HIGH-PERFORMANCE ULTRA-TRACE ANALYSIS IN MOLYBDENUM AND TUNGSTEN ACCOMPLISHED BY ONLINE COUPLING OF ION CHROMATOGRAPHY WITH SIMULTANEOUS ICP-AES

For the characterisation of trace elements in high purity Mo and W ana lytical methods with a detection limit in the ng/g-range have to be us ed. Today mass spectrometric methods are state of the art for such app lications. However, these methods in case of refractory metal analysis are time consuming, expensive, limited by isobaric interferences and therefore not very suitable for qualify control in an industrial labor atory. With respect to these drawbacks a cost and time efficient metho d was developed by on-line coupling of an ion chromatographic system t o a simultaneous ICP-AES (Inductively Coupled Plasma-Atomic Emission S pectrometry) instrument. Within the limitations caused by the hard- an d software of the system all parameters such as eluent concentration a nd flow rate, nebulizer and plasma gas how, sampling frequency, integr ation time and the number of simultaneously measured emission lines we re optimised. Further enhancement of the sensitivity was achieved by t he use of an ultrasonic nebulizer pushing the detection limits down to the pg/g- and ng/g-range for 22 representative elements.