 13 
Acknowledgements .............................................................................................. 14 
Annexes ............................................................................................................. 17 
Annex 1: List of abbreviations ............................................................................... 18 
Annex 2: JRC web announcement ......................................................................... 19 
Annex 3: Invitation letter to NRLs ......................................................................... 20 
Annex 4: Test item accompanying letter ................................................................ 21 
Annex 5: Confirmation of receipt form ................................................................... 22 
Annex 6: Questionnaire ....................................................................................... 23 
Annex 7: Homogeneity and stability results ............................................................ 25 
Annex 8: Results for total As ................................................................................ 26 
Annex 9: Results for Cd ....................................................................................... 28 
Annex 10: Results for Pb ...................................................................................... 30 
Annex 11: Results for Hg ..................................................................................... 32 
Annex 12: Results for iAs ..................................................................................... 34 
Annex 13: Overview of performance versus technique ............................................. 36 
Annex 14: Conformity as expressed by the participants. .......................................... 37 
Annex 15: Experimental details as reported by the participants ................................ 38 

 
 
 
 
Executive summary  

The European Union Reference Laboratory for Heavy Metals in Feed and Food (EURL-HM) 
organised a proficiency test (EURL-HM-23) for the determination of total As, Cd, Pb, Hg, 
and  inorganic  As  (iAs)  mass  fractions  in  palm  kernel  expeller  to  support  Directive 
2002/32/EC on undesirable substances in animal feed. This PT was open only to National 
Reference Laboratories (NRLs).  

The  EURL-HM-23  test  item  was  a  palm  kernel  expeller  spiked  with  As,  Cd,  Hg  and  Pb. 
The homogeneity and stability of the test item were  evaluated and the assigned values 
were derived from the results reported by the selected expert laboratories. 

Thirty four  National Reference Laboratories from thirty countries (all EU member states 
plus Iceland and Norway) registered to the exercise and reported results.  

Laboratory  results  were  rated  using  z-  and  zeta  (ζ-)  scores  in  accordance  with  ISO 
13528:2015.  The  following  relative  standard  deviations  for  proficiency  assessment  (σpt) 
were set according to the modified Horwitz equation: 15% for total As and iAs; 16% for 
Cd; 17% for Pb and 22% for Hg. 

More than 87% of the participating NRLs reported satisfactory results (according to the 
z-score)  for total As,  Cd, Pb and Hg, and more than 76%  for iAs, thus confirming their 
ability in monitoring maximum levels set by the EU Directive 2002/32/EC.  

Most of the laboratories provided realistic estimates of their measurement uncertainties. 

1 

 
 
 
 
1  Introduction 
Palm  kernel  expeller  (PKE)  is  a  by-product  from  the  crushing  and  expelling  of  oil  from 
the  kernel  (seed)  of  palm  tree  fruits.  Because  of  its  medium-grade  protein,  high  fibre, 
good level of residual oil and high palmitic acid, it is widely used in compound feeds for 
adult ruminant livestock such as dairy cow, beef cow and sheep [1],[2],[3]. 

The European Directive 2002/32/EC on undesirable substances in animal feed [4] set a 
maximum level for arsenic in PKE of 4 mg kg-1 relative to a feed with a moisture content 
of 12 %. In 2011 several notifications were introduced in the the Rapid Alert System for 
Food  and  Feed  (RASFF)  related  to  high  arsenic  content  in  PKE  to  be  imported  into  a 
Member State (https://webgate.ec.europa.eu/rasff-window/).  

The  European  Union  Reference  Laboratory  for  Heavy  Metals  in  Feed  and  Food  (EURL-
HM), hosted by the Joint Research Centre in Geel (JRC-Geel), organised the proficiency 
test  (PT)  EURL-HM-23  for  the  determination  of  total  arsenic  (As),  cadmium  (Cd),  lead 
(Pb),  mercury  (Hg)  and  inorganic  Arsenic  (iAs)  mass  fractions  in  PKE.  This  PT  was 
agreed  with  the  Directorate  General  for  Health  and  Food  Safety  (DG SANTE)  in  the 
annual work programme 2016 of the EURL-HM.  

This report summarises the outcome of this PT. 

2  Scope  

As  stated  in  Regulation  (EC)  No  882/2004  [5]  one  of  the  core  duties  of  EURLs  is  to 
organise interlaboratory comparisons for the benefit of NRLs.  

The present PT aims to assess the performance of NRLs in the determination of total As, 
Cd, Pb, Hg and iAs mass fractions in a PKE dry powder.  

In addition, participants were asked to evaluate the conformity of the analysed material 
according to the maximum levels (MLs) set in legislation. 

The  reported  results were assessed following the administrative and logistic procedures 
of the JRC Unit in charge of the EURL-HM, which is accredited for the organisation of PTs 
according to ISO 17043:2010 [6].  

This PT is identified as EURL-HM-23. 

3  Set up of the exercise 

3.1  Time frame 

The organisation of the EUR-HM-23 exercise was agreed upon by the NRL network at the 
10th  EURL-HM Workshop held in Brussels on September 28-29, 2015. The  exercise was 
announced  on  the  JRC  webpage  on  March  18,  2016  (Annex  2)  and  an  invitation  letter 
was  sent  (via  e-mail)  to  all  NRLs  of  the  network  on  April  4,  2016  (Annex  3).  The 
registration  deadline  was  set  to  April  29,  2016.  Samples  were  sent  to  participants  on 
May  12,  2016.  Dispatch  was  monitored  by  the  PT  coordinator  using  the  messenger's 
parcel  tracking  system  on  the  internet.  The  deadline  for  reporting  of  results  was  set  to 
June 30, 2016. 

3.2  Confidentiality 

The  procedures  used  for  the  organisation  of  PTs,  are  accredited  according  to  ISO 
17043:2010 [6] and guarantee that the identity of the participants and the information 
provided by them is treated as confidential. 

2

 
 
 
 
 
 
3.3  Distribution 

Each participant received: 

•  One bottle of the test item (approx. 20 g of material); 

•  The "Test item accompanying letter" (Annex 4); and 

•  A "Confirmation of receipt form" to be sent back to JRC-Geel after receipt of the 

test item (Annex 5). 

3.4  Instructions to participants 

Detailed  instructions  were  given  to  participants  in  the  "Test  item  accompanying  letter" 
mentioned  above.  Measurands  were  defined  as  "the  mass  fractions  of  total  As,  Cd,  Pb, 
Hg and iAs in palm kernel expeller dry powder". 

Participants  were  asked  to  perform  two  or  three  independent  measurements,  to  report 
their calculated mean (xi) and the associated expanded measurement uncertainty (U(xi)) 
together with the coverage factor (k) and analytical technique used for the analysis. 

Results  were  to  be  reported  relative  to  a  feed  with  a  moisture  content  of  12  %  as 
required by Directive 2002/32/EC.  

Upon specific request from DG SANTE, no instructions were provided by the EURL-HM to 
laboratories  on  how  to  perform  the  moisture  corrections  necessary  for  reporting,  since 
official control laboratories are supposed to know the proper procedure. 

Participants  received  an  individual  code  to  access  the  on-line  reporting  interface,  to 
report their measurement results and to complete the related questionnaire. A dedicated 
questionnaire  was  used  to  gather  additional  information  related  to  measurements  and 
laboratories (Annex 6). 

Participants were informed that the procedure used for the analysis should resemble as 
closely  as  possible  their  routine  procedures  for  this  type  of  matrix/analytes  and  mass 
fraction levels.  

The  laboratory  codes  were  given  randomly  and  communicated  to  the  participants  by 
e-mail. 

4  Test item 

4.1  Preparation 

The Belgian NRL (CODA-CERVA) kindly provided the starting material - 10 kg of PKE in 
granulated  form  -  that  was  used  for  the  preparation  of  the  test  items.  The  delivered 
material was directly stored at 4 °C until processing.  

The  material  was  first  cryogenically  milled  using  a  Palla  VM-KT  vibrating  mill  from 
Humboldt-Wedag (Köln, Germany). After milling, the material was sieved over a 250 µm 
stainless steel sieve. About 8.5 kg of the fine fraction was collected and stored at 4 °C.  

About 4.9 kg was mixed in a Dynamix CM-200 (WAB, Basel, Switzerland) for one hour. 
The material was then spiked with As, Cd, Pb and Hg: 4840.6 g of powder were placed in 
a 60  L plastic drum to  which 10 L  of MilliQ water were  added to make a homogeneous 
suspension. Then 1 L of spike solution was added to the suspension and was stirred for 
30  min.  The  spiked  material  was  freeze  dried  in  a  Martin  Christ  model  Epsilon  2-100D 
freeze  dryer  (Osterode,  Germany).  The  freeze  dried  palm  kernel  expeller  powder  was 
mixed in a Dynamix CM-200 for one hour.  

3

 
 
 
 
 
 
Portions of 20 g were manually filled into 100 ml amber glass acid-washed bottles using 
acid washed plastic spoons under an extraction point. The bottles were closed with acid 
washed inserts and screw caps.  

Each vial was identified with a unique number and the name of the PT exercise. 

4.2  Homogeneity and stability 

Measurements  for  the  homogeneity  and  stability  studies  were  performed  by  ALS 
Scandinavia AB (Luleå, Sweden).  

Inductively  coupled  plasma  mass  spectrometry  (ICP-MS)  was  used  after  microwave 
digestion  (0.3-0.5  g  of  sample  in  a  mixture  of  HNO3/H2O2)  to  determine  the  mass 
fractions of total As, Cd, Pb and Hg.  

The statistical treatment of data was performed by the EURL-HM.  

Homogeneity was evaluated according to ISO  13528:2015 [7]. The test item proved to 
be adequately homogeneous for the investigated analytes.  

The  stability  study  confirmed  that  the  material  was  stable  and  the  uncertainty 
contribution due to stability was set to zero (ust = 0) for all analytes.  

The  contribution  from  homogeneity  (uhom)  to  the  standard  uncertainty  of  the  assigned 
value  (u(xpt))  was  calculated  using  SoftCRM  [8].  The  analytical  results  reported  by  the 
expert laboratory and the statistical evaluation of the homogeneity and stability studies 
are presented in Annex 7 and Table 1. 

5  Assigned values and corresponding uncertainties 

5.1  Assigned values 

The assigned values (xpt) of the five measurands (mass fractions of total As, Cd, Pb, Hg 
and  iAs  in  palm  kernel  expeller  relative  to  a  moisture  content  of  12  %),  were  derived 
from  the  results  reported  by  expert  laboratories,  all  selected  on  the  basis  of  their 
demonstrated measurement capabilities.  

The following expert laboratories analysed one or more measurands: 

•  ALS Scandinavia AB (Luleå, Sweden);  
•  CSPA - Centro de Salud Pública de Alicante (Alicante, Spain); 
•  SCK-CEN - Studiecentrum voor Kernenergie (Mol, Belgium); 
•  UBA - Umweltbundesamt GmbH (Wien, Austria);  
• 
• 

Institute for Chemistry, University of Graz (Graz, Austria) 
JRC-Geel,  Directorate  F  -  Health,  Consumers  and  Reference  Materials  (Geel, 
Belgium) 

•  Faculty of Chemistry, University of Barcelona (Barcelona, Spain) 

Expert  laboratories  were  asked  to  use  the  method  of  analysis  of  their  choice  and  no 
further requirements were imposed regarding methodology. They were also requested to 
report their results together with the associated expanded measurement uncertainty and 
with  a  clear  and  detailed  description  on  how  their  measurement  uncertainty  was 
calculated.  Results  were  to  be  reported  relative  to  a  feed  with  a  moisture  content  of 
12 % as required by Directive 2002/32/EC. 

4

 
 
 
 
 
 
 
•  ALS  Scandinavia  used  inductively  coupled  plasma  mass  spectrometry  (ICP-MS) 
after  closed  microwave  digestion  of  the  sample  (approx.  0.3-0.5  g  in  closed 
Teflon  containers)  using  HNO3  and  H2O2.  Analyses  were  made  according  to  the 
modified  ISO  17294-1,  2  and  modified  US  EPA  Method  200.8  for  the 
measurement of total As, Cd, Pb and Hg.  

•  CSPA  used  ICP-MS  after  microwave  digestion  of  the  sample  (approx.  0.25  g  in 
quartz digestion vessels) using HNO3 and H2O2 for measuring total As, Cd and Pb. 
The measurement of Hg was performed by Direct Mercury Analyser (DMA).  

•  SCK-CEN  applied  instrumental  neutron  activation  analysis  (kÓ-NAA)  for  the 
determination  of  total  As,  Cd  and  Hg  mass  fractions.  Three  samples  of  (approx. 
350  mg)  were  transferred  in  standard  high-density  polyethylene  vials  and 
weighed.  Samples  were  irradiated  for  seven  hours  in  channel  Y4  of  the  BR1 
reactor under a thermal flux of 3 1011 n s-1 cm2 together with several IRMM-530 
(Al-0.1 % Au alloy) neutron flux monitors and two reference materials (SMELLS II 
and NIST 1633b 'Coal fly ash') used for validation. Three spectra of each sample 
were collected on a k0-calibrated HPGe detector under repeatability conditions: 1 
day, 2 days and 13-15 days after irradiation for the determination of As, Ca and 
finally Hg, respectively. Only an indicative value was reported for Hg.  

•  UBA used ICP-MS according to ISO 17294-2 for the determination of As, Cd and 
Pb.  The  measurement  of  Hg  was  done  by  Cold  Vapour  Atomic  Absorption 
Spectrometry (CV-AAS) according to ISO 12846, while iAs was determined using 
HPLC-ICP-MS according to ISO 17294-2. 

•  The  University  of  Graz  determined  total  As in about  250  mg  of  the  sample  after 
microwave-assisted  digestion  with  HNO3  by  ICP-MS  using  (i)  helium  as  the 
collision  cell  gas  to  remove  polyatomic  interferences  and  (ii)  74Ge  and  115In  as 
internal standards. For iAs, samples of about 500 mg were heated with a solution 
of CF3COOH/H2O2 (95 oC for 60 min) and analysed by HPLC-ICP-MS.  

• 

JRC-Geel  analysed  total  As  by  ICP-MS;  Cd  and  Pb  by  ID-ICP-MS;  and  Hg  by 
CV-AAS, applying the following experimental protocols:  

Samples  (0.25  to  0.5  g)  were  digested  in  a  Milestone  Ultraclave  micro-
wave digestion apparatus with (i) 5 mL concentrated nitric acid (for As) or 
with  (ii)  5  mL  concentrated  nitric  acid  and  0.5  mL  of  concentrated 
hydrofluoric acid (for Cd, Hg and Pb). 

Digests  for  As,  Cd  and  Pb  measurement  were  diluted  in  2  %  nitric  acid 
solution,  and  for  Pb  measurement,  about  1  µg/L  Tl  (IRMM-649  isotopic 
certified reference material) was added.  

As,  Cd  and  Pb  were  measured  on  an  Agilent  7500ce  inductively  coupled 
plasma  mass  spectrometer,  using  a  He-filled  collision  cell  for  As 
measurement.  Arsenic  was  measured  by  external  calibration  with  5 
standards.  

For isotope dilution measurements, samples were blended with IRMM-622 
(111Cd enriched) and Inorganic Ventures (206Pb enriched) isotopic certified 
reference  materials  prior  to  sample  digestion.  For  Cd  isotope  dilution 
measurements,  the  113Cd/111Cd  ratio  was  measured  using  digests  of  an 
unspiked  sample  and  tabulated  natural isotopic  abundances  as  reference. 
For  Pb  measurement,  the  Pb  molar  mass  was  measured  in  an  unspiked 
sample  using  the  Tl  internal  standard  (IRMM-649)  as  reference,  and  the 
isotope dilution measurement used the 206Pb/208Pb ratio, again using the Tl 
internal standard as reference.  

5

 
 
 
 
Digests  for  Hg  measurement  were  mixed  with  1  ml  of  a  6  %  potassium 
permanganate  solution and a 20 % hydroxylamine solution is added until 
the  solution  is  colourless.  The  digests  were  made  up  to  about  35  mL 
before  measurement.  Hg  was  measured  on  an  Analytik-Jena  Zeenit  600 
atomic  absorption  spectrometer  fitted  with  a  "Hydrea"  cold-vapour 
generation  system  and 
for  sample 
concentration.  Sub-samples  of  10  mL  of  digests  were  measured  batch-
wise alongside 4 standards for external calibration.  

Ir-coated  graphite 

furnace 

•  The University of Barcelona analysed iAs weighing about 0.2 g of test material in 
PTFE  vessels  and  carrying  out  a  microwave  digestion  with  a  HNO3/H2O2  solution 
followed by an HPLC-ICP-MS analysis.  

5.2  Associated uncertainties 

The  associated  standard  uncertainties  of  the  assigned  values  (u(xpt))  were  calculated 
following  the  law  of  uncertainty  propagation,  combining  the  standard  measurement 
uncertainty  of  the  characterization  (uchar)  with  the  standard  uncertainty  contributions 
from homogeneity (uhom) and stability (ust), in compliance with ISO Guide 35 [9]. 

(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6) = 	(cid:9)(cid:1)(cid:10)(cid:11)(cid:12)(cid:13)

(cid:14) + (cid:1)(cid:11)(cid:16)(cid:17)

(cid:14) + (cid:1)(cid:18)(cid:5)(cid:12)(cid:19)

(cid:14)

The uncertainty uchar is estimated according to the recommendations of ISO Guide 35 [9]:  

where  "s"  refers  to  the  standard  deviation  of  the  mean  values  obtained  by  the  expert 
laboratories and "p" refers to the number of expert laboratories.  

(cid:1)(cid:10)(cid:11)(cid:12)(cid:13) =

(cid:18)

√(cid:4)

Figure 1:  

Assigned values for EURL-HM-23. 

Circles  and  error  bars  represent 
reported  values  by  the  retained 
expert laboratories (xi± 2ui).  
The  solid 
line  represents  the 
assigned  value  (xpt)  while  the 
dashed 
the 
represent 
assigned range (xpt ± 2 u(xpt))  

lines 

6

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.3  Standard deviation of the proficiency test assessment, σpt 
All the relative standard deviations for PT assessment (σpt, in mg kg-1 and %) presented 
in Table 1 were calculated using the Horwitz equation modified by Thompson [10]. 

Table 1: 

Results  and  associated  expanded  measurement  uncertainties  (as)  reported  by 
expert  laboratories;  the  assigned  values  (xpt,  u(xpt)  and  U(xpt)(k=2));  the  standard 
uncertainties  (uchar,  ust  and  uhom);and  the  standard  deviation  for  PT  assessment  σpt. 
Values are expressed in mg kg-1 relative to PKE with a moisture content of 12 %. 

tot-As 

Cd 

Pb 

Hg 

iAs 

Expert 1 

2.2 ± 0.15 

1.4 ± 0.095 

0.83 ± 0.066 

0.046 ± 0.0046 

2.0 ± 0.2 

Expert 2 

2.14 ± 0.21 

1.21 ± 0.12 

0.902 ± 0.09 

0.0488 ± 0.0049 

Expert 3 

2.28 ± 0.103 

1.27 ± 0.0521 

0.822 ± 0.0127 

0.0484 ± 0.00227 

Expert 4 

2.624 ± 0.121 

1.589 ± 0.247 

Expert 5 

2.28 ± 0.4 

1.29 ± 0.019 

0.8461 ± 0.013 

0.0493 ± 0.007 

Expert 6 

2.17 ± 0.1 

Expert 7 

xpt 

uchar 

uhom 

ust 

u(xpt) 

U(xpt)* 

σpt 

σpt (%) 

u(xpt)/σpt 

2.28 

0.072 

0.037 

0 

0.081 

0.16 

0.34 

15% 

0.24 

1.35 

0.067 

0.015 

0 

0.068 

0.14 

0.22 

16% 

0.32 

0.850 

0.018 

0.008 

0 

0.020 

0.039 

0.145 

17% 

0.14 

0.0481 

0.00073 

0.00080 

0 

0.00109 

0.0022 

0.0106 

22% 

0.10 

2.07 ± 0.12 

1.97 ± 0.16 

2.01 

0.030 

0.032 

0 

0.044 

0.09 

0.30 

15% 

0.14 

6  Evaluation of results 

6.1  Scores and evaluation criteria 

Individual  laboratory  performance  was  expressed  in terms  of  z-  and  ζ-scores  according 
to ISO 13528:2015 [7]: 

=

z

i

x

i

x

pt

σ

pt

=z
i

x
i

x

pt

2
xu
(

)

i

+

2
xu
(

)

pt

Eq. 1 

Eq. 2 

7

 
 
 
 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 
-
   
 
 
 
 
 
 
 
-
 
 
 
 
 
 
where:   xi 

is the measurement result reported by a participant; 

u(xi) 

xpt 

u(xpt) 
s pt 

is the standard measurement uncertainty reported by a participant;  

is the assigned value; 

is the standard measurement uncertainty of the assigned value;  

is the standard deviation for proficiency test assessment. 

The interpretation of the z- and ζ- scores is done according ISO 13528:2015 [7]:  

|score| ≤ 2  

satisfactory performance 

(green in Annexes 8-13,15) 

2 < |score| < 3 

questionable performance 

(yellow in Annexes 8-13,15) 

|score| ≥ 3 

unsatisfactory performance  

(red in Annexes 8-13,15) 

The  z-score  compares  the  participant's  deviation  from  the  assigned  value  with  the 
standard  deviation  for  proficiency  test  assessment  (s pt)  used  as  common  quality 
criterion.  

The ζ-score states whether the laboratory's result agrees with the assigned value within 
the respective uncertainty. The denominator is the combined uncertainty of the assigned 
value u(xpt) and the measurement uncertainty as stated by the laboratory u(xi). The ζ-score 
includes all parts of a measurement result, namely the expected value (assigned value), 
its  measurement  uncertainty  in  the  unit  of  the  result  as  well  as  the  uncertainty  of  the 
reported  values.  An  unsatisfactory  ζ-score  can  either  be  caused  by  an  inappropriate 
estimation of the concentration, or of its measurement uncertainty, or both. 

The  standard  measurement  uncertainty  of  the  laboratory  u(xi)  was  obtained  by  dividing 
the  reported  expanded  measurement  uncertainty  by  the  reported  coverage  factor,  k. 
When  no  uncertainty  was  reported,  it  was  set  to  zero  (u(xi)  =  0).  When  k  was  not 
specified, the reported  expanded measurement uncertainty was considered as the half-
width of a rectangular distribution; u(xi) was then calculated by dividing this half-width by 
√3, as recommended by Eurachem and CITAC [11]. 

Uncertainty estimation is not trivial, therefore an additional assessment was provided to 
each  laboratory  reporting  measurement  uncertainty,  indicating  how  reasonable  their 
measurement uncertainty estimation was.  

The standard measurement uncertainty from the laboratory u(xi) is most likely to fall in a 
range  between  a  minimum  and  a  maximum  allowed  uncertainty  (Case "a": 
umin ≤ ulab≤ umax).  umin  is  set  to  the  standard  uncertainties  of  the  assigned  values  u(xpt).  It  is 
unlikely  that  a  laboratory  carrying  out  the  analysis  on  a  routine  basis  would  determine 
the  measurand  with  a  smaller  measurement  uncertainty  than  the  expert  laboratories 
chosen to establish the assigned value. umax is set to the standard deviation accepted for 
the PT assessment (s pt). Consequently, Case "a" becomes: u(xpt) ≤ u(xi) ≤ s pt.  

If  u(xi)  is  smaller  than  u(xpt)  (Case  "b")  the  laboratory  may  have  underestimated  its 
measurement  uncertainty.  Such  a  statement  has  to  be  taken  with  care  as  each 
laboratory  reported  only  measurement  uncertainty,  whereas  the  uncertainty  associated 
with the assigned value also includes contributions for homogeneity and stability of the 
test  item.  If  those  are  large,  measurement  uncertainties  smaller  than  uref  are  possible 
and plausible.  
If  u(xi)  is  larger  than  s pt  (Case  "c")  the  laboratory  may  have  overestimated  its 
measurement uncertainty. An evaluation of this statement can be made when looking at 
the  difference  between  the  reported  value  and  the  assigned  value:  if  the  difference  is 
smaller  than  the  expanded  uncertainty  U(xpt)  then  overestimation  is  likely.  If  the 
difference  is  larger  but  xi agrees  with  xpt  within their  respective  expanded  measurement 
uncertainties,  then  the  measurement  uncertainty  is  properly  assessed  resulting  in  a 

8

 
 
 
 
 
 
 
 
 
satisfactory performance expressed as a ζ-score, though the corresponding performance, 
expressed as a z-score, may be questionable or unsatisfactory.  

It should be pointed out that "umax" is a normative criterion when set by legislation. 

6.2  General observations 

Thirty four NRLs from thirty countries registered to the exercise, covering all EU member 
states  plus  Iceland  and  Norway.  All  registered  NRLs  reported  results.  The  participants 
having reported results are listed in the "Acknowledgment" section.  

Thirty  two  (out  of  34)  laboratories  reported  results  for  As,  Cd,  Pb  while  thirty  one 
laboratories for Hg. Only 21 results were reported for iAs (Table 2).  

Table 2:     Overview of the number of reported results per measurand (out of 34). 

Reported Results  Comments 

As 

Cd 

Pb 

Hg 

32 (94%) 

No results from laboratories 020 and 034 

32 (94%) 

No results from laboratories 020 and 034 

32 (94%) 

31 (91%) 

Of which one "less than X" value;  
No results from laboratories 020 and 034 

Of which one "less than X" value;  
No results from laboratories 022, 034 and 036 

iAs 

21 (62%) 

No results from 13 laboratories  

6.3  Laboratory results and scorings 

6.3.1  Performances 

Annexes 8 to 12 present the reported results as tables and graphs for each measurand, 
where  NRLs  are  denoted  as  "0XX".  The  corresponding  Kernel  density  plots,  obtained 
using the software available from the Statistical Subcommittee of the Analytical Methods 
Committee of the UK Royal Society of Chemistry [12] are also included. 

The laboratory performance for the "determination of total As, Cd, Pb Hg and iAs in PKE 
relative  to  12  %  moisture  content"  were  assessed  using  the  z-  and  ζ-scores,  since  the 
ISO 13528 recommendation (u(xpt) £  0.3 s pt) was fulfilled for all measurands.  

Total (As, Cd, Pb, Hg) and iAs 

Figures  1  and  2  present  the  laboratory  performances  for  total  As,  Cd,  Pb  and  Hg, 
assessed  by  the  z-  and  ζ-scores.  Most  of  the  participants  having  reported  results 
performed satisfactorily for these measurands: above 87% for the z-score and 77% for 
the  ζ-scores.  Twenty  three  laboratories  (out  of  34)  performed  satisfactorily  for  the 
determination of the four measurands (total As, Cd, Pb and Hg). Similarly, most of the 
participants  reporting  for  iAs  performed  satisfactorily  for  this  measurand,  with  76%  of 
the z-scores and ζ-scores ≤ 2. 

For As and Cd no direct correlations could be found between the analytical methods used 
by the laboratories and the quality of the reported results (see Annex 14).  

Two unsatisfactory performances and a truncated value ("less than")  were obtained for 
Pb applying AAS. This may be attributed to the relatively low level of Pb in the test item 
(0.85 mg kg-1) compared to the higher MRL for Pb in animal feed (10 mg kg-1). Annex 15 

9

 
 
 
 
 
 
 
 
 
 
shows  that  for  Pb  LODs  for  AAS  methods  are  generally  higher  than  those  for  ICP-MS 
methods.  Nevertheless,  laboratory  003  may  consider  re-evaluating  the  high  limit  of 
quantification reported ("less than 1.8"). 

Similarly, two laboratories using CV-AAS reported the highest Hg results leading to z-
scores above 3. Two other results for Hg obtained by AAS were flagged as unsatisfactory 
and questionable. 

Figure 2:  

Overview of laboratory performance per 
measurand according to z-scores. 

Corresponding number of laboratories 
indicated in the graph.  

Satisfactory (green); Questionable 
(yellow); Unsatisfactory (orange) 

Figure 3:  

Overview  of  laboratory  performance  per 
measurand according to ζ-scores.  

Corresponding  number  of  laboratories 
indicated in the graph.  

Satisfactory 
(yellow); Unsatisfactory (orange) 

(green); 

Questionable 

Truncated values 

Two "less than X" values were reported, one for Pb and one for Cd. The limit values "X" 
reported  by  the  laboratories  usually  correspond  to  the  limits  of  quantification  (LOQ)  or 
limits  of  detection  (LOD)  of  the  applied  methods.  Those  reporting  “less  than  X”  values 
were  not  included  in  the  data  evaluation.  However,  reported  “less  than  X”  values  were 
compared  with  the  corresponding  xpt  –  U(xpt).  If  the  reported  limit  value  “X”  is  lower 
than  the  corresponding  xpt  –  U(xpt),  this  statement  is  considered  incorrect,  since  the 
laboratory should have detected the respective analyte. The two "less than X" values in 
this exercise were correct statements.  

6.3.2   Uncertainties 

Figure  3  presents  the  uncertainty  assessment  per  measurand.  Most  of  the  participants 
(above  70%)  reported  realistic  measurement  uncertainty  estimates  for  Cd,  Hg,  Pb  and 
iAs (case "a": u(xpt) ≤ u(xi) ≤ σpt).  

A  lower  number  of  realistic  "case  a"  (59%)  is  obtained  for  total  As.  Of  the  19%  of 
underestimated  "case  b",  three  laboratories  reported  combined  uncertainties  ranging 
from 0.058 to 0.07 - to be compared to u(xpt) = 0.08 mg kg-1. Similarly, of the 22% of 
"case c", four laboratories reported combined uncertainties ranging from 0.35 to 0.37 - 
to be compared to s pt = 0.34 mg kg-1.  

10

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 4:  

Review of uncertainties reported per 
measurand. 

Corresponding number of laboratories 
indicated in the graph.  

Case "a" (green): u(xpt) ≤ u(xi) ≤ σpt  
Case "b" (yellow) u(xi) < u(xpt);  
Case "c" (blue)= u(xi) > σpt 

6.3.3  Compliance assessment 

When comparing the maximum levels (MLs) - set in the European Directive 2002/32/EC 
for  undesirable  substances  in  animal  feed  -  to  the  assigned  ranges  in  the  palm  kernel 
expeller (Table 3), one concludes that the test item is non-compliant for cadmium (only) 
for which xpt – U(xpt) > ML.   

Table 3:  

Maximum limits (MLs), assigned values and their associated expanded 
uncertainties. All values expressed in mg kg-1
content of 12 %. 

, relative to PKE with a moisture 

Elements 

xpt ± U(xpt)  

As 

Cd 

Pb 

Hg 

2.28 ± 0.16 

1.35 ± 0.14 

0.85 ± 0.039 

0.048 ± 0.0022 

MLs 

4 

1 

10 

0.1 

Participants  were  requested  to  assess  the  compliance  of  the  test  item  according  to 
Directive  2002/32/EC,  and  provide  proper  justification  to  support  their  statement.  In 
order  to  assess  the  consistency  of  the  laboratory  compliance  statement,  one  must 
consider the following three components:  

1)  the laboratory compliance statement (Compliant or Non-Compliant) 
2)  the laboratory measurement results:  

- 
- 

reported (or not) for the relevant analyte (Cd);  
to be compared to the relevant ML: xi - Ui > ML?  
3)  the laboratory justification (correct, incorrect or partially incorrect). 

The  answers  received  (Annex  14)  are  summarised  in  Table  4.  Sixteen  (out  of  34) 
laboratories  assessed  correctly  the  test  item  to  be  non-compliant  (47 %  true  non-
compliant,  TNC).  Other  four  laboratories  stated  the  material  to  be  non-compliant  while 
presenting  partially  incorrect  justifications  (12 %  false  non-compliant,  FNC).  Six 
laboratories  assumed  the  material  to  be  compliant  (17 %  true  compliant,  TC)  due  to 
either their low measurement results for Cd (cf. laboratories 003 and 036) or their large 
measurement uncertainty reported (cf. laboratories 004, 019, 005 and 013). Finally, four 
laboratories  gave  an  inconsistent  assessment  (12 %  false  compliant,  FC),  while  four 
other laboratories (12 %) did not provide any statement. 

11

 
 
 
 
 
 
  
 
 
 
 
 
Table 4:  

Laboratory statements on the compliance assessment, laboratory measurement 
results for Cd compared to the ML, laboratory justifications (correct, incorrect or 
partially incorrect) and a categorisation of the laboratory compliance assessment 
into FC (false compliant), TC (true compliant), TNC (true non-compliant) and FNC 
(false non-compliant).  

Laboratory 
Measurement 

Laboratory 
Justification 

Category 

Nr. of  
labs 

Laboratory  
Statement 

Compliant 

Non-Compliant 

xi – Ui > ML 

Correct 

None 

No Cd result  None 
xi – Ui £  ML 
xi – Ui > ML 

None 

Correct 

Part. incorrect 

xi – Ui £  ML 

Part. incorrect 

No Assessment 

Comment 

025: xi > ML 

007:  wrong  ML(As); 
012:wrong  ML(Cd);  
033: As & Hg 

008: xi > ML 

FC 

FC 

TC 

TNC 

FNC 

1 

2 

1 

6 

16 

3 

1 

4 

6.3.4  Additional information from the questionnaire 

The questionnaire was answered by all 34 participants. Different approaches were used 
to evaluate measurement uncertainties (Table 4). The majority of the NRLs carry out an 
in-house  validation  in  order  to  estimate  the  measurement  uncertainty  (19  out  of  34). 
Twenty-five out of 34 usually report uncertainty to their customers.  

Laboratories were asked to  report the  LODs  of the methods used for  the determination 
of  the  five  measurands.  Annex  14  presents  LODs,  the  general  experimental  conditions 
and  the  techniques  used  for  the  determination  of  total  As,  Cd,  Pb  and  Hg.  Large 
discrepancies  in  reported  LODs  are  observed  even  among  laboratories  using  the  same 
technique.  

Table 5:  

Approaches used to estimate measurement uncertainties. 
Multiple selections were possible. 

Approach followed for uncertainty calculation 

Number of labs.  

According to ISO-GUM 

According to ISO 21748 

Derived from a single-laboratory validation study 

Determined as standard deviation of replicate measurements 

Estimation based on judgment 

Derived from inter-comparison data 

According to the NORDTEST guidelines 

Applying the Horwitz equation 

7 

0 

19 

8 

1 

8 

2 

1 

The reported recovery factors ranged from 80 to 113 % and two main approaches were 
used for the determination of recoveries: spiking and use of reference materials.  

All  of  the  NRLs  stated  that  they  have  an  ISO/IEC  17025  accreditation  and  26  NRLs 
confirmed they are accredited for one or more of the investigated measurands in feed.  

12

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
For  some  participants,  the  unsatisfactory  performance  could  be  linked  to  a  lack  of 
experience (evaluated as number of analyses per year) for this type of analysis.   

7  Conclusion  

The  EURL-HM-23  PT  was  organised  in  2016  to  assess  the  analytical  capabilities  of  the 
NRLs for the EU using a palm kernel expeller spiked with As, Cd, Pb and Hg as test item. 

The overall performance of the participants in the determination of total As, Cd, Hg, Pb 
and iAs was satisfactory. This confirms the analytical capabilities of the NRLs to enforce 
the  European  Directive  2002/32/EC  setting  levels  for  undesirable  substances  in  feed. 
However, 13 out 34 did not report results for iAs. 

As for compliance assessment, only 47 % of the participants stated correctly (providing 
proper  justification)  that  the  test  item  was  non-compliant  according  to  the  maximum 
level  set  by  Directive  2002/32/EC  for  cadmium  in  palm  kernel  expeller.  Other 
laboratories  having  reported  satisfactory  results  should  therefore  improve  their 
assessment procedure selecting relevant MLs and phrasing accurately their justification, 
or providing realistic (not over-estimated) measurement uncertainties.   

Overall,  NRLs  reported  good  measurement  uncertainty  estimates,  thus  demonstrating 
the  effectiveness  of  the  various  PTs  and  training  courses  organised  by  the  EURL-HM  in 
the past 10 years. 

13

 
 
 
 
 
 
 
Acknowledgements  

The  EURL-HM  wishes  to  thank  the  Belgian  NRL  (CODA-CERVA)  for  providing  the  palm 
kernel expeller granulates later processed and used as test item for this proficiency test.   

The  authors  wish  to  thank  colleagues  from  the  JRC-Geel  site  for  their  valuable 
contributions during the preparation of the proficiency test item.  

The  thirty  four  laboratories  listed  hereafter  are  kindly  acknowledged  for  their 
participation in the PT. 

Organisation 

AGES GmbH 

CODA-CERVA 

Central Laboratory for Chemical Testing and Control (CLCTC) 

Croatian Veterinary Institute 

Department of Agriculture 

State Veterinary Institute Olomouc 

Central Institute for Supervising and Testing in Agriculture (UKZUZ) 

Danish Veterinary and Food Administration 

Technical University Denmark (DTU) Food 

Agricultural Research Centre 

Finnish Food Safety Authority Evira 

Laboratoire SCL de Bordeaux - NRL 

Federal Office for Consumer Protection and Food Safety (BVL) 

Regional Center Of Plant Protection And Quality Control Of Magnissia 

National Food Chain Office Food and Feed Safety 

National Food Chain Safety Office 

Matis ohf 

The State Laboratory 

Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle D'aosta 

Institute of Food Safety, Animal Health and Environment 

National Food and Veterinary Risk Assessment Institute 

Laboratoire National de Santé 

Public Health Laboratoy 

RIKILT 

National Institute of Nutrition and Seafood Research (NIFES) 

National Veterinary Research Institute 

Instituto Português do Mar e da Atmosfera (IPMA) 

Hygiene and Veterinary Public Health Institute 

Country 

Austria 

Belgium 

Bulgaria 

Croatia 

Cyprus 

Czech Republic 

Czech Republic 

Denmark 

Denmark 

Estonia 

Finland 

France 

Germany 

Greece 

Hungary 

Hungary 

Iceland 

Ireland 

Italy 

Latvia 

Lithuania 

Luxembourg 

Malta 

Netherlands 

Norway 

Poland 

Portugal 

Romania 

State veterinary and food institute Dolný Kubín, Veterinary and food institute Košice  Slovakia 

National Veterinary Institute 

National Laboratory of Health, Environment and Food (NLZOH) 

Laboratorio Arbitral Agroalimentario (MAGRAMA) 

National Food Agency 

Fera Science Ltd 

Slovenia 

Slovenia 

Spain 

Sweden 

United Kingdom 

14

 
 
 
 
 
 
References  

[1]  Manufacturing  tropical  oil  products,  (2016).  http://www.wilmar-international.com/our-

business/tropical-oils/manufacturing/tropical-oils-products/palm-kernel-expeller/. 

[2] 

[3] 

[4] 

[5] 

[6] 

[7] 

Palm  Kernel  Expeller, 
products/palm-kernel-expeller/. 

(2016).  http://www.kwalternativefeeds.co.uk/products/view-

T.T.  Sue,  Quality  and  Characteristics  of  Malaysian  Palm  Kernel  Cakes/Expellers,  (2001). 
http://palmoilis.mpob.gov.my/publications/POD/pod34-tang.pdf. 

European  Commission,  DIRECTIVE  2002/32/EC  OF  THE  EUROPEAN  PARLIAMENT  AND  OF 
THE  COUNCIL  of  7  May  2002  on  undesirable  substances  in  animal  feed,  Off.  J.  Eur. 
Communities. L 269 (2002) 1–15. doi:2004R0726 - v.7 of 05.06.2013. 

Commission  Regulation,  (EC)  No  882/2004  of  the  European  Parliament  and  of  the  Council 
of 29 April 2004 on official controls performed to ensure the verification of compliance with 
feed  and  food  law,  animal  health  and  animal  welfare  rules,  Off.  J.  Eur.  Union.  L165/1 
(2004). 

ISO/IEC  17043  “Conformity  assessment  –  General  requirements  for  proficiency  testing”, 
issued by ISO-Geneva (CH), International Organisation for Standardization, 2010. 

ISO  13528:2015  “Statistical  methods  for  use  in  proficiency  testing  by  interlaboratory 
comparisons”,  issued  by  ISO-Geneva  (CH),  International  Organisation  for  Standardization, 
2015. 

[8] 

SoftCRM, (n.d.). http://www.eie.gr/iopc/softcrm/index.html. 

[9] 

ISO  Guide  35  “Reference  materials  -  general  and  statistical  principles  for  certification”, 
issued by ISO-Geneva (CH), International Organisation for Standardization, 2006. 

[10]  M.  Thompson,  Recent  trends 

inter-laboratory  precision  at  ppb  and  sub-ppb 
concentrations in relation to fitness for purpose criteria in proficiency testing, Analyst. 125 
(2000) 385–386. doi:10.1039/B000282H. 

in 

[11]  Eurachem/Citac, 

“Quantifying  Uncertainty 

in  Analytical  Measurement,” 

2012. 

http://www.eurachem.org. 

[12]  Analytical  Methods  Committee,  Representing  data  distributions  with  kernel  density 
estimates, AMC Tech. Br. 4 (2006) 2. http://www.rsc.org/images/brief4_tcm18-25925.pdf. 

15

 
 
 
 
------------------       This is a blank page       ---------------- 

16

 
 
 
 
 
 
Annexes 

17

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex 1: List of abbreviations  

CV-AAS 

Cold Vapour Atomic Absorption Spectrometry 

DG SANTE 

Directorate General for Health and Food Safety 

DMA 

ET-AAS 

GUM 

HG-AAS 

HPLC 

Direct Mercury Analyser (also called Elemental Mercury Analyzer, EMA) 

Electro Thermal – Atomic Absorption Spectrometry  
(also called Graphite Furnace Atomic Absorption Spectroscopy, GF-AAS) 

Guide for the Expression of Uncertainty in Measurement 

Hydride Generation – Atomic Absorption Spectrometry 

High Performance Liquid Chromatography 

ICP-(Q)MS 

Inductively Coupled Plasma –(Quadrupole) Mass Spectrometry 

ID-GC-ICP-MS 

Isotope Dilution – Gas Chromatography – ICP-MS 

JRC 

LOD 

NRL 

PKE 

PT 

Joint Research Centre 

Limit of detection 

National Reference Laboratory 

Palm Kernel Expeller 

Proficiency Test 

Z-ET-AAS 

Zeeman ET-AAS 

18 

 
 
 
 
 
 
 
Annex 2: JRC web announcement 

19

 
 
 
 
 
 
 
 
Annex 3: Invitation letter to NRLs 

20

 
 
 
 
 
 
Annex 4: Test item accompanying letter 

21

 
 
 
 
 
 
Annex 5: Confirmation of receipt form 

22

 
 
 
 
 
Annex 6: Questionnaire 

23 

 
 
 
24

 
 
 
 
Annex 7: Homogeneity and stability results 

7.1 Homogeneity study (all values in mg kg-1) 

Bottle ID 
125 
23 
83 
149 
5 
67 
162 
59 
119 
182 
Mean 
sp 
0.3* sp 
Critical value 
sx 
sw 
ss 
ss ≤ 0.3 * σpt 

Where:  

As 

Cd 

Pb 

Hg 

R1 
2.58 
2.59 
2.56 
2.58 
2.43 
2.44 
2.59 
2.40 
2.51 
2.51 

R2 
2.40 
2.58 
2.47 
2.40 
2.47 
2.56 
2.44 
2.53 
2.46 
2.45 

R1 
1.46 
1.48 
1.41 
1.40 
1.42 
1.40 
1.37 
1.37 
1.39 
1.41 

R2 
1.38 
1.38 
1.39 
1.36 
1.39 
1.41 
1.36 
1.37 
1.40 
1.40 

R1 
0.90 
0.94 
0.88 
0.90 
0.92 
0.90 
0.89 
0.89 
0.89 
0.93 

R2 
0.91 
0.90 
0.91 
0.88 
0.90 
0.90 
0.91 
0.89 
0.88 
0.88 

R1 
0.0544 
0.0570 
0.0547 
0.0575 
0.0552 
0.0547 
0.0531 
0.0507 
0.0530 
0.0542 

R2 
0.0532 
0.0557 
0.0525 
0.0522 
0.0551 
0.0532 
0.0538 
0.0523 
0.0519 
0.0549 

2.50 
0.34 
0.10 
0.03 
0.04 
0.08 
0.00 
passed 

1.40 
0.22 
0.06 
0.01 
0.02 
0.03 
0.00 
passed 

0.90 
0.14 
0.04 
0.00 
0.01 
0.02 
0.00 
passed 

0.0540 
0.0106 
0.0032 
0.0000 
0.0014 
0.0015 
0.0009 
passed 

is the standard deviation of the sample averages, 

σpt  is the standard deviation for the PT assessment, 
sx 
sw  is the within-sample standard deviation, 
ss 

is the between-sample standard deviation, 

7.2 Stability study (at 60°C, all values in mg kg-1) 

Time 
As 

Cd 

Pb 

Hg 

0 w 

3 w 

5 w 

8 w 

2.18 
2.20 
1.21 
1.24 
0.879 
0.830 
0.0452 
0.0487 

2.11 
2.27 
1.19 
1.21 
0.823 
0.798 
0.0480 
0.0499 

2.25 
2.14 
1.19 
1.19 
0.832 
0.782 
0.0464 
0.0476 

2.17 
2.12 
1.24 
1.16 
0.855 
0.792 
0.0489 
0.0458 

Slope  
significance 
(a) 

Assessment 

No 

No 

No 

No 

Stable 

Stable 

Stable 

Stable 

(a) Slope of the linear regression significantly different from "0" at a 95 % level 

25 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Annex 8: Results for total As 

Assigned values: xpt = 2.28; U(xpt)  = 0.16 (k=2) and σpt = 0.34; all values in mg kg-1,  
relative to a feed with a moisture content of 12 %    

Lab Code 
001 
002 
003 
004 
005 
007 
008 
009 
010 
011 
012 
013 
014 
015 
016 
017 
018 
019 
020 
021 
022 
023 
024 
025 
026 
027 
028 
029 
030 
031 
032 
033 
034 
036 

U(xi) 

0.13 
0.14 
0.5 
1.2 
0.46 

Xi 
2.31 
1.96 
2.2 
2.3 
2.29 
2.180  0.327 
1.991  0.37829 
2.03 
1.99 
2.22 
2.4 
2.241  0.403 
2.251  0.116 
2.10 
2.4 
1.47 
3.6 
2.1 

0.34 
0.96 
0.06 
1.1 
0.47 

0.47 
0.55 
0.46 
0.7 

0.5 

0.37 
0.44 

2.4 
2.0 
2.06 
2.29 
2.021  0.303 
2.285  0.274 
2.50 
2.274  0.455 
3.10 
2.271  0.393 
2.2 
2.20 
2.29 

0.37 
0.50 
0.11 

0.78 

0.63 

ka 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
2 

2 
√3 
2 
2 
2 
2 
√3 
2 
2 
2 
2 
2 
2 

technique 
ICP-MS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
HG-AAS 
ICP-MS 
ICP-OES 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
AAS 
ICP-MS 
AAS 

ICP-MS 
AAS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 

u(xi) 
0.065 
0.07 
0.25 
0.6 
0.23 
0.1635 
0.189145 
0.235 
0.275 
0.23 
0.35 
0.2015 
0.058 
0.17 
0.48 
0.03 
0.366667 
0.235 

0.25 
0 
0.185 
0.22 
0.1515 
0.137 
0.363731 
0.2275 
0.39 
0.1965 
0.185 
0.25 
0.055 

z-scoreb 
0.08 
-0.94 
-0.24 
0.05 
0.02 
-0.30 
-0.85 
-0.74 
-0.85 
-0.18 
0.34 
-0.12 
-0.09 
-0.53 
0.34 
-2.37 
3.85 
-0.53 

ζ-score  uncert.c 
0.27 
-3.01 
-0.31 
0.03 
0.03 
-0.56 
-1.42 
-1.02 
-1.02 
-0.26 
0.33 
-0.19 
-0.31 
-0.97 
0.24 
-9.41 
3.51 
-0.73 

b 
b 
a 
c 
a 
a 
a 
a 
a 
a 
c 
a 
b 
a 
c 
b 
c 
a 

0.34 
-0.82 
-0.65 
0.02 
-0.76 
0.01 
0.64 
-0.02 
2.39 
-0.03 
-0.24 
-0.24 
0.02 

0.45 
-3.49 
-1.10 
0.03 
-1.52 
0.02 
0.58 
-0.03 
2.05 
-0.05 
-0.41 
-0.31 
0.08 

a 
b 
a 
a 
a 
a 
c 
a 
c 
a 
a 
a 
b 

c 

1.7 

0.7 

2 

ICP-MS 

0.35 

-1.70 

-1.62 

a √3 is set by the ILC coordinator when no coverage factor k is reported. The reported uncertainty was assumed to 
have a rectangular distribution with k=√3, 
b score evaluation colours: satisfactory, questionable, unsatisfactory, 
c Case "a": u(xpt) ≤ u(xi) ≤ σpt; Case "b": u(xi) < u(xpt); and Case "c": u(xi) > σpt 

26 

 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
27 

 
 
 
 
Annex 9: Results for Cd 

Assigned values: xpt = 1.35; U(xpt) = 0.14 (k=2); and σpt = 0.22; all values in mg kg-1,  
relative to a feed with a moisture content of 12 %    

Lab Code 
001 
002 
003 
004 
005 
007 
008 
009 
010 
011 
012 
013 
014 
015 
016 
017 
018 
019 
020 
021 
022 
023 
024 
025 
026 
027 
028 
029 
030 
031 
032 
033 
034 
036 

U(xi) 

0.1 
0.07 
0.2 
0.6 
0.34 

Xi 
1.4 
1.24 
1.1 
1.3 
1.32 
1.250  0.187 
1.213  0.23047 
1.29 
1.47 
1.45 
1.4 
1.403  0.421 
1.305  0.040 
1.26 
1.4 
1.50 
1.4 
1.3 

0.21 
0.56 
0.12 
0.3 
0.54 

0.19 
0.26 
0.24 
0.3 

0.3 

0.23 
0.19 

1.5 
1.49 
1.30 
1.26 
1.414  0.283 
1.433  0.201 
1.45 
1.411  0.282 
1.55 
1.303  0.275 
1.3 
1.33 
1.38 

0.22 
0.25 
0.07 

0.39 

0.36 

ka 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
2 

2 
√3 
2 
2 
2 
2 
√3 
2 
2 
2 
2 
2 
2 

technique 
ICP-MS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
AAS 
ICP-MS 
ICP-OES 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
AAS 
ICP-MS 
AAS 

ICP-MS 
AAS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 

u(xi) 
0.05 
0.035 
0.1 
0.3 
0.17 
0.0935 
0.115235 
0.095 
0.13 
0.12 
0.15 
0.2105 
0.02 
0.105 
0.28 
0.06 
0.1 
0.27 

0.15 
0 
0.115 
0.095 
0.1415 
0.1005 
0.207846 
0.141 
0.195 
0.1375 
0.11 
0.125 
0.035 

z-scoreb 
0.22 
-0.52 
-1.16 
-0.24 
-0.15 
-0.47 
-0.64 
-0.29 
0.55 
0.45 
0.22 
0.24 
-0.22 
-0.42 
0.22 
0.69 
0.22 
-0.24 

ζ-score  uncert.c 
0.57 
-1.46 
-2.08 
-0.17 
-0.17 
-0.88 
-1.04 
-0.53 
0.80 
0.71 
0.29 
0.23 
-0.66 
-0.73 
0.17 
1.63 
0.40 
-0.19 

b 
b 
a 
c 
a 
a 
a 
a 
a 
a 
a 
a 
b 
a 
c 
b 
a 
c 

0.69 
0.64 
-0.24 
-0.42 
0.29 
0.38 
0.45 
0.27 
0.92 
-0.23 
-0.24 
-0.10 
0.13 

0.90 
2.02 
-0.39 
-0.78 
0.40 
0.67 
0.45 
0.38 
0.96 
-0.32 
-0.40 
-0.15 
0.37 

a 
b 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
b 

a 

1.1 

0.4 

2 

ICP-MS 

0.2 

-1.16 

-1.19 

a √3 is set by the ILC coordinator when no coverage factor k is reported. The reported uncertainty was assumed to 
have a rectangular distribution with k=√3, 
b score evaluation colours: satisfactory, questionable, unsatisfactory, 
c Case "a": u(xpt) ≤ u(xi) ≤ σpt; Case "b": u(xi) < u(xpt); and Case "c": u(xi) > σpt 

28 

 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
29 

 
 
 
 
Annex 10: Results for Pb 

Assigned values: : xpt = 0.850; U(xpt) = 0.039 (k=2); and σpt = 0.145 ; all values in mg kg-1,  
relative to a feed with a moisture content of 12 %       

0.3 
0.24 

U(xi) 
0.08 

Xi 
0.84 
0.893  0.054 
< 1.8 
0.8 
0.85 
0.914  0.137 
0.876  0.1752 
0.879  0.167 
1.39 
0.828  0.132 
1.1 
0.891  0.267 
0.858  0.036 
0.79 
0.93 
1.39 
0.98 
0.84 

0.10 
0.47 
0.06 
0.2 
0.25 

0.19 

0.3 

0.19 

0.15 

0.88 
1.5 
0.848  0.170 
0.93 
0.583  0.117 
0.864  0.137 
0.94 
0.988  0.198 
0.985  0.246 
0.720  0.209 
0.79 
0.818  0.204 
0.828  0.041 

0.24 

0.18 

ka 
2 
2 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
2 

2 
√3 
2 
2 
2 
2 
√3 
2 
2 
2 
2 
2 
2 

technique 
ICP-MS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
AAS 
ICP-MS 
ICP-OES 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 

ICP-MS 
AAS 

ICP-MS 
AAS 
ICP-MS 
AAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 

Lab Code 
001 
002 
003 
004 
005 
007 
008 
009 
010 
011 
012 
013 
014 
015 
016 
017 
018 
019 
020 
021 
022 
023 
024 
025 
026 
027 
028 
029 
030 
031 
032 
033 
034 
036 

u(xi) 
0.04 
0.027 

z-scoreb 
-0.07 
0.30 

ζ-score  uncert.c 
-0.22 
1.29 

a 
a 

0.15 
0.12 
0.0685 
0.0876 
0.0835 
0.095 
0.066 
0.15 
0.1335 
0.018 
0.05 
0.235 
0.03 
0.066667 
0.125 

0.095 
0 
0.085 
0.075 
0.0585 
0.0685 
0.138564 
0.099 
0.123 
0.1045 
0.09 
0.102 
0.0205 

-0.35 
0.00 
0.44 
0.18 
0.20 
3.74 
-0.15 
1.73 
0.28 
0.06 
-0.42 
0.55 
3.74 
0.90 
-0.07 

0.21 
4.50 
-0.01 
0.55 
-1.85 
0.10 
0.62 
0.96 
0.93 
-0.90 
-0.42 
-0.22 
-0.15 

-0.33 
0.00 
0.90 
0.29 
0.34 
5.57 
-0.32 
1.65 
0.30 
0.30 
-1.12 
0.34 
15.07 
1.87 
-0.08 

0.31 
33.16 
-0.02 
1.03 
-4.33 
0.20 
0.64 
1.37 
1.08 
-1.22 
-0.65 
-0.31 
-0.78 

c 
a 
a 
a 
a 
a 
a 
c 
a 
b 
a 
c 
a 
a 
a 

a 
b 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 

a 

0.87 

0.28 

2 

ICP-MS 

0.14 

0.14 

0.14 

a √3 is set by the ILC coordinator when no coverage factor k is reported. The reported uncertainty was assumed to 
have a rectangular distribution with k=√3, 
b score evaluation colours: satisfactory, questionable, unsatisfactory, 
c Case "a": u(xpt) ≤ u(xi) ≤ σpt; Case "b": u(xi) < u(xpt); and Case "c": u(xi) > σpt 

30 

 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
31 

 
 
 
 
Annex 11: Results for Hg  

Assigned values: xpt = 0.0481; U(xpt)  = 0.0022 (k=2); and σpt = 0.0106 ; all values in mg kg-1,  
relative to a feed with a moisture content of 12 %        

Xi 
0.059 
0.052 
0.052 
0.07 
0.052 
0.052 
0.051 
0.0483 
0.093 
0.051 
0.046 
0.068 
0.052 
0.045 
0.058 
0.082 
0.0490 
0.048 
0.0543 
0.056 

0.0495 
0.054 
0.064 
0.0596 
< 0.08 
0.057 
0.06 
0.0392 
0.053 
0.0471 
0.110 

U(xi) 
0.006 
0.005 
0.008 
0.02 
0.015 
0.013 
0.00255 
0.0126 
0.012 
0.015 
0.004 
0.008 
0.008 
0.007 
0.023 
0.004 
0.0010 
0.01 
0.00217 
0.012 

0.0104 
0.014 
0.016 
0.0137 

0.011 
0.015 
0.010 
0.011 
0.0118 
0.006 

ka 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
2 
2 
2 

2 
2 
2 
2 

2 
2 
2 
2 
2 
2 

Lab Code 
001 
002 
003 
004 
005 
007 
008 
009 
010 
011 
012 
013 
014 
015 
016 
017 
018 
019 
020 
021 
022 
023 
024 
025 
026 
027 
028 
029 
030 
031 
032 
033 
034 
036 

technique 
ICP-MS 
DMA 
AAS 
AAS 
ICP-MS 
AMA-254 
AMA-254  
ICP-MS 
CV-AAS 
ICP-MS 
AMA-254 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
AAS 
DMA 
AAS 
AMA-254 
DMA 

AAS 
HG-CVAAS 
AAS 
ICP-MS 
ICP-MS 
ICP-MS 
ICP-MS 
DMA 
DMA 
ICP-MS 
CV-AAS 

u(xi) 
0.003 
0.0025 
0.004 
0.01 
0.0075 
0.0065 
0.001275 
0.0063 
0.006 
0.0075 
0.002 
0.004 
0.004 
0.0035 
0.0115 
0.002 
0.000333 
0.005 
0.001085 
0.006 

0.0052 
0.007 
0.008 
0.00685 

0.0055 
0.0075 
0.005 
0.0055 
0.0059 
0.003 

z-scoreb 
1.03 
0.37 
0.37 
2.07 
0.37 
0.37 
0.27 
0.02 
4.24 
0.27 
-0.20 
1.88 
0.37 
-0.29 
0.93 
3.20 
0.08 
-0.01 
0.58 
0.75 

0.13 
0.56 
1.50 
1.08 

0.84 
1.12 
-0.84 
0.46 
-0.09 
5.84 

ζ-score 
3.41 
1.43 
0.94 
2.18 
0.51 
0.59 
1.72 
0.03 
7.36 
0.38 
-0.92 
4.80 
0.94 
-0.84 
0.86 
14.85 
0.78 
-0.02 
4.01 
1.30 

0.26 
0.83 
1.97 
1.66 

1.59 
1.57 
-1.74 
0.87 
-0.17 
19.37 

uncert.c 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
a 
c 
a 
b 
a 
b 
a 

a 
a 
a 
a 

a 
a 
a 
a 
a 
a 

a √3 is set by the ILC coordinator when no coverage factor k is reported. The reported uncertainty was assumed to 
have a rectangular distribution with k=√3, 
b score evaluation colours: satisfactory, questionable, unsatisfactory, 
c Case "a": u(xpt) ≤ u(xi) ≤ σpt; Case "b": u(xi) < u(xpt); and Case "c": u(xi) > σpt 

32 

 
 
 
 
 
 
 
 
 
 
 
  
  
  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
33 

 
 
 
 
Annex 12: Results for iAs 

Assigned values: xpt = 2.01; U(xpt)  = 0.09 (k=2); and σpt = 0.30 ; all values in mg kg-1,  
relative to a feedingstuffs with a moisture content of 12 %    

Lab Code  Xi 

U(xi) 
0.17 
0.16 

0.5 
0.015 
0.325 

2.09 
1.96 

2.1 
0.086 
2.169 

1.9 

0.6 

1.321 
2.021 
1.98 
2.7 

3.3 
2.1 

0.33 
0.05 
0.45 
1.08 

0.68 

2.2 

0.4 

2.01 
1.08 
2.083 
1.885 

0.44 

0.312 
0.339 

2.2 
2.24 

2.43 
1.6 

0.37 
0.56 

0.24 
0.5 

ka 
2 
2 

2 
2 
2 

2 

2 
2 
2 
2 

√3 
2 

2 

2 
√3 
2 
2 

2 
2 

2 
2 

technique 
HPLC-ICPMS 
HPLC-ICP-MS 

AAS 
HPLC-ICP-MS 
HPLC-ICP-MS 

u(xi) 
0.085 
0.08 

0.25 
0.0075 
0.1625 

AAS 

0.3 

HPLC-ICP-MS 
HG-AAS 
ICP-MS 
HPLC-ICP-MS 

ICP-MS 
HPLC-ICP-MS 

0.165 
0.025 
0.225 
0.54 

0 
0.34 

HPLC-ICP-MS 

0.2 

ICP-MS 
AAS 
AAS 
ICP-MS 

0.22 
0 
0.156 
0.1695 

HPLC-ICP-MS 
ICP-MS 

HPLC-ICP-MS 
LC-ICP-MS 

0.185 
0.28 

0.12 
0.25 

z-scoreb 
0.25 
-0.18 

0.29 
-6.38 
0.52 

-0.38 

-2.29 
0.03 
-0.11 
2.27 

4.26 
0.29 

0.62 

-0.01 
-3.09 
0.23 
-0.42 

0.62 
0.75 

1.38 
-1.37 

ζ-score 
0.80 
-0.58 

0.34 
-43.40 
0.92 

-0.37 

-4.06 
0.15 
-0.15 
1.27 

29.40 
0.25 

0.91 

-0.01 
-21.33 
0.43 
-0.73 

0.98 
0.80 

3.26 
-1.63 

uncert.c 
a 
a 

a 
b 
a 

a 

a 
b 
a 
c 

b 
c 

a 

a 
b 
a 
a 

a 
a 

a 
a 

001 
002 
003 
004 
005 
007 
008 
009 
010 
011 
012 
013 
014 
015 
016 
017 
018 
019 
020 
021 
022 
023 
024 
025 
026 
027 
028 
029 
030 
031 
032 
033 
034 
036 

 a √3 is set by the ILC coordinator when no coverage factor k is reported. The reported uncertainty was assumed to 
have a rectangular distribution with k=√3, 
b score evaluation colours: satisfactory, questionable, unsatisfactory, 
c Case "a": u(xpt) ≤ u(xi) ≤ σpt; Case "b": u(xi) < u(xpt); and Case "c": u(xi) > σpt 

34 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
35 

 
 
 
 
Annex 13: Overview of performance versus technique 

Lab 

total As 

Cd 

ICP-MS 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

HG-AAS 

AAS 

Pb 

ICP-MS 

ICP-MS 

-- 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

Hg 

iAs 

ICP-MS 

HPLC-ICP-MS 

DMA 

HPLC-ICP-MS 

AAS 

AAS 

-- 

AAS 

ICP-MS 

HPLC-ICP-MS 

AMA 254 

HPLC-ICP-MS 

AMA 254  

ICP-MS 

CV-AAS 

ICP-MS 

-- 

AAS 

-- 

-- 

-- 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-OES 

ICP-OES 

ICP-OES 

AMA254 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

-- 

AAS 

-- 

AAS 

-- 

AAS 

HPLC-ICP-MS 

ICP-MS 

ICP-MS 

HG–AAS  

ICP-MS 

ICP-MS 

HPLC-ICP-MS 

AAS 

DMA 

AAS 

-- 

ICP-MS 

HPLC-ICPMS 

AMA-254 

-- 

ICP-MS 

ICP-MS 

ICP-MS 

DMA 

HPLC-ICP-MS 

AAS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

-- 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

-- 

AAS 

AAS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

ICP-MS 

-- 

ICP-MS 

ICP-MS 

ICP-MS 

-- 

AAS 

HG-CVAAS 

AAS 

-- 

ICP-MS 

AAS 

AAS 

ICP-MS 

ICP-MS 

-- 

ICP-MS 

ICP-MS 

DMA 

DMA 

ICP-MS 

CV-AAS 

-- 

-- 

-- 

-- 

HPLC-ICP-MS 

ICP-MS 

-- 

-- 

-- 

HPLC-ICP-MS 

LC-ICP-MS 

001 

002 

003 

004 

005 

007 

008 

009 

010 

011 

012 

013 

014 

015 

016 

017 

018 

019 

020 

021 

022 

023 

024 

025 

026 

027 

028 

029 

030 

031 

032 

033 

034 

036 

Z-Score evaluation colours: satisfactory, questionable, unsatisfactory. 

36 

 
 
 
  
 
 
 
Annex 14: Conformity as expressed by the participants.  

Lab  Comply 

If not compliant, specify why.a 

001 

002 

003 

004 

005 

007 

008 

009 

010 

011 

012 

013 

014 

015 

016 

017 

018 

019 

020 

021 

022 

023 

024 

025 

026 

Yes 

No 

Yes 

Yes 

Yes 

No 

No 

No 

No 

No 

No 

Yes 

No 

No 

? 

No 

? 

Yes 

Yes 

No 

No 

No 

No 

Yes 

No 

027 

No 

028 

029 

? 

Yes 

030 

No 

031 

No 

032 

033 

034 

036 

No 

No 

? 

Yes 

For Cd the maximum level is 1 mg/Kg in feed materials of vegetable origin 

> ML 

Result of Cd exceeds the maximum level (ML) as laid down in DIR 
2002/32/EC for "Feed materials of vegetable origin".  
Results of As, iAs, Pb and Hg do not exceed the MLs. 

because of exceeding ML for Cd (feed materials of vegetable origin 1 ppm) 
and exceeding ML for inorg. As (2ppm/88 % dry mass) 
Cd is more than 1 mg/kg 

Cd is above MRL (1,0 mg/kg) 

The content of cadmium (minus measurement uncertainty) is higher than 
maximum permitted content. 
Cd exceeds allowed maximum content (0.5 mg/kg 12 % moisture) 

Cd content is higher than 1 mg/kg 

Cd: Reg.value 1mg/kg. Our result 1.05mg/kg (after UM subtracted) 

Not compliant for Cd 

 (Note authors: No Cd results) 

Cd concentration: 1.456 mg/kg - 0.288 mg/kg = 1.168 mg/kg > 1 mg/kg 
(the maximum level for Cd in feed materials of vegetable origin) 
Out of limits for Cd 

Cd content value exceeds the maximum allowed 

Cd content is over the maximum level (1mg/Kg) 

The Cd content is over 1 mg/kg 

ML for Cadmium for plant ingredient is 1mg/kg, which is violated even 
after substracting the measurement uncertainty 
Non compliant for Cd 

Because concentration of Cd is above limit of 1 mg/kg (calculating 
Measurement Uncertainty ) 

The concentration of cadmium in the sample (after subtracting the 
uncertainty) is above 1 mg/Kg, which, according to regulation 574/2011 is 
the maximum limit for Feed materials of vegetable origin. 
Cd-level above ML ( 1 mg/kg) 

As, Cd, Hg are more then limit 

No MLs for iAs in palm kernel expeller (Note Authors: no Cd results) 

xi – Ui 

b 

Eval.c 

> ML 

FC 

> ML 

TNC 

< ML 

< ML 

< ML 

TC 

TC 

TC 

> ML 

FNC 

< ML 

> ML 

> ML 

FNC 

TNC 

TNC 

TNC 

> ML 

FNC 

TC 

TNC 

TNC 

< ML 

> ML 

> ML 

< ML 

> ML 

TNC 

> ML 

< ML 

nd 

TC 

FC 

> ML 

TNC 

> ML 

> ML 

TNC 

TNC 

> ML 

TNC 

> ML 

FC 

> ML 

TNC 

> ML 

TNC 

> ML 

> ML 

FC 

> ML 

TNC 

> ML 

TNC 

TNC 

FNC 

> ML 

> ML 

nd 

< ML 

TC 

a 

Wrong justifications are marked in yellow.  
b
 Maximum Level for Cd in palm kernel expeller set by DIR 2002/32/EC: ML = 1 mg kg-1 

c
 TNC: True Non-Compliant, TC: True Compliant, FNC: False Non-Compliant, FC: False Compliant.  

37 

 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Annex 15: Experimental details (as reported by the participants) 

Lab 
Code  Measurand 
001 
001 
001 
001 
002 
002 
002 
002 
003 
003 
003 
003 
004 
004 
004 
004 
005 
005 
005 
005 
007 
007 
007 

As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 

007 
008 
008 
008 
008 
009 
009 
009 
009 
010 
010 
010 
010 
011 
011 
011 
011 
012 
012 
012 
012 
013 
013 
013 

013 

Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 

Hg 

Digestion 
type 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
no dig. 
CMW 
CMW 
CMW 
-- 
Dry Ash 
OWD 
OWD 
CMW 
CMW 
CMW 
CMW 
CMW 
OMW 
OMW 
OMW 

no dig. 
CMW 
CMW 
CMW 
Dry Ash 
CMW 
CMW 
CMW 
CMW 
Dry Ash 
Dry Ash 
Dry Ash 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
none 
Dry Ash 
Dry Ash 
Dry Ash 
Pressure 
bomb 

Acid mixture 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
- 
HNO3/H202/HF 
HNO3/H202/HF 
HNO3/H202/HF 
-- 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/HCl 
HNO3/HCl 
HNO3/HCl 
HNO3/HCl 
HNO3 
HNO3 
HNO3 

no acids 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
-- 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/HCl 
HNO3/HCl 
HNO3/HCl 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
none 
-- 
-- 

Temperature 
(oC) 
166 
166 
166 
166 
150C/180 
150C/180 
150C/180 
- 
200 
200 
200 
-- 
445 
170 
170 
170 
220 
220 
220 
220 
200 
200 
200 
dry combustion 
 in oxygen 
max.190 
max.190 
max.190 
-- 
200 
200 
200 
200 
450 
450 
450 
180 
200 
200 
200 
200 
100-200  
100-200  
100-200  
200-650  
550 
450 
450 

Time  
(min) 
54  
54  
54  
54  
20/10  
20/10  
20/10  
- 
28 
28 
28 
-- 
24 h 
1 h 
1 h 
20  
25 
25 
25 
25 
10 
10 
10 
270s temp. 
programe 
51 
51 
51 
-- 
60  
60  
60  
60  
12 h 
24 h 
24 h 
50  
20  
20  
20  
20  
22  
22  
22  
3  
24 h 
24 h 
24h 

- 

3 

38 

Recovery 
% 
104 
104 
97 
95 
108 
90 
111 
101 
91.76 
98.21 
88.75 
94.12 
96 
88 
100 
112 
100 
100 
100 
100 
98-102 
98-102 
98-102 

98-102 
102 
89 
102 
102 
88 
95 
95 

102 
94.2 
100 
98 
100 
89 
100 
84 
93 
92 
83 

89 
93 
94 

LODs 
(mg/kg) 
0,005 
0,002 
0,003 
0,001 
0.0009 
0.0003 
0.004 
0.0002 
0.18 
0.075 
0.50 
0.010 
0.063 
0.01 
0.05 
0.025 
0,01 
0,003 
0,004 
0,019 
0,006 
0,006 
0,09 

0,0006 
0.00231 
0.00160 
0.00135 
0.000146 
0,1 
0,01 
0,01 
0,01 
0.100 
0.07 
0.5 
0.003 
0.008 
0.002 
0.005 
0.008 
0,5 
0,1 
0,5 

0.002 
0.001 
0.002 

0.001 

 
 
 
  
  
  
  
  
  
Lab 
Code  Measurand 
014 
014 
014 
014 
015 
015 
015 
015 
016 
016 
016 
016 
017 
017 
017 
017 
018 
018 
018 
018 
019 
019 
019 
019 
020 
020 
020 
020 
021 
021 
021 
021 
022 
022 
022 
022 
023 
023 
023 
023 

As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 

024 

024 

024 

024 
025 
025 
025 
025 

As 

Cd 

Pb 

Hg 
As 
Cd 
Pb 
Hg 

Digestion 
type 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
MW 
MW 
MW 
-- 
CMW 
CMW 
CMW 
CMW 

CMW 
CMW 
CMW 

CMW 
CMW 
CMW 

CMW 
CMW 
CMW 
Dry Ash 
Pressure 
bomb 
Pressure 
bomb 
Pressure 
bomb 
Pressure 
bomb 
CMW 
CMW 
CMW 
CMW 

Acid mixture 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/HCl 
HNO3/HCl 
HNO3/HCl 
HNO3, HCl 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
-- 
HNO3 
HNO3 
HNO3 
HNO3 

HNO3 
HNO3 
HNO3 

HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO/H2O2 
HNO/H2O2 
HNO/H2O2 
- 

HNO3/H2O2 

HNO3/H2O2 

HNO3/H2O2 

HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 

Temperature  
(oC) 
180 
180 
180 
180 
240 
240 
240 
240 

Time  
(min) 
30  
30 min 
30 min 
30 min 
15 
15 
15 
15 

15  
15  
15  
15  
10  
10  
10  
-- 
30  
30  
30  
30  

30  
30  
30  

40 
40 
40 
40 
20  
20  
20  
150 s 
Ramp/hold 
20/20 
Ramp/hold 
20/20 
Ramp/hold 
20/20 
Ramp/hold 
20/20 
20 
20 
20 
20 

185 
185 
185 
185 
180  
180  
180  
-- 
210 
210 
210 
210 

180 
180 
180 

200 
200 
200 
200 
200 
200 
200 
850 

180 

180 

180 

180 
200 
200 
200 
200 

39 

Recovery 
% 
104 
102 
100 
101 
100 
102 
110 
113 

97.3 
96.6 
99.6 
100.8 

95.8 
110 
103.5 
99.7 
105 
80 
85 
90 

101 
102 
96 
103 

LODs 
(mg/kg) 
0,010 
0,002 
0,005 
0,010 
0.003 
0.08 
0.02 
0.002 
0,01 
0,005 
0,03 
0,005 
0.06 
0.01 
0.07 
0.01 
1 
0.5 
0.1 
0.005 
0.03 
0.004 
0.02 
0.01 

0.00042 
0.0006 
0.0017 
0.0048 
0.0002 
0.08 
0.1 
0.05 

0.020 
0.005 
0.020 
0.005 

80-110 

0.067 

80-110 

0.0033 

80-110 

0.010 

80-110 
98 
110 
90 
92 

0.016 
0.04 
0.04 
0.04 
0.04 

 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Lab 
Code  Measurand 
026 
026 
026 
026 
027 
027 
027 
027 
028 
028 
028 
028 
029 
029 
029 
029 
030 
030 
030 
030 
031 
031 
031 
031 
032 
032 
032 
032 
033 
033 
033 
033 
034 
034 
034 
034 
036 
036 
036 
036 

As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 
As 
Cd 
Pb 
Hg 

Digestion 
type 
CMW 
CMW 
CMW 
CMW 
MW 
MW 
MW 
MW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
- 
CMW 
CMW 
CMW 

CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
CMW 
OWD 

CMW 
CMW 
CMW 

Acid mixture 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
- 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 

HNO3 
HNO3 
HNO3 
HNO3 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2O2 
HNO3/H2SO4 

HNO3 
HNO3 
HNO3 

Temperature  
(oC) 
220 
220 
220 
220 
200 
200 
200 
200 
200 
200 
200 
200 
230 
230 
230 
230 
210 
210 
210 
- 
200 
200 
200 

230 
230 
230 
230 
180°C 
180°C 
180°C 
200°C 

200 
200 
200 

CMW: closed microwave digestion; OWD: open wave digestion 

Time  
(min) 
20 
20 
20 
20 
30  
30  
30  
30  
8  
8  
8  
8  
50  
50  
50  
50  
30  
30  
30  
- 
40 
40 
40 

20 
20 
20 
20 
30. 
30. 
30. 
15 min. 

20  
20  
20  

Recovery 
% 
102 
100 
102 
105 
111 
111 
107 
103 

98,81 
98,81 
99,45 
96 
97 
94 
95 
102 
100 
100 
100 
100 
100 
100 
100 
100 

LODs 
(mg/kg) 
0.013 
0.0014 
0.006 
0.003 
0.05 
0.02 
0.27 
0.08 
0,002 
0,02 
0,02 
0,03 
0.01 
0.01 
0.02 
0.01 
10 
10 
10 
1 
0.020 
0.004 
0.006 
0.010 
0,025 
0,006 
0,02 
0,013 
0.005 
0.005 
0.010 
0.005 

100 
100 
100 
100 

0.2 
0.05 
0.05 
0.015 

40 

 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 
 
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doi:10.2787/370477 

ISBN 978-92-79-64421-4