Optimization of an inductively coupled plasma–optical emission spectrometry method for the rapid determination of high-precision Mg/Ca and Sr/Ca in foraminiferal calcite



[1] The ability to measure Mg/Ca and Sr/Ca in foraminiferal calcite has increased in importance following their identification as palaeoceanographic tracers with significant potential to constrain past changes in ocean chemistry and temperature. However, in order to tackle palaeoceanographic problems, it is essential to develop methods for the determination of these ratios that have both rapid sample throughput and high analytical precision. Here, we demonstrate the importance of simultaneous measurement for high-precision Mg/Ca and Sr/Ca analysis. Our method is readily applicable to automated analysis over a wide range of Ca concentrations and is not subject to significant matrix effects. Using a “dual view” inductively coupled plasma–optical emission spectrometer (ICP-OES), supported by a dedicated autosampler, we have investigated three nebulizers and two spray chambers and determined optimum analytical parameters. We show that there are consistent relationships between signal-to-noise ratio and gas flow rates and that the working sample dilution range has an important effect on linear response. Further, for this instrument it is important to manually constrain the timing of measurements to obtain truly simultaneous readings. Using the method developed, precisions of better than 0.21% are obtained for Mg/Ca and Sr/Ca in solutions containing between 1 and 4 ppm Ca with no significant matrix effect, using a Glass Expansion “Conikal” nebulizer coupled with a “Tracey” spray chamber, in autosampler mode.