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Valco Instruments Company, Inc.

Valco Instrument Co., Inc

Wayne E Wentworth

Stanley D Stearns

Huamin Cai

Stanley D Sterns

A method and apparatus are set forth which enables a gas chromatographic column output to be connected with a pulse discharge chamber in which chemically bound chlorine in volatile organic or inorganic samples is measured. A spark discharge is formed in the chamber to ionize and excite helium molecules to a metastable state. In turn, that transfers excitation to a trace of krypton gas in the chamber which is ionized, and the ionized krypton then preferentially binds with chemically bound chlorine. The latter binding occurs with the liberation of a photon centered at about 222 nanometers thereby defining a spectral region of interest which is measured by a photomultiplier tube to quantify chemically bound chlorine.

Chlorine specific gas chromatographic detector

A detection system measures very small concentrations of compounds of interest within gaseous samples. A spark discharge system induces pulsed spark discharges across a pair of electrodes within an inert gas in a gas flow chamber. Various reactions are induced by spark interaction with the flow of inert gas, and with any sample or dopant commingled with the inert gas, in the region of the pulsed spark discharge. This induces photon ionization which creates an instantaneous current flow within the gas flow chamber. Current flow is held constant for all concentrations of sample introduced into the gas flow by means of a control feedback system. The output of the control feedback system is indicative of sample concentration. The system responds linearly over approximately five orders of magnitude of sample concentration for use with the sample which will be described and low femtogram sensitivity is achieved.

System for detecting compounds in a gaseous sample using

A pulsed discharge photoinoization detector is set forth which comprises a plurality of closed chambers for receiving different types of carrier gas flowing there through between inlets and outlets. The carrier gases are exposed to a pair of electrodes forming a spark across each chamber and through each carrier gas. At least one component of each type of carrier gas is excited within each chamber by the spark discharges, and the resonance energies of each type of carrier gas are different. The sample to be analyzed is split and a portion is injected into each of the closed chambers where it is exposed to the excited carrier gases. Carrier gases, upon decay, serve as sources of ionizing radiation of differing energy which react with compounds within the sample gas producing ionization currents which are a function of the types of sample gas compounds and the types of carrier gases. Ionization currents are measured in each detector chamber simultaneously and are used to uniquely identify unknown compounds within the sample gas.

Apparatus and methods for identifying and quantifying compounds using a

A pulsed rare gas photoionization detector apparatus is set forth and incorporates a closed chamber for receiving a carrier gas flowing there through between inlets and outlets, and the carrier gas is exposed to a pair of electrodes forming a spark across the chamber and through the carrier gas. One component of the carrier gas is a dopant which selected from a plurality of rare gases. The sample to be analyzed is injected into the closed chamber where it commingles with the carrier gas. One reaction involves the formation of selected dopant in an excited state, which upon decay, serves as a source of ionizing radiation which reacts with sample compounds producing detectable events. These events are used to identify and quantify unknown compounds contained in the sample. The methods and apparatus are especially useful in selectively ionizing the compounds to be measured while not ionizing other constituents of the sample. This greatly enhances the signal-to-noise ratio for detecting impurity compounds. As an example, when the detection system is used to monitor air quality, the major constituents of air are not ionized.

Photoionization detector incorporating a dopant and carrier gas flow

A circular chamber is disclosed. Helium is introduced into the chamber to swirl in a circle to flow past a pair of spaced electrodes forming a spark in the helium. The chamber enables a sample detected by interaction with spark initiated ionization.

High voltage spark excitation and ionization system including disc

An isolated detector for gas is set forth and incorporates a closed source chamber in cooperation with a sample chamber through which sample gas flows. Gas within the source chamber comprises Krypton which is excited to a metastable state by a pulsed, high voltage, direct current spark. Subsequent decay of metastable argon emits ionizing radiation which passes through a membrane window into the sample chamber thereby ionizing selected constituents within the sample gas. Charged particles resulting from the ionization of selected constituents are collected with voltage biased electrodes in the sample chamber, and the magnitude of the resulting current flow is related to the concentration of the ionized molecules or compounds. The apparatus for generating ionizing radiation requires no external source of gas, is rugged, is relatively inexpensive to manufacture and operate, and exhibits an operating life much longer than source lamps used in prior art devices. The preferred embodiment of the invention is directed to the quantitative measure of impurities or pollutants in air samples.

Gas sampling apparatus including a sealed chamber cooperative with a

A pulsed discharge helium photon ionization detector comprises an elongate cylindrical body having an axial flow path. A helium source is connected to deliver helium flowing along this path. In the helium flow path, transversely positioned, facing electrodes are located to form a spark discharged across the helium flow path wherein the spark interacts with the helium to cause photon ionization. Downstream within view of the spark, a counter flow dopant gas injection tube is positioned to deliver dopant at a reduced flow rate. The dopant is swept back along the helium flow path past a set of electrode rings spaced along the flow path. The interaction of the photon ionization with the dopant creates a base current which can be detected by an electrometer across the terminals. A sample injection tube adds an eluted GC column sample or peak which changes the base current so that eluted sample is measured.

Improved system for detecting compounds in a gaseous sample using

A pulsed discharge helium ionization detector set forth and comprises an elongate cylindrical body having an axially flow path. A helium source is connected to deliver helium flowing along this path. At some location in the helium flow path, transversely positioned, facing electrodes are located. When provided with pulses discharged across the helium flow path wherein the discharge is either monopolar or bipolar pulses, the spark interacts with the helium to create photon ionization. Downstream within view of the spark, a counter flow sample injection tube is positioned to deliver samples at a reduced flow rate. The sample is swept back along the helium flow path past a pair of electrode rings spaced along the flow path. The interaction of the photon ionization with the sample creates a current which can be detected by an electrometer across the two terminals.

System for detecting compounds in a gaseous sample by measuring

A spark detection apparatus is set forth and incorporates a closed chamber for receiving a carrier gas flowing therethrough between inlets and outlets, and the carrier gas is exposed to a pair of electrodes forming a spark across the chamber and through the carrier gas. One component of the carrier gas is argon. The sample to be analyzed is injected into the carrier gas. One reaction involves the formation of metastable argon which upon decay serves as a source of ionizing radiation which reacts with sample compounds producing detectable events. These events are used to identify and quantify unknown compounds contained in the sample. The methods and apparatus are especially useful in measuring pollutant compounds in atmospheric samples since the ionizing radiation emitted from the decay of metastable argon is below the ionization potential of the major constituents of air. This greatly enhances the signal-to-noise ratio for detecting impurity compounds when the detection system is used to monitor air quality. Air is not energized.

System for identifying and quantifying selected constituents of gas

A sample is loaded along with a carrier gas into a column. The column discharge is introduced into a chamber downstream of spaced electrodes which create a pulsed DC spark. The spark produces a spectral emission and a metastable carrier gas dispersion that then reacts with molecules of the sample to bring the sample to an excited state. The excess energy surrendered by the sample is characteristic of the species and can be measured by detector electrodes in the chamber.

High voltage spark excitation and ionization detector system with

A spark detection apparatus is set forth and incorporates a closed chamber for receiving a carrier gas flowing therethrough between inlets and outlets, and the carrier gas is exposed to a pair of electrodes forming a spark across the chamber and through the carrier gas. Compounds of interest interact with the spark. The spark forms a diffusion of electrons or alternately ions during the spark distributed thereafter. The chamber includes a detector electrode spaced from the spark. High mobility particles (primarily electrons) are observed almost instantaneously with the spark while low mobility ionic particles diffuse more slowly after the termination of the spark. Using an inert carrier gas, high energy metastable molecules are dispersed and give up energy over time after the spark. The output is obtained from the electrode during, immediately after, or after a long delay relative to the spark. Another alternate output is obtained from the observed spectra during the spark and after the spark.

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Pearland, TX, United States of America

Wayne E Wentworth