Spectrophotometric techniques

Details Spectrophotometric techniques Spectrophotometric techniques

1996-11-22

1998-06-16

Snay, Jeffrey

Chemistry: analytical and immunological testing

Optical result

With claimed manipulation of container to effect reaction or...

422 8209, 422 8211, 356246, 356440, G01N 2726

Patent

active

057669570

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to spectrophotometric techniques using particular devices.
In EP-A-0171148, devices are disclosed for use in chemical (especially biochemical or clinical) test procedures, particularly for use in specific binding assay procedures. The devices typically possess a cavity into which sample liquid is drawn. One surface of the cavity is a surface of a transparent solid plate which acts as a light transmissive waveguide; for use in specific binding assays, this surface carries an immobilised reagent appropriate to the assay to be carried out in the device. The plate has an edge which is substantially optically smooth and transverse to the plane of the plate and in use in an assay procedure the device can transmit, for example, fluorescence from an adsorbed fluorescent material along the plate acting as a waveguide, transfer of useful light across the boundary of the plate occurring by the evanescent wave located very close to the interface.
We have now found that devices similar to those in EP-A-0171148 may be used as a cuvette in spectrophotometric assays. In the normal mode of use of the devices as described in EP-A-0171148, there is only a thin film of sample (typically of the order of 0.1 mm) present in the device; passing radiation through a path length of this dimension is not suitable for reliable spectrophotometric measurement. We have now found, however, that totally internally reflecting radiation within a modified form of the device allows the radiation to pass through the sample many times and therefore enables a suitable path length (for example, of up to 1 cm) to be built up. Such a path length is then suitable for reliable spectrophotometric measurement.
Devices for analysing substances and which employ multiple internal reflection are already known. In U.S. Pat. No. 5,273,633 (Tiansong Wang), a device for capillary zone electrophoresis is disclosed which comprises a long transparent capillary tube with a reflecting surface surrounding the outer surface of the capillary, the reflecting surface having an incident and exit window for the electromagnetic radiation. Similarly, in Analytical Chem., vol 55, no. 6, 1983, pp 951-955 (Wei Lei et al), a long capillary cell, in which in use multiple internal reflection of electromagnetic radiation occurs, is employed for the colorimetric determination of phosphorus. U.S. Pat. No. 3,431,424 (Henry W. Allen) discloses a complex optical fluid sampling device which in use also empoys multiply reflected radiation.
These prior art devices are all based on a circular geometry and this presents certain disadvantages. As specifically acknowledged in U.S. Pat. No. 5,273,633, the fact that radial reflection occurs places constraints on the size and orientation of the incident window and also, since the exiting radiation will be distributed around the entire circumference of the capillary, on the preferred shape of the exit window and the detection apparatus. Furthermore, these prior art devices are relatively large (of the order of 50-100 cm) and this makes them impractical for use in routine analytical work. The use according to the present invention of a device as described above (the modified form of the device disclosed in EP-A-0171148) overcomes these disadvantages.


DESCRIPTION OF THE INVENTION

Thus, according to one aspect of the present invention, we provide the use of a sample-collecting device as a cuvette in spectrophotometric assays, the device possessing a cavity or cavities each having a dimension small enough to enable sample liquid to be drawn into the cavity by capillary action, wherein a surface of the cavity is a surface of a transparent solid plate having a substantially rectangular cross-section and forming a wall of the cavity, the opposite surface of the cavity being an additional structure having a substantially rectangular cross-section and forming a wall of the cavity, and wherein a portion of said plate carries a reflective coating and a portion of said additional structure is refle

REFERENCES:
patent: 3431424 (1969-03-01), Allen
patent: 4810658 (1989-03-01), Shanks et al.
patent: 4978503 (1990-12-01), Shanks et al.
patent: 5141868 (1992-08-01), Shanks et al.
patent: 5273633 (1993-12-01), Wang
Analytical Chemistry, vol. 55, No. 6, 1983 Easton Pennsylvania, USA, pp. 951-955, Wei Lai et al. "Determination of phosphorus in natural waters by long capillaryC cell absorption spectrometry".

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