Trace species detection in the near infrared using Fourier transform broadband cavity enhanced absorption spectroscopy: initial studies on potential breath analytes.

Cavity enhanced absorption measurements have been made of several species that absorb light between 1.5 and 1.7 µm using both a supercontinuum source and superluminescent light emitting diodes. A system based upon an optical enhancement cavity of relatively high finesse, consisting of mirrors of reflectivity ∼99.98%, and a Fourier transform spectrometer, is demonstrated. Spectra are recorded of isoprene, butadiene, acetone and methane, highlighting problems with spectral interference and unambiguous concentration determinations. Initial results are presented of acetone within a breath-like matrix indicating ppm precision at <∼10 ppm acetone levels. Instrument sensitivities are sufficiently enhanced to enable the detection of atmospheric levels of methane. Higher detection sensitivities are achieved using the supercontinuum source, with a minimum detectable absorption coefficient of ∼4 × 10(-9) cm(-1) reported within a 4 min acquisition time. Finally, two superluminescent light emitting diodes are coupled together to increase the wavelength coverage, and measurements are made simultaneously on acetylene, CO(2), and butadiene. The absorption cross-sections for acetone and isoprene have been measured with an instrumental resolution of 4 cm(-1) and are found to be 1.3 ± 0.1 × 10(-21) cm(2) at a wavelength of 1671.9 nm and 3.6 ± 0.2 × 10(-21) cm(2) at 1624.7 nm, respectively.

Near-infrared broad-band cavity enhanced absorption spectroscopy using a superluminescent light emitting diode.

A fibre coupled near-infrared superluminescent light emitting diode that emits approximately 10 mW of radiation between 1.62 and 1.7 microm is employed in combination with a broad-band cavity enhanced spectrometer consisting of a linear optical cavity with mirrors of reflectivity approximately 99.98% and either a dispersive near-infrared spectrometer or a Fourier transform interferometer. Results are presented on the absorption of 1,3-butadiene, and sensitivities are achieved of 6.1 x 10(-8) cm(-1) using the dispersive spectrometer in combination with phase-sensitive detection, and 1.5 x 10(-8) cm(-1) using the Fourier transform interferometer (expressed as a minimum detectable absorption coefficient) over several minutes of acquisition time.

An unusual type of alpha1-antitrypsin deficiency in a child.

An unusual variant of serum alpha1-antitrypsin is described in a 15 5/6-year-old white male with a history of chronic pulmonary disease. The patient had a very low level of this protease inhibitor as demonstrated by tryptic inhibitory capacity and electroimmunoassay. Even though the patient's serum alpha1-antitrypsin was partially purified and concentrated, no phenotypic pattern was seen using conventional Pityping procedures (acid starch gel with crossed antigen-antibody electrophoresis or isoelectric focusing). Crossed antigen-antibody electrophoresis using agarose in both steps, immunoelectrophoresis, and agarose electrophoresis followed by immunofixation all revealed a slow-moving alpha1-antitrypsin, cathodal to the Pi Z region. Studies on sera from the patient's mother and two half-sibs showed that all three had clear Pi M phenotypic pattersn. Quantitative date on these sera suggested that the unusual variant may be inherited in a codominant fashion.

1 -Antitrypsin deficiency: a variant with no detectable 1 -antitrypsin.

No alpha(1)-antitrypsin could be detected in the serum of a 24-year-old man with advanced pulmonary emphysema by agarose electrophoresis, immnuno-electrophoresis, double diffusion in agarose gel, or alpha(1)-antitrypsin genetic typing by a combination of starch-gel electrophoresis and crossed antigen-antibody electrophoresis. A circulating alpha(1)-antitrypsin inactivator could not be demonstrated. Evidence was obtained in family members of genetic transmission of this new alpha(1)-antitrypsin variant.