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|Title: ||High precision measurements of Mg/Ca and Sr/Ca ratios in carbonates by cold plasma inductively coupled plasma quadrupole mass spectrometry|
|Authors: ||Chuan-Chou Shen;Han-Yi Chiu;Hung-Wei Chiang;Mei-Fei Chu;Kuo-Yen Wei;Stephan Steinke;Min-Te Chen;Yu-Shih Lin;Li Lo|
|Contributors: ||NTOU:Institute of Applied Geosciences|
|Keywords: ||Cold ICP-QMS;Mg/Ca;Sr/Ca;Carbonate;Foraminifera;Coral|
|Issue Date: ||2011-10-20T08:17:35Z
|Publisher: ||Chemical Geology|
|Abstract: ||abstract:We present a new high precision analytical method for the determination of Mg/Ca and Sr/Ca ratios in carbonates using an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) with a 650-W cold plasma technique and a desolvation introduction system. Signal intensities are detected in pulse-counting mode and Mg/Ca and Sr/Ca ratios are calculated directly from intensity ratios of 24Mg/43Ca and 86Sr/43Ca using external matrix-matched standards for every 4–5 samples to correct for instrumental mass discrimination and low-frequency ratio drift. Significant matrix effect of Ca content on Mg/Ca determination (− 0.018 Mg/Ca (mmol/mol)/[Ca] (ppm)), can be overcome by diluting [Ca] to 6–8 ppm in the sample solution or using an empirical correction. The Sr/Ca ratio affects the Mg/Ca determination, with a factor of − 0.32% Mg/Ca per mmol/mol. This is mainly caused by the influence of doubly charged 86Sr, which biases the intensity measurement of the 43Ca+ ion beam. This effect results in a trivial offset of less than 0.1% on Mg/Ca measurements for Quaternary foraminiferal and coral samples. The internal precision of our method ranges from 0.1 to 0.2%. Replicate measurements made on standards and samples show long-term external uncertainties (2σ) of Mg/Ca = 0.84% and Sr/Ca = 0.49%. The minimum sample size requirement is only 3.5 μg of carbonate. The application of this newly developed technique on the planktonic foraminifera Globigerinoides ruber from a core recovered in the southern South China Sea yields a glacial–interglacial difference in sea surface temperature (SST) of 3 °C. Three-year coral Sr/Ca data suggest that the seasonal SST ranged from 22.6–23.8 °C in winter to 26.9–27.9 °C in summer in Nanwan, south Taiwan, during 2000–2002. The coral-Sr/Ca inferred SSTs in 2002 match well with instrumental records, which demonstrates the validity of this ICP-QMS method.|
|Relation: ||236(3-4), pp.339–349|
|Appears in Collections:||[應用地球科學研究所] 期刊論文|
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