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Isotope analysis
(2017)
The variation of isotope ratios is increasingly used to unravell natural and technical questions. In the past the investigation and interpretation of such variations was the field of a limited number of experts. With new upcoming techniques and research topics in the last decades, such as provenance and authenticity of food, the number of published isotope data strongly increased. Instrumental developments such as the enhancement of inductively coupled plasma mass spectrometers (ICPMS) from an instrument for simple quantitative analysis to highly sophisticated isotope ratio machines influenced this process significantly. While in former times only experts in mass spectrometry were able to produce reliable isotope data, nowadays many laboratories, never been in touch with mass spectrometry before, produce isotope data with an ICPMS. Especially for such user isotope reference materials (IRM) are indispensible to enable a reliable method validation. The fast development and the broad availability of ICPMS also lead to an expansion of the classical research areas and new elements are under Investigation.
This presentation shows the basics and principles for isotope ratio determination using ICP-MS. Additionally, it provides three specific examples for isotope Ratio applications: isotope dilution mass spectrometry; provenancing of archaeoligical artifeacts by lead isotope Ratio Analysis and studies on boron uptake in bell pepper plants.
Boron isotope amount ratios n(10B)/n(11B) have been determined by monitoring the absorption spectrum of boron monohydride (BH) in a graphite furnace using high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Bands (0→0) and (1→1) for the electronic transition X1Σ+ → A1Π were evaluated around wavelengths 433.1 nm and 437.1 nm respectively. Clean and free of memory effect molecular spectra of BH were recorded. In order to eliminate the memory effect of boron, a combination of 2% (v/v) hydrogen gas in argon and 1% trifluoromethane in argon, an acid solution of calcium chloride and mannitol as chemical modifiers was used. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained around the 433.1 nm and 437.1 nm spectral regions are metrologically compatible with those reported by mass spectrometric methods. Moreover, for the evaluated region of 437 nm, an accuracy of 0.15‰ is obtained as the average deviation from the isotope reference materials. Expanded uncertainties with a coverage factor of k = 2 range between 0.15 and 0.44‰. This accuracy and precision are compatible with those obtained by mass spectrometry for boron isotope ratio measurements.