The aim of the key comparison CCQM-K105 was to demonstrate the measurement capabilities of the participating institutes with respect to the conductivity of multi-component aqueous salt solutions. Practical salinity results are currently not traceable to metrological references consistent with the International System of Units (SI). Nevertheless, salinity is one of the most important input quantities for oceanographic models, whose measurement data must be accurate on very long time scales. Thus, in order to determine the practical salinity value, there is a strong interest on the part of oceanographic researchers in establishing the traceability to the SI of conductivity measurements. To this end, the conductivity of a standard seawater sample, provided by the support laboratory (PTB), was measured in a way traceable to the SI. The nominal conductivity values of the solution were 5.3 S.m(-1) at 25 degrees C and 4.3 S.m(-1) at 15 degrees C. Thirteen institutes taking part in the comparison had to measure the conductivity values of the sample at both the temperatures. The median was chosen for both values as an estimator for the KCRV, evaluated on the basis of the Monte Carlo method. An institute requested to be excluded from the determination of the KCRV because of contact problems of its cell. At 25 degrees C the KCRV is 5.3024 S.m(-1) with an interval of confidence (at the 95.45 % level of significance) from 5.3005 S.m(-1) to 5.3044 S.m(-1). At 15 degrees C the KCRV is 4.2892 S.m(-1) with an interval of confidence (at the 95.45 % level of significance) from 4.2877 S.m(-1) to 4.2907 S.m(-1). For the "How far the light shines" statement the CMCs can cover the range 1 - 15 S.m(-1) both for the values 5.3 S.m(-1) at 25 degrees C and 4.3 S.m(-1) at 15 degrees C. This comparison is a follow-up of the CCQM Pilot Study P111.

A proficiency testing (PT) scheme was designed for measurements of pH and electrolytic conductivity (EC) of groundwater in Israel. A groundwater sample was used for preparation of test items fit-for-intended-use. The interlaboratory experiment was organized taking into account changes of the test item properties which occurred after sampling due to presence of CO 2 in the groundwater. A total of 34 PT participants reported pH measurements results, while 29 of them reported results of EC measurements. The pH results were normally distributed. However, a significant bias of the pH consensus value of the PT participants from the metrologically traceable certified value (obtained by the National Physical Laboratory of Israel) was detected. This bias was caused by the drift of the measurement response due to water stirring and CO 2 degassing from the sample during the measurement process. The bias of the EC consensus value from the metrologically traceable one was negligible, in spite of an abnormal distribution of the EC results of the PT participants.

The aim of the key comparison CCQM-K92 was to demonstrate the capabilities of the participating NMIs to measure electrolytic conductivity of an unknown sample.Two samples with nominal electrolytic conductivity values of 0.05 S.m(-1) and 20 S.m(-1) have been prepared for comparison. For the first time conductivity value larger than those given in the IUPAC document [1] was measured in CCQM comparison. Thus no calibration standards with similar conductivity value were available. The comparison was an activity of the Electrochemical Working Group (EAWG) of the CCQM and was coordinated by SMU.In the comparison NMIs from fifteen countries took part. The higher conductivity (20 S.m(-1)) was measured by ten participants. Good agreement of the results was observed for the majority of participants.

A new technique for quantification of human errors in chemical analysis using expert judgments is described. This technique is based on the house-of-security approach developed recently in the field of safety and security for prevention of terrorist and criminal attacks against an organization. The following relative quantification parameters (expressed in %) are proposed in the technique: (a) likelihood score of human error in a chemical analytical measurement/testing method, (b) severity score of human error for reliability of the test results, (c) importance score of a component of a laboratory quality system, and (d) effectiveness score of the quality system as a whole in preventing/blocking human error. As an example, 34 scenarios of human error in pH measurement of groundwater are discussed and quantified.

A questionnaire was completed by 14 participants (INMETRO, NIM, PTB, DFM, LNE, NMIJ, SMU, NIST, CENAM, GUM, NPLI, IPQ, BIM and KRISS) to study the influence of several variables in the preparation of Ag/AgCl electrodes on the accuracy of Harned cell measurements of pH. The performance of each national metrology institute in the last decade has been assessed based on their results in 8 key comparisons involving the measurement of pH of phosphate, phthalate, carbonate, borate and tetroxalate buffer materials (in CCQM - K9 and K9.2, K17, K18 and K18.1, K19 and K19.1 and K20 respectively). The performance of each laboratory has been correlated to the results of the questionnaire to determine the critical parameters in the preparation of Ag/AgCl electrodes and their sensitivities with respect to the accuracy of pH measurement. This study reveals that the parameters most closely correlated to performance in comparisons are area of electrode wire exposed to the electrolyte, diameter and porosity of the Ag sphere prior to anodisation, amount of Ag converted to AgCl during anodisation, stability times employed for electrodes to reach equilibrium in solution prior to measurement, electrode rejection criteria employed and purity of reagents.

The subsequent key comparison CCQM-K18.1 was started in order to evaluate the equivalence of metrology institutes as a follow-up to the previous key comparison CCQM-K18 for institutes that could not take part in the comparison at that time or did not consider their results representative of their capabilities. A carbonate buffer of a slightly different composition to that in CCQM-K18 was used.There were seven institutes plus the coordinating laboratory participating in this subsequent comparison. Most of the participating institutes showed significant improvement; in some cases the new results confirmed the previous ones. The reasons for this have still to be elucidated.

The key comparison CCQM-K18 was started in order to evaluate the equivalence of metrology institutes as a follow-up of the previous study CCQM-P52. As a sample a carbonate buffer solution was used with a composition slightly different to the usual one. There were 13 institutes participating in the comparison using a primary method for pH measurement. The fair agreement between the results reflects increased difficulty in measurement, where the buffer composition may slightly change during the measurement and extrapolation to the start time of measurement is usually necessary. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

A new method of acid value determination in vegetable oils has been developed. The method is based on (a) simple, rapid and complete extraction of acids from an oil test portion into reagent (0.05 mol dm(-3) triethanolamine (B) in the mixture of 50% H2O + 50% 2-PrOH) and (b) indirect titration of acids in BH+ form against aqueous alkali in the presence of a phenolphthalein indicator. Suitable metrological parameters of acid value determination have been obtained. The advantages of the method are (i) absence of a toxic solvent, (ii) extraction and titration of acids at room temperature, and (iii) no need for preliminary neutralization of acid admixtures in a solvent.