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Three chromatographic procedures were investigated regarding their potential for the quantification of aniline and 19 of its methylated and chlorinated derivatives in groundwater. These methods were based on liquid-liquid-extraction in combination with gas chromatography and single quadrupole mass spectrometry (GC/MS) according to German standard DIN 38407-16:1999 and its extension using tandem mass spectrometry (GC/MS-MS), both following liquid-liquid extraction, and as third alternative the direct injection of the water sample into a liquid chromatograph coupled to tandem mass spectrometry (LC/MS-MS). Results were compared using fortified water and real-world contaminated groundwater used in an interlaboratory comparison. It could be shown that GC/MS and GC/MS-MS yielded results deviating less than 10% from each other while all three procedure displayed quantification results deviating less than 15% from the intercomparison reference values in case of each analyte in the concentration range between 1 and 45 µg L-1. Though GC/MS-MS displays a ten-fold higher sensitivity than single quadrupole GC/MS, the precision of both methods in the concentration range was similar. LC/MS-MS has the advantage of no further sample preparation due to the direct injection and leads for methylanilines and meta-, para- substituted chloroanilines to results sufficiently equivalent to the standardised GC/MS method. However, LC/MS-MS is not suitable for ortho-chloroaniline derivates due to significantly lower ion yields than meta- and para-substituted chloroanilines.
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)%.
Evidence for the formation of difluoroacetic acid in chlorofluorocarbon-contaminated ground water
(2019)
The concentrations of difluoroacetic acid (DFA) and trifluoroacetic acid (TFA) in rainwater and surface water from Berlin, Germany resembled those reported for similar urban areas, and the TFA/DFA ratio in rainwater of 10:1 was in accordance with the literature. In contrast, nearby ground water historically contaminated with 1,1,2-trichloro-1,2,2-trifluoroethane (R113) displayed a TFA/DFA ratio of 1:3. This observation is discussed versus the inventory of microbial Degradation products present in this ground water along with the parent R113 itself. A microbial Transformation of chlorotrifluoroethylene (R1113) to DFA so far has not been reported for environmental media, and is suggested based on well-established mammalian metabolic pathways.
Fuel contamination of soils display complex and variable hydrocarbon mixtures with different volatility and toxicity characteristics. A recently suggested headspace procedure for the structure-based quantification of volatile hydrocarbons is evaluated regarding repeatability, reproducibility, and practical robustness. Three aliphatic and three aromatic fractions covering the boiling range between 69 and 216°C were defined as summation parameters by their respective equivalent carbon number ranges. A standard mixture of 35 aliphatic and aromatic hydrocarbons was used for calibration on basis of selected mass fragments specific for the aliphatics and aromatics, respectively. Two standard soils were fortified with the standard mixture or different fuels, respectively, and submitted to the analytical procedure. Limit of detection (LOD) and limit of quantification (LOQ) were for all fractions lower than 0.1 and 0.3 mg/kg, respectively. Analyte recovery was linear up to between 20 and 110 mg hydrocarbons/kg soil depending on the fraction. Hydrocarbon recovery ranged between 80% and 110% depending on the fraction and the repeatability was typically better than 10%. Finally, the impact of extraction solvent variation, column solid-phase polarity, and alternative summation of fractions were investigated. The procedure was applied to liner samples taken from a site contaminated with aviation fuel and its practicability is discussed.
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%
Microplastics are increasingly entering marine, limnic and terrestrial ecosystems worldwide, where they sorb hydrophobic organic contaminants. Here, the sorption behavior of the fuel-related water contaminants benzene, toluene, ethyl benzene and xylene (BTEX) and four tertiary butyl ethers to virgin and via UV radiation aged polypropylene (PP) and polystyrene (PS) pellets was investigated. Changes in material properties due to aging were recorded using appropriate polymer characterization methods, such as differential scanning calorimetry, Fourier transform infrared spectroscopy, gel permeation chromatography, X-ray photoelectron spectroscopy, and microscopy.
Pellets were exposed to water containing BTEX and the ethers at 130-190 mg/L for up to two weeks.
Aqueous sorbate concentrations were determined by headspace gas chromatography. Sorption to the polymers was correlated with the sorbate's Kow and was significant for BTEX and marginal for the ethers.
Due to substantially lower glass transition temperatures, PP showed higher sorption than PS. Aging had no effect on the sorption behavior of PP. PS sorbed less BTEX after aging due to an oxidized surface layer.
Process waters obtained from hydrothermal carbonization (HTC) of wheat straw, a biogas digestate derived thereof, and four woody biomass feedstocks were quantified regarding the total organic carbon (TOC) and selected organic compounds. HTC runs revealed that TOC loads were largely unaffected by process severity or type of feedstock whereas the C2–C6 fatty acids, determined by GC, displayed clear effects of temperature and feedstock. HPLC demonstrated simultaneously the initial increase and subsequent consumption of cellulose-derived furfural and 5-hydroxymethylfurfural as well as the increase of the lignin-derived 2-methoxyphenol. 2-Methylbenzofuran, an example for a substance potentially harmful to aquatic biota, was observed in high concentration in the HTC liquor from wheat straw-based feedstocks.
An interlaboratory comparison for the determination of aniline, nine methylated anilines and chlorinated anilines in contaminated groundwater (each compound between 1 µg L-1 and 750 µg L-1) was conducted as proficiency test for the selection of contract laboratories for a groundwater monitoring campaign. For the 13 participants, two different test sample series were prepared from a stabilized real case groundwater. Series A was the groundwater as sampled in the field and series B was prepared from series A by spiking with selected anilines. Homogeneity and stability investigations revealed that contaminated groundwater provides a viable basis for the preparation of ring test samples for the determination of anilines. Analytical procedures were limited to the standardized liquid–liquid extraction or solid-phase extraction in combination with gas chromatography/mass spectrometry (DIN 38407-16:1999). The robust consensus values were evaluated according to the standardized protocol of DIN 38402-45:2013. Robust reproducibility standard deviations ranged largely between 20?% and 60?% depending on the analyte. The proficiency assessment of individual participants combined the qualitative aspect of correct peak identification with the quantitative determination of individual concentrations within set limits in a unified approach. It could be shown that the accreditation status of laboratory and the existence of a standardized analytical procedure do not substitute a problem-related proficiency assessment of potential contractors.
KEY COMPARISON
Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (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 laboratory's measurement capability for the purity assignment of organic compounds of low structural complexity [molecular weight range 100300] 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 a-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.
The nature and concentrations of volatile organic compounds (VOCs) in chars generated by hydrothermal carbonization (HTC) is of concern considering their application as soil amendment. Therefore, the presence of VOCs in solid HTC products obtained from wheat straw, biogas digestate and four woody materials was investigated using headspace gas chromatography. A variety of potentially harmful benzenic, phenolic and furanic volatiles along with various aldehydes and ketones were identified in feedstock- and temperature-specific patterns. The total amount of VOCs observed after equilibration between headspace and char samples produced at 270 °C ranged between 2000 and 16,000 µg/g (0.2–1.6 wt.%). Depending on feedstock 50–9000 µg/g of benzenes and 300–1800 µg/g of phenols were observed. Substances potentially harmful to soil ecology such as benzofurans (200–800 µg/g) and p-cymene (up to 6000 µg/g in pine wood char) exhibited concentrations that suggest restrained application of fresh hydrochar as soil amendment or for water purification.