A Quick, Simple, and High-Throughput Method for Determining Li/Mg, Mg/Ca, Sr/Ca, and U/Ca Ratios in Coral Skeleton...

Information about sea surface temperature (SST) allows both local and global climate reconstructions dating back centuries to millennia. To determine SST variations over time, including the deep past, a number of proxies are used. Li/Mg, Mg/Ca, Sr/Ca, and U/Ca ratios in coral skeletons are the most commonly used high-resolution temperature proxies. Various methods, using different types of instrumentation, are employed to obtain high-precision data on the variation of these ratios in coral skeletons. Generally, each method has its own advantages and disadvantages; however, a common drawback of most is that they are time-consuming. This article presents a quick, simple, and high-throughput method for determining mentioned ratios in coral skeletons using quadrupole ICP-MS. The reduction of calcium concentration to 3 ppm in the analytical solutions, combined with optimized operating conditions and quasi-simultaneous measurement of each element pair, ensures excellent signal sensitivity and stability of ratio values during sample runs. The drift of ratio values was investigated using the in-house coral secondary standard NEP-3b. During some runs, the drift of ratios during the analysis was so low that it provided excellent repeatability of results without off-line mathematical correction of the obtained data. Due to the selected ICP-MS operating conditions, this high-sensitivity method enables for the analysis of all studied isotopes in a single measurement, whereas typical procedures require two sample preparations and separate measurements. As a result, this method doubles the throughput compared to the previous procedures while demonstrating comparable short- and long-term precisions, both of which were assessed using the international standard sample JCp-1.