Semiquantitative elemental analysis of water samples using double focusing inductively coupled plasma mass spectrometry

A rapid and fairly accurate semiquantitative method for the determination of trace amounts of metals in water samples of low and high salinity was successfully applied to a double focusing inductively coupled plasma mass spectrometer. The method was used at both low (m/ Δm=300) and medium (m/Δm=3000) resolution, establishing the corresponding molar response curve in both modes. The ionisation conditions (Tionandne) were calculated through the Saha equation by adjusting the molar response of a multi-element solution to a third order polynomial equation by least squares. The validation of the proposed methodology was performed by elemental analysis of a Riverine Water reference material (SLRS-3) from the National Research Council of Canada. Results obtained were in good agreement with the certified values, working at low resolution when no polyatomic interferences were found and at medium resolution when necessary. Matrix effects were also evaluated using sea-water samples, after a 5-fold dilution. An increase in the analytical response for all the elements, used as internal standards, in comparison with the corresponding curve in Milli-Q water was observed. However, once the ionisation conditions had been calculated on the same saline matrix, recoveries of most of the elements under study were satisfactory for semiquantitative analysis.