Filtern
Erscheinungsjahr
Dokumenttyp
Sprache
- Englisch (73) (entfernen)
Referierte Publikation
- ja (73) (entfernen)
Schlagworte
- Interlaboratory comparison (8)
- Extraction (5)
- Gas chromatography (5)
- Analysis (4)
- Brominated flame retardant (4)
- HPLC-MS/MS (4)
- Boden (3)
- Breath (3)
- Chiral separation (3)
- Groundwater (3)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (17)
- 1.7 Organische Spuren- und Lebensmittelanalytik (17)
- 4 Material und Umwelt (4)
- 6 Materialchemie (4)
- 5 Werkstofftechnik (3)
- 6.3 Strukturanalytik (3)
- 4.3 Schadstofftransfer und Umwelttechnologien (2)
- 5.3 Polymere Verbundwerkstoffe (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 1.2 Biophotonik (1)
Paper des Monats
- ja (1)
The role of matrix reference materials in the process of demonstrating the degree of equivalence of measurement results obtained from intercomparisons is outlined, reviewing exemplary selected experience gained at BAM regarding the determination of organic contaminants in environmental matrices.
The specific characteristics of reference materials employed in the process of demonstrating equivalence between laboratories in the course of proficiency testing as well as the development, comparison and validation of methods are elaborated. The demand is for series of appropriately characterised samples which are fit for the purpose and it is seen from representative examples that the utilisation of such tailor-made RM designed to tackle the specific need of an analytical problem dominates over certified matrix reference materials in this context. Concluding, the role of certified matrix reference materials in quality assurance is briefly looked at both from the users and providers points of view.
Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with GC/FID are typically 10%-20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation.
Determination of pentachlorphenol (PCP) in waste wood - method comparison by a collaborative trial
(2002)
Two independently developed and validated procedures for the determination of pentachlorophenol (PCP) in waste wood were compared by means of a collaborative trial. Both methods foresee quantification of PCP by gas chromatography (GC-ECD) after acetylation and differ with regard to the use of methanol or toluene/sulphuric acid, respectively, as solvent in the sonication extraction step. Test samples with established analyte homogeneity were prepared from a ground real life starting material. A total of 23 participating laboratories with experience in wood preservative analysis were instructed to apply both methods to three levels of content in the range of 0.520 mg PCP/kg. In case of the toluene/sulphuric acid extraction, lower recoveries and higher interlaboratory dispersion of results at the higher PCP contents were observed. Seen against the background of the Horwitz equation a reproducibility standard deviation of not, vert, similar19% for the methanol extraction at the 4.5 mg/kg level meets the requirement for a sound analytical method. Thus, the sonication extraction procedure with methanol has been annexed as a reference method to the German waste wood regulation.
Zinc dialkyl dithiocarbamoylsulfinates have been proposed as intermediates in the antioxidant action of the respective zinc dialkyl dithiocarbamate additives in hydrocarbon-based plastics and lubricants. As a model compound, zinc diisobutyl dithiocarbamoylsulfinate, [Zn(C9H18NO2S2)2], has been prepared and its crystal structure determined.
Bis(N,N-di-n-butyldithiocarbamato-?2S,S')(1,10-phenanthroline-?2N,N')zinc(II) ethanol hemisolvate, [Zn(C9H18NS2)2(C12H8N2)]·0.5C2H6O, (I), and bis(N,N-di-n-hexyldithiocarbamato-?2S,S')bis(1,10-phenanthroline-?2N,N')calcium(II), [Ca(C13H26NS2)2(C12H8N2)2], (II), are mixed-ligand complexes. In the first compound, the Zn atom has a distorted octahedral coordination, while in the second compound, the Ca atom is eight-coordinate, with four S and four N atoms forming a highly distorted cube.
The X-ray crystallographic study of the macrocyclic tetrakis-N[N-2-hydroxyethyl-piperazino]calix[4]resorcinarene·3CH3CH2OH·H2O (3) reveals a self-assembled dimeric capsule-like complex held together by an array of intermolecular hydrogen bonds. Pairs of concave molecules associate directly in bowl-to-bowl fashion and enclose an accessible supramolecular cavity of Å3 hosting one water and three ethanol molecules. The supramolecular arrangement displays alternating layers of facing bowls and interlocking lower rim aliphatic moieties. The helical conformation of the 2-hydroxyethyl piperazinomethyl moieties displays chirality of a bimolecular capsule frozen in the solid state. 3 crystallises in the triclinic space group P-1 with two symmetry independent molecules in the asymmetric unit. Two enantiomeric capsules form a racemic pair in the unit cell.
A method for the determination of the novel brominated flame retardant tetrabromobisphenol A bis(2,3-dibromopropylether), 1,1'-(isopropylidene)bis[3,5-dibromo-4-(2,3-dibromo-propoxy)-benzene] (TBBPA-dbpe), was developed. Technical TBBPA-dbpe was purified and the results of a thorough physical characterisation are reported. The application of APCI-MS is discussed and the fragmentation patterns are described. Quantification of TBBPA-dbpe was done by HPLC-DAD using external calibration. The validation of the method was accomplished using sediment and sewage sludge samples spiked with defined amounts of authentic TBBPA-dbpe. The average recovery rates of TBBPA-dbpe from spiked samples ranged from 35 to 91% (sediment) and from 57 to 98% (sewage sludge) depending on the respective extraction method. Pressurised fluid extraction (PFE) and fluidised bed extraction were superior to classical Soxhlet and sonication procedures and yielded recovery rates between 90 and 98% with relative standard deviations of 2%. The limits of detection (DTC), identification (ID) and determination (DTM) using HPLC-DAD were 10, 21 and 30 ng g-1 in sediment and 22, 44 and 72 ng g-1 in sewage sludge, respectively.
The validation of a robust quantification procedure for EtG in hair using GC–NCI–MS is presented. Aqueous extraction is followed by complete lyophylization of the extract and derivatization with pentafluoropropionic anhydride (PFPA) under controlled temperature and duration. Clean-up of extracts was dispensable and standard single quadrupole MS displayed sufficient selectivity and sensitivity. The method displayed a wide linearity range and enabled LOD of 0.68 pg/mg, LOQ of 2.4 pg/mg, and precision below 8.12%. Since EtG was seen to display prolonged stability in the aqueous extracts and after derivatization with PFPA this straightforward procedure allows a routine throughput of large quantities of samples with little proneness to procedural scatter of results. The method was applied to demonstrate the homogeneity of two hair reference materials with mean EtG contents of 8.48 pg/mg and 22.0 pg/mg. Aside from the application in homogeneity studies of hair reference materials predominantly in the concentration range of 10–50 pg/mg the method was also designed for daily routine quantification of real-world sample with regard to drinking behavior assessment.
Aim: The objective of the study was to provide conclusive evidence for the effect of particle size reduction as by milling on the extractable content of ethyl glucuronide (EtG) of hair samples. Methods: A number of real case hair samples and two pooled hair materials with EtG contents in the range of 1030 pg/mg were systematically compared with regard to the extraction yield of EtG after cutting to 23 mm length and pulverization with a ball mill. After the respective treatment the samples were submitted to aqueous extraction followed by quantification of EtG using HPLC-MS/MS. Results: It was unequivocally demonstrated that milling of hair samples prior to aqueous extraction significantly increases the extractable EtG content compared with cut hair. The effect ranged between 137 and 230% and was seen to occur regardless of the extent of pulverization. Cooling of samples was not necessary to prevent partial degradation of EtG during the grinding procedure. Conclusion: The options currently employed at choice in analytical practice (cutting or milling) were seen to significantly affect the extractable amount of EtG in hair. This is suspected to influence the degree of equivalence of quantification results obtained in different laboratories as well as their respective classification of a test subject's drinking behaviour on the basis of currently recommended cut-off values.
The reliability in measurement results obtained during environmental monitoring is crucial for the assessment and further planning of remediation efforts on the respective contaminated sites by the responsible authorities. A case study concerned with groundwater contaminated with perchloroethylene, trichloroethylene and 1,1,2-trichlorotrifluoroethane including their degradation products which involves private contract laboratories and an independent provider of quality assurance (QA) is presented. The experience gained with biannual monitoring campaigns over 14 years indicates that the selection of contractors on basis of accreditation status and successful performance in interlaboratory comparisons are not sufficient. Rather the auditing of the contractors by the QA provider prior to each campaign and the crosschecking of selected monitoring samples by the QA provider led to a lasting improvement of reliability in the contractors' measurement results. A mean deviation of 20% from the reference value determined by the QA provider for the crosschecked samples was reached.
The title compound, {2-[(2-carbamoylethyl)amino]-3-methylpentanoic acid}, C9H18N2O3, is of interest with respect to its biological activity. It was formed during an addition reaction between acrylamide and the amino acid isoleucine. The crystal structure is a three-dimensional network built up by intermolecular N–H···O and O–H···N hydrogen bonds.
The title compound [systematic name: (2R,3R,4S,5R,6R) 2-(acetoxymethyl)-6-propoxytetrahydro-2H-pyran-3,4,5-triyl triacetate], C17H26O10, was formed by a Koenigs-Knorr reaction of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide and n-propanol. The central ring adopts a chair conformation. The crystal does not contain any significant interactions such as hydrogen bonds.
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.
A practical method for the quantification of
total purgeable organic sulfur (POS) in highly contaminated
groundwater is described. Volatile organic sulfur
compounds (VOSC) are purged from the water samples by
a stream of oxygen and combusted. The emerging sulfur
dioxide is absorbed in H2O2 and converted to sulfate which
is quantified by ion chromatography and reported as mass
sulfur equivalent. The overall limit of quantification is
0.03 mg l1. The content of POS is balanced with the total
VOSC determined by GC-AED after liquidliquid extraction.
Separate determination of the non-volatile organic
sulfur compounds by direct combustion of the water sample
and adsorption to charcoal yielded a mass balance of
the total sulfur content. Semi-quantitative GC-MS after
purge & trap accumulation revealed that the VOSC mixture
is composed of C1C4 alkyl sulfides. The implementation
of the developed methodology for the quantification of
VOSC as potential catalyst poison in a cleaning plant
for groundwater contaminated with volatile haloorganics
(VOX) is presented.
The interlaboratory variability in the quantification of adsorbable organically bound halogens (AOX) in industrially contaminated soil is presented. Three consecutive rounds of a proficiency testing scheme, in which between 88 and 119 routine laboratories participated, yielded relative reproducibility standard deviations between 7 and 20% at AOX contents between 10.9 and 268 mg kg-1. Nineteen laboratories with established proficiency were invited to participate in the certification of the AOX content in three soil reference materials meant for the internal quality control in analytical laboratories. The certified values are (1349 ± 59) mg kg-1, (80 ± 7) mg kg-1 and (102 ± 8) mg kg-1, respectively.
The interconversion of the stereoisomers contained in technical 1,2,5,6,9,10-hexabromocyclododecane, a major brominated flame retardant increasingly found in the environment and in biota, was investigated at elevated temperatures. The application of pure enantiomers of the three constituents α-, β-, and γ-HBCD enabled the unambiguous elucidation of the individual isomerisation reactions as well as the quantification of all respective rate constants. At 160 °C the rate constants range over two orders of magnitude from 1.50 × 10-3 to 1.88 × 10-5 mol(%) s-1. A preliminary mechanistic explanation for the differences of the rate constants which govern the composition of HBCD diastereomers at equilibrium is given.