Emission Spectrometric Method and Analyzer for Traces of Nitrogen in Argon.

Abstract

b A simple method for determining trace quantities of nitrogen impurity in argon is required for control in the refining of high-purity argon. It was found that nitrogen in argon could be made to emit strong band spectra by several excitation methods. The best excitation source, however, is a silent electric discharge, which operates satisfactorily on flowing gas streams at atmospheric pressure. The nitrogen is determined by measuring the intensity of the 3371 A. band head of the second positive system. With this method, less than 0.1 p.p.m. of nitrogen in argon can be detected. Plant-stream analyzers for continuously recording the nitrogen content of argon have been built, using filter optics and photomultiplier detectors.A two-channel, ratio-recording instrument is described. Plant instruments have given satisfactory service for several years.

Development of a Detector for Ultratrace Nitrogen in Argon Using Low-Pressure, Capillary Glow Discharge Molecular Emission Spectrophotometry

“…Due to discharge in the nitrogen−argon gas mixtures, a couple of emission bands of nitrogen appeared around the range of 300− 400 nm. The more intense band resulted from the lowest vibrational transition of the C 3 Π u → B 3 Π g system of the nitrogen molecule. ,,, In the following experiments, the emission of 337 nm, which corresponds to the emission from the excited nitrogen, was selected to determine a trace amount of nitrogen in argon. The power supply voltage of a photomultiplier was set at −600 V. The emission intensity of the 337 nm band was sufficient to detect a trace amount of nitrogen; if the sample gas contains a large amount of nitrogen, the power supply of a photomultiplier should be adjusted to lower voltage to protect the photomultiplier from overloading.…”

“…In high-technology industries, specifications and quality control of argon used as an inert and atmospheric gas are becoming more severe and important . The continuous determination of impurities, especially nitrogen, in argon has been done by ordinary tools such as a silent discharge analyzer …”

Determination of molecular nitrogen with a photometric detector

“…In the Atmosphere to the semiconductor (1,2), nuclear (3, 4), and other (5, 6) industries. The most prominent methods for the detection of N2 are mass spectrometry (1,2,7) and gas chromatography (3)(4)(5).…”

“…On the other hand, molecular nitrogen is easily excited in argon discharges and flowing afterglows (9). In fact, the detection of nitrogen-elemental or in the form of its compounds-has been extensively investigated in the argon inductively coupled plasma (10,11), the argon microwaveinduced plasma (12)(13)(14), and other argon discharges (6,15,16). Limits of detection with photoelectric devices are generally in the parts-per-million range (10,(14)(15)(16), while a photographic method reaches below 0.1 ppm (6).…”