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Organisationseinheit der BAM
The CCQM-K148.a comparison was coordinated by the BIPM on behalf of the CCQM Organic Analysis Working Group for NMIs and DIs which provide measurement services in organic analysis under the CIPM MRA. It was undertaken as a "Track A" comparison within the OAWG strategic plan. CCQM-K148.a demonstrates capabilities for assigning the mass fraction content of a solid organic compound having moderate molecular complexity, where the compound has a molar mass in the range (75 - 500) g/mol and is non-polar (pKow < −2), when present as the primary organic component in a neat organic solid and where the mass fraction content of the primary component in the material is in excess of 950 mg/g.
Participants were required to report the mass fraction of Bisphenol A present in one supplied unit of the comparison material. Participants using a mass balance method for the assignment were also required to report their assignments of the impurity components present in the material. Methods used by the seventeen participating NMIs or DIs were predominantly based on either stand-alone mass balance (summation of impurities) or qNMR approaches, or the combination of data obtained using both methods. The results obtained using thermal methods based on freezing-point depression methods were also reported by a limited number of participants. There was excellent agreement between assignments obtained using all three approaches to assign the BPA content.
The assignment of the values for the mass fraction content of BPA consistent with the KCRV was achieved by most of the comparison participants with an associated relative standard uncertainty in the assigned value in the range (0.1 - 0.5)%.
Extraction, chromatographic separation, and quantification of low-concentration organic compounds in complex matrices are core challenges for reference material producers and providers of calibration services. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2014 the Organic Analysis Working Group (OAWG) initiated CCQM-K95.1 "Low-Polarity Analytes in a Botanical Matrix: Polycyclic Aromatic Hydrocarbons (PAHs) in Tea". This was a follow-on comparison from CCQM-K95 which was completed in 2014.
The polycyclic aromatic hydrocarbons (PAHs) benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) are considered priority pollutants by U.S. Environmental Protection Agency and are regulated contaminants in food, pose chromatographic separation challenges, and for which exist well-characterized measurement procedures and standard materials. BaA and BaP in a smoked tea were therefore selected as representative target measurands for CCQM-K95.1. Ten NMIs participated in CCQM-K95.1. The consensus summary mass fractions for the two PAHs are in the range of (50 to 70) ng/g with relative standard deviations of (6 to 10) %.
Successful participation in CCQM K95.1 demonstrates the following measurement capabilities in determining mass fraction of organic compounds, with molar mass of 100 g/mol to 500 g/mol and having polarity pKow −2, in a botanical matrix ranging in mass fraction from 10 ng/g to 1000 ng/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, (3) extraction of analytes of interest from the matrix, (4) cleanup and separation of analytes of interest from interfering matrix or extract components, and (5) separation and quantification using gas chromatography or liquid chromatography.
The comparison required the assignment of the mass fraction of folic acid present as the main component in the comparison sample. Performance in the comparison is representative of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molecular weight range 300–500] and high polarity (pKOW < −2).
Methods used by the eighteen participating NMIs or DIs were based on a mass balance (summation of impurities) or qNMR approach, or the combination of data obtained using both methods. The qNMR results tended to give slightly lower values for the content of folic acid, albeit with larger associated uncertainties, compared with the results obtained by mass balance procedures. Possible reasons for this divergence are discussed in the report, without reaching a definitive conclusion as to their origin.
The comparison demonstrates that for a structurally complex polar organic compound containing a high water content and presenting a number of additional analytical challenges, the assignment of the mass fraction content property value of the main component can reasonably be achieved with an associated relative standard uncertainty in the assigned value of 0.5%
Drug therapy for diabetes mellitus has increased significantly in recent years. 1,1-Dimethylbiguanide hydrochloride (metformin) is the most common drug used for the treatment of diabetes. Metformin is not metabolized in the human body and enters thewater cycle via sewage.
A new gas chromatography-mass spectrometry (GC-MS) method has been developed which enables the quantification of metformin in surface water samples even at low concentrations in the ng L-1 range.
A solid phase extraction (SPE) method for the preconcentration of metformin and the internal standard 1-butylbiguanide (buformin) was established, and the method parameters such as the composition and volume of the eluent were optimized. Derivatization of metformin and
buformin was obtained by using n-methyl-bis (trifluoroacetamide)(MBTFA). The reaction conditions of the derivatization, such as the reaction temperature and volume of the derivatization agent, were evaluated. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 3.9 ng L-1 and 12 ng L-1 in surface water samples. Linearity was shown over a concentration range of 10–50 ng L-1. The good performance of the method was demonstrated by comparison with a liquid chromatography tandemmass spectrometry (LC-MS/MS) method. The results indicate that the GC-MS method is a reliable and sensitive alternative for the quantification of metformin in surface water.
1.
The European Union (EU) has included tributyltin (TBT) and its compounds in the list of priority water pollutants. Quality standards demanded by the EU Water Framework Directive (WFD) require determination of TBT at so low concentration level that chemical analysis is still difficult and further research is needed to improve the sensitivity, the accuracy and the precision of existing methodologies. Within the frame of a joint research project “Traceable measurements for monitoring critical pollutants under the European Water Framework Directive” in the European Metrology Research Programme (EMRP), four metrological and designated institutes have developed a primary method to quantify TBT in natural water using liquid–liquid extraction (LLE) and species-specific isotope dilution mass spectrometry (SSIDMS). The procedure has been validated at the Environmental Quality Standard (EQS) level (0.2 ng L−1 as cation) and at the WFD-required limit of quantification (LOQ) (0.06 ng L−1 as cation). The LOQ of the methodology was 0.06 ng L−1 and the average measurement uncertainty at the LOQ was 36%, which agreed with WFD requirements. The analytical difficulties of the method, namely the presence of TBT in blanks and the sources of measurement uncertainties, as well as the interlaboratory comparison results are discussed in detail.
We have prepared and evaluated three whole water test materials containing eight polycyclic aromatic hydrocarbons (PAHs), six polybrominated diphenyl ethers (PBDEs) and tributyltin (TBT) with respect to homogeneity and short-term stability. The test materials were used as samples in two inter-laboratory comparisons. The materials were composed of natural mineral water and model suspended particulate matter (SPM) containing the target compounds at ng L-1 levels. The expanded uncertainty of the estimated mass concentrations in the final test materials was obtained by combining contributions from the homogeneity, the stability and the model SPM characterization.
The whole water materials were sufficiently homogeneous and stable at 4 °C for their intended use. In total, 12 out of 15 investigated target parameters could be assessed to be present with a relative combined expanded uncertainty below 25 %. The outcome of the two interlaboratory comparisons confirmed the good quality of the test materials and the level of uncertainties associated with the estimated mass concentrations. These findings are an important contribution towards the development of whole water matrix reference materials certified for PAH, PBDE and TBT in support of the Water Framework Directive of the European Union.
The European Water Framework Directive 2000/60/EC requires monitoring of organic priority pollutants in so-called whole water samples, i.e. in aqueous nonfiltered samples that contain natural colloidal and suspended particulate matter. Colloids and suspended particles in the liquid phase constitute a challenge for sample homogeneity and stability. Within the joint research project ENV08 ‘‘Traceable measurements for monitoring critical pollutants under the European Water Framework Directive 2000/60/EC’’, whole water test materials were developed by spiking defined amounts of aqueous slurries of ultrafinely milled contaminated soil or sediment and aqueous solutions of humic acid into a natural mineral water matrix. This paper presents the results of an European-wide interlaboratory comparison (ILC) using this type of test materials. Target analytes were tributyltin, polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons in the ng/L concentration range. Results of the ILC indicate that the produced materials are sufficiently homogeneous and stable to serve as samples for, e.g. proficiency testing or method validation. To our knowledge, this is the first time that ready-to-use water materials with a defined amount of suspended particulate and colloidal matter have been applied as test samples in an interlaboratory exercise. These samples meet the requirements of the European Water Framework Directive. Previous proficiency testing schemes mainly employed filtered water samples fortified with a spike of the target analyte in a water-miscible organic solvent.
Determination of tributyltin in whole water matrices under the European water framework directive
(2016)
Monitoring of water quality is important to control water pollution. Contamination of the aquatic systemhas a large effect on human health and the environment. Under the European Water Framework Directive(WFD) 2000/60/EC and the related directive on environmental quality standards (EQS) in the field of waterpolicy 2008/105/EC, the need for sensitive reference methods was highlighted. Since tributyltin (TBT) isone of the WFD listed priority substances a method was developed which is capable to qualify and quantifythe pollutant at the required low WFD EQS of 0.2 ng L⁻¹ in whole water bodies, i.e. in non-filtered watersamples with dissolved organic carbon and suspended particulate matter. Therefore special attention waspaid on the interaction of TBT with the suspended particulate matter and humic substances to obtain acomplete representation of the pollution in surface waters. Different water samples were investigatedvarying the content of organic dissolved and suspended matter. Quantification was performed usingspecies-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma massspectrometry (GC-ICP-MS). Different sample treatment strategies were evaluated and compared. Theprocess of internal standard addition was investigated and optimized, hence the equilibrium betweeninternal standards and matrix is of primary importance to perform accurate SSID. Samples spiked at EQSlevel were analyzed with a recovery between 95 and 105 %. Additionally real surface water samples wereinvestigated and the TBT concentration for the whole water body was determined and compared withconventional routine analysis method.
One of the unresolved issues of the European Water Framework Directive is the unavailability of realistic water reference materials for the organic priority pollutants at low nanogram-per-liter concentrations. In the present study, three different types of ready-to-use water test materials were developed for polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and tributyltin (TBT) at nanogram-per-liter levels. The first type simulated the dissolved phase in the water and comprised of a solution of humic acids (HA) at 5 mg L-1 dissolved organic carbon (DOC) and a spike of the target compounds. The second type of water sample incorporated the particulate phase in water. To this end, model suspended particulate matter (SPM) with a realistic particle size was produced by jet milling soil and sediments containing known amounts of PAHs, PBDEs and TBT and added as slurry to mineral water. The most complex test materials mimicked 'whole water' consequently containing both phases, the model SPM and the HA solution with the target analytes strongly bound to the SPM. In this paper, the development of concepts, processing of the starting materials, characterisation of the HA and model SPMs as well as results for homogeneity and stability testing of the ready-to-use test materials are described in detail.
Tributyltin is listed as one of the priority substances in the European Water Framework Directive (WFD). Despite its decreasing input in the environment, it is still present and has to be monitored. In the European Metrology Research Programme project ENV08, a sensitive and reliable analytical method according to the WFD was developed to quantify this environmental pollutant at a very low limit of quantification. With the development of such a primary reference method for tributyltin, the project helped to improve the quality and comparability of monitoring data. An overview of project aims and potential analytical tools is given.