IL34427A - Container for reagents or analytical samples - Google Patents

Description

Container for reagents or analytical samples This invention is concerned with a container primarily for reagents or analytical samples which are to. be subjected to optical measurements.

In recent years, analytical chemistry has rapidly developed in two main directions. Firstly, automatic analysing machines and machines which automatically perform the complicated operations of preparing analytical, samples have been developed. Secondly, simple methods and techniques have been devised to enable unskilled operators .to carry out reliable analyses. These developments apply particularly to photometric measurements, which often merely involve mixing a measured quantity of sample with a measured volume of, reagent and pouring it into the measuring cell of a photometer.

A number of attempts have been made to simplify the steps in the process of photometric measurement and to save the analyst as much work as possible by using mechanically prepared reagents in suitable forms. For example, the required volume of a reagent solution needed for a deter-' mination is packed in 'an individual small bottle ready for use by the analyst. If the solution is insufficiently stable, solid mixtures of reagents can also be packed into bottles .or plastics capsules, either by pouring in the solid materials or by pouring in a solution which is subsequently freeze-dried. Reagents prepared in the last-mentioned manner are widely used.

In this latter connection, it is particularly advantageous to use cells which can serve as storage containers for the reagent and also be used for the measurement very cheaply from transparent, rigid plastics materials and can therefore be thrown away after use. This saves the analyst the expense of buying expensive glass or quartz containers and pouring in the reagents, and the fact that the cells are used, once only results in the further advantage that they do not need to be cleaned and dried or rinsed after each measurement. Plastics cells are therefore used in most discontinuously-operating automatic analysing machines.

Plastics cells have not hitherto been used for manual operations, and have been found particularly unsuitable for use as storage vessels for reagents used for determination and for optical measurements or visual inter-pretation of analytical samples. The reason is .that there has been no simple method of sealing the cells. Eectanguli or square internal cross-sections or bases have been preferred, for ease of measurement. On the other,hand, in the injection moulding process, the openin must not be smaller than the internal cross-section so that the side walls of the cell must be- vertical or must diverge towards the open end of the cell by an angle of up to 5° from the vertical. This results in rectangular or square openings which are difficult to seal. It has ■ therefore been suggested, for example, to adhere a plastics headpiece having a round opening on the ordinary cell opening, so that the round opening can be sealed with a rubber or plastics stopper after the reagent has been introduced into the cell. Cells of this kind, however, are relatively expensive to produce and increase the cost by a factor of about or 6. The use of rectan ular sto ers or rubber caps has also been suggested. It is difficult, however, to obtain sealing-tightness at the corners. Furthermore, all these methods of sealing require special and expensive machines for inserting the stoppers or caps, or require manual operations which increase the expense of sealing.

We have now developed an improved form of container for reagents or analytical samples and, according to the present invention, we provide a container for reagents or analytical samples to be subjected to optical measurements, which comprises an open-topped cell formed of transparent and rigid material and having a rectangular or square base and sides, the internal walls being vertical or diverging towards the open end of the cell by an angle of up to 5° from the vertical, and a foil closure for the open top of the cell which can be sealed thereover by adhesion or welding.

The cell may be made of glass, quartz or, preferably, a plastics material. The cell material is preferably transparent in the whole or a part of the wavelength range 200 to 800 nm.

The cell material is preferably a plastics material which can be processed by injection moulding, for example polystyrene or a polymethacrylic acid ester, more particularly polymethacrylic acid esters derived from lower alcohols, for example polymethacrylic acid methyl, ethyl, propyl, isopropyl, butyl or tert. -butyl ester or methacrylic acid ester copolymers with various alcohols, more particularly lower alcohols. Poly methyl methacrylate and polyethyl methacrylate are particularly suitable, since they are very permeable to ultra-violet light - region without large energy losses. The cell can also be made of cellulose esters, for example cellulose acetate or butyrate or cellulose ester copolymers with various sarbexylio aside, mere particularly lower earbexylio aoid@, especially cellulose acetates or butyrates, such as "Acetobutyrate" . The following materials are also suitable: ionic ethylene copolymers containing carboxylic groups and cross-linked if required, (for example, copolymers of ethylene and other unsaturated monomers, such as acrylic acid derivatives), more particularly copolymers commercially available as Surlyn A (Trade Mark) and polymeric carbonic acid esters of aromatic bisphenols, for example those commercially available as Makrolon (Trade Mark).

The cell base is preferably square and has an optical path length (= length of the inner edge of the base) of 10 mm. The cell is preferably 30 to 60 mm high.

Advan ageously, the outer walls of the cell are plane parallel, but can also have other forms suitable for optical measurements and can be either vertical or at an angle to the vertical, for example at approximately the same angle as the internal walls. The cell walls are preferably between 0.3 and 10 mm. thick, more particularly between 1 and 5 mm. thick. ■ The size of the cell opening is preferably equal to the total internal cross-section of the cells, that is the internal walls are preferably vertical.

. The foil with which the cells are sealed is preferably formed of metal- (or metal alloy), preferably aluminium, and/or a plastics material and/or paper. The thickness of the foil is preferably from 5 to ,000^, and advantageously foil is not self-adhesive, it is coated with an adhesive.

Hot melt adhesives which attach the foil to the cell very firmly at room temperature and which are non-tacky in the non-adhered areas, are particularly suitable. Suitable kinds of foil coated with hot melt adhesive are commercially available. Aluminium foil can be very firmly secured to polymethacrylate cells, by, for example, melting or dissolving the commercial adhesive V 274/6 (manufactured by Ardal-Klebstoffwerke , Mainz) and applying it to the foil. A. uniform layer of solution can be applied with a brush- or a roller or, preferably, by spraying. The solvent is then allowed to evaporate, at an elevated temperature if required. Before or after coating, the foils can be repetitively printed by conventional methods, advantageously in such a manner that each cell seal is printed at least once with a text for labelling the contents. Alternatively, instead of coating the foil, the upper edge of .the cell or both the foil and the upper edge of the cell can be coated with adhesive.

Advantageously, the cell is sealed by placing an adhesive-coated foil on the cell and tightly pressing it with a flat plate. If a hot melt adhesive is used, the plate must be at the required temperature (for example 150°C). In the simplest case, and if the number of cells is small, an ordinary domestic iron can be used as the heating plate. If, on the . other hand, a number of cells have to be sealed at the same time, they are advantageously placed on a flat surface and the plate used should be slightly resilient or covered with foam plastics, so that when the cells are sealed, they are resiliently pressed against the foil so cells can advantageously be aligned by placing them in a frame made, for example, of wood, metal or plastics. The exact alignment greatly facilitates the subsequent cutting of the foil. The cells are adhesively sealed with a- heated metal plate, in the same manner as when a single cell is sealed.

In one embodiment of the invention, a temporary seal can be produced first. Temporary seals are important in cases where a freeze-dried reagent has to be preserved by sealing in a lyophilisation chamber in a nitrogen atmosphere. In such cases, the foil can be attached to the plates above the adjusting plates. After drying, the chamber is swept with dry nitrogen. While the chamber is closed, the hydraulic sealing device presses the foil on the cells firmly enough to obtain a temporary seal. The chamber is then opened, after which the cells are finally sealed with a heated metal plate.

Cells can be very tightly sealed in the aforementioned manner. The seals can withstand an internal pressure of approximately -2 atm. gauge or more, but can be very easily taken off by tearing the foil when the cell is used. Alternatively, the cell can be used after perforating the foil with a graduated pipette used for inserting a liquid sample.

The advantages of the container according to the invention are particularly evident when large numbers of cells are dealt with, for example, batches of 100 to 100,000, more particularly of 1,000 to 10,000. Stoppers do not have to be inserted separately, as in conventional' sealing methods - cells, which are closely packed together, is laid over the cells and the foil is firmly and simultaneously secured to the upper edges of all the cells by pressing with a flat metal plate. After the adhesion process, the foil between the cells is divided, for example by cutting.

A preferred form of cell for use in such a multiple sealing operation is shown, by way of example, in the accompanying drawing, in which: Figure 1 is a perspective view of the cell, and Figure 2 is an elevation of a row of such cells arranged side by side' and sealed with a single sheet of foil.

The cell comprises a square base 1 and rectangular, vertical side walls 2. The periphery of the open end of the cell is provided with a rebate on the outside to facilitate, division, as by cutting, of a foil closure 3 when a single sheet of foil is used to seal a plurality of cells (see Figure 2). The rebate 4- is advantageously from 0.2 to 1 mm wide and 0.2 to 15 ™i deep; its width must, however, be such that the upper edge of the cell which is adhered to the foil has a minimum width of approximately 0.2 mm and is preferably from 0.8 to 1.2 mm wide.

Alternatively, the outer periphery of the open top of the cell may be bevelled or outwardly rounded off.

Disposable cells are advantageously packed in groups when sold. Advantageously, therefore, a plurality of cells sealed with a single sheet of foil are not all separated from one another, but are cut into the groups required for packing. It is therefore unnecessary to form them into rou s as in traditional metho . another stage in the process to be eliminated, that is the labelling of each separate cell, since the cells can readily be sealed with printed foil. It is also unnecessary to use the expensive stoppering, labelling and grouping machines required in the conventional process.

The disposable cells according to the invention are "obviously preferable when used for simultaneously supplying and storing a measured quantity of reagent , for example if they contain a substrate/buffer mixture for kinetic enzyme determinations. The substrate buffer mixture may, for example,' be: a) primary potassium hydrogen phosphate, secondary potassium hydrogen phosphate, sodium pyruvate or NADH^ (which when dissolved in water, gives a reagent for determining lactate dehydrogenase), b) primary potassium hydrogen phosphate, secondary potassium hydrogen phosphate, DL-alanine, NADI^ and lactate dehydrogenase (for determining glutamate pyruvate transaminase) or c) primary potassium hydrogen phosphate, secondary potassium hydrogen phosphate, Na-L-aspartate , NADH^ and malate dehydrogenase (for determining glutamate oxalacetate transaminase).

After the test solution has been added, the measurement can be made immediately without risk of contamination or of loss of material when it is transferred from one vessel to another. ' If a number of reagents are required for the measurement which are stable for only a short time when · mixed, the cell can be provided with a partition dividing · amounts of the mutually incompatible materials can be introduced separately' into the chambers, for example in the form of solutions which are subsequently freeze-dried. After the test solution has been added, the reagents can be mixed, suitably by shaking.

The cells or groups of cells are advantageously packed in a metal container or metal foil together, if desired, with a drying agent.

In order that the invention may be more fully understood, the following examples are given by way of- illustration only: Example 1 (a) Coating the foil with a hot melt adhesive. 200 g of Ardal hot melt adhe£ive V 27 6 were dissolved in 2 litres of chloroform and sprayed on to 30W/-thick commercial aluminium foil, the back of which was repetitiously printed with labelling text. The foil was then heated to 1 0° for about 10 minutes. (b)- Preparation of cells for sealing.

Plastics cells as shown in Figure 1 , filled with a reagent , were placed on a 5 u thick foam plastics mat lying on a flat surface. The cells were pressed together in -Q. frame until they were closely packed so that the rebates in the cells formed continuous channels (as shown in Figure 2) (c) The adhesion and cutting processes.

The adhesive-coated foil was placed over the cells and covered with a second, uncoated aluminium foil, to protect the printing from scratches. A domestic iron set at 1^0° (wool) was then pressed on the foil for about 15. seconds. The foil was then cut with a knife along the channels formed by the rebates.

Example 2 1 kg of Ardal hot melt adhesive V 274/6 was melted and 100 ml of chloroform were added. The solution was poured into the reservoir of a curtain coating machine.. Aluminium foil was passed under the coating slots of the machine at a speed of 10 cm/min and was covered ith a thin film of adhesive. After travelling through a drying channel and cooling, the foil was rolled up again with a layer of paper (for example, siliconised paper) placed between the layers of foil to prevent them sticking together. Plastics cells as shown in Figure 1 were sealed in the manner described in Example 1(b) and (c).

Example 3 ' The preparation of a reagent for quantitatively determining glutamate oxalacetate transaminase (GOT).

About 6, 000 plastics cells as shown, in Figure 1 were packed together as closely as possible in 3 metal frames which were firmly clamped* with locking screws. The cells in the frames were then rinsed, dried and each was mechanically filled (at the rate of 50 cells per minute) with 1 ml of a solution containing the following components per 500 ml: 0.05 M ethylene diamine tetraacetic acid, 0.1 M phosphate buffer (a mixture of Na^PO^ and Na2HP0) pH = 7. , -4 0.25 M aspartic acid, 0.01 M ketoglutaric acid, 2 . 10 M dihydronicotinic acid amide adenine dinucleotide (NADELp), 10 mg malate dehydrogenase (MDH) and 10 mg lactate dehydrogenase (LDH) .

The solution in the cells was then freeze dried in a unit comprising four plates, the operating temperature of which could he adjusted. The upper plate gave protection against radiation and the lower three plates were used for adjustments. .The unit also comprised a hydraulic device for pressing the plates together.

An adhesive-coated foil, prepared as in Example 2, was secured to the lower side of the upper three plates so that the printed side was upwards and the adhesive-coated side was downwards. The filled cells in their three frames were placed on the lower three plates and freeze-dried in known manner. After they had been swept with nitrogen but before the freeze-drying chamber was opened, the plates, and consequently the cells between the plates and the foil, were pressed together by the hydraulic device for a short time. When the frames and cells were 'taken out of the chamber, the foil had already stuck firmly enough to the cells to prevent nitrogen from escaping. A plate heated to 150° was then pressed on the foil for 30 seconds, so that the foil adhered firmly to the upper edges of the cells. The foil between the cells was cut by running a knife along the channels formed by the rebates. The cells were not all separated by this process, but were left in groups of, say, 25. After the clamping screws had been loosened, the sealed, labelled groups of cells filled with reagent were taken out of the frame for subsequent packing.

When a cell was used, it was taken out of the group, thus simultaneously removing the foil closure. 2 ml of water and 0.5 ml of the test serum were added and mixed, and the decrease in extinction ΔΕ per minute was measured at 366 nm (in a layer 1 cm thick). The GOT concentration was calculated from the following formula: GOT concentration =. ΔΕ/min x 1.515 U/ml (U = international enzyme unit).

Similarly, a reagent was prepared for determining the glutamate pyruvate transaminase concentration. The solution, before freeze-drying, contained the following constituents per 500 ml: 0.1M phosphate buffer, pH = 7.4·, 0.8M DL-alanine, 0.01M -ketoglutaric acid, 2 . 10"^ M NADH2 and 10 mg LDH.

The solution for measuring the LDH concentration contained 2 . 0"^ M N DH2 in 0.02 M bicarbonate buffer solution, pH = 9.5. In the latter case, the freeze-dried product was subsequently dissolved not in water but in a solution of 6 . 10 M pyruvate in 0.1M phosphate buffer solution, pH = 7Λ.

Example 4- A commercial hot melt film (silicone paper coated with a hot melt adhesive) was pressed on printed .paper at about 180°C for a few seconds, using an iron or a heated roller. After cooling, the silicone paper could easily be taken off the printed paper, leaving all the fusion adhesive behind. The printed paper coated with hot melt adhesive was used to seal plastics cells as in Example 1(b) and (c).

Claims (9)

WHAT WE CLAIM IS:-

1. A container for reagents or analytical samples to be subjected to optical measurements, which comprises an open-topped cell formed of transparent and rigid material and having a rectangular or square base and sides, the internal walls being vertical or diverging towards the open end of the cell by an angle of up to 5° from the vertical, and a .foil closure for the open top of the cell, which can be sealed thereover by adhesion or welding.

2. A container according to claim 1, in which the cell material is transparent in the whole or a part of the wavelength range 200 to 800 nm.

3. A container according to claim 1 or 2, in which the cell material is polystyrene or polymethyl methacrylate .

4. -. A container according to any of claims 1 to 3, in which the periphery of the open top of the cell is rebated on the outside.

5. A container according to any of claims 1 to 4, in which the foil closure is formed of metal, paper and/or a plastics material.

6. A method of packing reagents or analytical samples in a container according to claim 1 , which comprises placing the reagent or substance to be analysed ίη· the cell and sealing the latter with the foil closure.

7. A method according to claim 6, in which a large number of closely packed cells are filled and sealed with a single foil closure extending over all the cells, 'and some or all of the sealed cells are then separated b cutting the foil between the cells.

8. · A method according to claim 6 or 7> in which one or more filled and sealed cells are packed, if desired, with a drying agent, in a metal container or in metal foil.

9. A container for reagents or analytical samples substantially as herein described with reference to the accompanying drawing. COHEN ZEDEK & SPISBACH P. O. Box 1169, Tel-Aviv Attorneys for Applicant