Report of the CCQM-K56

Transcription

1 Draft B Report of the CCQM-K56 Page 1/26 Report of the CCQM-K56 Ca, Fe, Zn and Cu in Whole Fat Soybean Powder Draft B (Final) Ma Liandi, Wang Qian Beijing, December 2009

2 Draft B Report of the CCQM-K56 Page 2/26 ABSTRACT The CCQM-K56 key comparison was organized by the inorganic analysis working group (IAWG) of CCQM as a follow-up to completed pilot study CCQM-P64 to test the abilities of the national metrology institutes to measure the amount content of nutritious elements in whole fat soybean powder. A pilot study CCQM-P64.1 was parallelized with this key comparison. National Institute of Metrology (NIM) P.R.China acted as the coordinating laboratory. 11 NIMs participated in CCQM-K56, four elements Ca, Fe, Zn and Cu in different concentration levels have been focused, different measurement methods (IDMS, ICP-MS, ICP-OES, AAS and INAA) and microwave digestion method were used. The agreement of the results of CCQM-K56 is very good, and obviously better than that of original P64, it shown that the capability of all of the participants had been promoted from the original pilot study to this key comparison.

3 Draft B Report of the CCQM-K56 Page 3/26 1 INTRODUCTION Food studies have been identified as key activities of CCQM. Considerable attention has been paid to improving accuracy and comparability in food analysis results. Besides toxic and harmful elements, essential elements in food are given attention to again because the lack of them can result in serious innutrition and potential diseases. The determination of them is also the need of quantitative mark of nutriments in nutrition labels of food products in many countries. Soybean as one kind of typical foodstuff serves as human being important source for the intake of protein, some essential elements and the raw material of many food products. The inorganic analysis working group of CCQM had organized successfully the pilot study CCQM-P64 for the determination of Cu,Zn,Fe and Ca in nonfat soybean powder. IAWG agreed that this should proceed to a key comparison (CCQM-K56) and run in parallel with a pilot study (CCQM-P64.1) as a follow-up for the completed pilot study P64. The focused elements are also Cu,Zn,Fe and Ca, but the sample changed into whole fat soybean powder. NIM () also acted as the coordinating laboratory. Scope of the study: The approximate levels of the chosen elements are: Ca:(1000~2000)mg/kg ; Fe:(30~100)mg/kg; Zn:(10~80)mg/kg; Cu:(5~20)mg/kg.

4 Draft B Report of the CCQM-K56 Page 4/26 2 LIST OF PARTICIPANTS There were 11 institutes registered in CCQM-K56. Table 1 contains the full names of all participating NMIs, Lab No. and contact persons. (Lab No. is also the Sample No.) Table 1 List of participants Lab No. Institute Full Name Country Contact Person Elements INRIM National Institute of Metrological Research Unit of Radiochemistry Spectroscopy and INTI Instituto Nacional de Tecnologia Industrial KRISS Korean Research Institute of Standards and Science NCM National Center of Metrology NIST National Institute for Standards and Technology NIM National Institute of Metrology P.R.China NIMT National Metrology Institute of NMIJ National Metrology Institute of Japan NMISA National Metrology Institute of South Africa PTB Physikalisch- Technische Bundesanstalt UME TUBITAK - National Metrology Institute Italy Luigi Bergamaschi Fe, Zn Argentina Liliana Valiente Ca, Fe, Zn, Cu Korea Euijin Hwang Ca, Fe, Zn, Cu Bulgaria Boryana Koleva Zn, Cu USA Gregory C. Turk. Ca, Fe, Zn, Cu China Ma Liandi Ca, Fe, Zn, Cu Thailand Charun Yafa Ca, Fe, Zn, Cu Japan Takayoshi Kuroiwa Ca, Fe, Zn, Cu South Africa Alex Barzev Ca, Fe, Zn, Cu Germany Detlef Schiel Ca, Fe, Zn, Cu Turkey Duran KARAKAS Fe, Zn, Cu

5 Draft B Report of the CCQM-K56 Page 5/26 3 TIME SCHEDULE Deadline for registration: 10 June 2007 Dispatch of the samples: the middle of the June 2007 Deadline for receipt of the result report: 31 December 2007 Discussion of Draft A at CCQM/ IAWG meeting: April 2008 Discussion of Draft A.2 at CCQM/ IAWG meeting: October 2008 Draft B report: April 2009

6 Draft B Report of the CCQM-K56 Page 6/26 4 SAMPLES Sample Preparation The source of material was whole fat soybean powder without any additives, the contents of protein and fat in which are 40.2% and 20.3% respectively. The sample was dried and milled, then sieved to yield a fraction with the particle size within 25-55µm. This fraction was blended in a mechanical blender for 6 hours. After a pre-homogeneity test it was packaged into clean brown glass bottles with plastic inner lids and screw caps, and then sterilized with cobalt-60 gamma radiation to 2.5 megarads. At last, each unit was vacuum packed in an aluminum-nylon pouch. Homogeneity testing 15 bottles were sampled randomly from 300 bottles, and two samples were sampled independently from each bottle. Three kinds of measurement methods were used to check the homogeneity of the samples. The one is XRF for all of the four elements, and the minimum sampling is 0.5g. The others are ICP-OES for Ca, Fe, Zn and ICP-MS for Cu after microwave digestion, and the minimum sampling is 0.1g. From different kinds of homogeneity test results, no statistically significant heterogeneity was found based on F test. Table 2 Measurement methods Homogeneity testing results Element F RSD Sampling (g) Ca % 0.5 XRF Fe % 0.5 Zn % 0.5 Cu % 0.5 Ca % 0.1 ICP-OES Fe % 0.1 Zn % 0.1 ICP-MS Cu % 0.1 Distribution The sample had been shipped on 14, 15, 16 May 2007 directly to all of the participants. Each participant received one numbered bottle containing about 25g sample. The sample No. is also the lab No.

7 Draft B Report of the CCQM-K56 Page 7/26 5 INSTRUCTIONS TO PARTICIPANTS The instructions sent to the participants by consisted of a technical protocol and a results report form. The technical protocol (appendix A) contained background information, sample handling and storage, drying before weighing, timing of the comparison, and information on sample homogeneity and sample preparation for measurements. The participants were free to choose the measurement procedure. The results report form contained entries relating to the measurement results, detailed uncertainty evaluation and description of the measurement procedures.

8 Draft B Report of the CCQM-K56 Page 8/26 6 METHODS OF MEASUREMENT The methods of measurement were left free to be selected by the participating institutes. But from the results of the CCQM-P64, we find that IDMS method is the best method for determining elements in food matrix materials. The relative standard deviation and the uncertainty of IDMS method are obviously better than other methods, so that IDMS is recommended for participants of CCQM-K56.. Most of participants had dried sample before weighing, IDMS, ICP-MS, ICP-OES, AAS, INAA measurement methods were used, and the digestion method mostly used microwave digestion. All participants reported more or less details on their procedure in their reports or additional information. Some details on measurements as derived from the reports are given in Table 3, and the statistics of measurement methods are given in Table 4. Table3 Institute Methods of measurement used: Approx. Procedure details sample mass (g) Sample dried Digestion method Measurement method INRIM 0.5 yes \ INAA INTI 0.5 yes microwave digestion AAS KRISS 0.2 yes microwave digestion IDMS NCM 0.3 yes microwave digestion ICP-MS NIST 0.5 yes microwave digestion ICP-OES 0.1(IDMS) IDMS(Fe\Cu\Zn) NIM 0.5(ICP-MS \ICP-OES) yes microwave digestion ICP-MS(Ca) ICP-OES(Ca) NIMT 0.25 yes microwave digestion IDMS NMIJ 0.3 yes microwave digestion ICP-OES(Ca) IDMS(Fe\Zn\Cu) NMISA 0.25 yes microwave digestion IDMS PTB 0.5(Ca) 0.3(Fe Zn Cu) yes microwave digestion IDMS UME 0.5 \ microwave digestion ICP-MS

9 Draft B Report of the CCQM-K56 Page 9/26 Table4 The statistics of measurement methods: Method number of methods used Ca Fe Zn Cu IDMS ICP-MS ICP-OES AAS INAA \ 1 1 \

10 Draft B Report of the CCQM-K56 Page 10/26 7 RESULTS AND DISCUSSION The CCQM-K56 reported values and uncertainties are summarised in table 5 to table 8. Table 5 CCQM-K56 Results of Ca Institute Result /mg.kg -1 n SD /mg.kg-1 u c /mg.kg -1 U /mg.kg -1 k INTI KRISS NIST NIM NIMT NMIJ NMISA PTB AVERAGE 1543 STDEV RSD 0.79% Note: NIM used ICP-OES and ICP-MS combined result. Table 6 CCQM-K56 Results of Fe Institute Result n SD u c U k /mg.kg -1 /mg.kg-1 /mg.kg -1 /mg.kg -1 INRIM INTI KRISS NIST NIM NIMT NMIJ NMISA PTB UME AVERAGE STDEV 2.99 RSD 5.6% Table 7 CCQM-K56 Results of Zn Institute Result n SD u c U k /mg.kg -1 /mg.kg-1 /mg.kg -1 /mg.kg -1 INRIM INTI

11 Draft B Report of the CCQM-K56 Page 11/26 KRISS NCM NIST NIM NIMT NMIJ NMISA PTB UME AVERAGE STDEV 0.76 RSD 2.1% Table 8 CCQM-K56 Results of Cu Institute Result n SD u c U k /mg.kg -1 /mg.kg-1 /mg.kg -1 /mg.kg -1 INTI KRISS NCM NIST NIM NIMT NMIJ NMISA PTB UME AVERAGE STDEV 0.24 RSD 2.4% Discussion the KCRV of the CCQM-K56: Several approaches to estimate the key comparison reference value (KCRV) were considered. The difference between the average and the median are compared in table 9. Table 9 Agreement of the average and the median Ca Fe Zn Cu n Average(mg/kg) Median(mg/kg) s u= (mg/kg) n

12 Draft B Report of the CCQM-K56 Page 12/26 t 0.05 (n) U= k u (k=t) U= k u (k=2) From the table 9, we can find that the average and the median are very similar for each element. All results of this comparison are approximately submitted by the Gauss Distribution,so the average and standard deviation of the mean of the data provide a justifiable basis for the KCRV and its uncertainty. We proposed the average as the KCRV of the CCQM-K56, and the standard deviation of the mean (u= uncertainties U(k=2) as the KCRU of the CCQM-K56. s n ) as the uncertainty of the KCRV, and expanded From the CCQM Inorganic Analysis Working Group meeting hold on 31 March-1 April 2008, there was a discussion on the homogeneity and its inclusion in the KCRV uncertainty, as well as the method for calculating the KCRV and its uncertainty. For this discussion, there were three aspects to expatiate on: 1. There are several methods were used in homogeneity test, and no statistically significant heterogeneity was found based on F test, it shown that the homogeneity is enough. Although the results RSD is not too little, the main reason is the method which was used in homogeneity test. If we used IDMS method to test the homogeneity, the RSD will be much smaller than that, but for the cost reason, we can t use it for so many samples testing. 2. From all of the results, we can find the number is exceeding 8 independent results from random samples for each element, so the uncertainty of the average has contained the uncertainty of the sample homogeneity. 3. We can t find any example in all of the finished CCQM key comparisons about that the sample homogeneity uncertainty was added to the KCRV uncertainty. After this discussion, we adopted the average as the KCRV of the CCQM-K56, and the standard deviation of the mean (u= uncertainties U(k=2) as the KCRU of the CCQM-K56. s n ) as the uncertainty of the KCRV, and expanded An update on progress with the draft A report in the CCQM Inorganic Analysis Working Group meeting hold in October 2008, and there was some discussion in the previous meeting as to whether the uncertainty of homogeneity should be included in ukcrv but it was concluded that this was not necessary. This was agreed amongst the working group. A draft B report was circulated to all of participants and IAWG members on 13 April 2009, and no farther comments were submitted, after a few modifications the draft B final report is completed. The figures about the K56 s results are followed. In figures the result points used different colour to show the different methods had been used, the red colour line given the average of all of the results and the expanded uncertainties.

13 Draft B Report of the CCQM-K56 Page 13/ CCQM-K56 Ca in Whole Fat Soybean Powder IDMS AAS ICP-MS INAA ICP-OES combined AVERAGE C(mg/kg) NMISA KRISS NMIJ PTB INTI NIM NIST NIMT CCQM-K56 Fe in Whole Fat Soybean Powder IDMS AAS ICP-MS INAA ICP-OES AVERAGE C(mg/kg) NIMT KRISS NIM NIST NMISA PTB INTI NMIJ INRIM UME 40

14 Draft B Report of the CCQM-K56 Page 14/26 CCQM-K56 Zn in Whole Fat Soybean Powder IDMS AAS ICP-MS INAA ICP-OES AVERAGE C(mg/kg) KRISS PTB NIMT NIST NMIJ NIM NMISA INRIM INTI UME NCM IDMS AAS ICP-MS ICP-OES AVERAGE 2 CCQM-K56 Cu in Whole Fat Soybean Powder C(mg/kg) INTI KRISS NIST NIM PTB NIMT NMIJ NMISA NCM UME

15 Draft B Report of the CCQM-K56 Page 15/26 Table 10 Agreement of the results of CCQM-K56, CCQM-P64.1 & CCQM-P64.1 Element Group Amount of results Average(mg.kg -1 ) SD(mg.kg -1 ) RSD ( %) Ca Fe Zn Cu CCQM-K CCQM-P CCQM-P APMP.QM-P CCQM-K CCQM-P CCQM-P APMP.QM-P CCQM-K CCQM-P * CCQM-P APMP.QM-P CCQM-K CCQM-P CCQM-P APMP.QM-P *The average of the Zn is not included the result of TINT because it is too high. From the table 10, very good agreement has been found from the results of K56, and the results of the P64.1pilot study are more dispersed than the results of K56; and the mean of each element in P64.1 is lower than which in K56, the same situation had occurd in P64 and APMP.QM-07, it shown that the lossing maybe occured in the digestion procedure adopted in the CCQM-P64.1 & APMP.QM-07. We also found that the relative standard deviation of the K56 is obviously smaller than original P64, it shown that the participants of K56 had promoted their measurement capability from the original pilot study.

16 Draft B Report of the CCQM-K56 Page 16/26 8 EQUIVALENCE STATEMENTS The equivalence statements have been calculated according to the BIPM guidelines. The degree of equivalence (and its uncertainty) between a NMI result and the KCRV is calculated according to the following equations: d i = ( xi xref ) U + 2 ( d i ) = 2 ( u( xi ) u( xref ) 2 Where x i is value submitted by ith participating NMI (i = 1; : : : ;N), and x ref is key comparison reference value (KCRV), and d i is value component x i x ref of the degree of equivalence (DoE) for NMI i (i = 1; : : : ;N), and u(x i ) is standard uncertainty associated with x i (i = 1; : : : ;N), relating to measurement capability only, and u(x ref ) is standard uncertainty associated with x ref, and U(d i ) is uncertainty component for a 95 % level of confidence of the DoE for NMI i (i = 1; : : : ;N). The equivalence statements for CCQM-K56 are given in Table Table 11 Equivalence Statements of Ca for CCQM-K56 Participant Result (amount content of Ca) u c KCRV d i u(kcrv) u(d i ) U(d i ) mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg NMISA KRISS NMIJ PTB INTI NIM NIST NIMT Table 12 Equivalence Statements of Fe for CCQM-K56 Participant Result (amount content of Fe) u c KCRV d i u(kcrv) u(d i ) U(d i ) mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg NIMT KRISS NIM

17 Draft B Report of the CCQM-K56 Page 17/26 NIST NMISA INTI PTB NMIJ INRIM UME Table 13 Equivalence Statements of Zn for CCQM-K56 Participant Result (amount content of Zn) u c KCRV d i u(kcrv) u(d i ) U(d i ) mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg KRISS PTB NIST NIMT NMIJ NIM NMISA INRIM INTI NCM UME Table 14 Equivalence Statements of Cu for CCQM-K56 Participant Result (amount content of u c KCRV d i u(kcrv) u(d i ) U(d i ) Cu) mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg INTI KRISS NIST NIM

18 Draft B Report of the CCQM-K56 Page 18/26 PTB NMIJ NMISA NIMT NCM UME CCQM-K56 Ca in Whole Fat Soybean Powder Degrees of equivalence: d i and expanded uncertainty U(d i ) (k=2) Average:1543mg/kg(KCRV) U(k=2):8.57mg/kg di=(xi-xref) /mg/kg NMISA KRISS NMIJ PTB INTI NIM NIST NIMT CCQM-K56 Fe in Whole Fat Soybean Powder Degrees of equivalence: d i and expanded uncertainty U(d i ) (k=2) Average:53.36mg/kg(KCRV) U(k=2):1.89mg/kg di=(xi-xref) /mg/kg NIMT KRISS NIM NIST NMISA INTI PTB NMIJ INRIM UME

19 Draft B Report of the CCQM-K56 Page 19/26 CCQM-K56 Zn in Whole Fat Soybean Powder Degrees of equivalence: d i and expanded uncertainty U(d i ) (k=2) Average:36.36mg/kg(KCRV) U(k=2):0.46mg/kg di=(xi-xref) /mg/kg KRISS PTB NIST NIMT NMIJ NIM NMISA INRIM INTI NCM UME CCQM-K56 Cu in Whole Fat Soybean Powder Degrees of equivalence: d i and expanded uncertainty U(d i ) (k=2) Average:10.12mg/kg(KCRV) U(k=2):0.15mg/kg di=(xi-xref) /mg/kg INTI KRISS NIST NIM PTB NMIJ NMISA NIMT NCM UME

20 Draft B Report of the CCQM-K56 Page 20/26 9 CONCLUSION The CCQM-K56 is a successful key comparison, because that excellent agreement is found from its results, and most of the results overlap within the expanded uncertainty. And from Table 10, we can find that the results of K56 are obviously better than that of original P64, it shown that the capability of all of the participants had been promoted from the original pilot study to this key comparison. From this international comparison, the capability of the NMIs which participated in K56 has been testified in determining elements in food matrix materials field, and the participants of P64.1 will get more experience for determation of whole fat metrix materials.

21 Draft B Report of the CCQM-K56 Page 21/26 10 ACKNOWLEDGEMENTS Thank Dr. Mike Sargent - chairman of IAWG/CCQM for his supports and helps, especially for reviewing the Technical Protocol, and thank all of the analysts from the participant institutes for their contributions as well as the contact persons: Country Institute Analysts Italy INRIM Luigi Bergamaschi, Laura Giordani Argentina INTI Margarita Piccinna Korea KRISS Euijin Hwang, Yong-Hyeon Yim, Kyoung-Seok Lee, Youngran Lim Bulgaria NCM Boryana Koleva USA NIST Laura J. Wood China NIM Ma Liandi, Wang Qian, ZhouTao, Lu Hai Thailand NIMT Charun Yafa, Pranee Phrukpatanachai Japan NMIJ Takayoshi Kuroiwa South Africa NMISA Alex Barzev Germany PTB Detlef Schiel Turkey UME Oktay CANKUR

22 Draft B Report of the CCQM-K56 Page 22/26 Appendix A Technical Protocol Introduction CCQM-K56 & CCQM-P64.1 Ca,Fe,Zn and Cu in Whole Fat Soybean Powder Technical Protocol The food studies have been identified as key activities of CCQM. Considerable attention has been paid to improve the accuracy and comparability for food analysis results. Besides toxic and harmful elements, essential elements in food are given attention again because the lack of them can result in serious innutrition and potential diseases. The determination of them is also the need of quantitative mark of nutriments in nutrition labels of food products in many countries. Soybean as one kind of typical foodstuff is human s important source for the intake of protein, some essential elements and the raw material of many food products. The inorganic analysis working group of CCQM had organized successfully the pilot study CCQM-P64 for the determination of Cu,Zn,Fe and Ca in nonfat soybean powder. IAWG had agreed that this should proceed to a key comparison (CCQM-K56) and run in parallel with a pilot study (CCQM-P64.1). The focused elements are also Cu,Zn,Fe and Ca, but the sample changed into whole fat soybean powder. NIM () also acts as the coordinating laboratory. Time schedule Deadline for registration: 10 June 2007 Dispatch of the samples: the middle of the June 2007 Deadline for receipt of the result report: 31 December 2007 Discussing of Draft A at CCQM/ IAWG meeting: April 2008 Draft B report: Oct, 2008 Samples Sample Preparation: The source of material was whole fat soybean powder without any additives, the contents of protein and fat in which are 40.2% and 20.3% respectively. The sample was dried and milled, then sieved to yield a fraction with the particle size within 25-55µm. This fraction was blended in a mechanical blender for 6 hours. After pre-homogeneity test it was packaged into clean brown glass bottles with plastic inner lid and screw cap, and then sterilized with cobalt-60 gamma radiation to 2.5 megarads. At last each unit was vacuum packed in aluminum-nylon pouch. Homogeneity testing: 15 bottles were sampled randomly from 300 bottles, and two samples were sampled independently from each bottle. Three kinds of measurement methods were used to check the homogeneity of the samples. The one is XRF for all of the four elements, and the minimum sampling is 0.5g. The others are ICP-OES for Ca, Fe, Zn and ICP-MS for Cu after microwave

23 Draft B Report of the CCQM-K56 Page 23/26 digestion, and the minimum sampling is 0.1g. From different kinds of homogeneity test results, no statistically significant heterogeneity was found based on F test. Distribution: Each participant will receive one numbered bottle containing about 25g sample. The sample No. will be also the lab No. The participants will be informed of the date of dispatching of samples. Participants are required to confirm the receipt of the sealed samples, to fill in the return receipt table and send it to us by or fax or mail. If there is any damage, please contact us immediately and NIM will mail out another one. Elements: The following elements are focused: calcium, iron, zinc and copper. The approximate levels of their concentrations are: Ca:(1000~2000)mg/kg; Fe:(30~100)mg/kg; Zn:(10~80)mg/kg; Cu:(5~20)mg/kg. Handling and storing instructions: To avoid any decomposition, the samples should be kept sealed until they are used. They should be stored at room temperature in its original bottle, capped tightly and not exposed to intense direct light and ultraviolet radiation. It should be carefully to open the sample bottle, and not retain the sample opening for long time to avoid contamination. Sample preparation for measurement Experiments have been done to determine the influence of moisture for sample weighing. Before weighing, the sample should be dried at 80 C for 6 hours and then balanced in desiccators to room temperature. When digestion is needed, acid digestion, dry ashing digestion and microwave digestion are all welcomed for CCQM-K56 and CCQM-P64.1. But from the experience of P64, microwave digestion seems better than other digestion methods; so that the microwave digestion is recommended for key comparison and more different digestion methods can be used simultaneously for P64.1 for deeply discussion. Measurement method Any measurement method can be used. But from the results of the CCQM-P64, we find that IDMS method is the best method for determining elements in food matrix materials. The relative standard deviation and the uncertainty of IDMS method are obviously better than other methods. So that IDMS is recommended for participants of CCQM-K56. And more than one kind of method could be used simultaneously in CCQM-P64.1. If IDMS method is used, please report the source of isotopic ally labelled spike material used. Reporting A suggestion for a summary report table will be enclosed (Excel sheet). The report should be sent to the coordinating laboratory (NIM) by before Aug 31, NIM will confirm the receipt of each report. If the confirmation does not arrive within 2 weeks, please contact us. In order to allow a sufficient evaluation of the comparison, the report must include: A final result and uncertainty summary. The results will be reported as mass faction [mg/kg]. At least six independent determinations should be performed (if applicable). If the final result has been calculated from more than one method, the individual results from the contributing methods must also be reported.

24 Draft B Report of the CCQM-K56 Page 24/26 A detail description of the applied method of measurement. If more than one method were applied, a detail description must be given for each method. Information about sample digestion and preparation. Information about the reference material used for calibration (origin, standard value, standard uncertainty and isotopic ratio if necessary) or other materials used in the analytical procedure. Calculation of the uncertainty expressed as a combined standard uncertainty and an expanded uncertainty at 95% confidence. Uncertainty should be evaluated according to the ISO Guide to the Expression of Uncertainty in Measurement, It should include: -The complete specification of the measurement equation including corrections e.g. for blanks and interferences. -The identification and quantification of all uncertainty sources -The values for the coverage factor (suggested to 2) and the expanded uncertainty Participation Participation is open to all interested CCQM members, official observers and other interested parties who have sufficient experience in this type of measurement. If the CCQM members do not participate itself, another competent institute may be nominated. Participants are allowed to choose the elements of their interest in the four elements. All participants must please clarify which comparison, CCQM K56 or CCQM-P64.1, who want to participate in. Coordinating laboratory and contact persons Ma Liandi National Institute of Metrology (NIM) No. 18, Bei San Huan Dong Lu, Chaoyang District, Beijing, , P.R.China Tel.: Fax: mald@nim.ac.cn Or to Miss Wang Qian wangq@nim.ac.cn. Ms. Wu Bing wubing@nim.ac.cn