We present a comparison of two different techniques: Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) and wavelength‐dispersive X‐Ray Spectroscopy by electron probe microanalyzer (EPMA) for obtaining Mg/Ca ratios in individual foraminifera shells. The goal is to assess the use of EPMA as an alternative technique for Mg/Ca analyses of single foraminiferal calcite shells. Foraminifera obtained from sediments (benthic, Uvigerina spp.) and from plankton tows (planktonic, Orbulina universa) were analyzed. All specimens were prepared in epoxy mounts and exposed in cross‐section such that multiple high‐resolution analyses could be completed on the shells using both techniques. We examined our data using statistical methods designed for the assessment and comparison of measurement techniques. In the case of Uvigerina, the mean difference for ratios obtained using EPMA and LA‐ICP‐MS is very small (−0.046 mmol mol⁻¹) and scale independent. The Limits of Agreement (LoA, the standard deviation of the bias plus the mean bias) is [−0.315, 0.223] mmol mol⁻¹. For samples with ratios lower than 13 mmol mol⁻¹, we found a mean EPMA–LA‐ICP‐MS bias of −2.44 mmol mol⁻¹ and a corresponding LoA of [−3.85, −1.04] mmol mol⁻¹. For ratios higher than 13 mmol mol⁻¹, there appears to be a scale dependent bias, meaning that the EPMA measured ratios become progressively larger than those of LA‐ICP‐MS as the Mg/Ca ratio increases, so the mean bias and LoA metrics are not meaningful. Results indicate that it is possible to use EPMA to collect Mg/Ca data, if the ratios are lower than ∼13 mmol mol⁻¹.

中文翻译：

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有孔虫的原位Mg / Ca测量：电子探针显微分析仪在激光烧蚀电感耦合等离子体质谱和波长色散X射线光谱之间的比较

我们对两种不同技术进行了比较：通过电子探针微分析仪（EPMA）进行的激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）和波长分散X射线光谱法，以获取单个有孔虫壳中的Mg / Ca比。目的是评估使用EPMA作为对单个有孔虫方解石壳进行Mg / Ca分析的替代技术。从沉积物（底栖动物，Uvigerina spp。）和浮游生物丝束（浮游生物，Orbulina universa）获得的有孔虫）进行了分析。所有标本都准备在环氧树脂底座中，并在横截面上暴露，以便可以使用两种技术在壳上完成多个高分辨率分析。我们使用旨在评估和比较测量技术的统计方法检查了数据。在Uvigerina的情况下，使用EPMA和LA‐ICP‐MS获得的比率的平均差非常小（-0.046 mmol mol ^-1），并且与规模无关。一致极限（LoA，偏差的标准偏差加上平均偏差）为[-0.315，0.223] mmol mol ^-1。对于比率低于13 mmol mol ^-1的样品，我们发现EPMA-LA-ICP-MS的平均偏差为-2.44 mmol mol ^-1和相应的LoA为[-3.85，-1.04] mmol mol ^-1。对于高于13 mmol mol ^-1的比率，似乎存在比例依赖性偏差，这意味着随着Mg / Ca比值的增加，EPMA测得的比率逐渐大于LA‐ICP‐MS的比率，因此平均偏差和LoA指标没有意义。结果表明，如果比率低于〜13 mmol mol ^-1，则可以使用EPMA收集Mg / Ca数据。