WO2013155622A1

WO2013155622A1 - Device for optical examination of small samples

Info

Publication number: WO2013155622A1
Application number: PCT/CA2013/050239
Authority: WO
Inventors: Paul WOITOVICH; Guenadi Rabinski
Original assignee: Woitovich Paul; Guenadi Rabinski
Priority date: 2012-04-17
Filing date: 2013-03-25
Publication date: 2013-10-24

Abstract

A device for optical examination of small liquid or semi-liquid or solid-state samples, suitable for use with an optical analytical apparatus employing an optical beam. The device includes a cuvette holder having a micro-cuvette mounted thereon and an adapter dimensioned to be inserted in a shaft of the analytical apparatus. The adapter has a slot for accommodating, wobble-free, the holder with the cuvette; the adapter can optionally have a shoulder with one or more arms. Light collimating or focusing or, more generically, "shaping" or "forming" means are provided on the adapter. In a working position, the horizontal light beam passes through the optional light collimating means and a sample in the cuvette to provide a reading indicative of the quality or other optical parameters of the sample. The holder can be immobilized in a partly withdrawn position to facilitate filling, emptying or cleaning of the cuvette.

Description

DEVICE FOR OPTICAL EXAMINATION OF SMALL SAMPLES

[0000] This application claims the benefit under 35 U.S.C. 119(e) of United States

Provisional Patent Application No. 61/625,277 filed on April 17, 2012, the entire contents of which is incorported herein by reference.

TECHNICAL FIELD

[0001] This invention relates to the optical analyses or measurements of small amounts of liquid or solid-state samples, for example by photometry, spectrophotometry, fluorometry, spectrofluorometry, etc. BACKGROUND ART

[0002] Typically, a light beam generated inside a spectrophotometer or another optical analytical apparatus passes through a transparent cell or cuvette which holds a liquid, semi- liquid, or solid-state sample. The cuvette may be disposed in a holder which in turn is placed in the shaft of the analytical apparatus. The cross-sectional dimensions of the shaft, in the horizontal plane, are typically 12.5 x 12.5 mm. The light beam is usually arranged to pass horizontally with its axis parallel to the shaft at a predetermined height from the bottom of the shaft. The holder has recesses or openings corresponding to the path of the said above light beam so as not to obstruct the transmission of the beam through the cuvette and the sample. [0003] In some instances, the holder has at least one lens disposed in the path of the light beam in order to collimate the light passing through the sample and the cuvette walls (or, more generically, change the shape of the light beam as required in a user's analytical apparatus) or, usually if the holder has two or more optical lenses, the incoming light is formed in a certain way to pass through a certain area of the sample located inside a cuvette and then the said light is re-collimated at the exit of the holder (or, more generically, the light changes its shape as required in a user's analytical apparatus).

[0004] Also known are arrangements in which the light beam passes through a drop of a liquid sample placed between two horizontal surfaces, either vertical (US Pat. Appl. 2011/0170094, Hamack et al) wherein the drop is held by surface tension, or horizontal surfaces (US Pat. Appl. 2008/0106742, Sahiri et al). [0005] Several sample holding arrangements have been proposed in recent years by Hellma GmbH (Germany) and Stama Scientific Ltd. (GB).

[0006] In many instances, only small quantities of sample are available. This applies primarily in biochemical, medical or pharmaceutical analysis. It is often difficult to introduce such small samples, often of a drop size only, into the measurement space, particularly where the cuvette, capillary or cell has a very small access opening or a relatively long sample delivery path. It is also important to avoid the formation of air bubbles in the sample and surrounding areas.

[0007] Another problem is the possibility of undesirable sample spills during the introduction of the cuvette into the shaft of the analytical apparatus.

[0008] Another concern is the necessity of a thorough cleaning of the cuvette (cell) or generally, the surfaces in contact with the sample, after or between measurements.

SUMMARY OF EMBODIMENTS OF THE INVENTION

[0009] With the above problems in mind, there is provided a device for optical examination of liquid (or semi-liquid, e.g. colloidal, or solid-state i.e. polymers) samples, the device compatible with an optical analytical apparatus employing a light beam. The device comprises: a cuvette holder; a cuvette (hereinafter also referred to as "microcuvette") having transparent walls, a bottom and an open top end, the holder dimensioned and shaped to receive the cuvette; and an adapter shaped and dimensioned to fit inside a shaft, or receptacle, of the analytical apparatus, the adapter having a slot which is dimensioned to receive the cuvette holder with the cuvette attached thereto, in a predetermined position in which the cuvette is disposed in a path of the light beam with the open end of the micro-cuvette pointing up; the adapter preferably comprising lenses and/or other optical components as required. [0010] Preferably, the cuvette has at least two parallel transparent walls for straight-linear light transmission. However, it is also feasible to provide the cuvette with another shape and provide additional optical elements for altering shape of light where required (i.e. light collimation).

[0011] In an embodiment of the invention, the adapter slot is vertical and the cuvette holder is shaped for a sliding fit in the slot so that the holder can be inserted into the slot, essentially without lateral movement, to a predetermined position in which the cuvette is in the path of the optical beam, the beam passing through the two parallel transparent walls of the cuvette.

[0012] In another embodiment of the invention, the slot is not entirely vertical, i.e. is tilted to a degree, and the cuvette is attached to the holder such that, when the holder is inserted into the slot, the open top of the cuvette points up.

[0013] In an embodiment of the invention, the cuvette holder has means for facilitating the insertion of the holder into the slot and for its removal therefrom.

[0014] In an embodiment of the invention, either the holder or the adapter, or both have retaining means for immobilizing the holder relative to the adapter. This feature is useful, inter alia, for the purpose of transportation of the analytical apparatus with the device. The retaining means may be means for immobilizing the holder in a position in which the holder is partially withdrawn from the slot and the cuvette, attached to the holder, is accessible e.g. for filling.

[0015] In all the embodiments of the invention, the cuvette should be situated so that, in operation, its open top is essentially pointing up regardless of the orientation of the slot.

[0016] The device is useful for optical analysis of small (microliter range) liquid, semi- liquid, and solid-state samples, wherein the sample is easy to deposit and remove and the cuvette is relatively easy to clean.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will be explained in more detail by way of the following description in conjunction with the drawings, in which

[0018] Fig. 1 is a schematic partly cross-sectional front view of the adapter and the cuvette holder with a cuvette attached thereto, the holder being inserted into the adapter which in turn is placed in a spectrophotometer well (shaft);

[0019] Fig. 2 is a schematic cross-sectional view of the adapter of Fig. 1;

[0020] Fig. 3 is a schematic side view of the cuvette holder with a syringe (not part of the invention); [0021] Fig. 4 is a schematic, partly sectional front view of another embodiment of the adapter;

[0022] Fig. 5 is a perspective view of an embodiment of the cuvette holder, and

[0023] Fig. 6 is a perspective view (not to scale) of a cuvette suitable for attachment to the holder of Fig. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] Shown in Fig. 1 is an assembly including a cuvette holder 10 which is slidable within a slot 12 of an adapter 14. The cross-sectional dimensions of the adapter are such - typically 12.5 mm x 12.5 mm - as to fit in a well (shaft) 16 of a conventional spectrophotometer 18 or another analytical apparatus (shown here schematically and not being part of the invention).

[0025] The cuvette holder 10 is shown in more detail in a side view (Fig. 3) and in a perspective view (Fig. 5). As shown in Fig. 1, Fig. 3 and Fig. 4, a cuvette 20 is attached, permanently or detachably, to the cuvette holder 10. The cuvette (or at least its transparent walls) is(are) made of glass or sapphire or quartz or of another material(s) having optical transparency within the desirable wavelength range(s), has small cavity (for example inside 1 mm x 1 mm x 1 mm) to accommodate small samples (of microliter range) and has at least two parallel optically transparent walls 22 (one wall visible in Fig. 3 and both in Fig. 6). The cuvette holder, made of steel, plastic or another suitable material, has a recess 24 which is shaped to not obscure the transparent walls 22 when a light beam (arrows 7 in Fig. 1) of an analytical or measuring apparatus, e.g. spectrophotometer, passes through the adapter/holder assembly (Fig. 1 and Fig. 4). As seen in Fig. 3, the cuvette is seated in a cavity, or pocket 25 and may form a tight fit with the side walls 27 of the pocket.

[0026] The recess 24 is shaped to enable the cuvette 20 to be filled with a sample using e.g. a syringe (or a pipettor, etc.) 26 (not part of the invention). The filling can be effected when the cuvette holder 10 is withdrawn, entirely or partly, from the adapter 14. To facilitate the withdrawal of the holder 10, it has a handle or grip 28 which is shaped to provide a stop for the holder 10 when inserted back into the slot 12 of the adapter 14.

[0027] Both the adapter and the cuvette holder can be manufactured from any conventional material capable of maintaining dimensional integrity, e.g. a metal or plastic. Some lateral flexibility of the holder may be acceptable. Typically, the holder is substantially rigid. [0028] It is advantageous that the cuvette holder 10 is still partly inserted in the slot 12 of the adapter 14 during the filling, emptying or cleaning of the cuvette 20, to enable proper positioning and stability of the cuvette. To this effect, as shown in Figs. 1, 2 and 3, retaining means are provided on the adapter, cuvette holder or both. The retaining means, in the embodiment illustrated herein, are a spring-loaded pin 30 and a corresponding dimple 32 in the cuvette holder. The pin 30 and the dimple 32 are positioned such that when the holder is withdrawn to a degree where the cuvette is accessible from outside, the dimple 32 engages the pin 30 which results in a tentative immobilization of the cuvette holder in a predetermined desired position. [0029] When a sufficient upward force is applied on the cuvette holder 10 to overcome the engagement of the pin and the dimple, the holder can be totally withdrawn from the slot 12 of the adapter 14, if necessary.

[0030] The measuring apparatus 18 functions by passing a light beam (represented by horizontal arrows in Fig. 1) through the sample cuvette 10, the beam in turn being directed for optical analysis as applicable. The light beam is usually collimated or focused before and after passing through the sample (or focused within the sample's volume). To this effect, lenses (or other optical components, when necessary) 34, 36 are provided in the walls of the adapter 14 in a way to allow the light beam to pass through the transparent parallel walls 22 of the cuvette. [0031] In an alternative embodiment of the invention as illustrated in Fig. 4, the adapter 14 has one or two arms 38 provided with e.g. collimating lenses 40 and extending sideways and shaped to reach around the shaft 16 to a position in which the light beam (arrows) of the analytical apparatus can pass through the lenses 40, through apertures 42, 44 in the adapter 14 and through the cuvette 20. The advantage of the embodiment of Fig. 4 may reside in a better collimating or focusing or, more generically, shaping of the light beam before and/or after passing through the sample as a result of allocating space for optical components outside a receptacle of an analytical apparatus (e.g., when some optical focusing elements may not fit within the apertures 42 of the adapter).

[0032] It is advantageous that the cuvette holder 10 is dimensioned to provide a tight sliding fit with the slot 12 of the adapter 14 to prevent wobbling of the cuvette holder inside the adapter, which could lead to erroneous readings of the sample. [0033] The cuvette 20 may be fixed to the cuvette holder, or it may be inserted tightly in the pocket 25 of the holder 10 as illustrated in Fig. 3 to enable replacement or substitution of the cuvette.

[0034] As will be seen in Fig. 1 , Fig. 4 and Fig. 5, the width W of the cuvette holder 10, apart from the grip 28, can be approximately equal to the corresponding width of the cuvette 20 (or simply the width when the cuvette has a square horizontal cross-section). As a result, the cuvette may occupy approximately the entire width of the slot 12 of the adapter 14. This can be advantageous as it minimizes the distance between the cuvette and the optical elements 34, 36.

[0035] While the cuvette 20 in the embodiments described herein is cuboidal, it is also feasible to use a cuvette of a different shape, e.g. cylindrical. However, such a choice puts additional onus on the optics of the device in order to counter the inevitable refraction of the optical beam of the apparatus on the cuvette surfaces.

[0036] In the drawings, the slot 12 is vertical and the open top of the cuvette is facing up. Alternatively, the slot may not be entirely vertical, if convenient, but the cuvette should preferably be positioned with its open top (end) facing up for optimum containment of the sample.

[0037] It is also feasible, within the scope of the present invention, to provide the slot 12 throughout the adapter, without a bottom wall. In such an embodiment, the cuvette holder may be shaped so as to provide an optical channel above and below the cuvette. Preferably, an optical element is provided below and/or above the cuvette to correct for meniscus effect of the sample. As a result, the holder would allow a light beam, passing substantially vertically, to pass through the cuvette and on for optical analysis.

Claims

CLAIMS What is claimed is:

1. A device for optical examination of liquid or semi-liquid samples, the device compatible with an optical analytical apparatus employing a light beam for analysis of the sample, the device comprising:

a cuvette holder,

a cuvette having optically transparent walls, a bottom and an open top end, the holder dimensioned and shaped to receive said cuvette, and

an adapter shaped and dimensioned to fit inside a shaft of the analytical apparatus, the adapter having a slot which is dimensioned to receive the cuvette holder in a predetermined position in which the cuvette, when attached to said holder with the open end facing up, is disposed in a path of the light beam.

2. The device according to claim 1 wherein the cuvette holder is shaped to allow access to said cuvette when attached to said holder.

3. The device according to claim 1 wherein the width of the holder is approximately equal to a corresponding width of the cuvette.

4. The device of claim 1 wherein the holder is slidably movable along the slot substantially without lateral movement.

5. The device of claim 1 wherein the slot is vertical.

6. The device of claim 1 wherein the slot is slanted relative to vertical.

7. The device according to claim 1 further comprising retaining means for immobilizing the holder relative to the adapter in a partially withdrawn position of the holder.

8. The device according to claim 1 wherein the retaining means comprises a spring- loaded pin.

9. The device according to claim 1 wherein the holder has a cavity to accommodate said cuvette.

10. The device according to claim 1 wherein the adapter comprises at least one optical element disposed in the path of the light beam and aligned with the cuvette when attached to said holder.

11. The device according to claim 1 wherein the adapter further comprises at least one arm extending outside the adapter, for mounting an optical element on said arm in the path of the light beam.

12. The device according to claim 1 wherein the adapter is dimensioned to fit inside a standard shaft of an optical analytical apparatus.

13. The device according to claim 1 wherein the cuvette has at least two parallel optically transparent walls.

14. A cuvette holder dimensioned and shaped for a placement within a longitudinal slot of an adapter that is dimensioned to fit in a shaft of an optical analytical apparatus employing a light beam for optical analysis of a sample, said holder comprising:

a body having a cuvette placement region adapted to receive a cuvette having side walls, a bottom and an open top, said body shaped to allow access to said cuvette for filling, emptying or cleaning of said cuvette when attached to said holder, said placement region disposed such that when said holder is disposed within the slot of said adapter and said adapter is disposed in the shaft, the cuvette is aligned with the light beam of the analytical apparatus for optical transmission of the beam through the cuvette.

15. The holder according to claim 14, further comprising retaining means for immobilizing the holder relative to the adapter.

16. The holder according to claim 14 wherein the body defines a cavity shaped to allow access to the cuvette.

17. The holder according to claim 14 wherein the width of the holder is approximately equal to a corresponding width of the cuvette.

18. The holder according to claim 14 wherein the body is rigid.