Optics: measuring and testing – Sample – specimen – or standard holder or support
Reexamination Certificate
2002-03-13
2004-04-06
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Sample, specimen, or standard holder or support
C356S367000, C250S461200
Reexamination Certificate
active
06717665
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polarimeters, and more particularly, to a sample cell and sample cell holder in which a thermo electric cooler is used to control the temperature of the sample cell and the liquid contained therein.
BACKGROUND OF THE INVENTION
A polarimeter is an instrument for measuring the optical activity exhibited by an optically active substance including inorganic and organic compounds. In particular, the plane of polarization of a linearly polarized light beam is rotated when passing through the optically active substance, and the rotation is determined by the specific substance, the concentration of that substance and the optical pathlength of the light through the substance contained in the sample cell, whereby the concentration of the specific substance can be calculated by the measured rotation. The optical rotation is also affected by the temperature of the substance contained in the sample cell, and thus it is desirable, and in many cases required by governing regulations, that the temperature of the sample substance be controlled to be at a set point for precise measurement.
As shown in FIG.
1
(A) and (B), a sample cell
11
is usually a cylindrical tube so as to minimize the amount of the sample substance that is in the cell but not in the light path, referred to as “dead volume”. A pair of flanges
15
are provided at opposite ends of the sample cell
11
, each with a beam aperture
18
therein for allowing the polarized light beam (shown as arrow
17
) to pass therethrough. The flanges are usually standard in size for properly positioning the sample cell
11
in the light path when the pair of flanges sit on the cell holder constituted by a pair of parallel rails
16
. The flanges may be removable from the sample cell
11
to facilitate cleaning of the cell. The temperature control of the sample substance is realized by circulating water in a water jacket
14
around the external surface of the sample cell
11
containing the sample substance
12
. The water jacket
14
is formed by an outer tube
13
communicated with a water tube
19
connected to a water source at a predetermined temperature. However, such a water temperature control system is complicated in structure, comprising a water jacket and cooling tubes. Furthermore, it is inconvenient to connect and disconnect the tubing when cleaning the cell and changing the sample. It also takes long time to change the temperature set point.
Recently, thermoelectric temperature control techniques such as thermo electric coolers (TEC) have been introduced for temperature control in a polarimeter. The temperature of one side of a TEC device, which is usually a flat plate in shape, is controllable by an electric current. Heat can be made to flow through the device in either direction as required. As shown in
FIG. 2
, a TEC element
63
with a heat sink
64
is provided to be thermally conductive with a rectangular cell holder
62
accommodating a rectangular sample cell
61
. A polarized light beam (shown as arrow
67
) passes through the sample cell
11
via the apertures
68
provided on the cell holder
12
. The solid TEC element
63
eliminates the complication and inconvenience of the water tubing required in the conventional cylindrical cell samples. Furthermore, the temperature of the cell holder
62
and therefore the sample cell
61
can be easily and quickly controlled at a set point. However, the rectangular sample cell
61
assumes a high dead volume and requires a larger sample volume to fill. This is costly when the measured substance is precious. The other problem with such a rectangular structural design is that the cell holder
62
can not work with conventional standard cylindrical sample cells which are commonly used in the industry. In addition this design was not able to control temperature within the limits required by relevant governing regulations.
SUMMARY OF THE INVENTION
An object of the invention is to provide a sample cell with a substantially cylindrical internal volume with its temperature controllable by a TEC element.
A further object of the invention is to provide a cell holder which is capable of holding both the inventive sample cell in a temperature controlled mode and conventional standard cells which are not temperature controlled by the cell holder. These conventional cells my be either of the water jacketed temperature controlled type or the non jacketed, non temperature controlled type.
A further object of the invention is to provide a cell holder for holding cylindrical sample cells with its temperature controllable by a TEC element.
A further object of the invention is to provide a cell holder with TEC temperature control unit which is capable to work with the conventional standard sample cells currently in common use.
To achieve the above objects, the sample cell of the present invention comprises a thermally conductive body enclosing a substantially cylindrical internal volume with an insulating outer cover which leaves one face exposed for complementarily contacting a temperature controlled baseplate so as to keep the sample cell at a predetermined temperature, and a means for positioning the sample cell at a predetermined position such that a measuring light beam longitudinally passes through the sample cell.
Thus, the temperature of the sample cell, which is less in dead volume, is controlled by the temperature control means. The water jacket system required for the conventional cylindrical sample cells is eliminated.
Preferably, the base plate which is fixedly positioned relative to the light path of the light beam for positioning purposes, is temperature controlled by means of being thermally conductive with a TEC element.
In a preferred embodiment, the heat transfer element is a cell mount on which the cylindrical sample cell rests. The cell mount is placed on the base plate in a predetermined position.
Preferably, the base plate comprises a slant upper surface on which the cell mount rests, and the cell holder further comprises a horizontal rail. The rail, on the one hand, stops the cell mount at a predetermined position on the base plate, and on the other hand, enables the inventive cell holder capable of supporting a conventional standard cylindrical sample cell by supporting its flanges directly resting on the rail and the slant upper surface of the base plate.
In another preferred embodiment, the heat transfer element is a cover resting on the cylindrical sample cell which sits on a pair of parallel rails. Preferably, the heat transfer element is detachably connected to the base plate so that the base plate can work with different heat transfer elements for different sizes of cylindrical sample cells.
REFERENCES:
patent: 3695772 (1972-10-01), Spyropoulos
patent: 4180739 (1979-12-01), Abu-Shumays
patent: 4467204 (1984-08-01), Kysilka et al.
patent: 4749276 (1988-06-01), Bragg et al.
patent: 5857341 (1999-01-01), Amakusa
patent: 6046804 (2000-04-01), Kawamura et al.
patent: 100 56 131 (1999-11-01), None
Bancroft Thomas G.
Wagner Jeff A.
Font Frank G.
Kaplan & Gilman LLP
Nguyen Sang H.
Rudolph Research Analytical
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