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Main text CCQM-K143 is a key comparison that assesses participants' ability to prepare single element calibration solutions. Preparing calibration solutions properly is the cornerstone of establishing a traceability link to the International System of Units (SI), and therefore should be tested in order to confirm the validity of CCQM comparisons of more complex materials. CCQM-K143 consisted of participants each preparing a single copper calibration solution at 10 g/kg copper mass fraction and shipping 10 bottled aliquots of that solution to the coordinating laboratory, the National Institute of Standards and Technology (NIST). The masses and mass fraction for the prepared solutions were documented with the submitted samples. The solutions prepared by all participants were measured at NIST by high performance inductively coupled plasma optical emission spectroscopy (HP-ICP-OES). The intensity measurements for copper were not mapped onto values of mass fraction via calibration. Instead, ratios were computed between the measurements for copper and simultaneous measurements for manganese, the internal standard, and all subsequent data reductions, including the computation of the KCRV and the degrees of equivalence, were based on these ratios. Other than for two participants whose measurement results appeared to suffer from calculation or preparation errors, all unilateral degrees of equivalence showed that the measured values did not differ significantly from the KCRV. These results were confirmed by a second set of ICP-OES measurements performed by the Physikalisch-Technische Bundesanstalt (PTB). CCQM-K143 showed that participants are capable of preparing calibration solutions starting from high purity, assayed copper metal. Similar steps are involved when preparing solutions for other elements, so it seems safe to infer that similar capabilities should prevail when preparing many different, single-element solutions. 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 (CIPM MRA).

In the present study, we have developed an exact matrix-matching inductively coupled plasma-optical emission spectroscopy (ICP-OES) as a low-cost alternative to the isotope dilution inductively coupled plasma-mass spectrometry (ICP-MS) method for accurate and precise measurements of nutrient elements K and Cu in infant formula. In spite of its high precision and accuracy, ICP-OES analysis of complex samples was not reliable due to biases originating from various matrix effects. The elaborated exact matrix-matching approach tested here demonstrated its potential to minimize biases due to matrix mismatch. The exact matrix-matching ICP-OES method was successfully validated by comparing the results with those from an isotope dilution ICP-MS method. Because the model provides reliable results without significant loss of precision, it will be an excellent choice for major element analysis in a complex sample, especially when isotope dilution is not applicable due to the lack of alternative isotopes or the high cost of enriched isotopes.

The relative atomic fraction of Cu(In,Ga)Se2 (CIGS) films is one of the most important measurements for the fabrication of CIGS thin film solar cells. However, the quantitative analysis of multi-element alloy films is difficult by surface analysis methods due to the severe matrix effect. In this study, the quantitative analysis of CIGS films was investigated by secondary ion mass spectrometry (SIMS). The atomic fractions of Cu, In, Ga and Se in the CIGS films were measured by alloy reference relative sensitivity factors derived from the certified atomic fractions of a reference CIGS film. The total ion intensities of the constituent elements were obtained by a total number counting method. The atomic fractions measured by SIMS were linearly proportional to those certified by inductively coupled plasma mass spectrometry using an isotope dilution method. The uncertainties were determined from the standard uncertainties in the measurements and those of a CIGS thin film certified reference material.

We prepared genomic DNA from human placenta, Escherichia coli, and Bacillus subtilis using various DNA extraction methods and quantified the genomic DNA using ultraviolet (UV) spectrophotometry, capillary electrophoresis (CE), and inductively coupled plasma optical emission spectrometry (ICP–OES). Application of ICP–OES unexpectedly led to a serious overestimation of phosphorus in B. subtilis genomic DNA prepared using cetyltrimethyl ammonium bromide (CTAB). Further investigations using reversed-phase high-performance liquid chromatography (RP–HPLC), ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS), and 31P nuclear magnetic resonance (NMR) identified the phosphorus impurity as lipoteichoic acid (LTA).

A certified reference material (CRM) of KRISS 109-03-SSD was developed for the analysis of hazardous elements in soil. The target elements were As, Cd, Cr, Cu, Hg, Ni, Pb, Zn being regulated by the Soil Environment Conservation Act. Starting material was collected from tailing dump of an unworked tungsten mine at Sangdong (Gangwon-do, Korea). The starting material under-went through a series of fabricating process steps of screening, drying, grinding, sieving, blending, bottling, sterilization and was certified according to the ISO Guide 35. Isotope dilution-inductively coupled mass spectrometry (ID-ICP/MS) and instrumental neutron activation analysis (INAA) were used for the measurement. Homogeneity was tested according to ISO 13528 annex B. The certified values were determined using the results from two different methods or from two independent measurements using a method. Finally, certified values of seven elements of arsenic, cadmium, chromium, copper, lead, nickel and zinc were determined. Mercury did not satisfied the criteria of homogeneity and the result would be provided for information only, together with iron and tungsten. It was also studied, the extractable fraction of elements by aqua regia according to the ISO 11466 protocol being frequently studied for the purpose of environmental monitoring. It was performed as a inter-laboratory study by 6 laboratories of a public institute and universities. Standard deviation among the laboratories was much bigger than the uncertainty of the certified value. The result of inter-laboratory study on the extractable fraction will be provided for information, only.

Quantitation of the trace amount of DNA by counting individual DNA molecules using a high-sensitivity flow cytometric setup has been developed and evaluated for the purpose of establishing a reference analytical procedure. Model DNA molecules, represented by lambda (λ) viral DNA (48 502 bp, double-stranded), were electro-focused to form a tightly bound flow stream on a detection point situated on the centre axis of fused silica tubing measuring 50 µm × 50 µm. The individual DNA particles that were stained with a fluorescent dye were detected individually with a high-sensitivity laser-induced fluorescence (LIF) detection system. Assuming all DNA particles in a given sample volume were detected and counted ('exhaustive counting'), its molar concentration can be calculated without the need for calibration materials. The validity of the proposed measurement method was thoroughly examined and discussed.

A method is described for the determination of dibutyltin (DBT) in sediment by isotope dilution using liquid chromatography inductively-coupled plasma/mass spectrometry (LC-ICP/MS). To achieve the highest accuracy and precision, special attentions are paid in optimization and evaluation of overall processes of the analysis including extraction of analytes, characterization of the standards used for calibration and LC-ICP/MS conditions. An approach for characterization of natural abundance DBT standard has been developed by combining inductively-coupled plasma/optical emission spectrometry (ICP/OES) and LC-ICP/MS for the total Sn assay and the analysis of Sn species present as impurities, respectively. An excellent LC condition for separation of organotin species was found, which is suitable for simultaneous DBT and tributyltin (TBT) analysis as well as impurity analysis of DBT standards. Microwave extraction condition was also optimized for high efficiency while preventing species transformation. The present method determines the amount contents of DBT in sediments with expanded uncertainty of less than 5% and its result shows high degree of equivalence with reference values of an international inter-comparison and a certified reference material (CRM) within stated uncertainties.

A novel approach for quantitation of DNA (oligonucleotides) with an unprecedented accuracy of approximately 1% is reported. Quantitation of DNA is commonly performed by measuring UV absorption or fluorescence from dyes intercalated into DNA. Both methods need accurate quantitation standards to yield more comparable results between laboratories. For establishing technically authentic standards for DNA quantitation, a new measurement approach carrying an inherent capability of absolute quantitation is demanded. The proposed approach is based on the stoichiometric existence of phosphorus (P) in DNA. The quantity of P from the phosphodiester backbone of a purified oligonucleotide was accurately determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) with yttrium internal standard via acid digestion. The number of moles of oligonucleotides was then calculated from that of P using the stoichiometry. The major issues regarding the validity of the suggested approach were (i) effective removal of extra P sources, (ii) quantitative recovery of P through the digestion process, and (iii) oligomeric purity of the target oligonucleotide. These issues were investigated experimentally using various analytical techniques such as matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), capillary electrophoresis, electrical conductometry, UV spectrometry, and gravimetry. In conclusion, it is feasible to certify pure oligonucleotide reference materials with uncertainties less than 1% using the proposed approach.

A double focusing sector field inductively coupled plasma mass spectrometer (ICP-MS) was used to determine Cd in two sediment reference materials (National Institute of Standards and Technology Standard Reference Material 1646a and National Institute for Environmental Studies Certified Reference Material No. 2). The isotope dilution method was used for quantification with 111Cd and 112Cd as the two isotopes. The isobaric interference from 112Sn to 112Cd was corrected using four interference correction equations. The software correction equation utilizing the natural abundance ratio of 112Sn∶117Sn resulted in over-estimation of the 112Sn intensity due to a non-uniform sensitivity of the sector field ICP-MS. The isobaric interference was more properly corrected when the 112Sn intensity was estimated using a mass bias corrected 112Sn∶117Sn ratio. Good agreement was achieved with the certified values in the analysis of the two sediment reference materials using the mass bias corrected ratios.

An analytical method for the simultaneous determination of some trace elements (Au, Fe, Mg, Li, Sr, Zn) in human serum by inductively coupled plasma atomic emission spectrometry (ICP-AES) with flow injection is described. Physical interference caused by the change of sample viscosity is discussed. When 100 μl of serum was injected, the relevant recoveries of > 99% for Li, > 98% for Cu and Mg, > 95% for Fe were obtained for an NIST SRM with R.S.D. > 1.3% using optimized flow injection parameters. The prepared lyophilized control serum for routine analysis in clinical laboratories was analyzed and verified for the validity of the technique employed in this experiment using NIST SRM 909 as a primary reference material.

An analytical method has been developed to determine trace impurities in pure Cu. The Cu matrix is separated from trace impurities by controlled potential electrodeposition. More than 99% of the Cu matrix can be removed with better than 90% efficiency of trace element recovery. Isotope dilution calibration is employed with the spike isotopes being added prior to electrodeposition. Analytical results for National Institute of Standards and Technology Standard Reference Materials (394 Unalloyed Copper I and 395 Unalloyed Copper II) are presented together with determination limits, recovery efficiency and optimized potential.