Measuring Nitroprussside and Ferrocyanide with Quantitative UV-Vis using FlareLab

Stellar irradiation is thought to be a significant contributor to the origin of life. UV light inter- acting with iron cyanide complexes plays an important role in prebiotic chemistry. The UV-Vis spectra of these iron cyanide complexes can be measured by the same source that drives the chemistry, providing a real-time in-situ quantitative analysis of prebiotically relevant UV-driven photochemistry. FlareLab is an experimental set-up that is capable of measuring the absorbance of molecules sensitive to UV and visible light in-situ whilst experimentally simulating stellar flaring. In this work we test FlareLab via the quiescent irradiation of samples. The quantities of such molecules can be measured, as examples of ferrocyanide and nitroprusside show. We measure the UV-Vis absorbance of ferrocyanide and nitroprusside, and relate this absorbance to known concentrations. We show that these absorbances can be combined to accurately predict the concentrations of ferrocyanide-nitroprusside mixtures that could be generated from ferrocyanide and nitroxyl salts irradiated by ultraviolet light. The ferrocyanide molar attenuation coefficients were found to be: ε_ferrocyanide(340 nm) = (2.2 ± 0.4) × 10^3 dm^2mol^−1. Whilst nitroprusside peaks would show the fol- lowing values: ε_nitroprusside(340 nm) = (4.1 ± 0.3) × 10^2 dm^2mol^−1, ε_nitroprusside(400 nm) = (1.71 ± 0.05) × 10^2 dm^2mol^−1, and εnitroprusside(500 nm) = 62.1 ± 1.7 dm^2mol^−1. Using these results, FlareLab will contribute understanding how time varied stellar irradiation interacts with a planet’s surface prebiotic photochemistry.