Torch glassware for use with inductively coupled...

Details Torch glassware for use with inductively coupled... Torch glassware for use with inductively coupled...

2001-01-10

2003-09-09

Tremblay, Mark (Department: 2876)

Optics: measuring and testing

By dispersed light spectroscopy

With sample excitation

C219S121500

Reexamination Certificate

active

06618139

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of spectrometers used for quantitative analysis, and more particularly to torch glassware for use with inductively coupled plasma-optical emission spectrometers.
BACKGROUND OF THE INVENTION
Spectrometric analysis entails the precise measurement of the interaction between a sample (analyte) and an energy source in order to determine the chemical composition of the aforementioned analyte. Techniques of spectrometric analysis vary both in the state in which an analyte is placed prior to testing, and in the type of energy to which the analyte is exposed. However, all spectrometric techniques are based upon relating the energy-dependent behavior of an analyte to its constituent quantity and quality.
In emission spectrometry the analyte to be tested is supplied with energy from a non-radiative external energy source, usually heat from a plasma flame or electric wire. Upon exposure to an external energy source, the analyte gains energy, and typically re-emits this energy in the form of photons. The quantity and scatter distribution of these released photons is then measured by a light sensitive spectrometer, and used for quantitation, since the energy emission pattern of an analyte is specific for each constituent of that analyte. Thus, this allows a quantitative analysis of the elemental composition of that analyte to be made.
The Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) is a species of plasma spectrometer that can quantitatively analyze various sample/analyte types to determine their elemental composition. Common sample sources include water, plant and animal tissues, geological specimens and industrial samples. Plasma spectrometers typically use a radio frequency and a stream of argon in a torch to generate plasma whose temperature can reach 10,000 degrees centigrade. The hot plasma created in this way is flame-like in appearance and is as hot as the surface of the sun. A stream of argon then carries an aerosol of the sample to be analyzed into the central channel of the plasma. As the sample encounters the hotter portion of the plasma its atoms go from their ground state to an excited state, or become ionizable, a situation in which some of the sample's electrons are stripped from outer valence shells. Eventually the electrons return to their ground states, and during this change in energy status they release a characteristic wavelength of light for each element present in the sample. It is this characteristic, or signature spectra pattern of light, which is used to identify given elements.
Referring now to
FIG. 1
, an outer tube
10
of a traditional ICP-OES torch is illustrated. Tube
10
is typically open-ended and may be formed of quartz. Proximate to its open end, tube
10
includes a substantially cylindrical outer surface
12
and a substantially cylindrical inner surface
14
. The plasma created by the stream of argon in the torch is, as described above, extremely hot. It is therefore necessary to inhibit the hot plasma from contacting tube
10
. If the plasma does contact tube
10
, the tube may be destroyed, or the life of tube
10
may be greatly reduced. To this end, a stream of relatively cool inert gas (illustrated by arrows
16
) is provided. The stream of cool inert gas is flowed generally radially within the inner surface
14
, with the hot plasma being contained within the stream of cool inert gas. Thus, the hot plasma is inhibited from contacting tube
10
by this “cushion” of cool inert gas.
In a conventional radially-viewed ICP-OES, the emitted light is viewed from the side of a vertically oriented plasma and focused on the entrance slit of the spectrometer. Referring now to
FIG. 2
, such had traditionally required that the emitted light be viewed through the sidewall of the outer tube
20
of the torch. However, it was discovered that more accurate results could be obtained by providing a slot
22
passing through the sidewall of the tube
20
. The slot
22
typically extends from the open end of the tube
20
longitudinally up the side wall thereof far enough that the entrance slit of the spectrometer is not obscured by the sidewall.
While this design provides more accurate results, it introduces new problems of its own. Tube
20
is still defined by a substantially cylindrical outer surface
24
and a substantially cylindrical inner surface
26
, and a stream of relatively cool inert gas (illustrated by arrows
28
) flowing generally radially within the inner surface
26
is still provided in order to inhibit the hot plasma from contacting tube
20
. However, it has been discovered that the lifespan of the tube
20
is greatly reduced as compared to tube
10
which included no slot. In particular, it has been discovered that when a tube
20
which includes a slot
22
is used, devitrification occurs adjacent the slot
22
, particularly along the side of the slot
22
downstream with respect to the radially flowing cool inert gas. It has been discovered that this problem is caused by the interruption in the flow of cool inert gas caused by the slot. More specifically, as the gas flows past slot
22
, at least a portion of the gas escapes through slot
22
(illustrated by arrows
30
). This escaping gas causes the “cushion” of cool inert gas proximate the slot
22
to degrade, and a portion of the hot plasma may be allowed to contact the inner surface
26
of tube
20
(as illustrated by arrow
32
). In more extreme cases, the hot plasma may be able to contact the edge
34
of the slot
22
downstream with respect to the radially flowing cool inert gas (indicated by arrow
38
), or even to escape tube
20
through slot
22
altogether and contact the outer surface
24
of tube
20
. This contact between the hot plasma and the tube
20
may cause the lifespan of the tube to be seriously shortened.
What is desired, therefore, is torch glassware for use with inductively coupled plasma-optical emission spectrometers which includes an outer tube and a stream of cool inert gas flowing radially within the inner surface thereof such that the cool inert gas creates a cushion between the tube and hot plasma contained within the stream of cool inert gas, which includes a slot passing through the sidewall of the tube to provide optimum results, which is designed such that the cushion of cool inert gas is not degraded by the slot, and which has a lifespan similar to the lifespan of torch glassware without a slot.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide torch glassware for use with inductively coupled plasma-optical emission spectrometers which includes an outer tube and a stream of cool inert gas flowing radially within the inner surface thereof such that the cool inert gas creates a cushion between the tube and hot plasma contained within the stream of cool inert gas.
Another object of the present invention is to provide torch glassware having the above characteristics and which includes a slot passing through the sidewall of the tube to provide optimum results.
A further object of the present invention is to provide torch glassware having the above characteristics and which is designed such that the cushion of cool inert gas is not degraded by the slot.
Still another object of the present invention is to provide torch glassware having the above characteristics and which has a lifespan similar to the lifespan of torch glassware without a slot.
These and other objects of the present invention are achieved by provision of torch glassware for use with inductively coupled plasma-optical emission spectrometers having an outer tube and a stream of cool inert gas flowing radially within the inner surface thereof such that the cool inert gas creates a cushion between the tube and hot plasma contained within the stream of cool inert gas. The outer tube includes a sidewall having an open end and having a slot passing therethrough. The slot extends longitudinally along the sidewall from the open end thereof and is defined at least in

Affiliated with

Also associated with

Rating

Torch glassware for use with inductively coupled... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Torch glassware for use with inductively coupled..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Torch glassware for use with inductively coupled... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3099900