Andrew O. Wright and Clayton D. Wood, and Kimberly J. Reynolds and Mark L. Malczewski, n increasingly important chemical used in the manufacture of electronic devices such as high-intensity light-emitting diodes (LEDs) is ultrahigh-purity (UHP) anhydrous ammonia. However, the presence of residual trace moisture in UHP ammonia is a matter of concern. Especially in blue and white LEDs, there is a strong correlation between device performance and moisture content in the process ammonia used during manufacturing. In addition, increasing chemical consumption is forcing many facilities to use bulk storage tanks as a single supply source instead of cylinders as supply sources for individual tools. In light of these trends, it is imperative to have a robust, continuous process instrument with a single-digit parts-per-billion detection limit that can measure moisture in ammonia. The challenge posed by moisture in ammonia has driven the development of continuous-detection instrumentation. Because ammonia and water are chemically similar, spectroscopic methods have proven to be the most promising option for detecting trace moisture in ammonia down to parts-per-billion levels. Since the mid-1990s, Fourier-transform infrared spectroscopy (FTIR) has been the method of choice for detecting these low levels of moisture. The performance of FTIR-based moisture measurement in ammonia has been enhanced by improved methods for handling ammonia samples and optimized spectral collection and data processing techniques. Dual-cell near-infrared absorption spectroscopy using a tunable diode laser over a narrow spectral bandwidth is another method for detecting trace spectroscopic levels of moisture in ammonia. This article describes the design and operation of a novel IR spectroscopic instrument, the DF-740 moisture analyzer, from Delta F (Woburn, MA). It also discusses the design of a calibration system for the generation of low levels of moisture in ammonia standards. Tunable Diode Laser Absorption Spectroscopy For use in process applications in which maintenance and user
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Infrared (IR) spectrometers measure the wavelength and intensity of the absorption of infrared light by a sample.
Gas sensors interact with a gas to initiate the measurement of its concentration. The sensor then provides output to an instrument to display the measurements.
Moisture meters are used to measure the moisture content in bulk solids, liquids and gases.
Laboratory and Calibration Gases
Laboratory and calibration gases are specialized for use as laboratory standards, as well as for detection, sample preparation, environmental monitoring and analysis applications.
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