Method and system for examining the composition of a fluid or so

Details Method and system for examining the composition of a fluid or so Method and system for examining the composition of a fluid or so

1993-12-01

1996-02-13

Willis, Davis L.

Radiant energy

Luminophor irradiation

With ultraviolet source

2504591, G01N 2164

Patent

active

054913446

ABSTRACT:
A method and system for examining the composition of a fluid or solid sample using fluorescence and/or absorption spectroscopy. In one embodiment, the system is adapted for use in examining liquid effluents as they elute from the end of a liquid chromatography column and comprises a Nd:YAG laser coupled to a harmonic generator. Pulses of the fourth harmonic therefrom are focused into a Raman shifter filled with a mixture of hydrogen and methane gases. The laser pulses have an intensity sufficient to produce an array of different-colored laser pulses by stimulated Raman scattering within the Raman shifter. These different-colored pulses are then dispersed according to their respective wavelengths and then launched into a plurality of optical fibers. The fibers tranmit the different-colored pulses to a specially-designed detection cell, where they simultaneously excite a flowing fluid sample contained within the cell at the same point of axial fluid flow. The fluid sample enters and exits the detection cell via tubes. Ultraviolet and visible lamp light is also used to illuminate the fluid sample, and the attenuation of this light is used to obtain an absorption spectrum of the sample. Optical fibers are used to transport fluorescent light, transmitted lamp light and a fraction of the Raman-shifted laser light to an imaging spectrograph. The light from each optical fiber is dispersed along a narrow strip by the spectrograph to produce an array of strips, each strip corresponding to one of the fibers, and is focused on the surface of a 2-dimensional CCD detector. The CCD detector converts each strip into electrical charges, which are digitized and processed by a computer to create an EEM. The aforementioned system is capable of obtaining an absorption spectrum from 200-479 nm with 0.5-5 nm spectral resolution and 10 fluorescence spectra simultaneously every 0.1-250 seconds for several hours, with crosstalk between channels of less than 10.sup.-4.

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