SAMPLE PLATE LIQUID SCINTILLATION COUNTER

Abstract: The present invention shows a new apparatus in the field of the liquid scintillation counting. The apparatus counts liquid scintillation of corresponding samples directly from the sample plates (10) which comprise several separate sample wells (11) or vials. The apparatus has one or several detectors in order to count one or several samples at a time. The sample plate (10) is placed in the counting position or before the counting position manually or automatically on a rigid plate holder (12) made of photon attenuating material and having holes (13) for the wells of the sample plate (10). The walls (17) of the holes are reflecting or scattering in order to guide the photons from the liquid scintillation sample (16) to the detectors, built of two photomultiplier tubes (14) operating in coincidence and situated on the opposite sides of the holes of the plate holder. The wells of the sample plate can be closed by an adhesive transparent tape (15). The apparatus can be used also for counting gamma radiation emitting samples if the holes of the sample plate are surrounded by gamma radiation sensitive detectors (19).

Description: SAMPLE PLATE LIQUID SCINTILLATION COUNTER BACKGROUND OF THE INVENTION Liquid scintillation counters are mainly used for measuring lo energy beta radiation emitting samples, which are of, for exampl biological or medical interest. The conventional liqu scintillation counters are designed to count samples which are the sample vials with the scintillation liquid. The volume of t sample vial is typically 6 or 20 milliliters. The sample vials a placed into sample racks, which have separate compartments f individual sample vials. The sample racks are placed on the convey of the automatic sample changer system of the counter. Because the above mentioned liquid scintillation counter is design to count vials, whose volume is up to 20 milliliters, serio difficulties are encountered, when the sample volume is a only f hundred microliter or less. Typically, this kind of samples a prepared in small vials, which are inserted into normal vials. addition, the handling of separate sample vials is very ti consuming and includes potential risk of setting the sample vials incorrect order into the sample racks. The sample changi mechanism of such an instrument is also rather complicated, becau the vial must be removed from the sample rack and must be position into a light tight radiation detection chamber, and after counti it must be returned back into the sample rack. In addition to the above mentioned conventional liquid scintillati counters one special purpose liquid scintillation counter exist namely 1205 Betaplate, which is manufactured by Wallac Oy, Finlan This instrument is designed to count liquid scintillation sampl directly from a filter mat, which is sealed into a plastic bag wi a small amount of scintillation liquid. On the same filter mat c be up to 96 samples and six samples are counted at a time. SUMMARY OF THE INVENTION The present invention shows a new apparatus which counts liqu scintillation or corresponding samples directly from the samp plates which comprises several separate sample wells or vials. typical plate of this kind is produced by a vacuum thermoformi process (deep drawing) from transparent material and has eight ro of wells arranged in twelve columns. The typical volume of t sample wells of such a 96-well sample plate is 200 - 4 microliters . Another this type of plate has four rows of wel arranged in six columns. The volume of the wells of such a 24-we sample plate exceeds one milliliter. In addition, sample plates wi two rows of wells arranged in three columns are available. T volume of the wells of such a 6-well sample plate is about milliliters. Thus the apparatus according to the present inventi is designed to count samples (including liquid scintillant) , t volume of which is from a few microliters up to ten milliliters. BRIEF DESCRIPTION OF THE DRAWINGS The apparatus according to the present invention will be describe in detail with reference to the attached drawings, wherein Figure 1 is a perspective view of the general principle of th apparatus according to the present invention. Figure 2 shows a vertical section of the counting conditions. Figure 3a shows a vertical section of the counting conditions, whe the plate holder is equipped with gamma radiation sensiti detectors. Figure 3b shows a section along the line A-A in Figure 3a. DESCRIPTION OF THE PREFERRED EMBODIMENTS In Figure 1 a sample plate (10), which has several sample wells ( is placed in the counting position or before the counting posit manually or automatically on a rigid plate holder (12) ,made of p attenuating material and having holes (13) for the wells of the s plate. In order to count one or several samples at a time, t apparatus has one or several detectors, built of two photomultipli tubes (14) working in coincidence and are situated on the opp sides of the plate holder (12). The apparatus has a mechanism, ( is not shown here),which presses said photomultiplier tubes in t down position tightly against said sample plate in order to form optically closed system with the sample plate well (11) and allow the up position free horizontal movement of said sample plate . The plate holder (12) can be a separate part or it can be fixed wi the photomultiplier tubes (14) which are beneath the sample pla (10). In this case the plate holder needs to surround only tho sample plate wells which are in that time in the counting positi defined by the photomultiplier tube pairs. Figure 2 shows a vertical section of the counting conditions. T wells (11) of the sample plate are closed by a transparent adhesi tape (15).The plate holder (12) has three different functions: 1) be a rigid support for the flexible sample plate (10), 2) separate optically the different sample wells (11) of the samp plate and thus to make it possible to count samples directly fr sample wells without cross talk between the samples and 3) to gui the photons from the liquid scintillation sample (16) to t photomultiplier tubes (1 ) . Thus the material of the plate hold must reflect or scatter light or the walls of the holes must coated by reflecting or scattering material ( 17 ) . The apparatus h in the front of the photomultiplier tubes changeable plates (18) f the different sample well diameters of the 96, 24 or 6 well samp plates . Figures 3a and 3b show that the apparatus according to the pres invention can be used also for counting gamma radiation emitti samples (20).The sample plate (10) with separate sample wells o vials (11), is placed in the counting position or before th counting position manually or automatically in a plate holder ( 12) whose holes are surrounded by gamma radiation sensitive detector (19). The body (12) of the sample holder can be made of materia which absorbs gamma radiation as much as possible. The walls (21) o the cylindrical gamma sensitive detectors (19) are reflecting s that the photons originating from the scintillation process followe by the absorption of the gamma radiation are guided to th photomultiplier tube pair working in coincidence and situated o the opposite sides of the holes of the plate holder. Instead of th detectors compraising two photomultiplier tubes, also on photomultiplier tube is possible. In this case there is a reflectin surface (22) in the bottom end of the cylindrical gamma sensitiv detectors (19) in order to reflect photons towards to th photomultiplier tube. The invention is not confined to the above embodiments alone, but it may show even considerable variation within the scope of the patent claims.

Claims: WHAT IS CLAIMED IS: 1. Apparatus for the counting of liquid scintillation samples f sample plates which comprise several separate sample wells vials, characterized in that - the apparatus has one or several sample plate holders for sample plates,and said sample plate holders are provided with ho for the wells of the sample plates, - the sample plate is placed on the sample plate holder so that wells of the sample plate are inserted in the holes of the sam plate holder so that the sample plate holder form optically separ compartments around the wells of the sample plate, - the sample plate holder is moved together with the sample pl one at a time manually or automatically in to the counting posit between two photomultiplier tubes which together form the detec of the apparatus, and which two photomultiplier tubes work coincidence and are situated exactly on the opposite sides of t well of the sample plate which in that time will be counted, - the inner surfaces of said holes of the sample plate holders reflective or scattering in order to guide the light from the liq scintillation sample which is in the sample well to s photomultiplier tube pair, - the apparatus has one or several detectors in order to count or several samples at a time. 2. Apparatus according to claim 1, characterized in that the we of the sample plate are closed by a transparent adhesive tape. 3. Apparatus according to claim 1, characterized in that the hol of the plate holder are surrounded by gamma radiation sensiti detectors in order to make the apparatus suitable for gamma count

Inventors: LEHTINEN KAUKO, SONNE VESA, YRJOENEN TAPIO, LEHTINEN, KAUKO, SONNE, VESA, YRJOENEN, TAPIO
Applicants: PHARMACIA AB, WALLAC OY
Application year: 1989
Main classification: G01T1
IPC codes: G01N21, G01T1, G01T7