OPTICAL EMISSION SPECTROSCOPE WITH A PIVOTABLY MOUNTED INDUCTIVELY COUPLED PLASMA SOURCE

Abstract

An optical emission spectrometry instrument may comprise an inductively coupled plasma generator (ICP) with an electromagnetic coil having input and ground connectors. The electromagnetic coil may be mounted to a mounting disk, and the input connector may be coupled to a power output of a radio frequency power source, and the ground connector may be connected to the mounting disk. A spectro-chemical source may be used for sample excitation. The spectro-chemical source and the ICP may have a longitudinal axis. An optical system may be included for viewing the spectro-chemical source with a fixed view axis. The electromagnetic coil may be mounted pivotably around one of its connectors so that the orientation of the ICP can be altered from a first orientation of its longitudinal axis to a second orientation of its longitudinal axis, and vice versa.

Claims

1.-9. (canceled)

10. An optical emission spectrometry instrument comprising an inductively coupled plasma generator (ICP) with an electromagnetic coil having a first connector and a second connector, wherein the electromagnetic coil is mounted to a mounting disk, and the first connector is coupled to a power output of a radio frequency power source, and the second connector is connected to the mounting disk, and further comprising: a spectro-chemical source for sample excitation, wherein the spectro-chemical source and the inductively coupled plasma generator have a longitudinal axis; and an optical system configured for viewing said spectro-chemical source with a fixed view axis, wherein the electromagnetic coil is mounted pivotably around one of the first or second connectors so that an orientation of the ICP is enabled to be altered from a first orientation of its longitudinal axis, which is parallel to the fixed view axis of the optical system, to a second orientation of its longitudinal axis, which is perpendicular to the fixed view axis of the optical system, and vice versa.

11. The optical emission spectrometer according to claim 10, wherein the electromagnetic coil is mounted pivotably around the first connector, and wherein the first connector is an input connector.

12. The optical emission spectrometer according to claim 11, wherein the second connector of the electromagnetic coil is a ground connector, which is electrically coupled to the mounting disk, and wherein the mounting disk has a sliding contact connected to the ground potential of the instrument.

13. The optical emission spectrometer according to claim 11, wherein the inductively coupled plasma generator is arranged on a rotatable disc, wherein the rotatable disc is configured to rotate around its center, wherein its center coincides with the coil input connector rotation axis.

14. The optical emission spectrometer according to claim 13, wherein the coupling of the input connector to the power output is a rotatable coupling allowing for a relative rotation of at least 90°.

15. The optical emission spectrometer according to claim 10, wherein the ICP is operated in argon at atmospheric pressure.

16. The optical emission spectrometer according to claim 10, wherein in the second orientation, in which the longitudinal axis is perpendicular to the fixed view axis of the optical system, a distance between the view axis and the coil equals the radius of the coil.

17. The optical emission spectrometer according to claim 10, wherein in the first orientation, the longitudinal axis coincides with the fixed view axis of the optical system.

18. A method of optical emission spectrometry, comprising: exciting a sample in a spectro-chemical plasma source of an inductively coupled plasma generator with an electromagnetic coil and a longitudinal axis to emit characteristic radiation, and observing the emitted characteristic radiation by an optical system having a fixed viewing axis, wherein an orientation of the inductively coupled plasma generator is enabled to be altered from a first orientation of its longitudinal axis, which is parallel to the fixed viewing axis of the optical system, to a second orientation of its longitudinal axis, which is perpendicular to the fixed view axis of the optical system, and vice versa, by swiveling the inductively coupled plasma generator around a pivot axis defined by the electromagnetic coil.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0030] The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0031] In the drawings:

[0032] FIG. 1 shows a schematic diagram of a side-on arrangement of an optical emission spectrometer in top and side view and

[0033] FIG. 2 shows a schematic diagram of an end-on arrangement of the atomic emission spectrometer in top and side view.

DETAILED DESCRIPTION OF THE INVENTION

[0034] In FIGS. 1 and 2, an optical emission spectrometer 1 with a user-selectable source view mode is schematically illustrated in side-on and end-on setting. The relative sizes of the components are not realistic. In reality, the spectrometer part is much larger than the source components. The optical emission spectrometer 1 shows three general components, an inductively coupled plasma generator 2 which effects ultraviolet and visible light radiation, a spectrometer 3 with a detector means 4 for detecting the radiation relative to spectral wavelength and an intermediately located interface 5 from which a constant flow of argon emerges, deflecting the plasma and providing cooling. In addition, the flow of Argon purges the optical path and removes Nitrogen and Oxygen, both absorbing UV radiation if present, thus allowing the full spectrum of the emitted light from the plasma 6 to enter the spectrometer 3 along a spectrometer optics view axis 7. The inductively plasma generator (ICP) 2 utilizes an electromagnetic coil 8 to excite a gas into a plasma in a region within or slightly beyond the end of a quartz tube. The generator 2 includes an injector for injecting a nebulized sample material into the plasma. The material becomes dissociated to atoms which are, by means of the plasma, transferred into an excited state to emit radiation including spectral lines characteristic of the atomic elements in the sample. The detector means 4 includes a detector system which may be any conventional or other desired type used for the purpose of the spectrometer, e.g. solid state CCD detector which effects signals proportional to the intensity of the corresponding lines. A computer subsequently processes the signal information, corrects for background and, with calibration, displays the results on a monitor.

[0035] The electromagnetic coil 8 of the ICP 2 includes a radio frequency (RF) power input 9 coupled to the power output 10 of a RF power source 11, and an output 12 being grounded.

[0036] The coil 8 and thus the inductively coupled plasma generator 2 is arranged off-centered on a rotatable mounting disk 13. The RF power input 9 of the coil 8 is arranged in the center of the mounting disk 13 and is coupled, via a co-axial twistable RF coupling 14, to the power source 11.

[0037] In order to change the orientation of the ICP source 2, the disk 13 can be rotated by 90 degrees around its center. Hence, the coil 8 is tilted likewise by 90 degrees around its power input 9. The RF coupling 14 allows the input 9 of the coil to rotate against the power output 10 of the RF generator 11. The ground connection 12 of the coil 8 is connected to the mounting disk 13 at a point distant from the center. The mounting disk 13 itself is grounded to the ground potential of the instrument by means of a sliding contact with a large contact surface.

[0038] The rotation of the disk 13 can be carried out manually by operating a toothed rotary knob 15 which interlocks with teeth 16 arranged circumferentially of the disk 13. In another alternative, a stepper motor for rotating the disk via a gear drive can be provided. Since the necessary angle of rotation of the ICP source is limited to 90° or a little more, it is also possible to effect the rotation from a horizontal position to an upright position of the axis of the ICP coil using a push rod or lever which is eccentrically attached to the disk.

[0039] By rotation of the disk 13, the spatial orientation of the source 2 relative to the view axis 7 of the spectrometer 3 can be changed from axially to radially and vice versa.

[0040] When changing the spatial orientation it might be necessary to adjust or exchange the interface 5 and quartz tube, which can be done manually.

[0041] An easily industrially applicable user selectable spatial orientation of the spectro-chemical source relative to the spectrometer optic view axis (axial/radial), provided by the invention as described, allows for optimum analytical figures of merit for almost all emission spectroscopic analysis applications which utilize a spectro-chemical source for sample excitation with a single instrument and thus improves the analytical capabilities of emission spectroscopy instruments beyond the current state of the art without the need of acquiring two dedicated instruments, resulting in a substantial cost saving for the end user

[0042] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.