Measuring and testing – Sampler – sample handling – etc. – Automatic control
Reexamination Certificate
2002-07-05
2003-05-20
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Automatic control
C073S863010
Reexamination Certificate
active
06564655
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus for the automatic sampling of liquids, in particular for use in field conditions, where samples of accurate volume are to be taken for example for analysis. In addition, the invention includes methods of sampling and sample preparation using said apparatus.
BACKGROUND OF THE INVENTION
During many environmental monitoring procedures, samples of water such as groundwater are extracted and stored for subsequent laboratory analysis. At present this is mainly done manually, though a variety of devices exist to assist the process. In order to prevent changes in composition through e.g. bacterial activity, samples may have to be stored and transported frozen, which results in significant cost. Once in the laboratory, organic residues are extracted from the sample by passing the sample through a solid phase extraction (SPE) unit. Residues are then eluted from the unit into a smaller volume and analysed by for instance chromatography (gas or liquid) and/or mass spectrometry. Considerable cost and effort can be saved if the SPE stage could be carried out at the time of sampling.
The basic process of SPE in field conditions is well known and devices such as simple syringes have been used for many years. A typical process might involve the following steps:
(i) attaching an SPE unit to a syringe;
(ii) placing a sample in a container, such as a disposable cup;
(iii) drawing an accurate volume of the sample through the unit; and
(iv) recording sample details and marking the unit accordingly.
The operation of such a process is manual, and often requires dexterity in manipulating simultaneously a sample cup, a syringe and a unit which may be difficult under adverse conditions (bad weather, or operation in a boat at sea for example). Furthermore, a number of discrete operations are required, each of which might fail or be subject to error. In particular, the sample volume must be known to +/−1.5% or better, and blockage of the unit before the full syringe volume is filled, or presence of bubbles in the syringe, will compromise this. Alternatively the sample might be measured into the cup, or the volume drawn through might be measured, but this will be difficult and time consuming under adverse field conditions. Furthermore, the details of the sample need to be recorded manually, and they again might be difficult or subject to error.
Devices which offer multi-function or multi-channel options, which are often automated, are known in the art. For instance, U.S. Pat. No. 5,167,802 describes a field-use autosampler which takes samples through a nozzle and directs them through a multi-way valve to an SPE cartridge, then into a vessel for volume readings. This is suitable for stand alone use but requires complex valving, has common sampling lines and plumbing upstream of the SPE cartridge. This means that cross-contamination is likely unless complex and time and sample consuming wash processes are used. In some situations however, the amount of sample available is limited and so these wash steps may not be possible.
U.S. Pat. No. 5,844,147 describes a method of field sampling in which the sample is drawn rapidly, stored under pressure and then passed through an SPE cartridge. This does not address the requirement for easier data handling in the field which a semi-automated device with accurate sample volume determination can give.
A simpler device, designed to be operated easily but with greater security of information and less scope for error, is required.
SUMMARY OF THE INVENTION
The present invention provides apparatus for sampling a liquid, said apparatus comprising:
i) a sampling device capable of automatically taking a known volume of liquid from a source;
ii) fixing means connected to said sampling device and removably attachable to a solid phase extraction (SPE) unit, the fixing means being arranged such that liquid taken from a sample by the sampling device is passed directly through the solid phase extraction unit
iii) a reading device able to read labels on an SPE unit attached to said fixing means;
iv) a controller arranged to log codes based upon a signal from the reading device, and thereafter issue instructions to an operator and/or operate the sampling device to take an appropriate volume of liquid in response to a signal from said reading device.
The apparatus of the invention allows sampling to be undertaken in a simple, one-handed operation in which the sample is metered. The possibility of errors arising in this operation is low.
The SPE unit employed in the apparatus of the invention may be in any of the known forms, including cartridges and discs. The pump is arranged to draw liquid directly through the SPE unit which means that the sample encounters the unit before any other part of the apparatus.
Suitably the fixing means allows firm fixing of an SPE unit to an end portion of the sampling device. They may for example, comprise a series of interconnectable elements, some of which are provided in the sampling device and other of which are provided around the top of the SPE unit such as the cartridge. These elements may take various forms including locking and sealing elements as are well known in the art. In particular, however, they comprise a female Luer fitting which is in the form of a “pistol grip” which interconnects with the male Luer fitting on the SPE unit. In this arrangement, the walls of the pistol grip are arranged to fit closely around the barrel of an SPE cartridge. A sealed fixed interconnection can be established by pushing the cartridge into the pistol grip and twisting it slightly.
Preferably, the apparatus of the invention forms part of a system which further comprises one or more SPE units, each of which carries a machine readable label, in particular a unique label which is readable by the reading device of the apparatus. Examples of such reading devices are barcode readers so that each SPE unit carries a barcode, preferably a unique barcode, which may be printed or embossed onto the surface.
A controller is able to log the label or code of each SPE unit which is fitted into the apparatus. Preferably, the controller includes an interlock means which inhibits the sampling device from operating unless an appropriate code has been read by the reader. Where barcodes (or other labels) are unique to each SPE unit this will preclude the possibility of the same SPE unit being used on more than one occasion in error.
Once the controller has recognised that an appropriate unused SPE unit is in position, it may issue instructions to an operator, for example by way of a display device. These instructions may include directions for setting the sampling device so that the correct volume of sample is drawn, or for starting the operation of the sampling device.
Suitably interlock means are also provided and set to prevent the operation of the sampling device unless any instructions issued by the controller have been correctly implemented by the operator.
Alternatively, or additionally, the operation of the sampling device is effected automatically by the controller once the SPE unit is in place and any instructions issued by the controller to the operator have been correctly implemented.
The controller suitably monitors the progress of the sampling device and stores this data automatically, so that the conditions under which each individual SPE device have been treated are recorded.
Suitably the apparatus further comprises a data input device such as a keyboard or buttons, which allows the operator to manually input data for instance, to record if it becomes necessary to ‘void’ a sample, and optionally also to record the reasons for this.
The sampling device is suitably one which uses vacuum or pump action to draw an accurately known volume of liquid. Such devices are known in the art and may include pistons or syringes having a fixed volume, which are used to draw up a known volume of liquid (see for example U.S. Pat. No. 3,607,092). Working on a broadly similar principle, tube devices such as t
Austen Malcolm Trayton
Backes Monica
Dodgson John Robert
Hedgeley Richard Lynn
Seymour Mark
Bianco Paul D.
Central Research Laboratories Limited
Fleit Martin
Fleit Kain Gibbons Gutman & Bonjini F.L.
Garber C D
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