GB2387642A

GB2387642A - A method and apparatus for drying coated microtitre plates after a rinsing operation

Info

Publication number: GB2387642A
Application number: GB0223180A
Authority: GB
Inventors: Ronan Patrick O'caoimh; Brendan Kevin Farrell; Maurice Andrew Hickey; James Walsh
Original assignee: Trinity Research Ltd
Current assignee: Trinity Research Ltd
Priority date: 2002-04-18
Filing date: 2002-10-07
Publication date: 2003-10-22
Anticipated expiration: 2022-10-07
Also published as: GB2387642B; GB0223180D0

Abstract

A drying tunnel 2 for drying off a rinsing solution from microtitre plates (3, fig 5) coated with an antigen or an antibody comprises a preheating zone 43 downstream of a drying zone 42. Infrared tubes 44, 45 located in the preheating 43 and drying 42 zones heat the plates (3). A pair of chains 28 convey the plates (3) through the tunnel 2 so that the residence time in the preheating zone 43 is approximately fifteen seconds and in the drying zone 42 is approximately thirty seconds. The plates (3) in drying zone 42 are heated to approximately forty five Celsius so that the rinsing solution is evaporated and convection currents are generated within wells (9, fig 5) of the plates (3). The temperature of the plates (3) in drying zone 42 is such that the coating is never damaged by too high a temperature. The resulting vapour is exhausted by a blower 61. An optical pyrometer 60 may be located in drying zone 42 and monitors the temperature of the plates (3) so that the tubes 44 maintain the temperature of the plates (3) via a control circuit (50, fig 4). A temperature sensor 62 and the control circuit (50) may monitor and ensure the temperature in preheating zone 42 does not exceed seventy Celsius.

Description

- I! "A method and apparatus for drying a coated microtitre plate after

rinsing" The present invention relates to a method and apparatus for drying a coated microtitre plate after rinsing, and in particular, for drying a microtitre plate coated with 5 a clinical diagnostic medium.

Clinical diagnostic mediums, for example, antibodies, antigens and the like are commonly coated on plates, for example, microtitre plates. The process for coating the microtitre plates with the antibody or antigen is a relatively well known process, 0 and after the antibody or antigen has been applied to the microtitre plates, the microtitre plates are rinsed with a rinsing medium for rinsing off any of the antibody or antigen medium which has not adhered to the plate. The rinsing medium used in general, is a buffer solution, typically, a solution of salt and water. Microtitre plates comprise a plurality of wells which define an inner surface onto which the antibody or antigen is coated. The buffer rinsing medium is then directed into the wells and subsequently drained therefrom. However, a residue of the rinsing medium remains within the wells, and is in general retained on the inner surface of each well over the antibody or antigen coating by surface tension. In order to dry off this residue of rinsing medium, the microtitre plates are typically inverted and vigorously tapped 20 against an absorbent material, for example, tissue paper or the like, in order to dislodge as much of the rinsing medium as possible from the inner surfaces of the wells. However, this method does not dislodge all the rinsing medium, and rinsing medium is still retained on the inner surfaces of the wells by surface tension. In order to dry off the remaining rinsing medium, it is necessary to leave the microtitre

plates for a period of approximately twelve hours, typically, overnight in either a humidity controlled environment which is controlled at a relative humidity of approximately 25%, or alternatively, in an incubator at a controlled temperature of approximately 37 C. While either of these two methods result in a complete drying 5 off of the rinsing medium, unfortunately, they add significantly to the cycle time for producing antibody or antigen coated microtitre plates. Without the drying step the normal process cycle time for a microtitre plate is two days, however, the drying off of the rinsing medium adds an additional day to the process cycle time, thus resulting in a total process cycle time of three days. Thus, the drying off of the lo rinsing medium adds over 30% to the normal process cycle time. This is undesirable, and leads to a relatively inefficient process.

There is therefore a need for a method and apparatus for reducing the process cycle time for processing antibody or antigen coated microtitre plates.

The present invention is directed towards providing a method and apparatus for drying a microtitre plate coated with a clinical diagnostic medium after rinsing.

According to the invention there is provided a method for drying a microtitre plate 20 after the microtitre plate has been rinsed with a rinsing medium, the microtitre plate having a plurality of wells formed therein, the inner surfaces of which are coated with a clinical diagnostic medium, the method comprising the step of directing radiation at the coated surfaces for heating the coated surfaces to a drying temperature insufficient to damage the clinical diagnostic medium coated thereon, but sufficient

- for evaporating the rinsing medium from the coated surfaces, and for setting up air convection currents within the wells for removing evaporate from the wells.

In one embodiment of the invention the radiation which is directed towards the 5 coated surfaces of the microtitre plate during drying is infrared radiation. Preferably, the infrared radiation which is directed towards the coated surfaces of the microtitre plate during drying is of short wavelength. Advantageously, the wavelength of the infrared radiation which is directed towards the coated surfaces of the microtitre plate during drying lies in the range of Mum to 2,um. Ideally, the wavelength of the 0 infrared radiation which is directed towards the coated surfaces of the microtitre plate during drying is in the range of 1.2.um to 1.7,um.

In one embodiment of the invention the drying temperature to which the coated surfaces are heated does not exceed 50 C. Preferably, the drying temperature to us which the coated surfaces are heated does not exceed 42 C. Advantageously, the drying temperature to which the coated surfaces are heated does not exceed 40 C.

Ideally, the drying temperature to which the coated surfaces are heated lies in the range of 38 C to 42 C, and preferably, the drying temperature lies in the range of 40 C to 42 C.

In another embodiment of the invention the coated surfaces of the microtitre plate are maintained at the drying temperature for a drying time in the range of 20 seconds to 40 seconds. Preferably, the drying time is approximately 30 seconds.

In a further embodiment of the invention the microtitre plate is preheated prior to drying, the coated surfaces of the microtitre plate being heated to a preheating temperature during preheating. Preferably, the microtitre plate is heated during preheating by directing radiation at the coated surfaces for raising the temperature of 5 the coated surfaces to the preheating temperature. Advantageously, the radiation which is directed towards the coated surfaces of the microtitre plate during preheating is infrared radiation.

In one embodiment of the invention the infrared radiation which is directed towards lo the coated surfaces of the microtitre plate during preheating is of short wavelength.

Preferably, the wavelength of the infrared radiation directed towards the coated surfaces of the microtitre plate during preheating lies in the range of Mum to plum.

Advantageously, the wavelength of the infrared radiation directed towards the coated surfaces of the microtitre plate during preheating lies in the range of 1.2'um to 1.7.um.

In one embodiment of the invention the microtitre plate is passed through a drying tunnel, and the radiation is directed at the coated surfaces as the microtitre plate passes through the drying tunnel. Preferably, the microtitre plate is passed through the drying tunnel at substantially constant speed.

In one embodiment of the invention the drying tunnel comprises a preheating zone in which the microtitre plate is preheated and a drying zone in which the microtitre plate is dried, the microtitre plate being passed sequentially through the respective zones from the preheating zone to the drying zone.

In another embodiment of the invention the air temperature in the preheating zone is maintained at a temperature not exceeding 80 C. Preferably, the air temperature in the preheating zone is maintained at a temperature not exceeding 70 C.

s In one embodiment of the invention the resident time of the microtitre plate in the preheating zone is in the range of 10 seconds to 20 seconds. Preferably, the resident time of the microtitre plate in the preheating zone is approximately 15 seconds. In one embodiment of the invention the resident time of the microtitre plate in the drying zone is in the range of 15 seconds to 60 seconds. Preferably, the resident time of the microtitre plate in the drying zone is in the range of 20 seconds to 40 seconds. Advantageously, the resident time of the microtitre plate in the drying zone 15 is approximately 30 seconds.

In one embodiment of the invention the microtitre plate is conveyed through the drying tunnel on a continuously moving conveying means. Preferably, the conveying means comprises a conveying chain. Advantageously, a plurality of microtitre plates 20 are conveyed sequentially through the drying tunnel.

In one embodiment of the invention the rinsing medium is drained from each microtitre plate prior to drying.

In another embodiment of the invention the rinsing medium is initially removed from each microtitre plate by inverting the microtitre plate. Alternatively, the rinsing medium is initially removed from each microtitre plate by aspirating using a vacuum.

s In one embodiment of the invention the clinical diagnostic medium coated onto the surface of the microtitre plate is an antibody.

In another embodiment of the invention the clinical diagnostic medium coated onto the surface of the microtitre plate is an antigen.

In a further embodiment of the invention the rinsing medium to be evaporated from the coated surfaces of the microtitre plate is a buffer solution.

In a still further embodiment of the invention the buffer solution is a saltwater 5 solution.

Additionally the invention provides apparatus for drying a microtitre plate after the microtitre plate has been rinsed with a rinsing medium, the microtitre plate having a plurality of wells, the inner surfaces of which are coated with a clinical diagnostic 20 medium, the apparatus comprising a drying tunnel defining an elongated conveying path for accommodating the microtitre plate therethrough, a conveying means for conveying the microtitre plate along the conveying path, the drying tunnel having a drying zone, and a drying zone radiation source located in the drying zone for directing radiation at the coated surfaces of the microtitre plate for heating thereof,

and a control means for controlling the drying zone radiation source for heating the coated surfaces to a drying temperature insufficient to damage the clinical diagnostic medium coated on the coated surfaces, but sufficient for evaporating the rinsing medium from the coated surfaces, and for setting up air convection currents in the 5 wells for removing evaporate from the wells.

In one embodiment of the invention the drying zone radiation source is an infrared radiation source. Preferably, the infrared radiation emitted by the drying zone radiation source is of short wavelength. Advantageously, the wavelength of the lo infrared emitted by the drying zone radiation source is in the range of 1pm to 2pm.

Ideally, the wavelength of the infrared emitted by the drying zone radiation source is in the range of 1.2,um to 1.7'um.

In one embodiment of the invention the drying zone radiation source is located 5 above the conveying path.

In another embodiment of the invention a reflector is provided in the drying zone above the drying zone radiation source for reflecting and directing radiation emitted by the drying zone radiation source at the coated surfaces.

In a further embodiment of the invention a first cooling means is provided for cooling the reflector in the drying zone.

In one embodiment of the invention the reflector in the drying zone defines a lower

wall of a first cooling chamber and separates the drying zone from the first cooling chamber, and the first cooling means comprises a means for circulating a cooling medium within the first cooling chamber for cooling the reflector. Preferably, a cooling medium inlet and a cooling medium outlet are provided to and from, 5 respectively, the first cooling chamber for accommodating the cooling medium for cooling the reflector in the drying zone.

In one embodiment of the invention the drying zone radiation source comprises a plurality of spaced apart elongated radiation emitting tubes extending in a direction 0 parallel to the conveying path.

In another embodiment of the invention the control means comprises a temperature sensor for monitoring the temperature of the coated surfaces of the microtitre plate in the drying zone, the control means being responsive to the temperature sensor for 15 controlling the heat output of the drying zone radiation source.

In a further embodiment of the invention the temperature sensor comprises an optical pyrometer for contactless sensing of the coated surfaces of the microtitre plate. In a further embodiment of the invention the drying tunnel comprises a preheating zone upstream of and adjacent to the drying zone for preheating the microtitre plate to a preheating temperature prior to entering the drying zone, and the conveying means conveys the microtitre plate sequentially through the preheating and the

drying zones.

In one embodiment of the invention the temperature of the air in the preheating zone is maintained at a temperature not exceeding 80 C. Preferably, the temperature of 5 the air in the preheating zone is maintained at a temperature not exceeding 70 C.

In another embodiment of the invention a preheating zone radiation source is located in the preheating zone for directing radiation at the microtitre plate for preheating the microtitre plate. Preferably, the preheating zone radiation source is an infrared 10 radiation source. Advantageously, the infrared radiation emitted by the preheating zone radiation source is of short wavelength. Preferably, the wavelength of the infrared emitted by the preheating zone radiation source is in the range of 1,um to 2,um. Advantageously, the wavelength of the infrared emitted by the preheating zone radiation source is in the range of 1.2'um to 1.7,um.

In one embodiment of the invention the preheating zone radiation source is located above the conveying path. Preferably, a reflector is provided in the preheating zone above the preheating zone radiation source for reflecting and directing radiation emitted by the preheating zone radiation source at the coated surfaces.

20 Advantageously, a second cooling means is provided for cooling the reflector.

In one embodiment of the invention the reflector in the preheating zone defines a lower wall of a second cooling chamber above the reflector and separates the preheating zone from the second cooling chamber, and the second cooling means

comprises a means for circulating a cooling medium within the second cooling chamber for cooling the reflector. Preferably, a cooling medium inlet and a cooling medium outlet are provided to and from, respectively, the second cooling chamber for accommodating the cooling medium for cooling the reflector in the preheating 5 zone.

In another embodiment of the invention the preheating zone radiation source comprises a plurality of spaced apart elongated radiation emitting tubes extending in a direction parallel to the conveying path.

In one embodiment of the invention the conveying means comprises a chain conveyor. Preferably, a pair of spaced apart chain conveyors are provided for conveying the microtitre plate along the conveying path. Advantageously, the conveying means is adapted for conveying a plurality of microtitre plates sequentially through the drying tunnel.

In another embodiment of the invention a means for inverting the microtitre plate for initially draining the rinsing medium therefrom is provided upstream of the drying tunnel. Alternatively, a means for aspirating the microtitre plate for initially removing 20 rinsing medium therefrom is provided upstream of the drying tunnel.

In one embodiment of the invention an air circulating means is provided for passing air through the drying tunnel for transferring evaporate from the drying tunnel.

Preferably, the air passed through the drying tunnel is passed through the drying

zone and the preheating zone for transferring evaporate from the respective zones.

A microtitre plate coated with a clinical diagnostic medium having been dried by the method according to the invention.

s Additionally the invention provides a microtitre plate coated with a clinical diagnostic medium having been dried by apparatus according to the invention.

Further the invention provides a microtitre plate coated with a clinical diagnostic lo medium having been dried by the method according to the invention and by the apparatus according to the invention.

The invention also provides a microtitre plate defining a surface coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried IS by the method according to the invention.

The invention further provides a microtitre plate defining a surface coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried by the apparatus according to the invention.

The invention also provides a microtitre plate coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried by the method according to the invention and by the apparatus according to the invention.

The invention will be more clearly understood from the following description of a

preferred embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: 5 Fig. 1 is a side elevational view of apparatus according to the invention for drying microtitre plates having been coated with a clinical diagnostic medium and subsequently rinsed, Fig. 2 is a partly cross-sectional end elevational view of the apparatus of Fig. 10 1, Fig. 3 is a transverse cross-sectional side elevational view of the apparatus of Fig. 1 on the line lil-lil of Fig. 2, 15 Fig. 4 is a block representation of a circuit diagram of the apparatus of Fig. 1, and Fig. 5 is a perspective view of microtitre plates in a frame of the type for which the apparatus of Fig. 1 is suitable for drying.

_ Referring to the drawings, there is illustrated apparatus according to the invention indicated generally by the reference numeral 1 which comprises a drying tunnel 2 for drying microtitre plates 3 arranged in a matrix 4 on a frame 5. The microtitre plates 3 will be well known to those skilled in the art, however, before describing the

apparatus 1 in detail, the relevant aspects of the microtitre plates 3 will first be described with reference to Fig. 5.

The microtitre plates 3 are formed with a plurality of receptacles 8 which define 5 respective wells 9 which in turn define an inner surface 10 which is coated with a clinical diagnostic medium, for example, an antibody or an antigen. The receptacles 8 are of a plastics material which is of a type which promotes adhesion of the antibody or antigen to the inner surface 10 of the wells 9. A carrier bracket 12 also of plastics material carries eight receptacles in line, and twelve carrier brackets 12 0 are accommodated in the frame 5, thereby providing an eight- by-twelve matrix of wells 9 in each frame 5.

The antibody or antigen in a carrier liquid medium is delivered into the wells 9, and allowed to bond to the inner surface 10. After a period of time when sufficient antibody or antigen has adhered to the inner surface 10, the carrier liquid and excess antibody or antigen is then discharged from the respective wells 9 by inverting the frame 5 or aspiration using vacuum. In order to remove any remaining carrier liquid and unattached antibodies or antigens, the wells 9 are subjected to a number of rinses with a rinsing medium, in general, a buffer solution, and typically a 20 salt/water rinse solution. After each rinse the frame 5 is inverted for discharging the rinsing medium from the wells 9, which is not retained by surface tension.

Alternatively, the rinsing medium which is not retained by surface tension can be removed by subjecting the frames 5 to a vacuum for aspiration thereof. After the last rinse and discharge of the rinsing medium by inverting the frames 5 of microtitre

plates 3, or by aspiration of the frames 5, the frames 5 of microtitre plates 3 are dried in the apparatus 1 by evaporating any remaining rinsing medium which is retained on the inner surface 10 of the wells 9 as a result of surface tension. After drying in the apparatus 1, the frames 5 of microtitre plates 3 are packaged in appropriate foil s pouches.

Retuming now to the apparatus 1 and referring in particular to Figs. 1 to 3, the apparatus 1 comprises an elongated main housing 20 which defines the drying tunnel 2, and which is supported on a support housing 6. The housing 20 comprises to a base 21, a pair of upstanding side walls 22 extending upwardly from the base 21, and a top wall 23 joining the side walls 22. End walls 24 extend downwardly from the top wall 23 between the side walls 22 at respective opposite ends of the housing 20 and terminate in lower edges 31 which define with the side walls 22 an upstream opening 25 to the drying tunnel 2 through which microtitre plates 3 are delivered into the drying tunnel 2, and a downstream opening 26 from the drying tunnel 2 through which the microtitre plates 3 on the frames 5 are delivered from the drying tunnel 2 :c will he, rlcr.rihr' hollow A conveying means comprising a pair of spaced apart endless conveying chains 28 20 extend parallel to each other through the drying tunnel 2 for conveying the frames 5 of microtitre plates 3 along a conveying path 27 from the upstream opening 25 to the downstream opening 26. The respective conveying chains 28 are carried on drive sprockets 29 located at the downstream end of the tunnel 2, and idler sprockets 30 located at the upstream end thereof. The drive sprockets 29 are rigidly carried on a

drive shaft 32, and the idler sprockets 30 are rigidly carried on an idler shaft 33.

Bearings 34 in the side walls 22 rotatably carry the shafts 32 and 33.

A drive means comprising an electrically powered drive motor 35 drives the drive s shaft 32 for driving the conveying chains 28 through the drive sprockets 29. A chain and sprocket drive 37 is provided between the drive motor 35 and the drive shaft 32 for transmitting drive between the drive motor 35 and the drive sprockets 29.

Lugs 38 are carried on some of the links of the conveying chains 28 at 0 predetermined spaced apart intervals for engaging the frames 5 carrying the microtitre plates 3 for conveying the microtitre plates 3 along the conveying path 27 through the drying tunnel 2. An in-feed chute 39 is provided for delivering the frames 5 with the microtitre plates 3 onto the conveying chains 28 through the upstream opening 25, and an out-feed chute 40 delivers the frames 5 of the dried microtitre plates 3 from the conveying chains 28.

The drying tunnel 2 defines a drying zone 42 in which the microtitre plates 3 are dried, and a preheating zone 43 upstream of the drying zone 42 within which the microtitre plates 3 are preheated prior to entering the drying zone 42. The preheating 20 zone 43 extends a distance A along the drying tunnel 2, while the drying zone 42 extends a distance B along the drying tunnel 2. The length B of the drying zone 42 is approximately twice the length A of the preheating zone 43.

A drying zone radiation source provided by a plurality of drying zone infrared tubes

44 are located in the drying zone 42 for directing infrared radiation downwardly towards the microtitre plates 3 as they are being conveyed through the drying zone 42 by the conveying chain 28 for drying the microtitre plates 3. A preheating zone radiation source provided by a plurality of preheating zone infrared radiation tubes 5 45 are located in the preheating zone 43 for directing infrared radiation downwardly at the microtitre plates 3 as they are being conveyed by the conveying chain 28 through the preheating zone 43 for raising the temperature of the microtitre plates 3 to a preheating temperature of approximately 45 C so that the microtitre plates enter the drying zone 42 at the preheating temperature.

The infrared tubes 44 and 45 in the respective drying and preheating zones 42 and 43 are carried on electrical holder connectors 26, which are in turn carried on and extend downwardly from a reflector 47. In this embodiment of the invention six infrared tubes 44 are provided in the drying zone 42, and three infrared tubes 45 are 15 provided in the preheating zone 43. The infrared tubes 44 in the drying zone 42 are arranged in two groups, each group comprising three spaced apart infrared tubes 44 extending parallel to each other and longitudinally of the drying tunnel 2. The infrared tubes 45 in the preheating zone 43 are arranged in one group of three which are parallel to and spaced apart from each other and extend longitudinally of the JO drying tunnel 2. Cables (not shown) extend from the holder connectors 46 to a control circuit 50 illustrated in block representation in Fig.4, as will be described below. The reflector 47 extends the length of the drying tunnel 2 between the respective

end walls 24 and between the side walls 22. Intermediate partition walls 54 extend downwardly from the top wall 23 and between the side wall 22 for supporting the reflector 47. The reflector 47 is shaped to form three longitudinally extending reflector portions 52 of arcuate transverse cross-section for reflecting infrared light 5 from the corresponding infrared tubes 44 and 45 downwardly onto the microtitre plates 3. The reflector 47 defines with the side walls 22, the top wall 23, the end walls 24 and the intermediate partition walls 54 two first cooling chambers 55 and one second cooling chamber 56 for cooling the reflector 47. The two first cooling chambers 55 are located above the drying zone 42, while the second cooling 10 chamber 56 is located above the preheating zone 43. First and second cooling means for cooling the reflector 47 comprise a cooling fan 59 which circulates air through the first and second cooling chambers 55 and 56. Ducts 57 from air outlets 53 connect the first and second cooling chambers 55 and 56 to the fan 59 which draws air from the cooling chambers 55 and 56 for in turn drawing ambient air into 15 the cooling chambers 55 and 56 through respective air inlets 58 in the top wall 23.

Two air inlets 58 are provided to each of the f ret and second cooling chamber 55 and 56. By cooling the reflector 47 discoloration of the reflector 47 is avoided, and thereby maximum efficiency of the drying tunnel is achieved.

20 An air circulating means comprising an air blower 61 is located in the support housing 6 beneath the tunnel 2, and delivers ambient air into the tunnel 2 through a duct 65 beneath the conveying chain 28. The duct 65 terminates in an outlet 66 through which the air is delivered into the tunnel 2 and is passed through the tunnel 2 in both upstream and downstream directions, namely, in the direction of the arrows

C, both under and over the microtitre plates 3 on the conveying chains 28 for removing evaporate from the tunnel 2. The air from the air blower 61 on passing through the drying zone 42 exits through the downstream opening 26, and the air from the air blower 61 on passing through the preheating zone 43 exits through the s upstream opening 25.

An optical pyrometer 60 located in the drying zone 42 monitors the temperature of the microtitre plates 3. The output of the optical pyrometer 60 is read by the control circuit 50 for in turn controlling the radiation output of the infrared tubes 44 in the 10 drying zone 42. In this embodiment of the invention the control circuit 50 controls the infrared radiation output of the infrared tubes 44 in the drying zone 42 so that the temperature of the coated surfaces 10 of the wells 9 of the microtitre plates 3 does not exceed a drying temperature of approximately 45 C, in order to avoid deterioration of the antibody or antigen coated onto the surfaces 10, and preferably, the drying temperature of the coated surfaces 10 of the microtitre plates 3 is maintained in the range of 40 C to 42 C.

A temperature sensor 62 in the preheating zone 43 monitors the air temperature in the zone 43. The control circuit 50 reads the output from the temperature sensor 62 20 for controlling the infrared radiation output of the infrared radiation tubes 45 in the preheating zone 43 for maintaining the air temperature in the preheating zone 43 at a temperature of anoroximateiY 70 C.

., The infrared tubes 44 and 45 in the drying zone 42 and the preheating zone 43,

respectively, are chosen to emit infrared radiation in the medium wave spectrum of wavelength in the range of 1.2 to 1.5 microns. It has been found that infrared radiation within this wavelength band has minimalheating effect on the air medium through which the infrared radiation passes, and only heats surfaces with which it 5 comes in contact. Thus, by directing the infrared radiation by the arcuate portions 52 of the reflector 47 onto the microtitre plates 3, only the surfaces of the microtitre plates 3 on which the infrared radiation impinges are heated. Thus, controlled heating of the microtitre plates 3, and in particular controlled heating of the surfaces 10 of the wells 9 which are coated with the antibody or antigen, can be achieved. By 0 monitoring the temperature of the microtitre plates 3 in the drying zone 42, the temperature of the microtitre plates can be controlled within tight tolerances.

The drive motor 35 drives the conveying chains 28 at a constant speed for in turn conveying the microtitre plates 3 through the drying tunnel 2 at a constant speed so 15 that the resident time of each microtitre plate 3 in the preheating zone 43 is approximately 15 seconds, and the resident time in the drying zone 42 is approximately 30 seconds. Thus, the total resident time spent by each microtitre plate 3 in the drying tunnel from the upstream opening 25 to the downstream opening 26 is approximately 45 seconds. However, in certain cases, it may be 20 necessary to increase or decrease the resident times spent by each microtitre plate in the respective preheating and drying zones 42 and 43. This is achieved by reducing the speed of the drive motor 35 for in turn reducing the speed of the conveying chain 28. However, in general, it is envisaged that a resident time of up to 23 seconds in the preheating zone may be required and a resident time of up to

HA 53 seconds in the drying zone may be required, thus giving a maximum resident time of each microtitre plate 3 through the preheating and drying zones of approximately 76 seconds. Although, in general, a maximum resident time in excess of 60 seconds should not be required.

s The control circuit 50 is housed in the support housing 6. Control panels 64 on the support housing 6 facilitate selecting the speed of the motor 35. Upper and lower set point temperatures within which the drying temperature is to be maintained by the optical pyrometer 60, and upper and lower set point temperatures at which the to air temperature within the preheating zone 43 is to be maintained by the temperature sensor 62 are selected and entered through the control panels 64. The flow rate of air through the air blower 61, and the fan speeds of the fan 59, are also selected and entered through the control panels 64.

15 In use, when steady state temperature conditions have been established in the drying tunnel 2, the drive motor 35 is operated at the selected constant speed for in, turn operating the conveying chains 28 also at constant speed. Steady state conditions are established when the air temperature in the preheating zone 43 is at a temperature of approximately 70 C. Frames 5 of microtitre plates 3 are then, 20 delivered and fed from the in-feed chute 39 onto the conveying chains 28 where they are conveyed through the preheating zone 43, and in turn the drying zone 42 and outputted on the out-feed chute 40. As discussed above, the conveying chains 28 are operated at a speed so that the resident time of each microtitre plate 3 in the preheating zone 43 is approximately 15 seconds and in the drying zone 42 is

approximately 30 seconds. The control circuit 50 controls the infrared tubes 45 for maintaining the air temperature in the preheating zone at approximately 70 C and for maintaining the temperature of the microtitre plates 3 at a drying temperature in the range of 40 C to 42 C in the drying zone 42 for evaporating the rinsing medium.

5 Evaporate from the microtitre plates 3 is exhausted from the drying zone 42 and the preheating zone 43 of the tunnel 2 by the air from the air blower 61.

Prior to placing the frames 5 of microtitre plates 3 in the apparatus 1 the frames 5 of microtitre plates 3 are subjected to a number of rinses with the rinsing medium. After lo each rinse the frames 5 of microtitre plates 3 are placed in a means for inverting the frames for discharging rinsing medium which is not retained on the microtitre plates 3 by surface tension. The inverting means typically is provided by a jig which is pivotally mounted for pivoting the frames of microtitre plates through 180 from a position with the wells 9 of the microtitre plates 3 facing upwardly for rinsing, to a position with the wells 9 of the microtitre plates 3 facing downwardly for discharging the rinsing medium therefrom. Alternatively, the rinsing medium which is removable by virtue of not being retained by surface tension on the microtitre plates may be removed by subjecting the frames 5 of microtitre plates 3 to a vacuum for aspiration thereof. It has been found that by virtue of the fact that the resident time of the microtitre plates 3 in the drying zone 42 is in the order of 30 seconds, the temperature of the microtitre plates 3 can be allowed to rise to a temperature of up to 45 C plus or minus 2 C or 3 C without damage to the antibody, antigen or other clinical diagnostic

coating on the microtitre plates. By heating the microtitre plates 3 to a temperature of approximately 45 C the rinsing medium is effectively flash dried without damaging the clinical diagnostic coating on the microtitre plates. With the microtitre plates at a temperature of approximately 45 C microconvection hot air currents are generated 5 within the wells, which effectively flash dry the rinsing medium from the wells 9.

It has also been found that by monitoring the temperature of the microtitre plates in the drying zone is sufficient for avoiding any danger of the temperature of the microtitre plates rising above a temperature which could lead to damage to the 0 clinical diagnostic coated on the microtitre plates. Additionally, while the infrared tubes 44 and 45 have minimal heating effect on the air within the drying and preheating zones, the infrared radiation from the infrared tubes 44 and 45 do heat components within the drying tunnel and the walls of the drying tunnel, which in turn transfer heat to the air within the drying tunnel. It is important that the air temperature should not be permitted to rise to a level which could cause heat transfer from the air within the drying tunnel to raise the temperature of the coated surfaces of the microtitre plate to a level at which the clinical diagnostic coating would be damaged. This is achieved by monitoring the air temperature in the preheating zone by the temperature sensor 62, and it has been found that once the 20 air temperature within the preheating zone is maintained at a temperature which does not exceed 70 C, damage to the clinical diagnostic coating on the microtitre plates is avoided.

The advantages of the invention are many. By virtue of the fact that the total time

spent by each microtitre plate 3 in the drying tunnel 2 is 45 seconds, and does not exceed 76 seconds, the drying time for evaporating the rinsing medium and drying the microtitre plates 3 is reduced from approximately one day to approximately 60 seconds. This thereby reduces the process cycle time for producing the antibody or s antigen coated microtitre plates from approximately three days to approximately two days.

Claims

1. A method for drying a microtitre plate after the microtitre plate has been rinsed with a rinsing medium, the microtitre plate having a plurality of wells formed 5 therein, the inner surfaces of which are coated with a clinical diagnostic medium, the method comprising the step of directing radiation at the coated surfaces for heating the coated surfaces to a drying temperature insufficient to damage the clinical diagnostic medium coated thereon, but sufficient for evaporating the rinsing medium from the coated surfaces, and for setting up air convection currents within the wells 10 for removing evaporate from the wells.

2. A method as claimed in Claim 1 in which the radiation which is directed

towards the coated surfaces of the microtitre plate during drying is infrared radiation.

15

3. A method as claimed in Claim 2 in which the infrared radiation which is directed towards the coated surfaces of the microtitre plate during drying is of short wavelength.

4. A method as claimed in Claim 2 or 3 in which the wavelength of the infrared 20 radiation which is directed towards the coated surfaces of the microtitre plate during drying lies in the range of 1 am to 2,um.

5. A method as claimed in Claim 2 or 4 in which the wavelength of the infrared radiation which is directed towards the coated surfaces of the microtitre plate during

2s drying is in the range of 1.2'um to 1.7.um.

6. A method as claimed in any preceding claim in which the drying temperature to which the coated surfaces are heated does not exceed 50 C.

7. A method as claimed in Claim 6 in which the drying temperature to which the coated surfaces are heated does not exceed 42 C.

8. A method as claimed in Claim 7 in which the drying temperature to which the 0 coated surfaces are heated does not exceed 40 C.

9. A method as claimed in Claim 8 in which the drying temperature to which the coated surfaces are heated lies in the range of 38 C to 42 C.

5

10. A method as claimed in Claim 9 in which the drying temperature lies in the range of 40 C to 42 C.

11. A method as claimed in any of Claims 6 to 10 in which the coated surfaces of the microtitre plate are maintained at the drying temperature for a drying time in the 20 range of 20 seconds to 40 seconds.

12. A method as claimed in Claim 11 in which the drying time is approximately 30 seconds.

13. A method as claimed in any preceding claim in which the microtitre plate is preheated prior to drying, the coated surfaces of the microtitre plate being heated to a preheating temperature during preheating.

s

14. A method as claimed in Claim 13 in which the microtitre plate is heated during preheating by directing radiation at the coated surfaces for raising the temperature of the coated surfaces to the preheating temperature.

15. A method as claimed in Claim 14 in which the radiation which is directed 10 towards the coated surfaces of the microtitre plate during preheating is infrared radiation.

16. A method as claimed in Claim 15 in which the infrared radiation which is directed towards the coated surfaces of the microtitre plate during preheating is of 15 short wavelength.

17. A method as claimed in Claim 15 or 16 in which the wavelength of the infrared radiation directed towards the coated surfaces of the microtitre plate during preheating lies in the range of 1,um to alum.

_

18. A method as claimed in Claim 17 in which the wavelength of the infrared radiation directed towards the coated surfaces of the microtitre plate during i preheating lies in the range of 1.2pm to 1.7,um.

19. A method as claimed in any of Claims 14 to 18 in which the microtitre plate is passed through a drying tunnel, and the radiation is directed at the coated surfaces as the microtitre plate passes through the drying tunnel.

s

20. A method as claimed in Claim 19 in which the microtitre plate is passed through the drying tunnel at substantially constant speed.

21. A method as claimed in Claim 19 or 20 in which the drying tunnel comprises a preheating zone in which the microtitre plate is preheated and a drying zone in 0 which the microtitre plate is dried, the microtitre plate being passed sequentially through the respective zones from the preheating zone to the drying zone.

22. A method as claimed in Claim 21 in which the air temperature in the preheating zone is maintained at a temperature not exceeding 80 C.

23. A method as claimed in Claim 22 in which the air temperature in the preheating zone is maintained at a temperature not exceeding 70 C.

24. A method as claimed in any of Claims 21 to 23 in which the resident time of 20 the microtitre plate in the preheating zone is in the range of 10 seconds to 20 seconds.

25. A method as claimed in Claim 24 in which the resident time of the microtitre plate in the preheating zone is approximately 15 seconds.

26. A method as claimed in any of Claims 19 to 25 in which the resident time of the microtitre plate in the drying zone is in the range of 15 seconds to 60 seconds.

5

27. A method as claimed in Claim 26 in which the resident time of the microtitre plate in the drying zone is in the range of 20 seconds to 40 seconds.

28. A method as claimed in Claim 27 in which the resident time of the microtitre plate in the drying zone is approximately 30 seconds.

29. A method as claimed in any of Claims 19 to 28 in which the microtitre plate is conveyed through the drying tunnel on a continuously moving conveying means.

30. A method as claimed in Claim 29 in which the conveying means comprises a 15 conveying chain.

31. A method as claimed in any of Claims 19 to 30 in which a plurality of microtitre plates are conveyed sequentially through the drying tunnel.

20

32. A method as claimed in any preceding claim in which the rinsing medium is drained from each microtitre plate prior to drying.

33. A method as claimed in Claim 32 in which the rinsing medium is initially removed from each microtitre plate by inverting the microtitre plate.

34. A method as claimed in Claim 32 in which the rinsing medium is initially removed from each microtitre plate by aspirating using a vacuum.

5

35. A method as claimed in any preceding claim in which the clinical diagnostic medium coated onto the surface of the microtitre plate is an antibody.

36. A method as claimed in any preceding claim in which the clinical diagnostic medium coated onto the surface of the microtitre plate is an antigen.

37. A method as claimed in any preceding claim in which the rinsing medium to be evaporated from the coated surfaces of the microtitre plate is a buffer solution.

38. A method as claimed in Claim 36 in which the buffer solution is a saiVwater 5 solution.

39. A method for drying a microtitre plate having a surface coated with a clinical diagnostic medium, after the coated surface has been rinsed with a rinsing medium, the method being substantially as described herein with reference to and as 20 illustrated in the accompanying drawings.

40. Apparatus for drying a microtitre plate after the microtitre plate has been rinsed with a rinsing medium, the microtitre plate having a plurality of wells, the inner surfaces of which are coated with a clinical diagnostic medium, the apparatus

comprising a drying tunnel defining an elongated conveying path for accommodating the microtitre plate therethrough, a conveying means for conveying the microtitre plate along the conveying path, the drying tunnel having a drying zone, and a drying zone radiation source located in the drying zone for directing radiation at the coated s surfaces of the microtitre plate for heating thereof, and a control means for controlling the drying zone radiation source for heating the coated surfaces to a drying temperature insufficient to damage the clinical diagnostic medium coated on the coated surfaces, but sufficient for evaporating the rinsing medium from the coated surfaces, and for setting up air convection currents in the wells for removing 0 evaporate from the wells.

41. Apparatus as claimed in Claim 40 in which the drying zone radiation source is an infrared radiation source.

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42. Apparatus as claimed in Claim 41 in which the infrared radiation emitted by the drying zone radiation source is of short wavelength.

43. Apparatus as claimed in Claim 41 or 42 in which the wavelength of the infrared emitted by the drying zone radiation source is in the range of Mum to 2pm.

44. Apparatus as claimed in Claim 43 in which the wavelength of the infrared emitted by the drying zone radiation source is in the range of 1. 2pm to 1.7,um.

45. Apparatus as claimed in any of Claims 40 to 44 in which the drying zone

- radiation source is located above the conveying path.

46. Apparatus as claimed in Claim 45 in which a reflector is provided in the drying zone above the drying zone radiation source for reflecting and directing 5 radiation emitted by the drying zone radiation source at the coated surfaces.

47. Apparatus as claimed in Claim 46 in which a first cooling means is provided for cooling the reflector in the drying zone.

0

48. Apparatus as claimed in Claim 47 in which the reflector in the drying zone defines a lower wall of a first cooling chamber and separates the drying zone from the first cooling chamber, and the first cooling means comprises a means for circulating a cooling medium within the first cooling chamber for cooling the reflector.

15

49. Apparatus as claimed in Claim 48 in which a cooling medium inlet and a cooling medium outlet are provided to and from, respectively, the first cooling chamber for accommodating the cooling medium for cooling the reflector in the drying zone.

20

50. Apparatus as claimed in any of Claims 40 to 49 in which the drying zone radiation source comprises a plurality of spaced apart elongated radiation emitting tubes extending in a direction parallel to the conveying path.

51. Apparatus as claimed in any of Claims 40 to 50 in which the control means

comprises a temperature sensor for monitoring the temperature of the coated surfaces of the microtitre plate in the drying zone, the control means being responsive to the temperature sensor for controlling the heat output of the drying zone radiation source.

52. Apparatus as claimed in Claim 51 in which the temperature sensor comprises an optical pyrometer for contactless sensing of the coated surfaces of the microtitre plate. to

53. Apparatus as claimed in any of Claims 40 to 52 in which the drying tunnel comprises a preheating zone upstream of and adjacent to the drying zone for preheating the microtitre plate to a preheating temperature prior to entering the drying zone, and the conveying means conveys the microtitre plate sequentially through the preheating and the drying zones.

54. Apparatus as claimed in Claim 53 in which the temperature of the air in the preheating zone is maintained at a temperature not exceeding 80 C.

55. Apparatus as claimed in Claim 54 in which the temperature of the air in the 20 preheating zone is maintained at a temperature not exceeding 70 C.

56. Apparatus as claimed in any of Claims 53 to 55 in which a preheating zone radiation source is located in the preheating zone for directing radiation at the microtitre plate for preheating the microtitre plate.

57. Apparatus as claimed in Claim 56 in which the preheating zone radiation source is an infrared radiation source.

s

58. Apparatus as claimed in Claim 57 in which the infrared radiation emitted by the preheating zone radiation source is of short wavelength.

59. Apparatus as claimed in Claim 57 or 58 in which the wavelength of the infrared emitted by the preheating zone radiation source is in the range of 1,um to 10 2,um.

60. Apparatus as claimed in Claim 59 in which the wavelength of the infrared emitted by the preheating zone radiation source is in the range of 1.2'um to 1.7,um.

15

61. Apparatus as claimed in any of Claims 56 to 60 in which the preheating zone radiation source is located above the conveying path.

62. Apparatus as claimed in Claim 61 in which a reflector is provided in the preheating zone above the preheating zone radiation source for reflecting and 20 directing radiation emitted by the preheating zone radiation source at the coated surfaces.

63. Apparatus as claimed in Claim 62 in which a second cooling means is provided for cooling the reflector.

64. Apparatus as claimed in Claim 63 in which the reflector in the preheating zone defines a lower wall of a second cooling chamber above the reflector and separates the preheating zone from the second cooling chamber, and the second s cooling means comprises a means for circulating a cooling medium within the second cooling chamber for cooling the reflector.

65. Apparatus as claimed in Claim 64 in which a cooling medium inlet and a cooling medium outlet are provided to and from, respectively, the second cooling lo chamber for accommodating the cooling medium for cooling the reflector in the preheating zone.

66. Apparatus as claimed in any of Claims 56 to 65 in which the preheating zone radiation source comprises a plurality of spaced apart elongated radiation emitting 15 tubes extending in a direction parallel to the conveying path.

67. Apparatus as claimed in any of Claims 40 to 66 in which the conveying means comprises a chain conveyor.

20

68. Apparatus as claimed in Claim 67 in which a pair of spaced apart chain conveyors are provided for conveying the microtitre plate along the conveying path.

69. Apparatus as claimed in any of Claims 40 to 68 in which the conveying! means is adapted for conveying a plurality of microtitre plates sequentially through

the drying tunnel.

70. Apparatus as claimed in any of Claims 40 to 69 in which a means for inverting the microtitre plate for initially draining the rinsing medium therefrom is 5 provided upstream of the drying tunnel.

71. Apparatus as claimed in any of Claims 40 to 69 in which a means for aspirating the microtitre plate for initially removing rinsing medium therefrom is provided upstream of the drying tunnel.

72. Apparatus as claimed in any of Claims 40 to 72 in which an air circulating means is provided for passing air through the drying tunnel for transferring evaporate from the drying tunnel.

15

73. Apparatus as claimed in Claim 72 in which the air passed through the drying tunnel is passed through the drying zone and the preheating zone for transferring evaporate from the respective zones.

74. Apparatus for drying a microtitre plate having a surface coated with a clinical 20 diagnostic medium after the coated surface has been rinsed with a rinsing medium, the apparatus being substantially as described herein with reference to and as illustrated in the accompanying drawings.

75. A microtitre plate coated with a clinical diagnostic medium having been dried

by the method as claimed in any of Claims 1 to 39.

76. A microtitre plate coated with a clinical diagnostic medium having been dried by the apparatus as claimed in any of Claims 40 to 74. i

77. A microtitre plate coated with a clinical diagnostic medium having been dried by the method as claimed in any of Claims 1 to 39 and the apparatus as claimed in any of Claims 40 to 74.

0

78. A microtitre plate defining a surface coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried by the method as claimed in any of Claims 1 to 39.

79. A microtitre plate defining a surface coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried by the apparatus as claimed in any of Claims 40 to 74.

80. Microtitre plates coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and having been dried by the method as claimed in any of 20 Claims 1 to 38 and the apparatus as claimed in any of Claims 40 to 74.

81. A microtitre plate defining a surface coated with a clinical diagnostic medium having been rinsed with a rinsing medium, and dried by the method as claimed in any of Claims 1 to 39, the microtitre plate being substantially as described herein

with reference to and as illustrated in the accompanying drawings.