Microplate Assembly Kit for Absorbance Measurement of Liquid Samples

Abstract

A kit for forming a microplate assembly for measuring absorbance of a liquid sample includes a top plate (1) having at least one group of a plurality of rods (12), each rod (12) having a flat rod bottom surface (121), a bottom plate (2), alignment guides for aligning the top plate (1) and the bottom plate (2) with respect to each other, and spacers for determining the distance of the top plate (1) and the bottom plate (2) from each other. The bottom plate (2) includes a plurality of wells (22), each well having a flat well bottom surface (221). The alignment guides are constructed and arranged such that each well (22) receives one rod (12) of each group of the plurality of rods. The spacer comprises a plurality of threaded adjustment bolts (13a, 13b, 13c) arranged such that when the top plate (1) and bottom plate (2) are assembled to form a microplate assembly, each flat rod bottom surface (121) is positioned parallel to a corresponding flat well bottom surface (221) at a predetermined distance (43) ranging from 0.5 mm to 5 mm.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates generally to the field of spectrophotometric measurements, and more particularly to a kit for forming a microplate assembly for spectrophotometric measurements of liquid samples. [Background technology]

[0002] 2. Background of the Invention A wide range of applications in life sciences involves the spectrophotometric measurement of liquid samples such as DNA, RNA and proteins in solution. Typically, the concentration of one component of a liquid sample, or the ratio of the concentrations of several components of a liquid sample, is unknown or requires confirmation and can be determined from such absorbance measurements. The determination of concentration can form part of quality or process control.

[0003] The concentration of a single attenuating component in a liquid sample may be determined from the following equation within the applicability of the Beer-Lambert law if the optical pathlength is known accurately and thus the linear relationship between absorbance and concentration. A = ε c L A is the absorbance, L is the optical path length, ε is the molar absorption coefficient, c is the concentration of a single attenuating component in the liquid sample.

[0004] In some applications, especially in early pharmaceutical research and development, the amount of liquid sample available is very limited and measurements need to be performed with minimal volumes of liquid sample in the μl (microliter) or ml (milliliter) range. At the same time, it is required to be able to handle a large number of liquid samples. Therefore, miniaturized and automated solutions using microplates in standardized formats (ANSI SLAS, previously known as ANSI SBS) are the technology of choice. Spectrophotometric measurements are typically performed using microplates with 96,384 or 1536 wells. To perform an automated absorbance measurement, a defined volume of liquid sample is pipetted into the wells and the absorbance is measured using an automated plate reader.

[0005] In conventional designs of standard microplates with open wells, there are several factors that can lead to inaccuracies in the optical path length, especially for small volumes of liquid samples. For example, deviations of the actual volume of the liquid sample from the desired volume, caused by imprecise pipetting or evaporation of the liquid sample between pipetting the sample into the wells and taking the measurement, can lead to deviations of the actual filling level in each well from the desired filling level and therefore the optical path length from the optical path length used in the calculation to determine the concentration. Furthermore, the formation of a meniscus can lead to non-uniform optical path lengths across the liquid-air interface, leading to significant deviations from the theoretically expected optical path length.

[0006] US Patent No. 8,605,279 (corresponding to US Patent Application Publication No. 2009 / 008168) discloses a microcuvette assembly in which a liquid sample is held in a fixed position between two flat surfaces placed on the upper and lower plates of the microcuvette assembly, but does not disclose wells. Instead, the flat surfaces between which the liquid sample is held project from the upper and lower plates, respectively, towards each other. This assembly requires very high precision in pipetting, both in terms of the positioning of the pipette and the amount of the liquid sample pipetted. Also, the distance between the flats needs to be adapted to the volume and surface tension of the liquid sample. Also, the liquid sample pipetted onto the flat surface of the lower plate is subject to mechanical influences such as vibration or rapid movement of the lower plate by placing the upper plate on the lower plate prior to the formation of the microcuvette assembly. This may complicate a fully automated and efficient handling of the plates of the microcuvette assembly using standard microplate handling equipment, even though the layout and dimensions of the microcuvette assembly may be similar to those of a standard microplate. Furthermore, between the time when the liquid sample is pipetted onto the flat surface of the lower plate and the time when the microcuvette assembly is formed with the corresponding flat surface of the upper plate, the fully exposed liquid sample may at least partially evaporate, and even after the formation of a (closed) microcuvette assembly in which the volume of the liquid sample is held between two corresponding flat surfaces of the upper and lower plates, the liquid sample may still partially evaporate through the uncovered sides.

[0007] It is therefore an object of the present invention to overcome the aforementioned drawbacks. Summary of the Invention

[0008] According to the present invention, these and other objects are achieved by a kit for forming a microplate assembly and a microplate assembly as specified by the features of the independent claims. Advantageous embodiments of the kit according to the invention are the subject of the dependent claims.

[0009] When used in the specification, including the appended claims, the singular forms "a", "an", and "the" include the plural unless the context clearly indicates otherwise. When the term "about" is used in relation to a particular numerical value or range of values, this should be understood to mean that the particular numerical value referred to in relation to "about" is included and expressly disclosed, unless the context clearly dictates otherwise. For example, if a range of "about" numerical value A to "about" numerical value B is disclosed, this should be understood to include and expressly disclose the range of numerical value A to numerical value B. Also, whenever a feature is combined with the term "or", the term "or" should be understood to also include "and", unless it is clear from the specification that the term "or" must be understood to be exclusive.

[0010] According to the present invention, a kit for forming a microplate assembly for measuring the absorbance of liquid samples is proposed. The kit comprises: - a top plate made of glass and comprising at least one group of a plurality of downwardly projecting rods arranged in a rod pattern, each of the rods having a downwardly facing flat bottom rod surface and a lateral outer rod surface extending upwardly from an outer periphery of the flat bottom rod surface, the flat bottom rod surfaces of all rods in each same group being disposed in a respective common first plane, each of the individual groups comprising the same number of rods and arranged in the same rod pattern; - a lower plate; - a plurality of alignment guides for aligning the upper plate and the lower plate with respect to one another when the upper plate and the lower plate are assembled to form a microplate assembly; a plurality of spacers that determine the distance between the upper plate and the lower plate when the upper plate and the lower plate are assembled to form a microplate assembly; Equipped with.

[0011] The bottom plate comprises a plurality of glass wells, the number of wells in the plurality of wells corresponding to the number of rods in each of the individual groups of rods, and the plurality of wells arranged in a well pattern corresponding to the rod pattern.

[0012] The term "well" as used herein means a hole or opening, or a depression, or similar compartment having a base, that is recessed relative to the surface of the plate in which it is formed and that in a position of use extends downward from the surface of the plate. A well typically includes a sidewall that extends from the bottom of the well to the top end of the well, which sidewall is typically in the plane of the surface of the plate in which it is formed. Thus, the well is configured to contain liquid in such a way that the liquid cannot easily escape from the well or move within the well.

[0013] Each well has a 0.7 mm 2 ~29mm 2 The flat well bases of all of the wells are disposed in a common second plane.

[0014] Each of the wells further includes a lateral inner well surface extending upwardly from a perimeter of the planar well bottom surface. The lateral inner well surface is dimensioned to surround the lateral outer rod surface when the upper and lower plates are assembled to form a microplate assembly. The alignment guides are arranged and configured such that they engage with one another to align the upper and lower plates such that each well of the plurality of wells receives one rod in each of the respective groups of rods when the upper plate is assembled with the lower plate to form a microplate assembly.

[0015] The plurality of spacers includes a plurality of threaded adjustment bolts.

[0016] Each threaded adjustment bolt in the plurality of threaded adjustment bolts is disposed in a threaded through hole in the upper plate or the lower plate, and one end of each threaded adjustment bolt protrudes from the upper plate or the lower plate, respectively, so that when the upper plate is assembled with the lower plate to form a microplate assembly, one end of each threaded adjustment bolt abuts against the lower plate or the upper plate, respectively, and the flat rod bottom surface of each rod in each individual group of rods is disposed parallel to the corresponding flat well bottom surface and faces the flat well bottom surface at a predetermined distance within the range of 0.05 mm to 5 mm, particularly 0.1 mm to 2 mm, and more particularly 0.2 mm to 1 mm.

[0017] The kit according to the invention offers the possibility to carry out (spectrophotometric) absorbance measurements with a fixed path length of the light beam through the sample, without losing the advantages of conventional microplates with wells.

[0018] In contrast to the assembly disclosed in US Patent No. 8,605,279, where the protruding surfaces are designated areas for depositing liquid samples, the lateral (lateral) inner well surfaces of each well of the lower plate prevent the liquid samples from shifting position since they are securely contained within their designated wells. For example, even if the lower plate or the microplate assembly moves due to possible vibration or shaking during assembly of the upper and lower plates to form a microplate assembly or during transfer of the microplate assembly to a plate reader or spectrometer, the liquid samples remain securely contained in their respective wells. Furthermore, the kit according to the invention is suitable for all kinds of liquid samples, regardless of any sample-dependent properties related to adhesive and cohesive forces and surface tension.

[0019] Each rod protruding downward from the upper plate is positioned such that when the upper plate is assembled with the lower plate to form a microplate assembly, the alignment guides engage with each other to align the upper and lower plates, and each rod is accommodated by a corresponding well (since the rod pattern corresponds to the well pattern). The flat rod bottom surfaces of all rods and the flat well bottom surfaces of the wells of the microplate assembly are arranged parallel to each other and face each other at a predetermined distance. This is achieved by means of threaded adjustment bolts, as described in more detail below. The liquid sample dispensed into the multiple wells of the lower plate at least partially wets the flat well bottom surfaces of each well and fills the entire space between the flat rod bottom surfaces and the flat well bottom surfaces. If the volume of the liquid sample may be affected by evaporation, evaporation is prevented or at least greatly reduced because the liquid sample is surrounded by the flat rod bottom surfaces, the well bottom surfaces, and the lateral inner well surfaces, thus greatly reducing the exposure of the liquid sample to air. The effect of possible evaporation of the liquid sample on the absorbance measurement can be further reduced by dispensing more sample liquid into the well than the minimum volume of liquid sample required to fill the entire space between the flat rod bottom and the flat well bottom. The additional amount of liquid sample is forced laterally into the space of the well not covered by the rod bottom, thus not affecting the optical path length, further reducing the effect of evaporation on the (spectroscopic) absorbance measurement.

[0020] The kit according to the present invention is relatively insensitive to the variation of the volume of the pipetted liquid sample. Even if the volume of the liquid sample actually dispensed into the well deviates from the target volume of the liquid sample dispensed into the well, the optical path length is not affected. For example, even if the volume of the liquid sample placed exceeds the target volume of the liquid sample, the excess sample liquid is pushed away by the rod, so that the desired optical path length is determined by the distance between the bottom surface of the rod and the bottom surface of the well. Therefore, by increasing the target volume of the liquid sample dispensed into the well to a volume slightly exceeding the minimum volume required to fill the entire space between the bottom surface of the rod and the bottom surface of the well, small variations in the pipetted volume (which may be caused by the pipetting device) do not have any effect on the absorbance measurement.

[0021] The threaded adjustment bolt is disposed in the threaded through-hole of the upper plate or the lower plate when the upper plate and the lower plate are assembled to form a microplate assembly, and one end of the threaded adjustment bolt protrudes and abuts against the respective opposing plate. Thus, the threaded adjustment bolt allows adjustment of the distance between the plates at different positions of the respective plates. Since the rods and wells are rigidly connected to the respective plates such that the flat rod bottoms are disposed in a common first plane and the well bottoms are disposed in a common second plane, the adjustment bolt can be disposed and adjusted to ensure that the flat rod bottoms of all individual rods are disposed parallel to and at a predetermined distance from the respective well bottoms such that the optical path length between each flat rod bottom and the corresponding flat well bottom is the same for all rods and wells.

[0022] Since the optical path length is determined by the adjustable distance between the flat rod bottom and the flat well bottom, the optical path length can be selected to be small enough so that even liquid samples with very high absorbance can be used for absorbance measurement without requiring dilution of the liquid sample. The optical path length can be selected almost independently of the sample volume.

[0023] As will be described in more detail below, the top plate may include only one group of rods, or may include two or more groups of downwardly projecting rods.

[0024] The outer dimensions of the lower plate and the upper plate can be easily adapted to standard dimensions according to the ANSI SLAS standards for microplates (in particular ANSI SLAS1-2004(R2012) for microplates), in which case the kit according to the invention offers the possibility to perform automated measurements using standard equipment, i.e. standard liquid handling devices (e.g. standard multichannel pipettes), standard plate handling devices and standard plate readers.

[0025] According to one embodiment of the kit according to the invention, the top plate comprises only one group of a plurality of downwardly projecting rods.

[0026] This embodiment allows easy (spectroscopic) measurement of absorbance with minimal volumes of liquid samples in a single optical path length. This embodiment even allows measurement of very small volumes of liquid samples, where the liquid sample dispensed into the wells forms only a single drop on the flat well bottom. Modern liquid handling instruments are capable of dispensing a drop of liquid sample into the center of the well, so that when the top plate is assembled with the bottom plate, the drop fills the microcuvette defined by the respective flat rod bottom and the respective flat well bottom.

[0027] According to another embodiment of the kit according to the invention, the top plate comprises two or more groups of downwardly projecting rods, in particular four groups of downwardly projecting rods, all rods of each rod of the same group having the same length, for example in the case of four groups of rods, the flat rod bottom surfaces of all the individual rods of a first group of rods are arranged in a first common plane of the rods of this first group, and the flat rod bottom surfaces of all the individual rods of a second group of rods are arranged in a first common plane (different from the first common plane of the rods of the first group) of the rods of this second group. Similarly, the flat rod bottom surfaces of all individual rods of the third group of rods are disposed in a first common plane of the third group of rods (different from the first common plane of the first and second groups of rods), and the flat rod bottom surfaces of all individual rods of the fourth group of rods are disposed in a first common plane of the fourth group of rods (different from the first common plane of the first, second, and third groups of rods).

[0028] This configuration allows measurements at different path lengths in the same volume of liquid sample (i.e., in the same well). The advantage of measuring at different path lengths in the same sample deposit is that the user can determine the most appropriate path length at which the measured signal best follows the correlation given by the Beer-Lambert law and can cover a wide range of concentrations of components in the sample. Furthermore, this allows the measurement principle to be extended from only measuring the absorbance at one defined path length to contextualizing the individual measurements. For example, the absorbance measurements at the individual path lengths can be contextualized by evaluating the slope of the obtained absorbance values ​​as a function of the path length.

[0029] According to a further aspect of the kit according to the invention, the plurality of threaded adjustment bolts comprises three threaded adjustment bolts arranged at the apexes (corners) of a triangle, preferably an isosceles triangle.

[0030] The arrangement of the three threaded adjustment bolts for determining the distance between the upper and lower plates in a triangle allows the adjustment of the respective distances at three separate positions on each plate (positions where the adjustment bolts are located). The adjustment of the respective distances at one position of the three threaded adjustment bolts allows the adjustment of the inclination of the upper plate relative to the lower plate around an axis defined by a line passing through the respective positions of the two other adjustment bolts. The arrangement of the three threaded adjustment bolts in a triangle thus allows the control of the distance and inclination of the upper plate relative to the lower plate, and thus allows the arrangement of the flat rod bottom surface parallel to the flat well bottom surface, as well as the arrangement of the bottom surfaces of this at a predetermined distance from each other, without overdetermination. It may be particularly advantageous to arrange the three threaded adjustment bolts at the corners of an isosceles triangle. This geometric arrangement of the three threaded adjustment bolts provides a high degree of stability and allows the adjustment of the inclination around a first axis corresponding to the base of the triangle, and around two further axes at symmetric angles to the first axis (corresponding to the legs of the triangle). A triangular arrangement of the threaded adjustment bolts is particularly advantageous, in which the base of the isosceles triangle runs parallel to the long side edge of each plate and the apex of the isosceles triangle is located midway between the long side edges of each plate. Strategically, the threaded adjustment bolts are arranged so that the base of the isosceles triangle is located as close as possible to the long side edge of each plate, the corner of the base of the triangle is located as close as possible to the end of the long side edge, and the apex is located as close as possible to the opposite long side edge of each plate and midway between the opposite long side edges. Such an arrangement may allow the inclination angle of the upper plate relative to the lower plate and the distance between the flat rod bottom surface and the flat well bottom surface to be adjusted and controlled with high precision.

[0031] According to a further embodiment of the kit according to the present invention, the rod pattern of each of the multiple rod groups (whether there is only one group of multiple rods or two or more groups, in particular four groups of multiple rods) is the same rectangular matrix having 96 positions in which the rods in each of the multiple rod groups are arranged.

[0032] The matrix positions are arranged along 8 rows and 12 columns, a first threaded adjustment bolt and a second threaded adjustment bolt of the three threaded adjustment bolts are both disposed between a bottom row (lowest tier) and a second-lowest row (second-lowest tier) of the rectangular matrix; A third threaded adjustment bolt of the three threaded adjustment bolts is disposed between the top row (topmost stage) and the second-highest row (second-topmost stage) of the rectangular matrix.

[0033] The first threaded adjustment bolt is positioned between the leftmost column (outermost left column) and the second leftmost column (second outermost left column) of the rectangular matrix, and the second threaded adjustment bolt is positioned between the rightmost column (outermost right column) and the second rightmost column (second outermost right column) of the rectangular matrix.

[0034] A third threaded adjustment bolt is disposed between the two center most columns of the rectangular matrix.

[0035] Arranging each individual rod within the same rectangular matrix with 96 positions, the matrix positions being arranged along 8 rows and 12 columns, has the advantage that such an arrangement corresponds to the arrangement of a standard microplate, allowing the handling of liquid samples and the use of standard equipment for handling microplates.

[0036] Locating three threaded adjustment bolts between the rows and columns ensures that the distance between each of the threaded adjustment bolts is as large as possible without placing the adjustment bolts outside the matrix. Maximizing the distance between each of the threaded adjustment bolts increases the precision of adjustment of the inclination of the upper plate relative to the lower plate, as well as the precision of adjustment of the distance between the bottom of the rod and the bottom of the well.

[0037] According to another aspect of the kit according to the invention, one end of each threaded adjustment bolt protruding from the upper plate or the lower plate, respectively, includes a convex end surface.

[0038] The convex end surface of one end of each threaded adjustment bolt protruding from the upper or lower plate essentially provides a single point of contact between the end of the threaded adjustment bolt and the respective other plate when the upper and lower plates are assembled to form the microplate assembly. In contrast, if the end of each threaded adjustment bolt instead comprises, for example, a flat surface, the contact area of ​​said flat surface with the respective other plate is either the entire flat surface, the edge of said flat surface, or a point on this edge. This may result in unexpected non-linearities or abrupt changes in the relationship between the distance between the upper and lower plates and the rotation of the threaded adjustment bolt. Furthermore, the reference axis of the inclination of the upper plate relative to the lower plate may not be clearly defined. Furthermore, if each plate is made of glass, at least in the area where the convex end of the threaded adjustment bolt contacts each plate, scratches and damage to the glass may be avoided by a sufficiently smooth convex end surface.

[0039] According to a further aspect of the kit according to the invention, the alignment guide comprises: a first flange extending downwardly from the top plate at a first lateral end of the top plate, the first flange including a first flange alignment surface; a second flange extending downwardly from the top plate at a second lateral end of the top plate opposite the first lateral end, the second flange including a second flange alignment surface; a first groove formed in a corresponding first lateral edge of the lower plate, the first groove having a corresponding first groove alignment surface; a second groove formed in a corresponding second lateral edge of the lower plate and having a corresponding second groove alignment surface; Equipped with.

[0040] Each of the first and second flange alignment surfaces and a corresponding one of the first and second groove alignment surfaces are shaped and positioned to engage with one another when the top plate and bottom plate are assembled to form a microplate assembly.

[0041] The alignment guide ensures that the upper plate is accurately aligned with the lower plate when the upper and lower plates are assembled to form a microplate assembly. In this regard, the "corresponding" first lateral end and the "corresponding" second lateral end of the lower plate refer to the respective lateral ends of the lower plate disposed on the same side as the first and second flanges extending downwardly of the upper plate. The first and second alignment flanges and the first and second alignment grooves, with their respective first and second flange alignment surfaces and first and second groove alignment surfaces, are typically formed to allow a user to easily and accurately align the upper and lower plates with each other when assembling the upper and lower plates. In particular, the substantially vertical first and second flange alignment surfaces and the first and second groove alignment surfaces ensure that the upper and lower plates are horizontally aligned upon engagement of the corresponding first and second flange alignment surfaces with the first and second groove alignment surfaces.

[0042] Furthermore, the alignment guides not only function as guides and alignment tools during assembly of the upper and lower plates, but also maintain the upper plate in its designated horizontal position relative to the lower plate. The arrangement of the alignment flanges and corresponding grooves at the opposing lateral ends of each plate is easily visible during assembly. This is advantageous compared to alignment means that are "hidden" during assembly. Furthermore, such arrangement of the alignment flanges and grooves at the opposing lateral ends of each plate ensures that the upper plate is stabilized relative to the lower plate against movement in directions other than toward and away from the lower plate.

[0043] According to another aspect of the kit according to the invention, the alignment guide comprises: - a third flange extending upwardly from the lower plate at a third lateral end thereof, the third flange including a third flange alignment surface, the third lateral end of the lower plate being distinct from the first and second lateral ends of the lower plate; a fourth flange extending upwardly from the lower plate at a fourth lateral end opposite the third lateral end of the lower plate, the fourth flange including a fourth flange alignment surface; a third groove formed in a corresponding third lateral edge of the top plate, the third groove having a corresponding third groove alignment surface; a fourth groove formed in a corresponding fourth lateral edge of the top plate, the fourth groove having a corresponding fourth groove alignment surface; It further comprises:

[0044] Each of the third flange alignment surface and the fourth flange alignment surface and a corresponding one of the third groove alignment surface and the fourth groove alignment surface are shaped and positioned to engage with one another when the top plate and bottom plate are assembled to form a microplate assembly.

[0045] Again, the "corresponding" third lateral edge and the "corresponding" fourth lateral edge of the upper plate refer to the respective lateral edges of the upper plate disposed on the same side as the upwardly extending third and fourth flanges of the lower plate, respectively. The placement of the third and fourth grooves at lateral edges different from the first and second lateral edges further enhances the stability of the microplate assembly and further prevents movement of the upper plate relative to the lower plate other than toward and away from the lower plate.

[0046] According to a further aspect of the kit according to the invention, - the first flange alignment surface comprises an inner alignment surface facing inwardly and two lateral alignment surfaces (lateral alignment surfaces) facing laterally outwardly, the inner alignment surface comprising at least one bulge projecting inwardly away from the inner alignment surface; - the first groove alignment surface comprises an outer alignment surface facing outward and two lateral alignment surfaces (lateral alignment surfaces) facing inward at the sides (lateral direction), the outer alignment surface comprising at least one inwardly recessed notch corresponding to the at least one bulge; - the second flange alignment surface comprises an inner alignment surface facing inwards and two lateral alignment surfaces (lateral alignment surfaces) facing outwards at the sides (lateral direction), the inner alignment surface comprising at least one bulge, preferably two such bulges, projecting inwards away from the second inner flange alignment surface; - the second groove alignment surface comprises an outer alignment surface facing outward and two lateral alignment surfaces (lateral alignment surfaces) facing inward at the sides (lateral direction), the outer alignment surface comprising at least one inwardly recessed notch corresponding to the at least one bulge, preferably two such notches corresponding to two bulges; Each of the bulges and a corresponding one of the notches are positioned and molded to engage one another when the top plate and bottom plate are assembled to form a microplate assembly.

[0047] The inwardly facing inner alignment surfaces and their corresponding outwardly facing outer alignment surfaces align and stabilize the upper plate relative to the lower plate primarily in a direction perpendicular to said surfaces when the upper and lower plates are assembled to form a microplate assembly. In addition to the alignment and stabilization provided by the inner and outer alignment surfaces, the lateral alignment surfaces aid in aligning and stabilizing the upper plate in directions other than perpendicular to the inner and outer alignment surfaces. Similar lateral alignment surfaces may also be provided on the third and fourth flange alignment surfaces and their corresponding groove alignment surfaces to further stabilize and aid in alignment of the microplate assembly. The bulges and their corresponding notches provide additional stability, particularly in directions other than perpendicular to the respective inner and outer alignment surfaces. In addition to stabilization, the bulges and notches may help define the orientation of the upper plate relative to the lower plate to prevent the upper and lower plates from being accidentally assembled in an undesirable orientation. One manner in which the bulges and corresponding notches define the orientation of the top plate relative to the bottom plate may be by providing a first flange alignment surface with one bulge and one notch corresponding to the first groove alignment surface, and a second flange alignment surface with two bulges and two notches corresponding to the second groove alignment surface. This arrangement of bulges and notches not only physically prevents incorrect assembly of the top and bottom plates, but also provides a clear visual guide for correct assembly of the top and bottom plates.

[0048] According to yet another aspect of the kit according to the present invention, the upper plate comprises a carrier plate made of a corrosion-resistant metal and including a plurality of through holes arranged in a rod pattern, with each individual rod in each group of the same plurality of rods being secured to a different individual through hole in the plurality of through holes.

[0049] The carrier plate made of corrosion-resistant metal with the glass rods attached makes it possible to take advantage of the advantageous optical properties of glass while at the same time allowing a reliable and robust handling of the entire top plate (carrier plate with the glass rods fixed in the through holes). In addition, both the glass rods and the carrier plate made of corrosion-resistant metal with the through holes can be produced simply and reliably and, being corrosion-resistant, can be cleaned and reused.

[0050] If only one group of rods is present, one individual rod of the single group of rods is fixed in each individual through-hole of the carrier plate. If more than one group of rods is present, one individual rod of each group of rods is fixed in each individual through-hole of the carrier plate. In particular, in the case of the four groups of rods mentioned above, one individual rod of each of the four groups of rods is disposed in each individual through-hole of the carrier plate.

[0051] According to a further aspect of the kit according to the invention, each individual rod of each group of the same plurality of rods is secured to a respective different individual through hole by adhesive.

[0052] Using an adhesive to secure each individual rod in a through hole is a simple and reliable way of attaching the rods to the carrier plate - no additional features, such as threads, are required that may complicate the manufacture of the component.

[0053] According to another aspect of the kit of the invention, the lower plate comprises a glass plate containing a plurality of wells arranged in the well pattern. The lower plate further comprises a frame made of a corrosion-resistant metal and housing the glass plate. The threaded adjustment bolt protrudes from the upper plate and is positioned such that an end of the threaded adjustment bolt abuts the glass plate when the upper plate is assembled with the lower plate to form a microplate assembly.

[0054] This embodiment has the advantage that such glass plates containing wells are easy to manufacture with high precision.Since glass is known to be a rather fragile material, a frame made of a corrosion-resistant metal that houses the glass plate ensures that the entire lower plate (i.e. the frame with the housed glass plate) is robust and therefore easy to handle.

[0055] By positioning the adjustment bolt protruding from the upper plate so that the end of the threaded adjustment bolt abuts the glass plate when the upper plate is assembled with the lower plate, the distance between the upper plate and the lower plate can actually be precisely adjusted by the adjustment bolt. Because the flat well bottom is part of the glass plate and not part of the metal frame, the threaded adjustment bolt abutting the glass plate ensures precise adjustment of the distance between the flat rod bottom and the flat well bottom.

[0056] According to a further embodiment of the kit according to the invention, both the rod and the well are cylindrical with a circular cross section.

[0057] Cylindrical (glass) rods having a circular cross section are easy to manufacture and are often suitable for directing a light beam that also has a circular cross-sectional beam profile.

[0058] As already mentioned, according to a further embodiment of the kit according to the invention, the outer dimensions of both the lower plate and the upper plate comply with the outer dimensions of the standard ANSI SLAS1-2004 (R2012) for microplates. In this case, the kit according to the invention offers the possibility to carry out automated measurements using standard equipment, i.e. standard liquid handling equipment (e.g. standard multichannel pipettes), standard plate handling equipment and standard plate readers.

[0059] According to the invention there is also proposed a microplate assembly for absorbance measurements of liquid samples, which is formed by the assembled upper and lower plates of the kit according to the invention, as described above.

[0060] The components and advantages of the microplate assembly have already been described above with respect to the kits that form the microplate assembly and will not be repeated here.

[0061] When the top and bottom plates are assembled to form a microplate assembly, the parallel arrangement of and the distance between the flat rod bottom surface and the flat rod well surface may be adjusted by a number of threaded adjustment bolts to compensate for slight deviations from the ideal geometry of the top and bottom plates that may result from the manufacturing process or temperature variations. The spacer with the threaded adjustment bolts may preferably be adjusted only once using a set of calibration measurements. For the calibration measurements, the wells may be filled with reference liquid samples whose concentrations and molar absorption coefficients of the components are precisely known. The deviations from the actual and expected path lengths may be calculated from the absorbance measurements using the formula defined by the Beer-Lambert law (see further above). The distance between the top and bottom plates (and therefore the distance between the rod bottom surface and the well bottom surface) may be subsequently adjusted such that the deviation between the actual and expected path lengths is reduced. This calibration procedure may be repeated until said deviations are reduced to a sufficiently small level. Any remaining deviations may be compensated during subsequent processing of the measurement data. [Brief description of the drawings]

[0062] Further advantageous aspects of the invention become apparent from the following description of embodiments of the invention with the aid of schematic drawings. [Figure 1] FIG. 1 shows a first embodiment of a kit according to the present invention, with all components of the kit shown in a perspective exploded view. [Diagram 2]FIG. 2 is a perspective view of the embodiment of the kit of FIG. 1 with the respective components of the upper and lower plates of the kit assembled. [Diagram 3] FIG. 3 is a bottom view of the top plate of the kit embodiment shown in FIG. 2. [Figure 4] FIG. 3 is a top view of the bottom plate of the embodiment of the kit shown in FIG. 2. [Diagram 5] FIG. 3 is a perspective view of one embodiment of a microplate assembly according to the present invention formed by the assembled top and bottom plates shown in FIG. 2. [Figure 6] FIG. 6 is a cross-sectional view of the microplate assembly shown in FIG. 5 taken along line VI-VI. [Figure 7] FIG. 7 is an enlarged view of detail VII of FIG. [Figure 8] FIG. 8 is a cross-sectional view of the kit and microplate assembly taken along line VIII-VIII in FIG. 5, with liquid samples contained in the wells, showing the upper and lower plates of the kit separated before assembly. [Figure 9] FIG. 8 is a cross-sectional view of the kit and microplate assembly taken along line VIII-VIII in FIG. 5, showing the top plate assembled to the bottom plate, with liquid samples contained in the wells. [Figure 10] 8, but showing a smaller amount of liquid sample contained in the well. [Figure 11] 9, but showing a smaller amount of liquid sample contained in the well. [Figure 12] FIG. 13 is a bottom view of the top plate of a second embodiment of a kit according to the present invention. [Figure 13] FIG. 13 is a side view of the top plate shown in FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] In Fig. 1 an exploded view of a first embodiment of a kit according to the invention is shown. The kit generally comprises an upper plate 1 and a lower plate 2. The upper plate 1 comprises a plurality of cylindrical rods 12 made of glass and having a circular cross section. The rods 12 are arranged in a rod pattern (in a first embodiment, a rectangular matrix of 8 rows and 12 columns defining 96 different positions in the matrix, as will be further explained below). The lower plate 2 comprises a metal frame 20 and a glass plate 21 containing a plurality of cylindrical wells 22 having a circular cross section arranged in a well pattern corresponding to the rod pattern (a corresponding matrix of 8 rows and 12 columns). In this embodiment, only one group of rods 12 (i.e. a single group of rods) is provided.

[0064] The top plate 1 comprises a carrier plate 10 made of a corrosion-resistant metal, for example (anodized) aluminum. The carrier plate 10 comprises a plurality of through holes 11 arranged in 96 different positions in a matrix for receiving the individual rods 12 of said group of rods, such that the individual rods 12 are arranged in a rod pattern (rectangular matrix). The carrier plate 10 further comprises three threaded through holes 18a, 18b, 18c. Three threaded adjustment bolts 13a, 13b, 13c are arranged in these threaded through holes 18a, 18b, 18c, with a first threaded adjustment bolt 13a of the three adjustment bolts being arranged in the through hole 18a, a second threaded adjustment bolt 13b of the three threaded adjustment bolts being arranged in the threaded through hole 18b and a third threaded adjustment bolt 13c of the three threaded adjustment bolts being arranged in the through hole 18c. The three threaded adjustment bolts 13a, 13b, 13c function to adjust the distance of the top plate 1 from the bottom plate 2 (and thus the distance 43 between each flat rod bottom surface 121 of each individual rod 12 and the flat well bottom surface 221 of the corresponding well 22, see FIG. 9) relative to one another when the top plate 1 is assembled with the bottom plate 2 to form a microplate assembly.

[0065] The lower plate 2 comprises a frame 20 made of a corrosion-resistant metal, for example (anodized) aluminum. The frame 20 houses a glass plate 21. The glass plate 21 is fixed by three clamping screws 23 (only two of them are labeled in FIG. 1 ) that pass through threaded holes in the metal frame 20, thereby clamping and holding the glass plate 21 in place in the metal frame 20.

[0066] Figure 2 shows the first embodiment of the kit already shown in Figure 1, but with the respective components of the upper plate 1 and the lower plate 2 of the kit assembled: the rods 12 are fixed in the through holes 11 of the carrier plate 10 (one group of individual rods 12 for each individual through hole 11), the threaded adjustment bolts 13a, 13b, 13c are arranged in the through holes 18a, 18b, 18c so as to protrude downwards from the upper plate 1 thus formed. The glass plate 21 is inserted into the metal frame 20 at d and fixed to the metal frame by means of the tightening screws 23.

[0067] As already briefly mentioned above, in this first embodiment of the kit, the rod pattern is a rectangular matrix with 96 different positions, these 96 different positions of the matrix being arranged along eight rows R1 to R8 (labeled with letters A to H on the carrier plate 10 in Figs. 1 and 2) and along twelve columns C1 to C12 (labeled with numbers 1 to 12 on the carrier plate 10 in Figs. 1 and 2). The first and second threaded adjustment bolts 13a, 13b are arranged between the second lowest row R7 and the lowest row R8 of the rectangular matrix, the first threaded adjustment bolt 13a is arranged between the outermost left column C1 and the second outermost left column C2, and the second threaded adjustment bolt 13b is arranged between the second outermost right column C11 and the outermost right column C12. The third threaded adjustment bolt 13c is located between the top row R1 and the second top row R2 and between the central rows C6 and C7. The threaded adjustment bolts 13a, 13b, 13c thus form an isosceles triangle 19 (shown by dotted lines in FIG. 2) whose corners are located as far away from each other as possible to ensure high accuracy of adjustment with the three threaded adjustment bolts 13a, 13b, 13c.

[0068] The alignment guides are provided at a first lateral edge 14 and a second lateral edge 15 of the upper plate 1 opposite the first lateral edge 14, and at a corresponding first lateral edge 24 and a corresponding second lateral edge 25 of the lower plate 2. The alignment guides function to align the upper plate 1 and the lower plate 2 relative to one another when the upper plate 1 and the lower plate 2 are assembled to form a microplate assembly. In a first embodiment shown in Figures 1 and 2, the alignment guides comprise a first flange 140 extending downwardly from the upper plate 1 at the first lateral edge 14 (see Figure 3) of the upper plate 1, and a second flange 150 extending downwardly from the upper plate 1 at the second lateral edge 15 of the upper plate 1. The alignment guide further includes a first groove 240 formed in a corresponding first lateral end 24 of the lower plate 2 and a second groove 250 formed in a corresponding second lateral end 25 of the lower plate 2 (see FIG. 4).

[0069] The geometry of the first and second flanges 140, 150 and the geometry of the first and second grooves 240, 250 can also be seen in Figures 3 and 4. Figure 3 shows a bottom view of the (assembled) upper plate 1 and Figure 4 shows a top view of the (assembled) lower plate 2 of Figure 2.

[0070] In FIG. 3, the first lateral end 14 of the top plate 1 is shown to be on the left side of the top plate 1. The first flange 140 comprises a first flange alignment surface 141 extending downwards (i.e., out of the plane of the paper towards the reader) from the top plate 1. The first flange alignment surface 141 comprises an inner alignment surface 142 facing inwards and two lateral alignment surfaces 143 facing laterally outwards. Said alignment surfaces 141, 142, 143 are embodied as essentially vertical flat walls connected to each other via rounded edges. Furthermore, the inner alignment surface 142 comprises a bulge 144 projecting inwards away from the inner alignment surface 142.

[0071] The second lateral end 15 of the top plate 1 is shown to be on the right side of the top plate 1. The second flange 150 includes a second flange alignment surface 151 that includes an inwardly facing inner alignment surface 152 and two laterally outwardly facing lateral alignment surfaces 153 that mirror their corresponding counterparts on the first lateral end 14 of the top plate 1. The second inner flange alignment surface 152 includes two bulges 154 that project inwardly away from the inner alignment surface 152.

[0072] 3, in FIG. 4, the first lateral end 24 of the lower plate 2 is shown to be on the left side of the lower plate 2, and the second lateral end 25 of the lower plate 2 is shown to be on the right side. The first groove 240 comprises a first groove alignment surface 241 formed in the first lateral end 24. The first groove alignment surface 241 comprises an outer alignment surface 242 facing outwardly and two lateral alignment surfaces 243 facing laterally inwardly. Additionally, the outer alignment surface 242 further comprises an inwardly recessed notch 244 corresponding to the bulge 144 of the upper plate 1.

[0073] Similarly, the second groove 250 located at the second lateral end 25 of the lower plate 2 comprises a second groove alignment surface 251. The second groove alignment surface 251 comprises an outwardly facing outer alignment surface 252 and two laterally inwardly facing lateral alignment surfaces 253 that mirror their corresponding counterparts at the first lateral end 24 of the lower plate 2. The second inner groove alignment surface 252 comprises two inwardly recessed notches 254 that correspond to the two bulges 154 of the upper plate 1.

[0074] The shape of all alignment surfaces 241, 242, 243 of the first groove 240 at the first lateral end 24 of the lower plate 2, including the notch 244, matches the shape of the corresponding alignment surfaces 141, 142, 143 of the first flange 140 of the upper plate 1, including the bulge 144. This is similarly true for the alignment surfaces 151, 152, 153 of the second groove 250 at the second lateral end 25 of the lower plate 2, including the notch 245, which matches the shape of the corresponding alignment surfaces 251, 252, 253 of the second flange 150 of the upper plate 1, including the two bulges 154. When the upper plate 1 is assembled with the lower plate 2, the inner and outer alignment surfaces 142, 152, 242, 252 of the upper plate 1 and the lower plate 2, respectively, ensure that the upper plate 1 is accurately aligned with the lower plate 2 in the longitudinal direction (horizontal direction in the plane of the drawing). Respective lateral alignment surfaces 143, 153, 243, 253 ensure that the top plate is accurately aligned laterally (vertically in the plane of the drawing) with respect to the bottom plate. Bulges 144 and 154 and notches 244 and 254 further assist with alignment and stability as well as ensure that top plate 1 is assembled with bottom plate 2 in the correct orientation.

[0075] As further shown in FIG. 4 , the alignment guide further comprises a third flange 260 extending upwardly from the third lateral end 26 of the bottom plate 2 and a fourth flange 270 extending upwardly from a fourth lateral end 27 opposite the third lateral end 26 of the bottom plate 2. The alignment guide further comprises a corresponding third groove 160 in the corresponding third lateral end 16 of the top plate 1 and a corresponding fourth groove 170 in the corresponding fourth lateral end 17 of the top plate 1. The third flange 260 and the fourth flange 270, as well as the corresponding third groove 160 and the fourth groove 170, further assist in the alignment procedure and stability of the microplate assembly.

[0076] 4 further shows a glass plate 21 assembled in an aluminium frame 20. The correct orientation of the glass plate 21 in the aluminium frame 20 is ensured by a chamfered edge 210 of the glass plate 21 and a corresponding chamfered edge 200 of the aluminium frame 20.

[0077] FIG. 5 shows a perspective view of one embodiment of a microplate assembly according to the invention formed by the assembled top plate 1 and bottom plate 2 of the kit described above. As can be seen in FIG. 5, the various alignment flanges and grooves of the top plate 1 and bottom plate 2 engage with each other. As can be further seen in FIG. 5, the flanges further comprise outwardly facing concave surfaces, of which only the concave surface 155 of the second flange 150 and the concave surface 275 of the fourth flange 270, which are arranged at the second end 15 of the top plate 1, are visible in FIG. 5. The first flange 140 of the top plate 1 and the third flange 260 of the bottom plate 2 are also provided with corresponding concave surfaces (not visible in FIG. 5). The concave surfaces are rectangular and recessed inwards by, for example, 0.5 mm. They serve as gripping / contact surfaces for corresponding standard equipment for fully automated handling of the top plate 1 and the bottom plate 2 or the microplate assemblies formed therefrom. The outer dimensions preferably comply with the outer dimensions of the standard ANSI SLAS1-2004(R2012) for microplates, which specifies a length of 127.76 mm + / - 0.5 mm and a width of 85.48 mm + / - 0.5 mm.

[0078] When the top plate 1 is assembled with the bottom plate 2 to form a microplate assembly, the top plate 1 rests on the bottom plate 2 only via the end faces of the three threaded adjustment bolts 13a, 13b, 13c. By adjusting the threaded adjustment bolts 13a, 13b, 13c, the distance between the top plate 1 and the bottom plate 2 can be adjusted at the position of each threaded adjustment bolt 13a, 13b, 13c. This allows adjustment of not only the (parallel) distance between the top plate 1 and the bottom plate 2, but also the inclination of the top plate 1 relative to the bottom plate 2.

[0079] FIG. 6 is a cross-sectional view of the microplate assembly along the line VI-VI in FIG. 5. The first threaded adjustment bolt 13a and the second threaded adjustment bolt 13b are arranged in two respective threaded through-holes 18a, 18b of the carrier plate 10 (see FIG. 1). FIG. 7 is an enlarged view of detail VII in FIG. 6. It can be seen that the first threaded adjustment bolt 13a has an end 131a with a convex end surface that rests on the upper surface 213 of the glass plate 21 of the lower plate 2. The carrier plate 10 itself does not rest its lower surface 101 on the upper surface 213 of the glass plate 21, but rather there is a small gap between the upper surface 213 of the glass plate 21 and the lower surface 101 of the carrier plate 10, so that the entire upper plate 1 rests as a whole on the lower plate 2 only at the points where the convex end surfaces of the three threaded adjustment bolts 13a, 13b, 13c contact the upper surface 213 of the glass plate 21.

[0080] Figures 8 and 9 show cross-sectional views of the top plate 1 and bottom plate 2 along line VIII-VIII in Figure 5 of a kit or a microplate assembly, respectively. In Figure 8, the top plate 1 and bottom plate 2 are separated (kit), and in Figure 9, the top plate 1 is assembled with the bottom plate 2 (microplate assembly).

[0081] As can be further seen in these figures, the glass rods 12 include a flat rod bottom surface 121 and a lateral outer rod surface 122 extending upwardly from the periphery of the flat rod bottom surface 121. The rods 12 are cylindrical rods having a circular cross section. In this embodiment, the flat rod bottom surface 121 is a circular surface having a diameter of 3 mm, and the lateral outer rod surface 122 is formed as a circular outer cylindrical surface. For the volume of liquid sample typically used in such applications, the diameter of the circular flat rod bottom surfaces 121 may be as small as 0.5 mm. All of the flat rod bottom surfaces 121 are disposed on a common first plane 127. The glass that constitutes the rods 12 is preferably quartz glass. The flat rod bottom surface 121 and the flat top surface 123 of each rod 12 are polished to a surface roughness R a = 0.3 or less.

[0082] As can be seen, the top surfaces 123 of the rods 12 are arranged in the through holes 11 such that the top surfaces 123 are slightly recessed relative to the upper surface 102 of the carrier plate 10 to avoid scratches on the top surfaces 123 of the rods 12. Each rod 12 is fixed in the respective through hole 11 by adhesive. To ensure that all flat rod bottom surfaces 121 are arranged in a common first plane 127, the rods 12 may be fixed in the respective through holes 11 with the help of corresponding spacers (not shown), which are preferably made of plastic and define a small distance between the rod top surfaces 123 and the upper surface 102 of the carrier plate 10 (slightly recessed arrangement).

[0083] The wells 22 of the glass plate 21 are also cylindrical and include a flat well bottom 221 shaped as a circular surface with a diameter of 6 mm. However, if the volume of the liquid sample is very small, the diameter of the circular flat well bottom 221 may be as small as 1 mm. The area of ​​the flat well bottom is typically less than 0.7 mm. 2 ~29mm 2Each cylindrical well 22 of the glass plate 21 further includes a lateral inner well surface 222 shaped as an inner cylindrical surface. The flat well bottoms 221 are disposed in a common second plane 227. The flat well bottoms 221 of each well 22 are polished to have a surface roughness R a Similarly, the bottom surface 211 of the glass plate 21 may have the same surface roughness R a or at least in the area of ​​the bottom surface 211 traversed by the light beam 40 for measuring the absorbance, to the same surface roughness.

[0084] As can be further seen, the well 22 is partially filled with a liquid sample 225. A meniscus 226 forms on the surface of the liquid sample 225 due to cohesive forces within the liquid sample and adhesive forces between the liquid sample and the lateral inner surface 222 of the well 22. The concave meniscus 226 shown forms when adhesive forces are stronger than cohesive forces, as is typically the case for aqueous solutions. When the top plate 1 is assembled with the bottom plate 2 to form the microplate assembly, the rod 12 is lowered into the well 22 and immersed in the liquid sample 225, with the distance between the flat rod bottom surface 121 and the flat well bottom surface 221 defined by the three threaded adjustment bolts 13a, 13b, 13c.

[0085] In FIG. 9, a light beam 40 emitted by a light source 41 traverses the rods 12 and the liquid samples 225 contained in the wells 22 on the way from the light source 41 to a detector 44 in order to measure the (spectrally resolved) transmission of light through the liquid sample (from which the absorbance of the liquid sample can be calculated). The optical path length of the light through the liquid sample corresponds to the distance 43 between the flat rod bottom 121 and the flat well bottom 221 and is in the range of 0.05 mm to 5 mm, in particular 0.1 mm to 2 mm, in particular 0.2 mm to 1 mm. This distance between the flat rod bottom 121 and the flat well bottom 221, and therefore the optical path length through the liquid sample, is constant over the entire cross section of the light beam 40, since the flat rod bottom 121 of each rod 12 is arranged parallel to the flat well bottom 221 of each well 22. The small meniscus 228 formed between the lateral inner well surface 222 of the well 22 and the lateral outer rod face 122 of the rod 12 is not crossed by the light beam 40 and therefore this meniscus 228 does not influence the transmission / absorbance measurement. Even if the volume of the liquid sample 225 and therefore the filling level of the liquid sample 225 may be slightly affected by evaporation, the optical path length is not affected. However, as already mentioned above, since each liquid sample 225 is essentially surrounded by the lateral inner well surface 221 and the carrier plate 10, evaporation is completely avoided or at least greatly reduced.

[0086] 10 and 11 show cross-sectional views similar to those of FIGS. 8 and 9, but with a significantly smaller amount of liquid sample 225 contained in the wells 22. Here, only a single drop of liquid sample 225 is dispensed into each well 22 at the center of the respective well 22. The volume of liquid sample 225 is small enough not to wet the entire flat well bottom 221, forming a drop having a curved surface 229 on the flat well bottom 221. Modern liquid handling equipment is capable of dispensing such small amounts of liquid sample 225 into each well and at the center of the respective well 22 with high precision. As shown in FIG. 11, even in this situation, the optical path length remains constant over the entire cross-section of the light beam 40.

[0087] 12 and 13 show respectively a bottom view and a side view of the upper plate 3 of a second embodiment of a kit according to the invention. The lower plate of this second embodiment may be identical to the lower plate 2 of the first embodiment of the kit. In this second embodiment, the upper plate 3 comprises four groups of rods, each of which has a diameter of, for example, 2 mm. The rods or rods of the same group all have the same length, while the lengths of the rods 32, 33, 34, 35 of the different groups are different. In each through-hole 31 provided in the carrier plate 30, one rod 32, 33, 34, 35 of each of the rods is arranged (one of the through-holes is shown in dashed lines in FIG. 12). The through-holes 31 are arranged in the carrier plate 30 in the same matrix arrangement as the rods 12 of the first embodiment of the kit, and the circular through-holes 31 have the same circular shape as in the first embodiment. Each rod 32, 33, 34, 35 of the four groups of rods comprises a flat rod bottom surface 321, 331, 341, 351 and an outer rod surface 322, 332, 342, 352. The fixing of the four rods 32, 33, 34, 35 into each of the respective through holes 31 of the carrier plate 30 is performed in the same manner as described for the first embodiment of the kit. This means that when the four rods 32, 33, 34, 35 are fixed in the through holes 31 by adhesive, the flat rod bottom surfaces 321 of all rods 32 of this (e.g., first) plurality of rods are arranged in a first common plane 327. Similarly, the flat rod bottom surfaces 331 of all rods 33 of another (e.g., second) plurality of rods are arranged in another first common plane 337 different from the first common plane 327. Furthermore, the flat rod bottom surfaces 341 of all rods 34 of a further (e.g., third) plurality of rods are disposed in a further first common plane 347 that is different from the first common planes 327, 337. Finally, the flat rod bottom surfaces 351 of all rods 35 of a further (e.g., fourth) plurality of rods are disposed in a further first common plane 357 that is different from the first common planes 327, 337, 347. Meanwhile, the flat well bottom surfaces 22 of the glass plate 21 are all disposed in the same second common plane 227 (see the first embodiment).As a result, the distances between the flat rod bottom surfaces 321, 331, 341, 351 and the flat well bottom surfaces 221 of the wells 22 of the glass plate 21 are different. As already mentioned above, this results in different optical path lengths being available for the same volume of liquid sample (i.e. in the same well), allowing transmission / absorbance measurements at four different optical path lengths. This allows the user to determine the most appropriate optical path length at which the measured signal best follows the correlation given by the Beer-Lambert law. Other features of the top plate 3 of the second embodiment of the kit may be identical to those of the top plate 1 of the first embodiment of the kit. These will therefore not be described again here. As mentioned above, the bottom plate of the second embodiment of the kit (not shown in Figures 12 and 13) may be identical to the bottom plate 2 of the first embodiment of the kit.

[0088] The embodiments of the kit and the microplate assembly according to the present invention are described above with the aid of the drawings. However, the present invention is not limited to these embodiments, but rather many variations and modifications are possible without departing from the teachings underlying the present invention. Therefore, the scope of protection is not limited to the embodiments, but rather is defined by the appended claims.

Claims

1. 1. A kit for forming a microplate assembly for measuring absorbance of a liquid sample, comprising: - an upper plate (1, 3) made of glass and comprising at least one group of downwardly projecting rods (12; 32, 33, 34, 35) arranged in a rod pattern, each of said rods (12; 32, 33, 34, 35) having a downwardly facing flat rod bottom surface (121; 321, 331, 341, 351) and lateral outer rods extending upward from the periphery of said flat rod bottom surface (121; 321, 331, 341, 351); a top plate (1, 3) having a flat rod bottom surface (122; 322, 332, 342, 352), the flat rod bottom surfaces (121; 321, 331, 341, 351) of all the rods (12; 32, 33, 34, 35) in each same group being arranged in a respective common first plane (127; 327, 337, 347, 357), each individual group having the same number of rods (12; 32, 33, 34, 35) arranged in the same rod pattern; - a lower plate (2), a plurality of alignment guides for aligning the upper plates (1, 3) and the lower plate (2) with each other when assembling the upper plates (1, 3) and the lower plate (2) to form the microplate assembly; a plurality of spacers for determining the distance between the upper plate (1, 3) and the lower plate (2) when the upper plate (1, 3) and the lower plate (2) are assembled to form the microplate assembly; Equipped with the lower plate (2) comprises a plurality of glass wells (22), the number of wells (22) in the plurality of wells (22) corresponding to the number of rods (12; 32, 33, 34, 35) in each group of individual rods (12; 32, 33, 34, 35), the plurality of wells (22) being arranged in a well pattern corresponding to the rod pattern; Each of the wells (22) faces upward and is 0.7 mm ２ From 29mm ２ the flat well bottom surfaces (221) of all the wells (22) are arranged in a common second plane (227); each of said wells (22) further comprises a lateral inner well surface (222) extending upward from the periphery of said flat well bottom surface (221), said lateral inner well surface (222) being dimensioned to surround said lateral outer rod surfaces (122; 322, 332, 342, 352) when said upper plate (1, 3) and said lower plate (2) are assembled to form said microplate assembly; the plurality of alignment guides are arranged and configured to engage with each other to align the upper plate (1, 3) and the lower plate (2) such that, when the upper plate (1, 3) is assembled with the lower plate (2) to form the microplate assembly, each well of the plurality of wells (22) receives one rod (12; 32, 33, 34, 35) in each group of individual plurality of rods (12; 32, 33, 34, 35); the plurality of spacers comprising a plurality of threaded adjustment bolts (13a, 13b, 13c); Each threaded adjustment bolt (13a, 13b, 13c) of the plurality of threaded adjustment bolts is disposed in a threaded through-hole (18a, 18b, 18c) of the upper plate (1, 3) or the lower plate (2), and one end (131a) of each threaded adjustment bolt (13a, 13b, 13c) protrudes from the upper plate (1, 3) or the lower plate (2), respectively, so that when the upper plate (1, 3) is assembled with the lower plate (2) to form the microplate assembly, The kit, wherein the one end (131a) of each of the threaded adjustment bolts (13a, 13b, 13c) abuts against the lower plate (2) or the upper plate (1, 3), respectively, and the flat rod bottom surface (121; 321, 331, 341, 351) of each rod (12; 32, 33, 34, 35) in each group of individual rods (12; 32, 33, 34, 35) is arranged parallel to the corresponding flat well bottom surface (221) and faces the flat well bottom surface (221) at a predetermined distance within a range of 0.05 mm to 5 mm.

2. 2. The kit according to claim 1, wherein the top plate (1) comprises only one group of downwardly projecting rods (12).

3. 2. The kit according to claim 1, wherein the top plate (3) comprises two or more groups of downwardly projecting rods (32, 33, 34, 35), all rods (32, 33, 34, 35) in the same group having the same length.

4. 4. The kit according to any one of claims 1 to 3, wherein the plurality of threaded adjustment bolts consists of three threaded adjustment bolts (13a, 13b, 13c) arranged at the vertices of a triangle (19).

5. the rod pattern of each group of rods (12; 32, 33, 34, 35) is the same rectangular matrix having 96 positions in which the rods (12; 32, 33, 34, 35) in each group of rods are arranged, the locations of the rectangular matrix are arranged along 8 rows (R1-R8) and 12 columns (C1-C12); a first threaded adjustment bolt (13a) and a second threaded adjustment bolt (13b) of the three threaded adjustment bolts (13a, 13b, 13c) are both disposed between the bottommost row (R8) and the second-lowest row (R7) of the rectangular matrix; a third threaded adjustment bolt (13c) of the three threaded adjustment bolts (13) is disposed between the top row (R1) and the second-highest row (R2) of the rectangular matrix; The first threaded adjustment bolt (13a) is disposed between the leftmost column (C1) and the second leftmost column (C2) of the rectangular matrix; The second threaded adjustment bolt (13b) is disposed between the rightmost column (C12) and the second column (C11) from the right end of the rectangular matrix; 5. The kit according to claim 4, wherein said third threaded adjustment bolt (13c) is arranged between the two central most columns (C6, C7) of said rectangular matrix.

6. 4. The kit according to claim 1, wherein the one end (131a) of each threaded adjustment bolt (13a, 13b, 13c) protruding from the upper plate (1, 3) or the lower plate (2), respectively, is provided with a convex end surface.

7. The alignment guide is a first flange (140) extending downwardly from said top plate (1, 3) at a first lateral end (14) of said top plate (1, 3) and comprising a first flange alignment surface (141); a second flange (150) extending downwardly from the top plate (1, 3) at a second lateral end (15) opposite the first lateral end (14) of the top plate, the second flange (150) comprising a second flange alignment surface (151); a first groove (240) formed in a corresponding first lateral edge (24) of said lower plate (2) and provided with a corresponding first groove alignment surface (241); a second groove (250) formed in a corresponding second lateral edge (25) of said lower plate (2) and provided with a corresponding second groove alignment surface (251); Equipped with 4. The kit of claim 1, wherein each of the first flange alignment surface (141) and the second flange alignment surface (151) and a corresponding one of the first groove alignment surface (241) and the second groove alignment surface (251) are shaped and positioned to engage with each other when the upper plate (1, 3) and the lower plate (2) are assembled to form the microplate assembly.

8. The alignment guide is a third flange (260) extending upwardly from the lower plate (2) at a third lateral end (26) of the lower plate (2) and comprising a third flange alignment surface (261), wherein the third lateral end (26) of the lower plate (2) is different from the first lateral end (24) and the second lateral end (25) of the lower plate (2); a fourth flange (270) extending upwardly from the lower plate (2) at a fourth lateral end (27) opposite the third lateral end (26) of the lower plate (2), the fourth flange (270) comprising a fourth flange alignment surface (271); a third groove (160) formed in the corresponding third lateral edge (16) of said upper plate (1, 3) and having a corresponding third groove alignment surface (161); a fourth groove (170) formed in a corresponding fourth lateral edge (17) of said upper plate (1, 3) and provided with a corresponding fourth groove alignment surface (171); Furthermore, 8. The kit of claim 7, wherein each of the third flange alignment surface (261) and the fourth flange alignment surface (271) and a corresponding one of the third groove alignment surface (161) and the fourth groove alignment surface (171) are shaped and positioned to engage with each other when the upper plate (1, 3) and the lower plate (2) are assembled to form the microplate assembly.

9. - said first flange alignment surface (141) comprises an inner alignment surface (142) facing inwards and two lateral alignment surfaces (143) facing outwards at the sides, said inner alignment surface (142) comprising at least one bulge (144) projecting inwards away from said inner alignment surface (142); - said first groove alignment surface (241) comprises an outer alignment surface (242) facing outwards and two lateral alignment surfaces (243) facing inwards at the sides, said outer alignment surface (242) comprising at least one inwardly recessed notch (244) corresponding to said at least one bulge (144); - the second flange alignment surface (151) comprises an inner alignment surface (152) facing inward and two lateral alignment surfaces (153) facing outward at the sides, the inner alignment surface (152) comprising at least one bulge (154) projecting inward away from the second inner flange alignment surface (152); - said second groove alignment surface (251) comprises an outer alignment surface (252) facing outwards and two lateral alignment surfaces (253) facing inwards at the sides, said outer alignment surface (253) comprising at least one inwardly recessed notch (254) corresponding to said at least one bulge (154); 8. The kit of claim 7, wherein each of the bulges (144, 154) and a corresponding one of the notches (244, 254) are positioned and shaped to engage with each other when the upper plate (1, 3) and the lower plate (2) are assembled to form the microplate assembly.

10. 4. The kit according to claim 1, wherein the upper plate (1, 3) comprises a carrier plate (10) made of a corrosion-resistant metal and comprising a plurality of through holes (11, 31) arranged in the rod pattern, and each individual rod (12; 32, 33, 34, 35) in each of the same groups of rods is fixed in a different individual through hole (11, 31) in the plurality of through holes.

11. 11. The kit according to claim 10, wherein each individual rod (12; 32, 33, 34, 35) in each of the same groups of rods is fixed in a respective different individual through-hole (11, 31) by adhesive.

12. 4. The kit according to claim 1, wherein the lower plate (2) comprises a glass plate (21) having the plurality of wells (22) arranged in the well pattern, the lower plate (2) further comprises a frame (20) made of a corrosion-resistant metal and accommodating the glass plate (21), and the threaded adjustment bolts (13a, 13b, 13c) protrude from the upper plate and are positioned so that ends of the threaded adjustment bolts (13a, 13b, 13c) abut against the glass plate (21) when the upper plate (1, 3) is assembled with the lower plate (2) to form the microplate assembly.

13. 4. The kit according to any one of claims 1 to 3, wherein both the rod (12; 32, 33, 34, 35) and the well (22) are cylindrical with a circular cross section.

14. 4. The kit according to claim 1, wherein the outer dimensions of both the lower plate (2) and the upper plate (1, 3) comply with the outer dimensions of the standard ANSI SLAS 1-2004 (R2012) for microplates.

15. A microplate assembly for measuring the absorbance of liquid samples, said microplate assembly being formed by the assembled upper plate (1, 3) and lower plate (2) of the kit according to any one of claims 1 to 3.

Images