Gadolinium – Determination of gadolinium and its compounds in workplace air using inductively coupled plasma mass spectrometry (ICP-MS)

The working group "Air Analyses" of the German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) developed and verified the presented analytical method. This analytical method is a validated measurement procedure for the determination of gadolinium [7440-54-2] and its compounds in workplace air in a concentration range of one tenth up to twice of the general dust limit value for the respirable dust fraction in Germany of 1.25 mg/m³. For sampling, a defined volume of air is drawn through a membrane filter (cellulose nitrate). The flow rate is set to 10 l/min and sampling duration is 2 hours. Gadolinium is extracted with a mixture of hydrochloric and nitric acid or just nitric acid, depending on the digesting method - open hot-block or microwave-assisted pressure digestion. The samples are subsequently analysed using mass spectrometry with inductively coupled plasma (ICP-MS). The quantitative determination is based on a calibration function. The limit of quantification is 0.002 µg/m³ (open hot-block digestion) and 0.001 µg/m³ (microwave-assisted pressure digestion), respectively, based on an air sample volume of 1200 l and 20 ml digestion volume. The mean recovery is 95.1% (open hot-block digestion) and 94.7% (microwave-assisted pressure digestion), respectively. The expanded uncertainty for the validation range of 0.167 to 2.5 mg/m³ is 23.5 to 25.0%.