A universal method for quantitative analysis of clay components, in terms of mineral composition, using ATR-FT-IR spectroscopy (in the mid-IR and far-IR regions) combined with partial least squares (PLS) regression technique (ATR-FT-IR-PLS) is reported. For the PLS method development, altogether 222 samples covering natural clay sources and various archaeological/cultural heritage artefacts were used as calibration and validation standards. This is the largest calibration set used for creating an ATR-FT-IR-PLS method for clay minerals. The quantitative compositions of these standards containing combinations of altogether 29 minerals for the PLS method were determined using XRD analysis. The developed ATR-FT-IR with PLS method is quick and easy to use, and enables analysis of very small sample amounts (down to a few mg). This is very important when working with samples from archaeological and cultural heritage objects. The developed ATR-FT-IR-PLS method enables quantifying the contents of 7 main classes of minerals in different clays with a root mean square error of prediction (RMSEP) ranging from 0.9 to 5.1 g/100g. This means that in some cases, depending also on the content of the mineral in the sample, the accuracy is at a semiquantitative level. This quantitative method was successfully applied to 11 cultural heritage case-study samples.

Graphical abstract

中文翻译：

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使用 ATR-FT-IR 光谱和 PLS 方法对含粘土材料进行定量矿物学分析

使用 ATR-FT-IR 光谱（在中红外和远红外区域）结合偏最小二乘法 (PLS) 回归技术 (ATR-FT- IR-PLS) 报告。对于 PLS 方法的开发，共有 222 个涵盖天然粘土来源和各种考古/文化遗产人工制品的样品被用作校准和验证标准。这是用于创建粘土矿物 ATR-FT-IR-PLS 方法的最大校准集。使用 XRD 分析确定了这些包含用于 PLS 方法的总共 29 种矿物质组合的标准的定量组成。使用 PLS 方法开发的 ATR-FT-IR 快速且易于使用，并且可以分析非常少量的样品（低至几毫克）。这在处理来自考古和文化遗产对象的样本时非常重要。开发的 ATR-FT-IR-PLS 方法能够量化不同粘土中 7 类主要矿物的含量，预测均方根误差 (RMSEP) 范围为 0.9 至 5.1 g/100g。这意味着在某些情况下，还取决于样品中矿物质的含量，准确度处于半定量水平。该定量方法已成功应用于 11 个文化遗产案例研究样本。还取决于样品中矿物质的含量，准确度处于半定量水平。该定量方法已成功应用于 11 个文化遗产案例研究样本。还取决于样品中矿物质的含量，准确度处于半定量水平。该定量方法已成功应用于 11 个文化遗产案例研究样本。

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