US 5,317,378 A · Enhancing emission of excited radiation in an analytical sample subjected to exciting radiation

Abstract

A spherical sample cell (FIG. 4A) bears an external inwardly specular laye defining a hollow imaging mirror 11D and an optical aperture 11E. The mirror acts as an integrator of both the exciting radiation for irradiating the sample and the resulting excited radiation to be analysed, the former entering and the latter exiting through the aperture 11E. Optical integration resulting from multiple internal reflections provides multifold increase in excited radiation compared with bare cells, which is of particular advantage in Raman spectrophotometry. Alternatively, the mirror may be provided in two complementary halves in a two-part cell-holder, in which case any conventional sample cell that fits within the mirror may be used. Spectrophotometers adapted for use with the sample cell or the cell holder as well as methods based on them are described.

Claims39

Dependent claims

An analytical optical sample-cell within which a fluid sample will in operation be subjected to exciting radiation at the sample station of an analytical instrument for the purpose of enabling the excited radiation emitted by the sample to be analysed, the fluid sample being pervious to both radiations, comprising:

a) a hollow imaging mirror having an inner imaging surface which in operation surrounds the sample and acts as a specular optical integrator by virtue of the fact that the said mirror enables both radiations to be multiply reflected within the sample;
b) a hollow bulbous fluid-sample retaining part defined by a wall having a small filling orifice, an outer surface to which the inner imaging surface of the hollow imaging mirror adheres and a substantially co-extensive inner surface adapted to enclose the sample completely except for the small filling orifice, via which the bulbous part may be filled with fluid sample by means of a syringe, the wall of the bulbous part being pervious to both radiations;
and
c) a single optical aperture in said mirror through which the exciting radiation will be admitted and the excited radiation will exit, the area of the actual imaging surface of the said mirror being between 51 and 98 percent of the total area represented by the sum of the area covered by the imaging surface and the area of the optical aperture, said sum being substantially equal to the area of said outer surface of the bulbous part, excluding the filling orifice area.

1 more element

An optical holder for a plain analytical sample-cell in which there are distinguished a first sample-retaining cell portion, within which a fluid sample will in operation be subjected to exciting radiation at the sample station of an analytical instrument for the purpose of enabling the excited radiation emitted by the sample to be analysed, and a second cell portion for filling and handling the cell, said second portion longitudinally extending from the first cell portion, the first cell portion and the sample being transparent to both radiations, said optical holder comprising:

a) two relatively displaceable co-operating members which in operation are eased apart by the user for interposing a filled sample cell as aforesaid therebetween and then are gently pressed together for nesting the sample cell therebetween;
b) a complementary part of a hollow imaging mirror in each member within which part a first cell portion as aforesaid will be nested as the members are pressed together;
c) a single optical aperture in one of the two complementary parts, through which the exciting radiation will be admitted and the excited radiation will exit;
d) a complementary part in each member of sample cell positioning means that will engage a second sample-cell portion as aforesaid as the members are pressed together;
and
e) co-operating registration means in each member ensuring that when the members are brought into close abutment with the sample cell nested therebetween the two complementary mirror parts define a complete hollow imaging mirror acting as a specular integrator by virtue of the fact that the said mirror enables in operation both radiations to be multiply reflected within it and hence within the sample and the complementary sample cell positioning parts define a complete sample-cell positioning means which engages the second sample cell portion and locates the first sample cell portion within the hollow imaging mirror.

3 more elements

A method of spectrophotometry comprising the steps of:

a) injecting a fluid sample in an analytical optical sample-cell comprising a hollow imaging mirror having an inner imaging surface surrounding the sample and thus acting as a specular optical integrator, except for an area not significantly larger than that occupied by an optical aperture, by virtue of the fact that the said mirror enables, in the performance of this method, both exciting radiation impinging upon the sample and excited radiation emitted by the sample to be multiply reflected within the sample;
b) locating the analytical optical sample-cell at the sample station of a suitable spectrophotometer having an aperture stop;
c) irradiating the sample with a narrow beam of exciting radiation directed through the optical aperture of the hollow imaging mirror along such path as will cause the beam to undergo multiple reflections in the volume within said mirror;
d) imaging a chosen zone of near optimum energy density from within the hollow imaging mirror close to the optical aperture onto the aperture stop of said suitable spectrophotometer and thus collecting the radiation excited in the molecules of the sample that is available at the chosen zone as a result of the multiple reflections taking place within the hollow imaging mirror and transferring it to said aperture stop with an advantageously predetermined optical matching, the said zone thus representing the effective source of excited radiation;
and
e) analysing by means of said suitable spectrophotometer the excited radiation collected.

3 more elements

A method of spectrophotometry comprising the steps of:

a) filling a plain analytical sample-cell with a fluid sample to be analysed;
b) placing the plain analytical sample-cell between relatively displaceable co-operating members of an optical holder for said cell, each member comprising a complementary part of a hollow imaging mirror provided with an optical aperture in one of the parts;
c) urging the said parts to abut with the plain analytical sample-cell nesting within the hollow imaging mirror;
d) locating the optical holder at the sample station of a suitable spectrophotometer having an aperture stop;
e) irradiating the sample with a narrow beam of exciting radiation directed through the central region of the optical aperture along such path as will cause the beam to undergo multiple reflections within the volume of said hollow imaging mirror;
f) imaging a zone of near optimum high energy density from within the hollow imaging mirror close to the optical aperture onto the aperture stop of said suitable spectrophotometer and thus collecting the radiation excited from the molecules of the sample that is available at the chosen zone as a result of the multiple reflections taking place within the hollow imaging mirror and transferring it onto said aperture stop with an advantageously predetermined optical matching, the said zone thus representing the effective source of stimulated radiation;
and
g) analysing by means of the spectrophotometer the excited radiation collected.

5 more elements

Dependencies are inferred from the claim text.

Enhancing emission of excited radiation in an analytical sample subjected to exciting radiation

Life of this patent

Enhancing emission of excited radiation in an analytical sample subjected to exciting radiation

Life of this patent

Abstract

Claims39