A gas sensor comprising: a substrate; a grating array disposed on top of the substrate and comprising grates; and voids defined by the grates and configured to confine gas molecules for absorption of light and analysis. A method of gas sensing comprising: generating first light; converting the first light into second light using grates of a grating array; resonating the second light within the grating array; confining gas molecules in voids defined by the grates; and causing the gas molecules to absorb the second light within the voids.

A system for measuring a target gas via laser absorption spectroscopy in an open-air configuration, comprising a mid-infrared distributed feedback interband cascade laser (mid-IR DFB-ICL) having a wavelength selected to correspond with a spectral absorption line of the target gas and first electronic circuitry to control the laser temperature, current and modulation frequency. The mid-IR DFB-ICL is mounted to a heat sink. The system includes an optical component that projects a beam of the mid-IR DFB-ICL onto a distal backscattering directionally-reflective target and an optical receiver assembly that receives a fraction of the laser light that is backscattered from the directionally-reflective target and focuses the collected light onto an uncooled photodetector having a spectral bandwidth and optical configuration selected to optimize signal-to-noise response to received laser light. The optical receiver assembly comprises a primary mirror for receiving laser light backscattered from the directionally-reflective target and focusing the collected light onto the uncooled photodetector.

An optical cell comprises first and second opposed reflecting elements, an entrance aperture in the first reflecting element and an exit aperture in the second reflecting element, wherein the entrance and exit apertures are configured such that, in operation, light introduced into the cell via the entrance aperture is reflected at least once by the second reflecting element and at least once by the first reflecting element before leaving the cell via the exit aperture.

A method of detecting a geometrical phase change of an intrinsic property of a molecular isomerization includes a series of steps, such as simulating molecular isomerization of the molecule through application of a single shaped pulse to generate a molecular polarization. The steps include separating the real and imaginary parts of a nonlinear susceptibility in a detected molecular signal by controlling a phase of a reference field. The steps include assigning a phase function to obtain separation of the real and imaginary parts. Furthermore, a broadened vibrational lineshape is calculated. The step of identifying conical intersections also occurs. Various pathways of a wave packet in an excited state potential energy surface is discussed and may include multiple laser pulses and methods of detection. The spectral phase may be used to create interference of the wave packet in the excited state to identify and control a wavepacket's pathway and control photoisomerization.

A high-sensitivity nanosecond to millisecond transient absorption spectrometer for measurements of miniscule signals under low excitation intensities includes an excitation source generating a >100 Hz, <5 ns pulsewidth excitation pulse for exciting a light absorbing sample, a probe light source for generating a high photon flux probe light beam producing an average irradiance greater than 1 μW m.sup.-2 nm.sup.-1 for measuring the transient absorption spectrum of the sample before and after excitation by the excitation source, a DC-coupled detector capable of measuring light for enabling synchronous measurement of both the transmission of the probe light beam and the change in transmission of the probe light beam between a signal with the excitation pulse present and a signal in the absence of the excitation pulse, and a digital oscilloscope with a trigger rearm time capable of collecting every trigger event at frequencies including 1MHz, for enabling sequential noise subtraction protocols.

A measuring apparatus for measuring a spectrum of a gaseous sample includes a tunable laser light source to provide an illuminating light beam, a sample cell with an inner surface to provide scrambled light that is transmitted through the gaseous sample, a detector to detect intensity of transmitted scrambled light and a pressure control system to maintain an absolute pressure of the gaseous sample smaller than 50 kPa inside the sample cell to reduce spectral widths of spectral features of the gaseous sample. The measuring apparatus measures spectral transmittance values of the sample by modulating the spectral position of the illuminating light, and detecting the intensity of the transmitted light at different spectral positions. The divergence of the illuminating light beam in a transverse direction is greater than 30° to cause multiple consecutive reflections of the scrambled light from the inner surface.

This invention provides a UV spectroscopy apparatus and method for controlled drug waste diversion detection. The spectroscopy apparatus employs sample cells which have optimized optical path length such that the measured maximum absorbance of the drug is less than the detection limit of the system. Hence the full unsaturated absorption spectrum of the drug is revealed in the UV wavelength region from 230 nm (or even down to 195 nm) to 400 nm. This full spectrum analysis improves the specificity for drug identification and the accuracy for drug concentration verification. The spectral library of the apparatus comprises the spectra of preservative-free controlled drugs, common excipients, as well as typical diluents, which enables the identification of controlled drugs from different manufacturers and/or diluted with different types of diluents.

Disclosed is a method for measuring the absorbance of light of a substance in a solution in a measuring cell (23; 223′), said method comprising the steps of: transmitting (S1) a first light beam (27; 27′) from a light source (25; 25′) towards a beam splitter (29; 29′); dividing (S3) the first light beam (27; 27′) into a signal light ray (31; 31′) and a reference light ray (33; 33′) by the beam splitter (29; 29′); modulating (S5) the signal light ray (31; 31′); modulating the reference light ray (33; 33′); providing (S9) the measuring cell (23; 23′) such that the signal light ray (31; 31′) passes through the measuring cell; detecting (S11) a signal in a detector (39; 39′), which signal is the combined signal intensity of the signal light ray (31; 31′) and the reference light ray (33; 33′) detected by the detector (39; 39′); performing synchronous detection (S15) of the detected signal in order to reconstruct the intensities of the signal light ray (31; 31′) and the reference light ray (33; 33′) from the combined signal detected by the detector (39; 39′), said synchronous detection being based on the modulation performed to the signal light ray and the reference light ray. Disclosed also is a measuring device for carrying out said method.

A method for preparing an intermediate by a reduced glutathione-indicated amino acid Maillard reaction is provided. The method includes a two-stage reaction at an increased temperature. A reduced glutathione is added after different times of a low-temperature reaction, and a subsequent Maillard reaction is effectively inhibited on a basis wherein a substance is interacted with an intermediate degradation product to reduce a formation of colored substances. Comparing with a browning of Maillard products after a high-temperature stage, a reaction time with a best color inhibition effect is found to be the optimal preparation condition of the intermediate, and the intermediate is prepared in an aqueous medium at a low temperature under this optimal preparation condition. The method uses the water soluble reduced glutathione as a tracer to improve a tracing accuracy comparing to cysteine.

An embodiment provides a method for measuring zinc and copper in an aqueous sample, including: reducing an aqueous sample containing an amount of zinc and an amount of copper with a reducing agent; buffering the reduced aqueous sample; chelating the amount of copper in the buffered aqueous sample with a copper(I) chelating agent; measuring the amount of copper in the aqueous sample by measuring a first change in intensity of the absorbance of the copper chelated aqueous sample; chelating the amount of zinc in the buffered aqueous sample with a zinc(II) chelating agent; and measuring the amount of zinc in the aqueous sample by measuring a second change in intensity of the absorbance of the zinc chelated aqueous sample. Other aspects are described and claimed.