基于紧凑型双调制法拉第旋转光谱仪的一氧化氮同位素分析仪。

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

作者信息

Zhang Eric, Huang Stacey, Ji Qixing, Silvernagel Michael, Wang Yin, Ward Bess, Sigman Daniel, Wysocki Gerard

机构信息

Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA.

Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.

出版信息

Sensors (Basel). 2015 Oct 14;15(10):25992-6008. doi: 10.3390/s151025992.

DOI:10.3390/s151025992

PMID:26473876

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC4634453/

Abstract

We have developed a transportable spectroscopic nitrogen isotopic analyzer. The spectrometer is based on dual-modulation Faraday rotation spectroscopy of nitric oxide isotopologues with near shot-noise limited performance and baseline-free operation. Noise analysis indicates minor isotope ((15)NO) detection sensitivity of 0.36 ppbv·Hz(-1/2), corresponding to noise-equivalent Faraday rotation angle (NEA) of 1.31 × 10(-8) rad·Hz(-1/2) and noise-equivalent absorbance (αL)min of 6.27 × 10(-8) Hz(-1/2). White-noise limited performance at 2.8× the shot-noise limit is observed up to ~1000 s, allowing reliable calibration and sample measurement within the drift-free interval of the spectrometer. Integration with wet-chemistry based on acidic vanadium(III) enables conversion of aqueous nitrate/nitrite samples to gaseous NO for total nitrogen isotope analysis. Isotopic ratiometry is accomplished via time-multiplexed measurements of two NO isotope transitions. For 5 μmol potassium nitrate samples, the instrument consistently yields ratiometric precision below 0.3‰, thus demonstrating potential as an in situ diagnostic tool for environmental nitrogen cycle studies.

摘要

我们开发了一种便携式光谱氮同位素分析仪。该光谱仪基于一氧化氮同位素异构体的双调制法拉第旋转光谱，具有近散粒噪声限制性能和无基线操作。噪声分析表明，次要同位素（¹⁵NO）的检测灵敏度为0.36 ppbv·Hz⁻¹/²，对应于1.31×10⁻⁸ rad·Hz⁻¹/²的噪声等效法拉第旋转角（NEA）和6.27×10⁻⁸ Hz⁻¹/²的噪声等效吸光度（αL）min。在长达约1000 s的时间内观察到白噪声限制性能达到散粒噪声限制的2.8倍，从而能够在光谱仪的无漂移区间内进行可靠的校准和样品测量。与基于酸性钒（III）的湿化学方法相结合，可将硝酸盐/亚硝酸盐水溶液样品转化为气态NO，用于总氮同位素分析。同位素比率测定通过对两种NO同位素跃迁的时分复用测量来完成。对于5 μmol硝酸钾样品，该仪器始终能产生低于0.3‰的比率精度，因此展示了其作为环境氮循环研究原位诊断工具的潜力。