Detlef Lück’s research while affiliated with Federal Institute For Materials Research and Testing and other places

The resource-saving utilisation of recovered waste wood is a matter of growing concern. In several European countries, this utilisation is governed by regulations and is dependent on the contents of certain trace elements and organic compounds. Thus, for decision-making with respect to waste wood management (recycling or combustion), reliable analytical data are needed and, due to their great economic and environmental impact, must be assured by appropriate quality control. To support the improvement in quality assurance in waste wood analysis, for the first time, a wood reference material was certified for its mass fractions of arsenic, cadmium, chromium, copper, lead, mercury, and pentachlorophenol (PCP). These analytes were selected because they represent typical constituents of wood preservatives most widely used in the past. Material preparation and testing of homogeneity and stability were carried out by BAM Federal Institute for Materials Research and Testing. The certification measurements were performed involving selected laboratories with documented expertise in the field of waste wood analysis. The certified values and their corresponding uncertainties were assigned in full compliance with the requirements of ISO Guide 35. The certified mass fractions and their expanded uncertainties (k = 2) are as follows: (3.1 ± 0.5) mg/kg for As, (3.02 ± 0.24) mg/kg for Cd, (36.4 ± 2.6) mg/kg for Cr, (22.9 ± 1.7) mg/kg for Cu, (0.60 ± 0.14) mg/kg for Hg, (39 ± 4) mg/kg for Pb, and (7.9 ± 0.6) mg/kg for PCP. The certified material is available as European Reference Material ERM®-CD100.

An efficient solid phase extraction (SPE) method using bis-(2-ethylhexyl)-phosphate (HDEHP) coated reverse phase C18 support has been developed for the pre-concentration of Gadolinium (Gd) and Gd contrast agents widely used in magnetic resonance imaging (MRI). Enrichment of Gd in the ionic form has been compared with strong cation exchange material Chromabond SA (SCX), weak ion exchange material Chelex-100 and also with lanthanide specific HDEHP modified reverse phase C18. The determination of Gd and its complexes after enrichment were performed using inductively coupled plasma mass spectrometry (ICP-MS) and on the basis of 158Gd. Among the three SPE materials, HDEHP coated reverse phase C18 SPE has been found to be most efficient, yielding a hundredfold Gd enrichment with > 95% recovery for linear and cyclic contrast agents like Gd-DTPA (Magnevist), Gd-DOTA (Dotarem), Gd-BOPTA (Multihance), and Gd-BT-DO3A (Gadovist). The developed SPE method has been successfully applied to the surface water and waste water samples originated from different places in Berlin, Germany. The results were in good agreement with the results obtained with direct measurement with ICP-MS. The developed pre-concentration method can be efficiently used for the determination of trace levels of gadolinium in the environment even with less sensitive analytical techniques.

A highly sensitive method for the determination of gadolinium based MRI contrast agents in environmental water samples has been developed using hydrophilic interaction chromatography (HILIC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). The contrast agents used in the present study are Gd-DTPA (Magnevist), Gd-DTPA-BMA (Omniscan), Gd-DOTA (Dotarem), Gd-BOPTA (Multihance) and Gd-BT-DO3A (Gadovist) which represent both classes of linear and macro cyclic and also ionic and non ionic contrast agents. A study of various parameters responsible for the efficient separation was performed and resulted in an optimum mobile phase composition of 20 mmol L−1 ammonium acetate in 60/40 ACN/water mixture at a flow rate of 0.1 mL min−1 in combination with a micro concentric type PFA nebuliser and ICP-MSdetection of the 158Gd isotope. All contrast agents have shown excellent linearity between 0.1 μg L−1 and 100 μg L−1 (R2 > 0.99) for each MRI contrast agent with RSD values found to be less than 2% for triplicate measurements. The limit of quantification (LOQ) for all contrast agents were found to be less than 100 ng L−1 which allows the developed method to be employed in environmental trace analysis. Enrichment of water samples for the determination of contrast agents was performed by using a surface evaporation approach. The developed method has been applied successfully for the separation and determination of contrast agents in surface and waste water treatment plant samples. The MRI agent speciation results were compared with ICP-MS measurements for the total Gd concentrations.

The mass fraction of potassium hydrogen phthalate (KHP) from a specific batch was certified as an acidimetric standard. Two different analytical methods on a metrological level were used to carry out certification analysis: precision constant current coulometric and volumetric titration with NaOH. It could be shown that with a commercial automatic titration system in combination with a reliable software for the end-point detection it is possible to produce equivalent results with the same accuracy in comparison to a definite method handled by a fundamental apparatus for traceable precision coulometry. Prerequisite for titrations are that a high number of single measurement are applied which are calibrated with a high precision certified reference material.

A European standard for the determination of Cr(vi) in solid material has been elaborated in the framework of an international co-operation and finally validated in the course of an interlaboratory comparison. The procedure is based on the alkaline digestion prescribed by EPA method 3060A followed by ion chromatography and determines an operationally defined content of Cr(vi), including water-soluble and insoluble chromates. A preliminary robustness study was carried out in order to compare different extraction methodologies and to study the equivalency of different analytical methods for the determination of Cr(vi) in alkaline extracts of soil and waste materials. During an interlaboratory validation trial with 19 European laboratories a set of 4 samples (2 soil and 2 waste samples) was analysed to determine performance characteristics for different combinations of digestion and detection methods. With the procedures prescribed by the new European standard (EN 15192) acceptable results were obtained for both soil samples and one of the waste samples (sludge). However, for the second waste sample (fly ash) a large deviation in analytical results was observed. This indicates that particularly for waste materials a possible occurrence of strong matrix effects has to be considered and supplementary quality control data are needed in order to assess the validity of analytical results. The accuracy of the determination of Cr(vi) in solid matrices remains a challenging field in terms of maximum extraction efficiency and minimum species interconversion.