Abstract: Disclosed are spectroscopy systems and methods. A spectroscopy system can include a reference cell and a multi-pass sample cell. The reference arm can include an etalon and a reference cavity containing a reference gas. A system can include a fractional sublimation cold trap. Detectors of the reference and sample arms can detect both intensity and absorption spectra of impinging beams. A frequency calibration based on a reference absorption spectra can be used to analyze a sample absorption spectrum. The analysis can provide information regarding an absorption band shift of the sample absorption spectrum, said shift being related to the isotope concentration of the sample.

Abstract: Spectrophotometers and spectroscopy processes are described that can provide for in-line calibration at every spectral acquisition as well as for continuous response correction during sample processing. The spectrophotometers include multiple polychromatic light sources that include characteristic emission spectra for use as an internal wavelength drift calibration system that is independent of environmental factors. Correction functions provided by the internal calibration process can be applied continuously and across an entire sample spectrum. The intensity response of each spectrometer in a spectrophotometer can also be monitored and continuously corrected for stray light, dark current, readout noise, etc.

Abstract: Analysis techniques by generation and interpretation of multivariate data that can provide for highly accurate analyte detection are described. Protocols can include a tiered principal component analysis (PCA) utilizing a partial least squares (PLS) approach for classification of a sample. Methods include selection of a particular local model for each classification category. The classification categories are determined based on assessment of sample characteristics such as solution absorbance, acidity, analyte oxidation state distribution, temperature, presence of one or more interferents, etc.

Abstract: Spectrophotometers and spectroscopy processes are described that can provide for in-line calibration at every spectral acquisition as well as for continuous response correction during sample processing. The spectrophotometers include multiple polychromatic light sources that include characteristic emission spectra for use as an internal wavelength drift calibration system that is independent of environmental factors. Correction functions provided by the internal calibration process can be applied continuously and across an entire sample spectrum. The intensity response of each spectrometer in a spectrophotometer can also be monitored and continuously corrected for stray light, dark current, readout noise, etc.

Abstract: A fiber optic probe and optical coupler assembly, and methods for making the assembly and reproducibly aligning a plurality of optical fibers therein. The coupler is used with a probe that includes a housing or probe body, a probe tip, at least one light-transmitting fiber, at least one light-receiving fiber spaced apart from the light-transmitting fiber, and (if desired), in-line devices such as filters and lenses positioned in optical communication with the fibers. The coupler includes at least one aligning pin that helps maintain the transmitting and receiving fibers in precise, reproducible relative alignment therein; thus, the coupler can be cut to install filters and other in-line devices, then readily re-assembled for use with the cut ends precisely and accurately realigned. The coupler is simple and rugged, and can be manufactured and assembled without the need for high-precision machining or optical alignment procedures.

Abstract: A fiber optic probe for ATIR (Attenuated Total Internal Reflection) spectrophotometry. The probe includes a housing that contains an optical element or lens, a light-transmitting fiber that directs incident light to the lens, a light-receiving fiber that receives reflected light from the sample interface, a coupler for holding these components in precise alignment, and a flexible armor casing that provides strain relief and protection for the optical fibers. The lens is shaped and dimensioned so that light from the transmitting fiber is reflected at the interface between the lens and the surrounding medium (such as a liquid to be analyzed). The reflected light is transmitted via the transmitting fiber to a suitable spectrophotometer, where the light signal is recorded and analyzed to determine the composition of the sample. The probe is particularly suitable for analyses of fluids and slurries with high optical absorbance.

Abstract: A fiber optic Raman probe and optical coupler assembly, and a method for making the assembly and reproducibly aligning a plurality of optical fibers therein. The probe includes a housing or probe body, a probe tip with a window for protecting the interior of the housing, at least one light-transmitting fiber, at least one light-receiving fiber spaced apart from the light-transmitting fiber, an optical coupler, and (if desired), in-line devices such as filters and lenses positioned in optical communication with the fibers. The coupler assembly includes aligning means that helps maintain the fibers in precise, reproducible relative alignment of the fibers; thus, the assembly with the fibers can be cut to install filters and other in-line devices, then readily re-assembled with the cut ends accurately re-aligned, for use. The probe is simple and rugged, and can be manufactured and assembled without the need for high-precision machining or optical alignment procedures.

Abstract: A multiplexed spectrophotometry apparatus, including a rotary multiplexer fitted with a plurality of fiber terminals, a spectrophotometer mounted to the multiplexer and rotatable therewith, and a programmable on-board computer. The spectrophotometer includes precision optics, a charge coupled device (CCD) detector, electronics, and a cooling system, all contained in a compact, streamlined housing that is shaped to promote the radiation of heat from the spectrophotometer and thereby prevent excessive heating during operation of the apparatus. The spectrophotometer is mounted directly to the multiplexer so that any selected terminal can readily be brought into precise, reproducible alignment with the spectrophotometer input. All components of the apparatus are contained in a compact housing adapted for either rack-mounted or bench-top use.

Abstract: A fiber optic probe and optical coupler assembly for light scattering measurements, and a method for making the assembly and aligning a plurality of optical fibers therein. The probe includes a probe body with a window across its tip for protecting the interior, at least one light-transmitting fiber, at least one light-receiving fiber, and (if desired), in-line devices such as filters and lenses positioned in optical communication with the fibers. A fiber optic coupler maintains the relative alignment of the fibers, which can be cut to install filters and other in-line devices. The coupler allows the cut ends to be re-aligned quickly and accurately without the need for time-consuming procedures or costly precision alignment equipment. The probe is simple, rugged, requires no high-precision machining or optical alignment procedures in assembly, and is economical to manufacture.

Abstract: An optical probe for conducting light scattering analysis is disclosed. The probe comprises a hollow housing and a probe tip. A fiber assembly made up of a transmitting fiber and a receiving bundle is inserted in the tip. A filter assembly is inserted in the housing and connected to the fiber assembly. A signal line from the light source and to the spectrometer also is connected to the filter assembly and communicates with the fiber assembly. By using a spring-loaded assembly to hold the fiber connectors together with the in-line filters, complex and sensitive alignment procedures are avoided. The close proximity of the filter assembly to the probe tip eliminates or minimizes self-scattering generated by the optical fiber. Also, because the probe can contact the sample directly, sensitive optics can be eliminated.

Abstract: An apparatus and method for determining acid concentrations in solutions having acid concentrations of from about 0.1 Molar to about 16 Molar is disclosed. The apparatus includes a chamber for interrogation of the sample solution, a fiber optic light source for passing light transversely through the chamber, a fiber optic collector for receiving the collimated light after transmission through the chamber, a coating of an acid resistant polymeric composition upon at least one fiber end or lens, the polymeric composition in contact with the sample solution within the chamber and having a detectable response to acid concentrations within the range of from about 0.1 Molar to about 16 Molar, a measurer for the response of the polymeric composition in contact with the sample solution, and, a comparer of the measured response to predetermined standards whereby the acid molarity of the sample solution within the chamber can be determined.

Abstract: A tetraethyl orthosilicate-based, sol-gel glass composition with additives selected for various applications. The composition is made by mixing ethanol, water, and tetraethyl orthosilicate, adjusting the pH into the acid range, and aging the mixture at room temperature. The additives, such as an optical indicator, filler, or catalyst, are then added to the mixture to form the composition which can be applied to a substrate before curing. If the additive is an indicator, the light-absorbing characteristics of which vary upon contact with a particular analyte, the indicator can be applied to a lens, optical fiber, reagant strip, or flow cell for use in chemical analysis. Alternatively, an additive such as alumina particles is blended into the mixture to form a filler composition for patching cracks in metal, glass, or ceramic piping.

Abstract: A method for validating a process stream for the presence or absence of a substance of interest such as a chemical warfare agent; that is, for verifying that a chemical warfare agent is present in an input line for feeding the agent into a reaction vessel for destruction, or, in a facility for producing commercial chemical products, that a constituent of the chemical warfare agent has not been substituted for the proper chemical compound. The method includes the steps of transmitting light through a sensor positioned in the feed line just before the chemical constituent in the input line enters the reaction vessel, measuring an optical spectrum of the chemical constituent from the light beam transmitted through it, and comparing the measured spectrum to a reference spectrum of the chemical agent and preferably also reference spectra of surrogates.

Abstract: A fiber optic probe for detecting scattered light, with transmitting and receiving fibers having slanted ends and bundled together to form a bevel within the tip of the probe. The probe comprises a housing with a transparent window across its tip for protecting the transmitting and receiving fibers held therein. The endfaces of the fibers are slanted, by cutting, polishing and the like, so that they lie in a plane that is not perpendicular to the longitudinal axis of the respective fiber. The fibers are held in the tip of the probe using an epoxy and oriented so that lines normal to the slanted endfaces are divergent with respect to one another. The epoxy, which is positioned substantially between the transmitting and receiving fibers, is tapered so that the transmitting fiber, the epoxy and the receiving fiber form a bevel of not more than 20 degrees. The angled fiber endfaces cause directing of the light cones toward each other, resulting in improved light coupling efficiency.

Abstract: A temperature probe and a method for using said probe for temperature measurements based on changes in light absorption by the probe. The probe comprises a first and a second optical fiber that carry light to and from the probe, and a temperature sensor material, the absorbance of which changes with temperature, through which the light is directed. Light is directed through the first optical fiber, passes through the temperature sensor material, and is transmitted by a second optical fiber from the material to a detector. Temperature-dependent and temperature-independent factors are derived from measurements of the transmitted light intensity. For each sensor material, the temperature T is a function of the ratio, R, of these factors. The temperature function f(R) is found by applying standard data analysis techniques to plots of T versus R at a series of known temperatures.

Abstract: A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

Abstract: A method for measuring the concentration of a chemical substance by spectrophotometry comprising the steps of placing a sample of a photoreactive substance between the light source and a spectrophotometer, obtaining an absorption spectrum of the substance using a fixed amount of light from the light source, obtaining a second absorption spectrum after a short interval, comparing the two to determine the concentration of the chemical substance from the difference in the spectra. If the chemical substance is not photoreactive, a photoreactive mixture can be made with a photoreactive dye that has photoreactive properties unique to the mixture. Alternatively, an optically transparent substrate can absorb the substance or the dye/substance mixture.

Abstract: A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

Abstract: An on-line, fiber-optic based apparatus for monitoring the concentration of a chemical substance at a plurality of locations in a chemical processing system comprises a plurality of probes, each of which is at a different location in the system, a light source, optic fibers for carrying light to and from the probes, a multiplexer for switching light from the source from one probe to the next in series, a diode array spectrophotometer for producing a spectrum from the light received from the probes, and a computer programmed to analyze the spectra so produced. The probes allow the light to pass through the chemical substance so that a portion of the light is absorbed before being returned to the multiplexer. A standard and a reference cell are included for data validation and error checking.

Abstract: A probe for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables.