Nitric oxide isotopic analyzer based on a compact dual-modulation Faraday rotation spectrometer.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Spectroscopy

Background:

• Nitrogen isotopes are crucial for understanding environmental processes.
• Accurate in situ measurement of nitrogen isotopes is challenging.
• Existing methods often require complex laboratory analysis.

Purpose of the Study:

• To develop a transportable spectroscopic analyzer for nitrogen isotopic analysis.
• To achieve high sensitivity and precision for environmental samples.
• To enable in situ measurements of the nitrogen cycle.

Main Methods:

• Utilized dual-modulation Faraday rotation spectroscopy of nitric oxide (NO) isotopologues.
• Achieved near shot-noise limited performance and baseline-free operation.
• Integrated wet-chemistry with acidic vanadium(III) for sample conversion to gaseous NO.
• Employed time-multiplexed measurements for isotopic ratiometry.

Main Results:

• Demonstrated minor isotope ((15)NO) detection sensitivity of 0.36 ppbv·Hz(-1/2).
• Achieved noise-equivalent Faraday rotation angle (NEA) of 1.31 × 10(-8) rad·Hz(-1/2).
• Obtained ratiometric precision below 0.3‰ for 5 μmol potassium nitrate samples.

Conclusions:

• The developed instrument shows potential as an in situ diagnostic tool for environmental nitrogen cycle studies.
• The high sensitivity and precision enable reliable measurements within a drift-free interval.
• This technology advances the field of environmental isotope analysis.