Metal speciation in acidified mountain streams in central Sweden.
Determination of piperazine in working atmosphere and in human urine using derivatization and capillary gas chromatography with nitrogen- and mass selective detection
A reliable routine method is presented for the determination of piperazine down to the sub-ppm level in aqueous solutions and in urine. The method includes a two-phase derivatization procedure with ethyl- or isobutyl chloroformate as the reagent, followed by a capillary gas chromatographic determination using nitrogen- or mass selective detection. The addition of ammonia ensured a quantitative recovery. Detection limits for piperazine in urine were ca. 20 ng/ml using nitrogen-selective and ca. 1 ng/ml with mass-selective detection. The calibration plots were linear in the investigated range, 100–10 000 ng/ml with nitrogen-selective and 30–3000 ng/ml with mass-selective detection. The precision was ca. 6% at a concentration of 300 ng/ml. Acid anhydrides were investigated as alternative reagents in the two-phase derivatization procedure, and heptafluorobutyric acid anhydride in aqueous solutions gave approximately 100% recovery. However, in urine the recoveries of the investigated acid anhydride derivatives were unsatisfactory.
SIMULTANEOUS OBSERVATIONS OF RAINWATER AND AEROSOL CHEMISTRY AT A REMOTE MIDLATITUDE SITE
Determination of isocyante and aromatic amine emissions from thermally degraded polyurethanes in foundries
Thermal degradation of polyurethanes can cause emissions of isocyanates and aromatic amines into work atmospheres. Results from laboratory studies on the use of 4,4′-methylenediphenyl isocyanate (MDI)-based polyurethane bound foundry core materials showed that anilines and phenyl isocyanates are major degradation products, but the possibility for emissions of MDI and its corresponding diamine, 4,4′-methylenedianiline, also was demonstrated. Results from field investigations in two different foundries showed that of these degradation products, mainly anilines and phenyl isocyanates are found in foundry work atmospheres, whereas MDI and methylenedianiline concentrations were negligible. The selection of air sampling and analytical procedures for, as well as interpretation of results from, simultaneous determination of isocyanates and their corresponding amines are discussed.