Automated cleaning of foraminifera shells before Mg/Ca analysis using a pipette robot

作者:Johnstone, Heather J. H.*; Steinke, Stephan; Kuhnert, Henning; Bickert, Torsten; Paelike, Heiko; Mohtadi, Mahyar
来源:Geochemistry Geophysics Geosystems, 2016, 17(8): 3502-3511.
DOI:10.1002/2016GC006422

摘要

The molar ratio of magnesium to calcium (Mg/Ca) in foraminiferal calcite is a widely used proxy for reconstructing past seawater temperatures. Thorough cleaning of tests is required before analysis to remove contaminant phases such as clay and organic matter. We have adapted a commercial pipette robot to automate an established cleaning procedure, the Mg-cleaning protocol of Barker et al. (2003). Efficiency of the automated nine-step method was assessed through monitoring Al/Ca of trial samples (GeoB4420-2 core catcher). Planktonic foraminifera Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from this sample gave Mg/Ca consistent with the habitat range of the three species, and 40-60% sample recovery after cleaning. Comparison between manually cleaned and robot-cleaned samples of G. ruber (white) from a sediment core (GeoB16602) showed good correspondence between the two methods for Mg/Ca (r=0.93, p<0001, n=27). Average Al/Ca in robot-cleaned samples was 0.05 mmol/mol, showing that the samples are cleaned effectively by the robot. The robot offers increased sample throughput as batch sizes of up to 88 samples/blanks can be processed in approximate to 7 h with little intervention.