Recommendations and Protocols for the Use of the Isotope Ratio Infrared Spectrometer (Delta Ray) to Measure Stable Isotopes from CO₂: An Application to Volcanic Emissions at Mount Etna and Stromboli (Sicily, Italy)

Figure 2

Raw signal (1 Hz) and overlapped Allan deviation obtained for 1800 s using a fixed range dilution system (yellow tube) for δ¹³C (a) and δ¹⁸O (b) and without a dilution system for δ¹³C (c) and δ¹⁸O (d). Red values and lines represent the theoretical signal expected from the analyzed sampling bag. Dashed square represents the subset of measurements (on a time required to obtain 99% of the precision) used to calculate the average value used for the test of accuracy. Box-and-whisker plots for the deviations of δ¹³C (e) and δ¹⁸O (f) measured values from theoretical values of reference gases used in this study (see Methods and Appendix 1).

(a)

(b)

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(e)

(f)