Online flow digestion of biological and environmental samples for inductively coupled plasma-optical emission spectroscopy (ICP-OES)

A novel type of interface for gas removal has been developed for coupling a high-temperature/high-pressure online flow digestion system to an ICP spectrometry instrument. It consists of a porous polypropylene tube with an inner rod made of PEEK which causes the formation of a thin film (100 μm) of liquid at the inner surface of the porous tube, thereby considerably increasing the ratio of gas exchange area to liquid volume and simultaneously decreasing the dead volume. Thus very efficient removal of the gaseous reaction products, such as CO2 and NOx, which are known to affect the ICP stability, was achieved. Even at high flow rates and with a high carbon content in the samples more than 99% of the gases were removed. Applying ICP-OES detection excellent recoveries were obtained for most elements except for Sb, Ag and Ga. Good agreement between certified and measured values was obtained for online determinations of elements in various biological and environmental standard reference materials. Low standard deviation and detection limits in the lower μg/g range were found. This new tube interface combines low costs with robust properties, compact design and ease of handling.