Geostandards and Geoanalytical Research Bibliographic Review 2020

The use of RMs for calibration and quality control purposes of analytical techniques is essential for geoanalytical research and related scientific fields to obtain reliable results. This review encompasses RMs used in traditional geochemistry as well as for palaeoclimate research or environmental and other related applications. The systematic research comprises more than 7200 individual publications from nineteen scientific (i.e., peer-reviewed) journals. Additionally, some specific publications of further journals are included. A total of 630 of these articles present measurement results for RMs, which represent about 9% of all surveyed publications (Table 1; Figure 1). In 2020, publications included data that were obtained by new analytical developments or improved analytical protocols for established RMs. In addition, this year’s survey identified some

Here, we present the Geostandards and Geoanalytical Research Bibliographic Review 2020-an overview of scientific publications in 2020 that contribute important data for geoanalytical reference materials (RMs).
The use of RMs for calibration and quality control purposes of analytical techniques is essential for geoanalytical research and related scientific fields to obtain reliable results. This review encompasses RMs used in traditional geochemistry as well as for palaeoclimate research or environmental and other related applications. The systematic research comprises more than 7200 individual publications from nineteen scientific (i.e., peer-reviewed) journals. Additionally, some specific publications of further journals are included. A total of 630 of these articles present measurement results for RMs, which represent about 9% of all surveyed publications (Table 1; Figure 1). In 2020, publications included data that were obtained by new analytical developments or improved analytical protocols for established RMs. In addition, this year's survey identified some recently developed RMs for various scientific topics. All data we refer to in this review have been compiled in the GeoReM database that is freely available online (Jochum et al. 2005, http://georem.mpch-mainz.gwdg.de). The recent Application Version 30 of GeoReM (as of January 2021), which includes more than 3800 RMs of numerous providers worldwide, will be replaced by Application Version 31 (March 2022). Appendix S1 contains the full list of publications surveyed for 2020, which are the topic of this review and also are included in the GeoReM database in alphabetical order. The GeoReM reference citation in Appendix S1 is preceded by a key code: at first, there is serial number followed by the GeoReM-ID, which enables fast and easy queries within the database. An overview of the names and abbreviations of RM providers is given in Appendix S2.
Since 2019, the Max Planck Society and many German universities have faced the challenge of limited access to some of the major publishing houses (e.g., Elsevier) as pointed out in the Geostandards and Geoanalytical Research Bibliographic Review 2019 (Weis et al. 2021). Therefore, some journals, which have been part of the research for the GGR Bibliographic Review for many years, cannot be accessed and surveyed in this review. For this reason and also to broaden the spectrum of research topics, this review includes for the second time journals from other publishers that present relevant data for RMs such as  The share of scientific papers providing data for isotopic systems is very high (62%) compared with the number of papers referring to trace elements (23%) or even major elements (12%, Figure 4). The percentage of papers focusing on single or very few specific elements is with 23% relatively high compared with studies on major elements (12%, Figure 4). Figure 5 shows the distribution of the most important providers of RMs within our study. 28% of the articles publish data for USGS RMs, 25% for NIST RMs and 11% for GSJ RMs. All other distributors have a share lower than 5%. USGS, NIST and GSJ are institutions providing many RMs of various matrices explaining the high amount of published data. GeoReM contains data for 424 RMs from NIST, 138 from USGS, 49 from GSJ, whereas for example there are only eight MPI-DING glasses, provided by the Max Planck Institute for Chemistry (Jochum et al. 2006). Currently, the USGS is not distributing its existing RMs due to an internal reorganisation. Nevertheless, the USGS Geological Reference Materials project will be proceeded both with development of new RMs and replacement RMs and also  1 3 1 with updated documentation for the established RMs (https://www.usgs.gov/centers/geology%2C-geophysics% 2C-and-geochemistry-science-center/science/developmentusgs-geochemical).
The increasing relevance of isotopic systems, regarding both radiogenic and stable isotopes, is also reflected by a number of studies, which provide data sets consisting of values for many different RMS. In the following, we show some examples for thorough studies regarding one or more isotopic systems on a wide range of RMs: An et al. (2020) have presented new Ba isotope data for thirty-four geological reference materials of various matrices, such as silicates, carbonates, sediments and soils. These RMs cover a wide range of Ba mass fractions from 6.4 µg g -1 up to 1900 µg g -1 . The zinc (Zn) stable isotope system is used to investigate natural and anthropogenic processes in various disciplines like Earth and planetary sciences or biomedical research. For there is a lack of well-characterised matrix-matched RMs, Druce et al. (2020) have published Zn isotopic data for eighteen reference materials including many previously uncharacterised RMs. A large study on Cd isotopes with results for rock and soil RMs of different providers covering a range of -0.251 to 0.632& relative to NIST SRM 3108 has been conducted by Liu et al. using a MC-ICP-MS technique with double spike correction (Liu et al. 2020). Isotopic signatures of Pb, Nd, Sr, Zn, Cu and Fe are commonly used as sensitive geochemical tracers. Vanderstraeten et al. (2020) developed a chromatographic protocol to separate the six elements of interest, which enables the amount of material required for sample preparation and isotopic analysis to be minimised by combining sequentially several columns. In addition to data for several RMs, they reported the first combined isotopic data for two dust RMs, namely BCR-23 and ATD.
In 2020, several new RMs have been characterised of which we present a few samples here. For many analytical techniques such as microanalysis, it is essential to use matrixmatched RMs for calibration and quality control. A set of four selenium-rich rocks (GBW07397 to GBW07400) has been formalised as CRMs for mass fractions of selenium, arsenic, copper, zinc, molybdenum, cadmium, lead, vanadium and silver by Tang et al. (2020). Zhang et al. (2020) introduced the RMJG rutile -a new microanalytical RM of natural origin for U-Pb dating and Hf isotopic analysis. Zircon is a mineral widely used in U-Pb geochronology, but also for trace element mass fractions and Li, O and Hf isotopic studies. Many of the established natural zircon RMs are nearly exhausted. Therefore, there is need of additional and replacement RMs. A new natural zircon RM 'SA01' is proposed by Huang et al. (2020) on the basis that this zircon megacryst is homogenous and therefore suitable for U-Pb geochronology as well as O and Hf isotope geochemistry by microanalytical techniques. For environmental and biological research, Haraguchi et al. (2020) developed the CRM 'NIMD-01' for the analysis of mercury speciation and some trace elements in human hair. Synthetic RMs have the advantage of offering higher homogeneity compared with many natural materials. Therefore, Ke et al. 1 3 2 solution 'GSB-Mg' as a RM for Mg isotopic measurements. The isotopic composition of GSB-Mg is similar to Mg isotopic compositions of carbonate rocks and marine sediments, and therefore, it is suitable as a RM for samples with these matrices ).
These are a few examples for new developments of RMs with different matrices and for various fields of science from traditional geochemistry to biomedicine. This review shows that a substantial number of publications in 2020 focussed on both newly developed RMs and analytical data achieved by improved methods. This reflects the persistent importance of RMs in numerous analytical techniques across geoanalytical and related research.