4,4'-Methylenediphenyl diisocyanate (MDI) is the most important of the isocyanates used as intermediates in the chemical industry. Among the main types of damage after exposure to low levels of MDI are lung sensitization and asthma. Protein adducts of MDI might be involved in the etiology of sensitization reactions. It is therefore necessary to have sensitive and specific methods for monitoring the isocyanate exposure of workers. To date, urine metabolites or protein adducts have been used as biomarkers in workers exposed to MDI. However, with these methods it is not possible to determine if the biomarkers result from exposure to MDI or to the parent aromatic amine 4,4'-methylenedianiline (MDA). This work presents a procedure for quantitating isocyanate-specific hemoglobin adducts. Blood proteins are used as markers of exposure and possibly as markers of dose size for the modifications of macromolecules in the target organs where the disease develops. For the quantitation of hemoglobin adducts, N(1)-[4-(4-isocyanatobenzyl)phenyl]acetamide (AcMDI) was reacted with the tripeptide valyl-glycyl-glycine and with valine yielding N-[4-(4-acetylaminobenzyl)phenyl]carbamoyl]valyl-glycyl-glycine and N-[4-[4-(acetylaminobenzyl)phenyl]carbamoyl]valine, respectively. N-[4-[4-(Acetylamino-3,5-dideuteriobenzyl)-2, 6-dideuteriophenyl]carbamoyl]valine was synthesized from valine, as was N(1)-[4-(4-isocyanato-3,5-dideuteriobenzyl)-2, 6-dideuteriophenyl]acetamide, for use as an internal standard. These adducts were cleaved in 2 M HCl to yield the corresponding hydantoins, 3-[4-(4-aminobenzyl)phenyl]-5-isopropyl-1, 3-imidazoline-2,4-dione (MDA-Val-Hyd) and 3-[4-(4-amino-3, 5-dideuteriobenzyl)-2,6-dideuteriophenyl]-5-isopropyl-1, 3-imidazoline-2,4-dione, respectively. In globin of rats exposed to MDI, MDA-Val-Hyd could be found in a dose-dependent manner. The adduct was identified by HPLC/MS/MS and quantified by GC/MS after derivatization with heptafluorobutyric anhydride. The amount of MDA-Val-Hyd found after acid hydrolysis of globin at 100 degrees C is about 12 times larger than the sum of N-acetyl-4, 4'-methylenedianiline (AcMDA) and MDA obtained from mild base hydrolysis of hemoglobin. The MDA-Val-Hyd is an isocyanate-specific adduct. MDA and AcMDA released after mild base hydrolyses result most likely from a sulfinamide adduct which is a typical adduct of arylamines. According to these results, higher amounts of isocyanate adducts than arylamine adducts should be expected in workers exposed to isocyanates.

A novel highly selective sample cleanup procedure based on the use of molecularly imprinted polymers (MIPs) as solid-phase extraction materials has been evaluated with respect to its applicability and routine use in environmental analysis. The method comprises the combination of a restricted access material (RAM) and a MIP allowing a selective sample preparation to be achieved in the online mode. This combination is called the size-selective sample separation and solvent switch (six-SPE). The RAM column combines size exclusion and adsorption chromatography, reducing the concentration of matrix molecules by a cutoff of 15 kDa. The MIP column selectively retains the triazine analytes whereas the residual matrix is not retained and separated completely. Thus, the automated RAM-MIP is capable of excluding all matrix and nontarget compounds. The cleaned and enriched extract is subsequently eluted to an HPLC column and analyzed by LC-MS. A complete on-line analysis cycle including multidimensional solid-phase extraction, separation, and detection takes less than 15 min. Terbuthylazine, atrazine, propazine, simazine, ametryn, prometryn, irgarol, and also the metabolites deethylatrazine and deisopropylatrazine can be determined without any matrix interferences, e.g., by humic acids. The whole setup is fully automated and may be continuously operated. Nonspecific interactions with the polymer are below 1% in all cases. The accuracy of the LC-MIP-LC-MS system was controlled using a certified reference material (Aquacheck). The applicability of the method to the cleanup of real samples was demonstrated by injection of contaminated river water samples. The stability of different polymers was tested by consecutive injections, and it was shown that the performance of the materials did not vary even after more than 300 enrichment and desorption cycles.

An approach for the size measurement of particulate (nano)materials by transmission electron microscopy was evaluated. The approach combines standard operating procedures for specimen preparation, imaging, and image analysis, and it was evaluated on a series of certified reference materials and representative test materials with varying physical properties, including particle size, shape, and agglomeration state. The measurement of the median value of the minimal external particle diameter distribution was intra-laboratory validated. The validation study included an assessment of the limit of detection, working range, selectivity, precision, trueness, robustness, and ruggedness. An uncertainty that was associated to intermediate precision in the range of 1–7% and an expanded measurement uncertainty in the range of 7–20% were obtained, depending on the material and image analysis mode. No bias was observed when assessing the trueness of the approach on the certified reference materials ERM-FD100 and ERM-FD304. The image analysis method was validated in an inter-laboratory study by 19 laboratories, which resulted in a within-laboratory precision in the range of 2–8% and a between-laboratory precision of between 2% and 14%. The automation and standardization of the proposed approach significantly improves labour and cost efficiency for the accurate and precise size measurement of the particulate materials. The approach is shown to be implementable in many other electron microscopy laboratories.

The formation of the benzo[a]pyrene (B[a]P) diones (B[a]P-1,6-dione, B[a]P-3,6-dione, B[a]P-6,12-dione) as the main products of oxidative degradation of B[a]P has been observed under atmospheric conditions in air particulate matter. Samples were collected at two different sites in Munich, Germany. Total B[a]P dione concentrations were determined by APCI/LC−MS and ranged between 8 and 605 pg m-3. The formation of the direct mutagen B[a]P-epoxide was not observed. B[a]P dione concentrations did not correspond with B[a]P and total carbon concentrations, but showed a correlation with solar irradiation. B[a]P dione concentrations were higher on daytime filters compared to filters collected during the night. Lower concentrations of B[a]P diones were observed at the site with higher traffic contributions, suggesting a major role of atmospheric transport. Rapid, high-volume sampling indicates that the B[a]P dione formation is not dependent on B[a]P concentrations, but on photochemical conditions.

No abstract

No abstract

No abstract

Analytical difficulty and the economic importance of controlling mycotoxin levels in food and feed led the Community Bureau of Reference (BCR) to prepare a series of certified reference materials (CRM) for various mycotoxins. Because of the wide acceptance of these CRM and the need to ensure the comparability and traceability of measurements in the future it is necessary to prepare and certify new batches of mycotoxin reference materials (RM). In the following text two different approaches for evaluation of the characterisation uncertainty of CRM will be compared using the certification of aflatoxin M(1) (AfM(1)) in milk powder as an example. The conventional approach is based on evaluation of characterisation exercise data; the alternative approach is based on measurement uncertainties of the employed analytical methods. Because laboratories are using totally different approaches to estimate the measurement uncertainties, combination of the uncertainties obtained from the participating laboratories was not recommended. Therefore, a new integrated approach for assessment of the measurement uncertainties of the analytical methods on the basis of additional data collected during the characterisation exercise will be described. The conventional approach was found to be the most appropriate and economical approach to evaluate the characterisation uncertainty as a characterisation exercise must be performed anyway to establish the property values of candidate (C)RM, irrespective of whether or not reliable measurement uncertainties can be provided by the laboratories. An integrated approach for assessment of measurement uncertainties based on additional characterisation data as applied here to enable use of an uncertainty-based approach provides more information but is too time-consuming and cost-intensive to become common practice.