Customer Spotlight: Group of Plant Nutrition at the Institute of Agricultural Sciences @ ETH Zurich

Her field of interest is phosphate cycling in the soil-plant system and her preferred 'tool' is oxygen stable isotopes in phosphates. This analytical tool allows having a deeper insight in the phosphorus cycling in the soil/plant system. Here, changes in the oxygen isotopes ratio in phosphate are caused by biotic processes, such as enzymatic hydrolysis of organic matter, each of which entails a specific isotopic effect. This has proven useful in understanding P cycle in the environment, e.g. during the first stages of soil development or inside plants under stress conditions. Under specific conditions, ¹⁸O in phosphate could also be used as a tracer of P sources in the environment. 
 
For phosphate analysis, the group predominantly analyses Ag₃PO₄ samples to determine the ¹⁸O isotopic signature of the phosphate, which has previously been extracted from different soil and plant pools. There is a widespread “dogma” amongst the community that Ag₃PO₄ sample analysis is particularly challenging. Besides the laborious preparation and clean-up procedure to generate the Ag₃PO₄ samples, Dr. Tamburini reports that the vario PYRO cube^® has never had any difficulty performing this analysis. For each sample, a small amount of glassy carbon is added to the silver capsule to increase the availability of carbon to the pyrolyzed sample. The system blanks are very small which is important for this analysis and the quality of the resultant CO chromatography is excellent with good separation from any N₂ and a sharp symmetrical peak shape. 
 
The group runs, on average, around 4,000 samples without renewing the glassy C furnace. The run size is generally around 112 to 120 samples and this takes around 20 to 22 hours to complete. With the good sensitivity offered by the instrument, the group is able to run samples between 200 and 300 µg, if not less. This is important for the team because the amount of Ag₃PO₄ that it produces from the preparation of soil samples is often small, mainly because it sometimes deals with samples where little phosphate is present. The group also uses the O₂ elemental composition results from the vario PYRO cube^® to check the purity of the samples 
 
Speaking about what first impressed her about Elementar, Dr. Tamburini said:  

We had to look for different companies and instrument solutions when applying for money, and the things that attracted me were the innovative preparation system of the vario PYRO cube, the straightforward way of use of all components of the system, and the 'modularity' of it. The Elementar staff were also extremely competent and attentive to our particular requirements, so it made the difference. 

Dr. Tamburini explained that the zero blank sample delivery system, the ease of changing mode from combustion to pyrolysis and the accuracy and reliability of the IRMS are among the instrument's most helpful features. She said that in addition to the analytical advantages related to the IRMS measurements, the instruments have also helped to optimize sample preparation (from soil extracts to Ag₃PO₄) within the laboratory.