Rosemarie Philipp

Experimental design for TBT quantification by isotope dilution SPE–GC–ICP–MS under the European water framework directive

In Europe the maximum allowable concentration for tributyltin (TBT) compounds in surface water has been regulated by the water framework directive (WFD) and daughter directive that impose a limit of 0.2 ng L(-1) in whole water (as tributyltin cation). Despite the large number of different methodologies for the quantification of organotin species developed in the last two decades, standardised analytical methods at required concentration level do not exist. TBT quantification at picogram level requires efficient and accurate sample preparation and preconcentration, and maximum care to avoid blank contamination. To meet the WFD requirement, a method for the quantification of TBT in mineral water at environmental quality standard (EQS) level, based on solid phase extraction (SPE), was developed and optimised. The quantification was done using species-specific isotope dilution (SSID) followed by gas chromatography (GC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). The analytical process was optimised using a design of experiment (DOE) based on a factorial fractionary plan. The DOE allowed to evaluate 3 qualitative factors (type of stationary phase and eluent, phase mass and eluent volume, pH and analyte ethylation procedure) for a total of 13 levels studied, and a sample volume in the range of 250-1000 mL. Four different models fitting the results were defined and evaluated with statistic tools: one of them was selected and optimised to find the best procedural conditions. C18 phase was found to be the best stationary phase for SPE experiments. The 4 solvents tested with C18, the pH and ethylation conditions, the mass of the phases, the volume of the eluents and the sample volume can all be optimal, but depending on their respective combination. For that reason, the equation of the model conceived in this work is a useful decisional tool for the planning of experiments, because it can be applied to predict the TBT mass fraction recovery when the experimental conditions are drawn. This work shows that SPE is a convenient technique for TBT pre-concentration at pico-trace levels and a robust approach: in fact (i) number of different experimental conditions led to satisfactory results and (ii) the participation of two institutes to the experimental work did not impact the developed model.

Determination of tributyltin in whole water matrices under the European Water Framework Directive

Monitoring of water quality is important to control water pollution. Contamination of the aquatic system has 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 water policy 2008/105/EC, the need for sensitive reference methods was highlighted. Since tributyltin (TBT) is one of the WFD listed priority substances a method was developed which is capable to qualify and quantify the pollutant at the required low WFD EQS of 0.2ngL(-1) in whole water bodies, i.e. in non-filtered water samples with dissolved organic carbon and suspended particulate matter. Therefore special attention was paid on the interaction of TBT with the suspended particulate matter and humic substances to obtain a complete representation of the pollution in surface waters. Different water samples were investigated varying the content of organic dissolved and suspended matter. Quantification was performed using species-specific isotope dilution (SSID) and gas chromatography with inductively coupled plasma mass spectrometry (GC-ICP-MS). Different sample treatment strategies were evaluated and compared. The process of internal standard addition was investigated and optimized, hence the equilibrium between internal standards and matrix is of primary importance to perform accurate SSID. Samples spiked at EQS level were analyzed with a recovery between 95 and 105 %. Additionally real surface water samples were investigated and the TBT concentration for the whole water body was determined and compared with conventional routine analysis method.

Final report on key comparison CCQM-K55.b (aldrin): An international comparison of mass fraction purity assignment of aldrin

Under the auspices of the Organic Analysis Working Group (OAWG) of the Comit? Consultatif pour la Quantit? de Mati?re (CCQM) a key comparison, CCQM K55.b, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2010/2011. Nineteen national measurement institutes and the BIPM participated. Participants were required to assign the mass fraction of aldrin present as the main component in the comparison sample for CCQM-K55.b which consisted of technical grade aldrin obtained from the National Measurement Institute Australia that had been subject to serial recrystallization and drying prior to sub-division into the units supplied for the comparison. Aldrin was selected to be representative of the performance of a laboratorys measurement capability for the purity assignment of organic compounds of medium structural complexity [molar mass range 300 Da to 500 Da] and low polarity (pKOW < ?2) for which related structure impurities can be quantified by capillary gas phase chromatography (GC). The key comparison reference value (KCRV) for the aldrin content of the material was 950.8 mg/g with a combined standard uncertainty of 0.85 mg/g. The KCRV was assigned by combination of KCRVs assigned by consensus from participant results for each orthogonal impurity class. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 0.3% to 0.6% using a mass balance approach and 0.5% to 1% using a qNMR method. The major analytical challenge posed by the material proved to be the detection and quantification of a significant amount of oligomeric organic material within the sample and most participants relying on a mass balance approach displayed a positive bias relative to the KCRV (overestimation of aldrin content) in excess of 10 mg/g due to not having adequate procedures in place to detect and quantify the non-volatile content?specifically the non-volatile organics content?of the comparison sample. There was in general excellent agreement between participants in the identification and the quantification of the total and individual related structure impurities, water content and the residual solvent content of the sample. The comparison demonstrated the utility of 1H NMR as an independent method for quantitative analysis of high purity compounds. In discussion of the participant results it was noted that while several had access to qNMR estimates for the aldrin content that were inconsistent with their mass balance determination they decided to accept the mass balance result and assumed a hidden bias in their NMR data. By contrast, laboratories that placed greater confidence in their qNMR result were able to resolve the discrepancy through additional studies that provided evidence of the presence of non-volatile organic impurity at the requisite level to bring their mass balance and qNMR estimates into agreement. 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 (CIPM MRA).

Tributyltin—critical pollutant in whole water samples—development of traceable measurement methods for monitoring under the European Water Framework Directive (WFD) 2000/60/EC

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.

Two-dimensional truncated nucleation in the anodic film formation of calomel on mercury

Abstract The anodic deposition of the first monolayer of calomel has been investigated by current-time and current-potential curves. A new theoretical model for two-dimensional nucleation and growth has been developed that considers a stop in nucleation caused by a drop in monomer supersaturation. Growth was assumed to proceed via surface diffusion. This mechanism explains the experimental current-time transients well. We determined data for the critical nucleus formation, such as Gibbs free energies, line tensions and nucleation rates. These change with overpotential in a sensible way.

Final report on key comparison CCQM-K55.c (L-(+)-Valine): Characterization of organic substances for chemical purity

Under the auspices of the Organic Analysis Working Group (OAWG) of the Comit? Consultatif pour la Quantit? de Mati?re (CCQM) a key comparison, CCQM K55.c, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2012. Twenty National Measurement Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of valine present as the main component in the comparison sample for CCQM-K55.c. The comparison samples were prepared from analytical grade L-valine purchased from a commercial supplier and used as provided without further treatment or purification. Valine was selected to be representative of the performance of a laboratorys measurement capability for the purity assignment of organic compounds of low structural complexity [molecular weight range 100?300] and high polarity (pKOW > ?2). The KCRV for the valine content of the material was 992.0 mg/g with a combined standard uncertainty of 0.3 mg/g. The key comparison reference value (KCRV) was assigned by combination of KCRVs assigned from participant results for each orthogonal impurity class. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 1 mg/g to 6 mg/g when using mass balance based approaches alone, 2 mg/g to 7 mg/g using quantitative 1H NMR (qNMR) based approaches and from 1 mg/g to 2.5 mg/g when a result obtained by a mass balance method was combined with a separate qNMR result. The material provided several analytical challenges. In addition to the need to identify and quantify various related amino acid impurities including leucine, isoleucine, alanine and ?-amino butyrate, care was required to select appropriate conditions for performing Karl Fischer titration assay for water content to avoid bias due to in situ formation of water by self-condensation under the assay conditions. It also proved to be a challenging compound for purity assignment by qNMR techniques. There was overall excellent agreement between participants in the identification and the quantification of the total and individual related structure impurities, water content, residual solvent and total non-volatile content of the sample. Appropriate technical justifications were developed to rationalise observed discrepancies in the limited cases where methodology differences led to inconsistent results. The comparison demonstrated that to perform a qNMR purity assignment the selection of appropriate parameters and an understanding of their potential influence on the assigned value is critical for reliable implementation of the method, particularly when one or more of the peaks to be quantified consist of complex multiplet signals. 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 (CIPM MRA).

An interlaboratory comparison on whole water samples

Abstract The European Water Framework Directive 2000/60/EC requires monitoring of organic priority pollutants in so-called whole water samples, i.e. in aqueous non-filtered 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 ultra-finely 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.

A novel GC-MS method for the determination and quantification of metformin in surface water

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 the water 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 tandem mass 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.

Final report on CCQM-K47: Volatile organic compounds in methanol

At the October 2005 CCQM Organic Analysis Working Group Meeting (IRMM, Belgium), the decision was made to proceed with a Key Comparison study (CCQM-K47) addressing the calibration function for the determination of volatile organic compounds (VOCs) used for water quality monitoring. This was coordinated by CENAM and NIST. Benzene, o-xylene, m-xylene and p-xylene were chosen as representative VOCs. The solvent of choice was methanol. Key Comparison CCQM-K47 demonstrated the capabilities of participating NMIs to identify and measure the four target VOCs in a calibration solution using GC-based methods. The measurement challenges in CCQM-K47, such as avoiding volatility loss, achieving adequate chromatographic resolution and isolating potential interferences, are typical of those required for value-assigning volatile reference materials. Participants achieving comparable measurements for all four VOCs in this Key Comparison should be capable of providing reference materials and measurements for VOCs in solutions when present at concentration levels greater than 10 ?g/g. 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 (CIPM MRA).

Final report on CCQM-K38: Determination of PAHs in solution

Solutions of known mass fraction of organic analytes of interest are typically used to calibrate the measurement processes used in the determination of these analytes. Appropriate value assignments and uncertainty calculations for these calibration solutions are critical. For the Mutual Recognition Arrangement (MRA) developed by the CIPM, there are numerous Calibration and Measurement Capability Claims (CMCs) published in Category 3 Organic Solutions in the CIPM MRA Appendix C. Additional CMCs in this category are being proposed and reviewed. Evidence of successful participation in formal, relevant international comparisons is needed to support these claims. A CCQM pilot study conducted in 2004 was comprised of three parts: CCQM-P31a Organic Solution—Polycyclic Aromatic Hydrocarbons (PAHs), CCQM-P31b Organic Solution—Polychlorinated Biphenyl (PCB) Congeners, and CCQM-P31c Organic Solution—Chlorinated Pesticides. The results from the CCQM-P31a study are summarized below for the PAHs. After review of the P31a results at the April 2004 Organic Analytical Working Group (OAWG) meeting (Sevres 2004) and the October 2004 OAWG meeting (Beijing 2004), it was decided to proceed with a key comparison study for PAHs in solution (CCQM-K38) with a concurrent second pilot study for the PAHs in solution (CCQM-P31a.1). CCQM-K38 was conducted during the same time period as a PAHs in soil pilot study (CCQM-P69) coordinated by CENAM and BAM. This Key Comparison study demonstrated a high level of equivalence in capabilities of the participating NMIs to successfully identify and measure five PAHs (phenanthrene, fluoranthene, benz[a]anthracene, benzo[a]pyrene, and benzo[ghi]perylene) in a solution using GC/MS-based methods. The PAHs measured in CCQM-K38 were selected to be representative of PAHs typically used as calibrants in the determination of the PAHs found in environmental samples and to provide the typical analytical measurement challenges encountered in the value-assignment of these PAH calibration solutions, such as volatility losses and resolution from potential interferences and other PAHs present as components in the solution during chromatographic separation. The abilities demonstrated by the laboratories that provided comparable measurements for all five PAHs in this Key Comparison should be indicative of their ability to provide reference measurements for a suite of PAHs in solutions when present at levels greater than 3 µg/g provided the laboratory demonstrates an acceptable degree of separation of the PAHs in the specific solution being analyzed. 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).