Abstract: An RF power generator (10) for an induction coil (26) for exciting an inductively coupled plasma in a torch (27) for spectrometry. The generator (10) comprises a switching circuit (12) for alternately switching ON and OFF solid state switching devices (20) via gate drive voltages (22) for supplying RF power into a resonant load circuit (16) comprising the induction coil (26) and parallel connected capacitance (25). The gate drive circuits (24) for each solid state switching device (20) each include a portion (30) that is mutually inductively coupled with leads of the induction coil (26) to provide the gate drive voltages (22). The circuit allows for reduced componentry and therefore a relatively inexpensive RF power generator for exciting and sustaining an inductively coupled plasma for spectrometry.

Abstract: A calibrated spectroscopy instrument and a method for calibrating a spectroscopy instrument are disclosed. The spectroscopy instrument includes a monochromator having a drive mechanism comprising a pair of spur gears for rotating a diffraction grating of the monochromator for selecting a desired wavelength. The drive mechanism is calibrated to account for eccentricities in the spur gears to provide an accurate conversion between selected angular settings for the drive mechanism and the wavelength of the diffracted light from the monochromator. The drive mechanism comprises a pinion spur gear and a main spur gear which each have an AGMA (American Gear Manufacturers' Association) rating of at least 10, which allows errors due to random tooth to tooth variations to be neglected. A calibration algorithm is derived which is based on the error due to eccentricities in the spur gears following a precise geometric cyclic pattern.

Abstract: A spectroscopy system for spectro-chemical analysis of a sample includes a plasma torch (50) for generating a microwave induced plasma (90) as a spectroscopic source. The plasma forming gas is nitrogen which can contain an oxygen impurity. Thus the system includes a nitrogen generator (70) which is preferably supplied with compressed atmospheric air from a compressor (75) for oxygen to be removed from the air by adsorption. The invention allows the use of an on-site nitrogen gas generator and thus gives cost savings because the need to obtain supplies of bottled high purity gas is eliminated.

Abstract: A flow through cell (100) for use in a spectrophotometer for analysis of dissolved chemical substances in a flowing liquid stream is made up of at least an intermediate body member (114) located between two other body members (112, 116). The body members are of regular shape, for example rectangular parallelepiped and are clamped together, for example by machine screws (134, 136). Thus the cell is relatively easily manufacturable. The clamped together body members define a flow through passage which includes a hole (118) through the intermediate body member (114) and a liquid inlet region at one end of the hole and a liquid outlet region at the other end of the hole, which regions may be provided by galleries (150, 152) in scaling gaskets (130, 132) between the body members. The two other body members each include an optically transparent window (142, 146) at an end of the hole (118) thereby providing an optical pathway (A, A?) through part of the flow through passage.

Abstract: An electrode for use in a reduced pressure region in a mass spectrometer whereby the electrode is subject to deposition of dielectric (non-conducting) substances thereon, which can cause unstable performance of the mass spectrometer. The surface portion of the electrode that is for providing an equipotential boundary of an electric field for influencing charged particles is made rough, in contrast to the prior art of providing a polished surface. The rough surface provides projections and cavities, which may have a regular or irregular occurrence, which it has been found significantly reduces the deposition of dielectric substances from the charged particles thereon. A preferred structure is for a rod electrode (42) to have a screw thread (44) formed thereon whereby the thread crests (43) along the rod electrode provide projections (43) and the thread roots (45) provide cavities.

Abstract: A spectrophotometer having an optical system for directing a beam of substantially monochromatic excitation light to a liquid sample contained in a well (3) of a well plate for interaction with the sample for absorption or emission measurements to analyse the sample. The optical system includes two apertures (46, 28) for establishing a Kohler illumination region outside the well, that is an excitation beam region between conjugate images (18, 21) of the two apertures. This excitation beam region is then demagnified and imaged (10, 9) into the well (3). The invention provides for the shape of the Kohler illumination region to correspond to the shape of the well space so that all of the liquid sample is uniformly illuminated without the well obstructing any portion of the illuminating excitation beam of light.

Abstract: A mass spectrometer in which a substance is introduced into a plasma (28) which contains analyte ions as the plasma (28) is passing through an aperture (42), for example in a skimmer cone (40) between two vacuum regions (38) and (44) so that the substance interacts with the plasma (28) thereby reducing the concentration of interfering polyatomic or multicharged ions in the plasma by reactive or collisional interactions. The substance may be supplied via passage (60) having an outlet (63) in skimmer cone (40). The invention gives improved attenuation of interfering ions because the substance is supplied directly into the plasma (28) as it is substantially radially confined by aperture (42) and before an ion beam (58) is extracted. Alternatively or additionally a substance may be supplied directly into the plasma within aperture (36) in sampling cone (34).

Abstract: A RF power generator for exciting inductively coupled plasma for spectrometry includes an induction coil for exciting the plasma as part of its load circuit. The load circuit also comprises a capacitor connected in parallel with the induction coil. The RF power generator is a free running oscillator having a switching circuit of two MOSFETs alternately switchable on and off via a feedback control circuit from the load circuit. RF power from the switching circuit is coupled to the load circuit via an inductor. The inductor and load circuit is resonant at a first frequency, which is lower than the operating frequency of the power generator.

Abstract: Apparatus (10) for measuring absolute specular reflectance of a surface of a sample (22) includes a sample holder (12), a light source (18) for transmitting an incident light beam (16) onto a surface of the sample (22) and a detector (26 ) for detecting a specularly reflected component of the incident light. The light source (18), sample holder (12) and detector (26) are mounted and operatively associate (14, 24, 28) to be relatively moveable to vary the angle of incidence of light (16) onto sample (22) and to correspondingly automatically vary the relative position of the detector (26) such that the angle of reflection equals the angle of incidence. In the absence of the sample (22) or upon removal of the sample holder (12), light (16) impinges directly onto detector (26) to directly allow measurement of the absolute intensity of the light beam (16) as a reference measurement. This avoids the need to use intervening optical components such as mirrors which may degrade over time.

Abstract: A plasma source mass spectrometer (20) having an ion beam extraction electrode (45) associated with a skimmer cone (40) to restrict the pumping of gas from a region (60) immediately behind the skimmer cone orifice (42) to provide a higher pressure (e.g. 1–10?2 Torr) in the region (60) compared to the pressure downstream of the electrode (45) (e.g. 10?3–10?4 Torr). This provides a collisional gas volume (60) for plasma (28) for attenuating polyatomic and multicharged interfering ions prior to extraction of an ion beam (49). In one embodiment a substance (e.g. hydrogen) can be supplied into the region (60) to assist attenuation of polyatomic and multicharged interfering ions by reactive or collisional interactions.

Abstract: A mass spectrometer and method of mass spectrometry in which polyatomic and doubly charged ion interferences are attenuated by establishing an electron population through which a beam of particles containing elemental sample ions and the interfering ions is passed such that the interfering ions preferentially undergo ion-electron recombination and thus dissociation to remove a significant number of the interfering ions. Means (30 or 32) for providing a population of electrons (34 or 36) in an ICP-MS (22) may comprise a magnetic field means such as an electric coil, or an electron generating device. The population of electrons has an electron number density (>1011 cm?3 to 1014 cm?3), a free electron energy (>0.01 eV to <5 eV) in a region at a low pressure (<10 Torr), such that for a predetermined path length (1–4 cm) of the ions through the electron population, the interfering ions will preferentially be attenuated by the dissociative recombination process.

Abstract: A torch for producing an inductively coupled or microwave induced plasma for use in spectrochemical analysis. The torch includes a central tube (25) for conveying a flow of a gas carrying sample aerosol to a plasma (17) produced in the torch. The tube (25) has an inlet (31) and an outlet (39) of smaller size than the inlet and is shaped to deliver a substantially laminar flow of the gas at the outlet (39). The tube (25) is tapered along at least a substantial portion of its length such that its cross-section area gradually and smoothly reduces towards its outlet (39) along at least a substantial portion of its length. It has been found that such a tapered tube is resistant to obstruction by salts deposited from samples containing high levels of dissolved solids.

Abstract: A mass spectrometer in which a substance is introduced into a plasma (28) which contains analyte ions as the plasma (28) is passing through an aperture (42), for example in a skimmer cone (40) between two vacuum regions (38) and (44) so that the substance interacts with the plasma (28) thereby reducing the concentration of interfering polyatomic or multicharged ions in the plasma by reactive or collisional interactions. The substance may be supplied via passage (60) having an outlet (63) in skimmer cone (40). The invention gives improved attenuation of interfering ions because the substance is supplied directly into the plasma (28) as it is substantially radially confined by aperture (42) and before an ion beam (58) is extracted. Alternatively or additionally a substance may be supplied directly into the plasma within aperture (36) in sampling cone (34).

Abstract: A source for reducing drift of a hot spot by producing infrared (IR) light with an insulating housing; an electrical power supply; first and second resistance elements having first and second resistivities; a third resistance element having a third resistivity; the third resistance element disposed between the first and second resistance elements, with the resistivity of the third resistance element having a value greater than the resistivity of both the first and second resistance elements. Alternatively, the first and second resistance elements can have cross-sectional areas that are greater than that of the third resistance. A method of reducing drift of a hot spot in a radiating element of a source of IR illumination by applying constant polarity substantially constant direct current from the power supply and reversing polarity in less than 24 hours, by a square wave AC source, or a Class E amplifier at constant power.

Abstract: A method and apparatus for the spectrochemical analysis of a sample in which a solid state array detector (82) is used to detect radiation (62) of spectrochemical interest. The invention involves the use of a shutter (72) adjacent the entrance aperture (70) of a polychromator (74-80) to expose the detector (82) to the radiation (62) for varying lengths of time whereby for short duration exposure times charge accumulation in elements (i.e. pixels) of the detector (82) due to high intensity components of the radiation is limited and for longer exposure times charge accumulation in elements (pixels) of the detector (82) due to feeble intesity components of radiation (62) is increased. This ensures that each reading of the detector (82) includes at least one exposure in which the amount of charge accumulated at each wavelength of interest is neither too little or too great.

Abstract: A spectrometry instrument with exchangeable accessories (34, 48, 50, 52) providing, for example, different sample presentation facilities. The accessories include a manually operable cam-lock facility (54, 68) for quick and easy attachment of an accessory to the instrument. The instrument also includes an electrical circuit (86-90), which is completed by a circuit portion (100) in an accessory when the accessory is attached to the instrument, for generating a unique identifying voltage (94) to thereby identify that accessory. This allows for automatic loading in a controlling computer of programs for setting up and running the instrument for measurement regimes using that accessory.

Abstract: A mass spectrometer having an ion optics system in a first vacuum region, which diverts ions travelling in a first direction from a source, characterized by an initial pressure, through an angle such that neutral particles and photons from the source continue in the first direction and are removed. The diverted ion beam is then directed into a quadrupole mass analyzer arrangement in a second vacuum region, which comprises a set of fringe electrodes followed by a linear mass analyzer and then an ion detector. The first vacuum region is characterized by a pressure intermediate the initial pressure and a second vacuum region pressure. The set of quadrupole fringe electrodes are configured to divert the ion beam prior to passage of the ion beam into the linear quadrupole mass analyzer and to shield the linear quadrupole mass analyzer entrance from a substantial portion of the trajectory of the ion beam in the first vacuum region.

Abstract: Spectroscopy apparatus for spectrochemical analysis of a sample having an excitation source (60) for providing spectral light (62) of the sample for analysis. The spectral light (62) is analysed via an optical system (64-66-68) that includes a polychromator (70, 74-80) and solid state multielement array detector (82). The elements (i.e. pixels) of the detector (82) are serially reel by means (84) to provide light intensity measurements as a function of wavelength. A problem is that the elements (pixels) of the detector (82) continue to accumulate change during the serial read-out. This is avoided by providing an optical shutter (72) for blocking the spectral light (62) whilst elements (pixels) of the detector (82) are being serially read. Shutter (72) has a piezoelectric actuator which is preferably a bimorph mounted as a cantilever. It is preferably located adjacent to the entrance aperture (70) of the polychromator.

Abstract: A plasma source for a spectrometer for spectrochemical analysis of a sample is characterized by use of the magnetic field component of applied microwave energy for exciting a plasma. The source includes a waveguide cavity (10) fed with TE10 mode microwave power. A plasma torch (16) passes through the cavity (10) and is axially aligned with a magnetic field maximum (18) of the applied microwave electromagnetic field. Magnetic field concentration structures such as triangular section metal bars (20) may be provided. In an alternative embodiment a resonant iris may be provided within a waveguide and the plasma torch positioned relative thereto such that the microwave electromagnetic field at the resonant iris excites the plasma.

Abstract: An ultraviolet/visible/infrared spectrophotometer, with a pulsed light source (10), has a monochromator with variable slit width to provide variable spectral resolution. The dynamic range at the detectors (24, 28) is reduced by varying the pulse energy emitted by the light source (10) in accordance with the wavelength and slit width settings (34, 36), and/or by varying the slit height in accordance with the slit width. The ligth source (10) may be a xenon flash lamp.