Determination of Monomethylhydrazine with a High-Throughput, All-Fiber Near-Infrared Spectrometer Based on an Integrated Acoustooptic Tunable Filter and an Erbium-Doped Fiber Amplifier

Abstract

A novel integrated acoustooptic tunable filter (IAOTF) has been developed. This tunable filter is based on the Bragg interactions between waveguide and surface acoustic waves. Compared to (bulk) AOTF, its advantage include all-fiber construction, smaller size, narrower spectral resolution (1.7 nm), higher diffraction efficiency (37%), and lower rf power requirement (150 mW). A relatively narrow spectral tuning range (about 80 nm) is the only drawback for this integrated tunable filter. However, this disadvantage was overcome by judiciously using the filter for measurements in which its tuning range is coincident with the light source and also with absorption bands of analytes. In fact, an all-fiber, compact, high-throughput near-infrared spectrophotometer has been successfully constructed by synergistic use of this integrated AOTF and the erbium-doped fiber amplifier (EDFA), which has been shown to provide high intensity and wide spectral band-width in the near-infrared region from 1500 to 1600 nm. This spectral region is particularly useful for the determination of samples which have O-H and/or N-H groups. The all-fiber nature, compactness, high throughput, and high sensitivity of this spectrophotometer make it particularly suitable for on-line and real-time detection of trace gases in hostile environments, including leak detection of monomethylhydrazine (at a limit of detection of 191 ppm), which is often used as the hypergolic propellant for the space shuttle thruster systems.

Near-Infrared Spectrometric Determination of Di- and Tripeptides Synthesized by a Combinatorial Solid-Phase Method

“…Instrumentation. The NIR spectrophotometer used in this work was the same as that used in our previous studies. − The only difference between the spectrometer used in this work and that used previously is that two identical 1-mm core optical fibers were used to direct the light from the sample beam to the sample and from the sample to the InGaAs detector. This modification was made to facilitate measurements of peptides directly in the reaction chamber cell.…”

“…13.14 As a consequence of this development, a NIR spectrophotometer based on the AOTF should be very sensitive, should have high light throughput, high stability, and no drift. In fact, we recently developed an AOTF-based NIR spectrometer and successfully used it for a variety of spectroscopic and analytical measurements including the determination of trace amounts of monomethylhydrazine and the study of inclusion complex formation between cyclodextrins and aromatic compounds, as well as the detector for flow injection analysis. − …”

Near-Infrared Spectrophotometric Determination of Tri- and Tetrapeptides

“…As a consequence of this development, a NIR spectrophotometer based on the AOTF should be very sensitive, should have high light throughput, high stability, and no drift. In fact, we recently developed an AOTF-based NIR spectrometer and successfully used it for a variety of spectroscopic and analytical measurements, including the determination of trace amounts of monomethylhydrazine and the study of the inclusion complex formation between cyclodextrins and aromatic compounds, as well as the detector for flow injection analysis (5)(6)(7)(8)(9).…”