Showing papers by "John Munthe published in 1994"

Experiences with the analytical procedures for the determination of methylmercury in environmental samples

Abstract: The analytical method using ethylation, gas chromatography–cold vapor atomic fluorescence spectroscopy (GC–CV AFS), combined with different pretreatment procedures, has been used for the determination of methylmercury (MeHg) in various aqueous and solid environmental samples. Different types of samples with varying matrices and MeHg concentration levels require different pretreatment procedures in order to isolate/separate MeHg from the sample matrix, and to overcome interferences in the ethylation reaction process. Limitations of different pretreatment procedures (solvent extraction into methylene chloride, distillation under nitrogen flow and alkaline digestion) are discussed and recommendations are given. The influence of the quality of the ethylating reagent on the analytical results is also examined.

Determination of mercury isotope ratios in samples containing sub-nanogram amounts of mercury using inductively coupled plasma mass spectrometry

Abstract: The determination of sub-nanogram amounts of mercury demands systems of high sensitivity. To determine isotopic ratios a large signal is required to obtain a high number of counted ions. It was found that the precision in the isotope ratio determination in samples containing less than 300 pg of mercury is limited by the counting statistics. With 300 pg of mercury the precision was 0.2%(relative standard deviation) in the 202Hg: 199Hg ratio. The detection limit was lowered by concentration of mercury vapour on gold traps, and the sensitivity of the instrument was increased 4–6-fold by addition of nitrogen or hydrogen to the central gas flow.