Abstract: A graphite tube assembly for use in the atomic absorption spectroscopic measurement of samples, particularly liquid samples, during the passage of a beam of radiation through a graphite tube is disclosed. The graphite tube assembly includes a graphite tube and a sample holding platform which are cooperatively adapted to allow the platform to be removed and reinserted, or exchanged with another platform, while maintaining a preselected orientation of the platform with respect to an inlet port extending through the wall of the graphite tube.

Abstract: Stray light produced in a monochromator by the diffuse reflection of the incoming light beam specularly reflected from the surface of the diffraction grating is practically eliminated by interposing a black glass "absorbent-reflector" in the path of the specularly reflected beam. The small percentage of radiation that is not absorbed by the absorbing glass is reflected to an opposite blackened wall which diffuse reflects an extremely small percentage of the beam back to the absorbent-reflector where a very negligible part is returned to the grating surface and eventually to the monochromator exit slit.

Abstract: Disclosed are methods and apparatus for concentrating a looked-for element from a solution for flameless atomic absorption spectroscopy. The tip of an electrode is dipped into a sample vessel containing the solution and an electric current is passed through the electrode and solution to electrodeposit the components of the solution on the electrode. The electrode with the electrodeposition is removed from the sample vessel and inserted into the graphite tube. The tube is then heated and the sample components electrodeposited on the electrode are atomized for analysis by the measuring beam of the atomic absorption spectrometer.

Abstract: A sample feeding device includes a turntable driven by a servomotor and mounted on a carrier driven by a separate servomotor. The turntable servomotor and the carrier servomotor, as well as a movable intake tube, are controlled by a control device.

Abstract: Apparatus for injecting a selected one of a plurality of samples into a graphite tube atomizer of a flameless atomic absorption spectrometer. A sample dilutant or blank solution, a standard solution for calibrating the spectrometer, and each of a plurality of unknown sample solutions are continuously fed into separate overflow vessels mounted in a turntable driven by a servomotor and monitored by a suitable analog-to-digital encoder. Each of the vessels overflow into a common drain channel and the vessels are positioned by a control system so that a small sample from selected vessels that may contain an unknown sample, dilutant, or calibrating standard, is drawn by a pump into an intake tube. A servomechanism then repositions the tube into the graphite tube atomizer and the pump reverses to inject the solution into the atomizer.

Abstract: A method and circuitry for maintaining the precise temperature of atomic absorption spectroscopy graphite specimen tubes over wide temperature ranges independently of the tube emission factor. The infrared radiation of a heated tube is measured by a detector, the signal from which is amplified in a variable gain amplifier, then compared with an externally generated "temperature select" signal, and the error signal therefrom controls a circuit that in turn controls the heating power to the graphite tube. A second measurement of the heated tube is made by a detector sensitive only to short wavelength radiation, e.g., visible, which is substantially unaffected by emission factors, and the signal therefrom adjusts the gain of the variable gain amplifier to thereby correct the infrared generated signal for variation in tube emission factors.

Abstract: Disclosed is a system for the measurement of the atomic absorption of gaseous samples including a reaction vessel and conduits for supplying liquid sample, carrier gas and a reagent to the vessel. A discharge conduit is coupled between the reaction vessel and the measuring cell of an atomic absorption spectrometer. The reaction vessel has a drain conduit and a relief valve in the drain conduit. Control means are provided for controlling the flow of liquid sample, carrier gas, reagent and gaseous sample through the corresponding conduits in accordance with the predetermined program for making consecutive measurements. A pressure sensor is provided for sensing pressure in the reaction vessel above a specified pressure indicative of incomplete draining of the vessel and below a specified pressure indicative of substantially complete draining of the vessel.

Abstract: Method and apparatus for generating a gaseous test sample from a liquid sample and for transferring this test sample into a measuring cuvette of an atomic absorption spectrometer, in which an inert gas flow is directed through a sample vessel and into a measuring cuvette and, after the air has been displaced from the sample vessel, a reagent is added for generating a gaseous test sample, the test sample being carried into the measuring cuvette by the inert gas flow, wherein prior to the adding of the reagent, the flow rate of the inert gas flow is changed-over from a higher value to a lower value.

Abstract: Apparatus for determining the concentration of the various components of a sample, which includes a spectrophotometer for receiving a sample to be analyzed and performing extinctions of the sample at a plurality of preselected wavelengths to form a sample spectrum; memory devices for storing a standard spectra of each of the individual components; circuitry for weighting the sample spectrum at different wavelengths in conformity with each of the standard spectra and providing estimated values of the concentrations of the components from the sample spectra thus weighted; circuitry for reconstructing the sample spectrum as a linear combination of the estimated values of the concentrations and the standard spectra; a subtractor for forming a difference spectrum from the sample spectrum and the reconstructed sample spectrum; circuitry for weighting the difference spectrum at different wavelengths in conformity with each of the standard spectra and providing corrective values of the concentrations of the component

Abstract: The fluid flow switching apparatus includes a housing defining a chamber, a bore in communication with the chamber, fluid inlet and outlet ports respectively in communication with the chamber and bore, and a valve body movable within the chamber and carrying a sealing means for sealing about the bore. The valve body carries a pin which projects laterally into a cam track formed in the housing and which serves to releasably lock the valve body in a position enabling flow between the inlet and outlet ports through the chamber and bore and in a valve closed position preventing flow between the inlet and outlet ports. The valve body is movable manually between the valve open and closed positions by consecutive depressions of a push key connected to the valve body.

Abstract: Closure for a sample vial utilized to introduce sample into a gas chromatograph in accordance with the head space method. The closure includes a flexible disc for closing the opening through the neck of the vial and overlying the margin of the neck about the vial opening. A cap having a central aperture defining an annular shoulder about the aperture overlies the disc. The cap has an annular depending skirt encompassing the disc for clamping about the neck of the vial to retain the disc and the cap on the vial. A portion of the closure is deformable for venting the vial to atmosphere in response to a pressure within the vial when the closure is applied thereto in excess of a predetermined pressure.

Abstract: The invention relates to a spectrometer including a rotatable dispersive element, a stepping motor for varying the angular position of said dispersive element, a program transmitter for controlling said stepping motor, a timing generator and a recording instrument.

Abstract: Gaseous measuring samples like element hydrides are generated from liquid samples by reacting the same with reducing reagents in a reactor. In the reactor a countercurrent of inert gas strips the volatile reduction products from the reactor to convey the products to the measuring cell of an analytical measuring instrument. Various embodiments of the apparatus automatically controlling the supply of liquid sample and reagents to the reactor are disclosed such as mechanically or pneumatically controlled pumps. In each measuring cycle the reactor and respective components are washed to prevent contamination of succeeding samples; also, analytical determination of blank values as well as reference values can be included in each measuring cycle.

Abstract: Atomic absorption spectrometer sample supply apparatus for producing a gaseous sample for analysis and for transferring the sample to the atomic measuring cuvette. The sample supply is in a sealed vessel and, by directing the flow of a pressurized inert gas, the sealed sample vessel is first purged of contaminating air, a volatilizing reagent is forced by inert gas pressure into the sample, and a small specimen of the gaseous sample is transferred by gas pressure into the cuvette inlet tube.

Abstract: An automatic sampling apparatus for withdrawing samples from a continuously flowing liquid for analysis by a flameless atomic absorption spectrometer includes a sample vessel which, at predetermined times, receives pumped samples of the liquid to be tested, a neutral dilutant liquid, or a calibrated liquid for recalibrating the spectrometer system. A probe having a pipette-like tip is mechanically actuated to dip into the sample vessel and an intake and dispensing pump connected to the probe draws a small sample into the probe tip whereupon the probe mechanism lifts and rotates the probe and inserts the tip into the graphite atomizer tube of the atomic absorption spectrometer. The probe mechanism then returns the probe where it is first flushed with a flushing liquid pumped through the probe and is then returned to the sample vessel to draw the next test sample.

Abstract: Inaccuracies resulting from measuring the internal temperature of absorption spectrophotometer graphite tube furnaces by pyrometric measurements of a spot on the external surface of the graphite tube are overcome by a novel arrangement in which the pyrometer detector measures the interior through the tube end and at an angle that permits a view of the entire interior length without interfering with the spectrophotometer sample beam.

Abstract: Disclosed is a sample feeding apparatus having a housing defining first and second chambers sealed one from the other and a needle movable longitudinally with respect to the housing. The first and second chambers continuously receive carrier and purging gases respectively through suitable conduits. The needle has an opening normally in communication with the second chamber for continuously purging the needle. Upon application of a sample vessel to a member telescopically received about the housing, the needle is displaced through a seal into the first chamber. Carrier gas is thus provided through the needle into the head space of a sample vessel and the sample will flow to the injection block of a gas chromatograph in response to pressure compensation between the injection block and head space. Upon withdrawal of the sample vessel from below the sampling apparatus, the needle is spring returned to its initial position preventing carrier gas from flowing from the first chamber through the needle.

Abstract: A precision digital flow rate control system particularly suitable for controlling the flow of an inert gas into the atomizing furnace of an atomic absorption spectrometer. The selection of the desired flow rate is made by switching the flow through one or more of the plurality of tubes having restrictors that limit the flow according to digital steps. The flow is switched by directional control solenoid valves that direct the flow either through a flow restrictor to the atomizing furnace or through an identical flow restriction to a vent. Therefore, there will always be a constant flow through each valve and, since the inlet pressure regulator will always see a constant load, it can maintain a very constant pressure to the valves.

Abstract: The graphite sample tube used in flameless atomic spectroscopy is mounted in coaxial bores of two separated heating electrodes, each supported by a cooling jacket for carrying off the excess heat produced by the sample tube. Instead of being sealed with sealing rings, the cooling jackets contain seamless tubing that is tightly pressed in the grooves and carries a flow of suitable coolant. The tubing eliminates fluid eddies and thermal stresses which inevitably leads to coolant leaks. An additional feature is that one of the two cooling jacket housings is pivotally movable by a pneumatic actuator for easy removal of the graphite sample tubes and the inspection of the bores of the electrodes.

Abstract: A graphite tube atomizer for flameless atomic absorption spectroscopy includes a graphite tube disposed to permit passage of a measuring beam therethrough. The graphite tube is engaged at opposite ends by annular contact pieces which are coupled to a source of electrical current. The contact pieces are supported in housing portions which serve to surround the graphite tube and provide a chamber into which cooling gasses can be admitted. The cooling gasses also serve to reduce deterioration of the graphite tube. The housing portions are selectively movable either toward or away from each under the power of a drive mechanism. The housings may be urged by the drive mechanism toward each other so the contacts mounted thereon are in selectable pressure engaging contact opposite ends of the graphite tube.