Optics: measuring and testing – Sample – specimen – or standard holder or support – Fluid containers
Reexamination Certificate
1999-06-14
2001-06-19
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Sample, specimen, or standard holder or support
Fluid containers
C356S244000, C422S105000, C422S105000
Reexamination Certificate
active
06249345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cuvette for measuring the absorption of irradiation in liquid samples.
2. Description of the Prior Art
The cuvettes to be taken into account here are used applied in absorption photometers which measure the spectral transmission factor, the spectral retransmission factor or the spectral absorption measure (extinction) of a sample. From the measurement of these values conclusions may be made as to the qualitative or quantitative composition of the sample.
Photometers function in a certain wavelength region, whose selection is effected by color or interference filters. With the spectral photometers on the other hand the light of the illumination means is spectrally disaggregated with a monochromator. With calorimeters the determination of the concentration is effected by color comparison with a standard solution of the same substance. The irradiation may in particular lie in the region of the visible light, in the IR or UV region. The selection may be dependent of the sample to be analyzed. The material selection of the cuvette is in turn directed to the spectral region for which this is to be used.
From DE 17 73 233 C3 there is known a vessel for the optical examination of small fluid quantities which has a lower part with a cross section rectangular on the inside and optically transparent walls and an upper part with larger diagonals than the lower part, wherein the upper part is designed cylindrically. The vessel is closed below and open at the top and at the outside on the lower rectangular part there are attached perpendicular ribs, which extend to the outer dimension of the upper part, wherein the ribs end at a covering on an imagined enveloping cylinder of the upper part. The vessel is suitable as a measuring cuvette and also as a reaction vessel for manual or mechanized sample preparation. The rectangular cross section of the lower vessel part permits two different layer thicknesses for the photometric measurement. The ratio of the layer thicknesses is about 2:1. With this cuvette there is still required a considerable fluid quantity in order to sufficiently fill the lower part for the photometric measurement. Furthermore the stability of the cuvette is not particularly good, since it tapers downwards. Finally there is only a slight variability of the layer thickness.
For the UV region until now cuvettes of quartz glass have been used. These are very expensive and on account of the danger of contamination by the previous sample, on account of the required cleaning work and by way of the danger of breakage they are more unfavorable in the handling.
Indeed for examinations in the UV range often only the smallest of sample quantities are available, without it being known whether these are present in a concentration suitable for a measurement. An example is the DNA photometry with which by measurement in the UV range the ratio of DNA/RNA, the presence of proteins and the opaqueness of a sample are measured. With this it is the case of a routine examination in the genome analysis, for which many times only a small quantity may be branched off. This must be diluted many times in order to fill a cuvette sufficiently with regard to measuring technology. As a result of this the concentration of the sample may be very different. Only after filling into a cuvette may it then be ascertained that with the given concentration and layer thickness a photometric measurement is not possible. Then the sample must be removed, diluted again, again filled into a cuvette and examined. The dilution may however also be so great that the photometric measurement lies on the limit of proof and thus is very erroneous.
Standard cuvettes have a quadratic cross section with outer dimensions of 12.5×12.5 mm. Absorption photometers have a cavity with a corresponding cross section, into which the cuvettes may be inserted. Transversely through this cuvette cavity runs the beam path of the illumination means. Absorption photometers of various manufacturers differ by the distance of the beam path to the floor of the cuvette cavity. Also the irradiation with adsorption photometers of various manufacturers has various cross sections. Until now the cuvette geometries are adapted to the various apparatus types. The use of a single cuvette type for small measuring volumes with various apparatus types is not possible at present.
Furthermore the known plastic cuvettes have a flat bearing in the cuvette cavity. Thus it is difficult to manufacture the cuvettes such they have an exact positioning in the cuvette cavity and do not wobble or jam therein.
Proceeding from this it is the object of the invention to provide a cuvette which favors the adsorption-photometric measurement of the smallest sample quantities of differing concentrations and has an increased stability. Further it is the object of the invention to provide a cuvette which with a simple manufacturability permits a more exact positioning in the cuvette cavity. Finally the object of being able to use a cuvette in absorption photometers with a various arrangement and formation of the beam path is to be achieved.
SUMMARY OF THE INVENTION
According to a first variant of the invention a cuvette for the measurement of the absorption of irradiation in liquid samples which at least in the regions of windows is of a transparent plastic has
an inner space,
which is formed in an essentially box-shaped upper part with an upper opening for filling and removing sample fluid
and in a smaller, essentially box-shaped lower part for the measuring volume, which connects via a transition, preferably a tapering transition, in particular a transition with slants,
two pairs of planar parallel windows in the lower part lying opposite one another, wherein the distance of the windows of the one pair is different to the distance of the windows of the other pair, in order to make available various layer thicknesses for the measurement of the samples
and four feet flush with the corners of the upper part, which extend away from the upper part at least up to the level of the floor of the lower part.
This cuvette has the measuring chamber in the essentially box-shaped lower part which preferably has a content capacity of maximally 200 &mgr;l, preferably about 50 &mgr;l. It thus makes do with only very small sample quantities of e.g. minimally about 50 &mgr;l. At the same time a funnel-shaped connection between the upper and lower part may simplify the filling and emptying of the cuvettes. On the other hand the sample may also fill up the box-shaped upper part. The whole content capability of the cuvette is formed by the upper and lower part and by way of this has a very large volume region of e.g. about 50 &mgr;l to maximally about 2000 &mgr;l.
Furthermore by way of the two pairs of windows with a various distance there is a variability of the layer thicknesses for the measurement. Preferably the ratio of the distances is 5:1 so that the variability is very particularly large. For example layer thickness of 10 mm and 2 mm are realized. With this, during the measurement a region switch-over is possible for example in that one rotates the cuvette about 90° into the measuring position without having to pour the sample again or having to reject the sample. For a switch-over of the region by rotating the cuvette, the upper part preferably has a square cross section. Furthermore at the same time as an absorption measurement a fluorescence measurement or luminescence measurement at an angle of 90° to the irradiation axis of the absorption measurement is possible, and specifically on both sides of the cuvette.
Although the cuvette only has a very small measuring chamber and its inner space below is very narrow and small, by way of the four feet extending away from the corners of the upper part at least up to the level of the floor of the lower part, it has a high stability and an exact alignment in the measuring apparatus. The feet may furthermore protect the windows from contact and scratching, in particul
Goemann-Thoss Wolfgang
Harnack Kurt
Kraack Jan
Treptow Rainer
Brown & Wood LLP
Eppendorf-Netheler-Hinz GmbH
Font Frank G.
Punnoose Roy M.
LandOfFree
Cuvette does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cuvette, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cuvette will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2539318