GB2211935A - Sample preparation - Google Patents

Abstract

Sample tubes (I) inserted in a common manifold (A) connected (B) to a vacuum source. Samples aliquots can be taken or reagents added to the tubes (I) through lines (D) <IMAGE>

Description

MUL PURPOSE SAMPL3 PREPARiTION EQUIPriX T.

INTRODUCTION.

This invention relates to a multi-purpose sample preparation equipment for use in laboratories where chemical analyses or syntheses are performed.

Complex substances, such as plant material, are degraded into their simple, soluble components before chemical analyses can be performed. This is often achieved by digesting a known weight of the sample material with strong acids or bases at high temperatures. Por example, the Kjeldahl acid digestion is the standard technique used for the measurement of total nitrogen in sample materials. Open glass tubes have been widely used for this purpose. However, sophisticated and expensive fume extraction and scrubbing facilities are required since toxic and corrosive fumes are evolved on heating. The fumes may be liberated into the atmosphere constituting an environmental hazard.

More recently, sealed digestion vessels constructed from PTFE or teflon and stainless steel have been used for sample preparation, thus eliminating the need for fume extraction equipment. However, these vessels are expensive, they require costly oven facilities for heating and are restricted to one function only.

Most sample preparative digestions can be carried out in ambient air, but certain analyses involving organic compounds, such as amino acids, may require an oxygen-free environment for sample digestion to prevent oxidation of the organic material. This is often achieved by bubbling nitrogen through the reactants before sealing the digestion vessel but oxygen entry into the vessel cannot be completely eliminated. If oxygen inadvertantly enters the vessel, for example through a leaky seal, the reaction could be ruined. An alternative and more satisfactory approach to prevent oxidation would be to digest sample materials in a replenishing atmosphere of inert gas, thus assuring the complete exclusion of oxygen.

However, this would be difficult with conventional digestion techniques. In addition, provision of a controlled gas atmosphere may be a prerequisite for organic synthesis reactions.

Organic compound syntheses, derivatisation procedures and some acid digestion techniques involve evaporative steps, and the subsequent addition of other reagents and solvents.

Evaporation is normally carried out with a rotary evaporator.

Sample solutions are transferred from the digestion vessel to a flask attached to the evaporator and the flask is heated in a water bath. This equipment is expensive and can only evaporate a limited number of samples at one time, thus restricting sample through-put. In addition, sample transfer is time consuming, inevitably leads to reduced end-product recovery and maybe potentially hazardous if the compolLais are toxic. Therefore, it would be advantageous if digestions or syntheses, and evaporation were conducted in a sealed system without the need to transfer samples, inhere reagents could be added and sample aliauots removed. This would also reduce the glass-ware requirements for sample preparation.The provision of a gas-flovit would also enhance the rate at which solvents were evaporated.

The present invention makes it possible for multiple sample digestions, organic compound syntheses, derivatisation and extraction procedures to be carried out in a controlled oxygen-free atmosphere of inert replenishing gas (if required), with evaporation, reagent addition and sample aliquot removal facilities, contained within a single piece of equipment.

Therefore, the need for other evaporation equipment is removed. Safety of handling potentially toxic compounds is improved, the number of samples that may be dealt with is increased and a greater volume of sample can be recovered, compared with conventional methods. The equipment can be used in conjunction with a controlled heat source. Fumes are removed from the equipment with a conventional water vacuum pump, and are thus safely disposed of without the need for fume treatment facilities. However, some form of cooling system, such as an ice-trap or refrigeration unit, may be connected between the sample preparation equipment and water pump to condense fumes of toxic compounds and solvents for their safe containment and disposal.

DESCRIPTION.

The Multi-Purpose Sample Preparation Equipment is comprised of a manifold of chemically resistant material, such as PTFE, or PVC may be-used as a low cost alternative. The manifold is constructed to accommodate as rn2ny test-tubes as necessary, either as a cylinder (A) with multiple test-tube facility or as single units (F). The single units are connected with rods (H) which are inserted through the units on both sides and bolted at each end. Spacers (G) are made with identical channels through them and these can be intersnaced between the units to enable the manifold to accept extra large test-tubes.

A series of cylinder manifolds can be fitted together to form a multiple manifold, as shown in Figure 1.

Two continuos channels run through the length of the manifold.

The large, central channel is attached to the vacuum pump by a connector (B) fitted at one end of the manifold. Inlets into the central channel are positioned at each test-tube siting.

A branch system can be used to connect the vacuum outlets when several cylinders are fitted together. A ater pump, fitted with an anti-suckbsok device, is used to provide the vacuum and waste fumes are safely washed away. Highly toxic and poisonuous fumes can be collected in an ice trap or by some form of refrigeration system for safe containment and disposal.

The smaller channel (C) is connected to an air or inert gas supply. Channels at each test-tube siting connect the gas channels to the outside of the manifold and, by way of a Buyer or similar fitting (L), feed the gas through the sample line (D) into the test-tubes.

Test-tubes are fitted into the manifold through inserts (E).

A range of test-tube sizes can be used by the production of a range of sizes of inserts. There are several types of inserts which cn be envisaged being used. Three types are specified in this description.

The upper dimension of the insert is constant to fit the hole in the manifold. An O'ring of a chemical-resistant rubber secures the fit of the insert into the manifold. In type (i) the internal dimension of the lower half of the insert varies to receive different size test-tubes. An O'ring secures the fit of the tube in the insert and gives a vacuum tight seal. In type (ii) the internal dimension of the lower half of the insert varies to receive different size test-tubes.

The seal is placed so that it cushions the rim of the tube and forms an effective seal when vacuum is applied. In type (iii) the lower part is tapered to fit the neck of the testtube. .4 range of sizes is produced.

Sample aliquots can be irithdranm and reagent additions made to the test-tubes via the sample line (D). This is a length of tubing passed into the test-tube through an inlet on the top of the manifold positioned above each test-tube. The tubing is firmly located in the manifold by a gas and vacuum tight seal (J). The height of the tubing in each test-tube can be varied by withdrawing or pushing the tubing through tthe seal.

A Luer or similar fitting (L) is attached to the end of each sample line. This fitting connects to a syringe to facilitate sample removal and reagent addition. The Luer fitting of the sample line connects to the gas inlet channel on the side of the manifold.

The test-tubes are seated in a temperature controlled heating block (M).

Claims (24)

CLAIMS.

1. The Multi-Purpose Sample Preparation Equipment (hereafter referred to as The Equipment), comprises a manifold of chemically inert material into which test-tubes are inserted.

There are means by which different size test-tubes can be inserted. There is a vacuum attachment and a connection to a gas source oe choice. Sample aliquots can be removed and reagents added. Evaporation can be achieved and the rate of evaporation can be controlled. There is a sealed containment of toxic fumes within the equipment and by means of the vacuum attachment these fumes can be safely washed away or trapped in a cold trap. The tubes can be heated and the chemical process of extraction can b achieved. By this invention multiple samples can be processed and all procedures can be carried out without the removal of the reaction tubes.

2. Equipment as claimed in Claim 1 where the manifold is mad of a chemically inert material, such as PTFE, which can be moulded into a single cylinder with multiple test-tube facility.

3. Equipment as claimed in Claim 1 where the manifold is made of a chemically inert material, such as PTFE, which can be moulded into single units which are fitted together by rods inserted through the units and bolted at each end. The units are used in a number to make a manifold of the required test-tube facility.

4. Equipment as claimed in Claim 3 where spacers can be fitted between the single units to adapt the system to use extra-large test-tubes.

5. Equipment as claimed in any preceding Claim where the tube inserts are usually made of the same material as the manifold. These are made in a variety of sizes to fit different size test-tubes.

6. Equipment as claimed in Claim 1 where a vacuum is applied to one end of the manifold and pulls through the length of the manifold and tubes.

7. Equipment as claimed in Claims 1 and 6 where the application of a lo vacuum, produced by a water pump, will extract toxic fumes which can be washed away or trapped as required.

8. Equipment as claimed in Claims 1, 6 and 7 where the application of a strong vacuum riill effect evaporation and reduce the level in the test-tubes.

9. Equipment as claimed in Claims 1, 6, 7 and 8 where a tube can be connected to the vacuum outlet as a waste line for fumes given off, if a vacuum is not required.

10. Equipment as claimed in Claim 1 where a gas inlet is sited at one end of the manifold. The gas is directed into each test-tube. The gas is used in reactions or processes requiring an inert gas, such as nitrogen, to provide a replenishing inert atmosphere or a process requiring a gas to complete a chemical reaction.

11. Equipment as claimed in Claims 1 and 10 where evaporation can be achieved by directing a strong stream of gas onto the surface of the reactants.

12. Equipment as claimed in Claims 1 and 6-11 where evaporation is enhanced when the gas stream is used in conjunction with the vacuum.

13. Equipment as claimed in Claims 10-12 ere gas can be bubbled through the fluid to mix the reactants and prevent bum?ing .

14. Equipment as claimed in Claims 1 and 10-13 where the chemical process of extraction is achieved by using the gasstream to produce a strop turbulence.

15. Equipment as claimed in Claim 1 where a narrow bore gas tight opening is sited in the manifold over each test-tube, through which a hard, flexible line is passed. This line can be lowered or raised in the test-tube according to the requirements of the chemical process. The adjustment of the line is effected by pushing or pulling the line through the gas -seal.

16. Equipment as claimed in Claims 1 and 15 where the line into the test-tube has a Luer or similar fitting on the end.

17. Equipment as claimed in Claims 1, 10, 15 and 16 where the fitting on the line into the test-tube is connected to a branch of the gas line to facilitate gas entry into the tube.

18. Equipment as claimed in Claims 1, 15 and 16 There the line into the test-tube can be disconnected from the gas line and connected to a graduated syringe to facilitate the removal of sample aliquots of knorn volume.

19. Equipment as claimed in Claims 1, 15 and 16 where the line into the test-tube can be disconnected from the gas line and connected to a graduated syringe to facilitate reagent addition.

20. Equipment as claimed in Claim 1 where the tubes are heated by a method of choice.

21. Equipment as claimed in Claim 1 where sample preparations are carried out without the need for removal of the reaction tubes.

22. Equipment as claimed in Claims 1 and 18 where progress of a reaction can be monitored by removing small aliquots of the sample for analysis without interrupting the reaction process.

23. Equipment as claimed in Claims 1, 2 and 3 where a number of manifolds can be clipped together to form a unit, thereby enlarging the system. An attachment to the vacuum pump will join al] the vacuum outlets into one single vacuum line.

24. A ulti-Purpose Sample Preparation Equipment substantially as described herein vftth reference to Figures 1-5 of the accompanying drawings.