CA2766635C - Sample preparation for mass spectrometry analysis systems - Google Patents

Abstract

The present invention relates to the preparation of samples for subsequent analysis, in particular for mass spectrometry analysis, and may for example replace traditional dried blood spot (DBS) or dried plasma spot (DPS) techniques. Methods according to the invention generally involve collecting the sample in a sampling tip and extracting the sample from this sampling tip, for example through injection into wells of the analytical system through which the sample is to be analysed. A sampling tip is provided and has a hollow body with opposite open extremities respectively defining input and output ends and a cavity between these extremities. A filling material provided within the cavity for receiving the sample from the input end of the body, while the output end is designed to allow an extraction of the sample therefrom. Collecting, extracting and overall sample preparation methods are also provided.

Description

SAMPLE PREPARATION FOR MASS SPECTROMETRY ANALYSIS SYSTEMS
FIELD OF THE INVENTION
The present invention refers to the field of chemical analysis and more particularly concerns the preparation of samples, such as, but not limited to, blood samples and other biological substances, for analysis through mass spectroscopy or similar techniques.
BACKGROUND
to Dry blood spot techniques (DBS) are gathering a lot of attention.
Through traditional DBS, a small drop of blood, obtained by pricking the finger, heel or toe of the subject, is gathered on a market spot of on special paper. The blood spot is later punched out, mixed with a solvent containing an internal standard or not through processes such as shaking, vortexing, centrifugation and/or sonication. These steps are time-consuming which limits the analytical throughput.
DBS is very advantageous over liquid blood or plasma sample collection as it is much less intrusive for the subject, and because DBS paper or card can easily be stored and transported without requiring special care or refrigeration. A drawback of DBS is however the lengthy extraction process including the punching step, which reduces the analysis throughput and increases the analysis time usually performed in mass spectroscopy systems. There is therefore the need for new sampling support as well as new sample preparation methods procedures which conserve the advantages of standard DBS whiles alleviating at least some of its drawbacks.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is provided a method for preparing a sample for analysis. The method includes the steps of:
a) Collecting said sample, said collecting including the substeps of:

2 i. providing a sampling tip including a hollow body having opposite open extremities respectively defining an input end and an output end, the body defining a cavity between said open extremities, the sampling tip further including a filling material provided within the cavity;
ii. depositing the sample on the filling material from the input end of the body;
and iii. allowing the sample to dry on the filling material for a sufficient drying period; and b) extracting the sample from the cavity, said extracting including the substeps of:
i. inserting a solvent within the cavity from the output end of the hollow body and allowing the solvent to contact the sample for a contact period; and ii. expelling the sample and solvent mix out of the cavity from the output end of the hollow body.
is In accordance with another aspect of the invention, there is further provided a sampling tip for receiving a sample, which can be used in a method such as described above. The sampling tip includes a hollow body, preferably conical or pyramidal-shaped, having opposite open extremities respectively defining an input end and an output end, the body defining a cavity between said open extremities. A
filling material is provided within the cavity for receiving the sample from the input end of the body. The output end of the body is designed to allow an extraction of the sample therefrom. Preferably, the input end of the body is adapted for connection to an automated system.
In accordance with yet another aspect of the invention, there is provided a method for collecting an analyte sample for analysis. The collecting method includes the steps of:
i. providing a sampling tip including a hollow body having opposite open extremities respectively defining a sample input end and a sample output

3 end, the body defining a cavity between said open extremities, the sampling tip further including a filling material provided within the cavity;
ii. depositing the sample on the filling material from the input end of the body;
and iii. allowing the sample to dry on the filling material for a sufficient drying period.
Advantageously, the collected sample can be easily stored and transported without requiring complex conservation measures.
In accordance with another aspect of the invention, there is also provided a method for extracting a sample from the cavity of a sampling tip in which it has been collected according to the method above. The extracting method includes the steps of:
i. inserting a solvent within the cavity from the output end of the hollow body and allowing the solvent to contact the sample for a contact period; and ii. expelling the sample and solvent mix out of the cavity from the output end of the hollow body of the sampling tip.
The samples are preferably received after extraction in the wells of an analysis systems. An optional step of drying the samples in these wells may also be provided.
Preferably, the collecting method, extracting method or both can be performed by an automated system. Further preferably, a plurality of samples can be processed by a single automated system, either serially or in parallel, through the use of a plurality of corresponding sampling tips.
It will be readily understood that the samples prepared according to embodiments of the invention described herein can be analysed through any one of a number of techniques.

4 Other features and advantages of the invention will be better understood upon a reading of preferred embodiments thereof with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGs. 1A through 1C illustrate the steps of a sample collecting method according to an embodiment of the invention; FIGs. 1D and 1F illustrate the steps of a sample extracting method according to an embodiment of the invention.
FIGs. 2A to 2C are cross-sectional views of a sampling tip at various stages of the collecting and extracting methods shown in FIGs. 1A though 1E.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The present invention relates to the preparation of samples for subsequent analysis, in particular for mass spectrometry analysis. It will be readily understood that embodiments of the present invention may be used in conjunction with a plurality of sample analysis processes, such as, but not limited to, Laser Diode Thermal Desorption (LDTD), direct analysis techniques such as, but not limited to, MALDI as well as chromatographic system combined or not to mass spectrometry or spectrometry.
The sample to be analysed may be any appropriate substance, preferably in the liquid state, and further preferably biological substances such as blood, plasma, saliva, urine, liver cells or biological tissues, It may also be embodied by buffer solutions and aqueous samples such but not limited to water from river, also to plant or plant extract, food or food extract and forensic samples etc. It will be readily appreciated that embodiments of the present invention may for example replace traditional dried blood spot (DBS) or dried plasma spot (DPS) techniques with highly advantageous results.

4a Embodiments of the present invention generally involve collecting the sample in a sampling tip and extracting the sample from this sampling tip, for example through injection into wells of the analytical system through which the sample is to be analysed. While preferred embodiments of a sampling tip, collecting method, extracting method and overall sample preparation process are presented below, one skilled in the art will understand that various aspects of the disclosed embodiments may be used individually and that numerous variants thereof could be used without

5 departing from the scope of the present invention.
Sampling tip Referring to FIG. 2A, there is shown a sampling tip 20 for receiving a sample according to one embodiment of the invention. The sampling tip 20 includes a hollow to body 22. Preferably, the hollow body 22 is conical or pyramidal-shaped, but it could alternatively have a different profile, such as tubular or irregular-shaped.
The hollow body 22 has opposite open extremities respectively defining an input end 24 and an output end 26, the body 22 defining a cavity 28 between its open extremities.
In the illustrated embodiment, the input end 24 is embodied by the wider extremity of the conical-shaped body 22, whereas the output end 26 is embodied by the thinner extremity. Preferably, the hollow body is made of plastic, inert polymer,glass or inert metal, with different cavity volumes and body length. Markings, a bar code or other forms of identification could be provided on the hollow body for identification and traceability purposes, or on a separate label attached to the hollow body.
A filling material 30 is provided within the cavity 28 of the hollow body 22.
The filling material is preferably fibrous, and can for example be made of cellulose fiber, polymeric material, glass fiber, and the material may optionally be treated with chemical or by a physical treatment such as heat for example. In the preferred embodiment, the filling material forms a three dimensional mass substantially blocking the cavity along a portion of its length. It may be introduced in the cavity in any appropriate manner, form example by forming one or more balls of fiber introduced into the cavity from one of its extremities. The filling material preferably defined a sample-receiving surface 32 facing the input end 24 of the hollow body 22,

6 for receiving the sample thereon. Although the sample-receiving is shown as flat in the enclosed drawings, it may have a different shape, such as curved or irregular.
The output end 26 of the body 22 is designed to allow an extraction of the sample therefrom, as will be further explained below with reference to an extraction method according to one embodiment of the invention. Preferably, the input end 24 of the body 22 is adapted for connection to an automated system, as will also be further explained below.
lo Sample collecting method Referring to FIGs. 1A to 1C, the steps of a sample collecting method according to an embodiment of the invention are illustrated. Although the illustrated embodiment involves an automated system for processing a plurality of samples, one skilled in the art will readily understand that the collecting method according to the invention could .. be embodied through a manual process and/or on a single sample without departing from the scope of the present invention.
The method first involves (FIG. 1A) providing a number of sampling tips 20, one for each sample to be collected. In the illustrated embodiment, the sampling tips 20 are mounted on a tip holder 36 which can be embodied a supporting structure having a plurality of openings 38 therein shaped to receive and hold the sampling tips.
As mentioned above, the sampling tips 20 include a hollow body having opposite input and output ends, and they are preferably mounted in the tip holder so that the input is easily accessible.
?5 In the illustrated embodiment, the collecting method is robotized through the use of one or more sampler robots 42. Optionally, the sampler robot 42 may be used in a preliminary step of collecting samples 40 from a sample holder 46 having a plurality of wells 48, each well containing one such sample 40 (see FIG. 1A). The sampler robot

7 preferably includes a plurality of sampling containers spaced apart in the same configuration as the wells 48 of the sample holder 46. The sampling containers are adapted to extract the samples 40 from the wells 48, for example through an appropriate pump mechanism. Additionally or alternatively, the same or a different sampler robot 42 may be used to insert the sampling tips 20 into the openings 38 of the tip holder 36.
The collecting method next involves depositing a sample 40 on the filling material 30 of each sampling tip 20, from the input end 24 of the corresponding hollow body 22.
io For this purpose, the sampler robot 42 is preferably moved over the tip holder 36 with the sampling containers 44 aligned with the input ends 24 of the sampling tips 20, and the samples 40 ejected out of the containers 44 into the sampling tips 20 (see FIG.
1B). As shown in FIG. 2B, the sample 40 in each sampling tip 20 is retained on the sample-receiving surface 32 of the filling material 30, therefore facing the input end is .. 24 of the sampling tip 20.
The collecting method next involves allowing the sample 40 to dry on the filling material 30 for a sufficient drying period 50. The length of the drying period 50 may vary depending on the application, amount of sample on the filling material, nature of 20 the sample, etc. It may range from a few seconds to a few hours or days. By "sufficient", it is understood that the drying period is long enough so that the liquid within the sample has completely evaporated, leaving a dry residual onto and/or into the filling material. For example, purely for illustrative purposes and for the sake of comparison, in the case of blood samples, it is usually recommended en the field of 25 DBS to leave the sample to dry for at least 2 hours, although.
Once the sample is sufficiently dried the sampling tips 20 may be removed from the tip holder, manually, through the sampler robot 42 (see FIG. 1C) or using a different device.

8 As those skilled in the art will readily understand, dried samples can be stored, packaged and transported without the need for special measures or equipment.
As such, once collected in the sampling tips, the samples can be easily transferred to another location and/or stored for a long period of time, to be analysed in a different context.
Sample extracting method Referring to FIGs. 1D and 1E, there is also provided a method for extracting a sample from the cavity of a sampling tip in which it has been collected, for example according to the method above.
The extracting method according to the illustrated embodiment of the invention is preferably performed on an automated system, and further preferably on the same system used for the sample collection, including sampler robot 42. It will be readily understood that this is in no way [imitative of the present invention, and that the sample collection and extraction can be performed at completely different locations through completely different systems without departing from the scope of the present invention.
The extracting method first includes the step of inserting a solvent 34 within the cavity of each sampling tip, and allowing the solvent to be in contact with the sample for a contact period 56.
The solvent may be any substance appropriate for use in the context of the analytical system through which the sample is destined to be processed. As such it preferably includes an internal standard or any organic or inorganic chemicals or a mixture of all the above, which might improve the extraction efficiency. For example, the solvent

9 may be embodied by Methanol, Acetonitrile, Water or Ethyl acetate, to name only a few.
Preferably, the solvent is inserted into the cavity 28 through the output end 26 of the hollow body. In the illustrated embodiment, with particular reference to FIG.
1D, each sampling tip is adapted for connection to a pump mechanism part of the sampler robot which is positioned over a solvent plate 52 provided with wells 54 each containing a sufficient quantity of solvent. The pump mechanism is activated in order to draw solvent in each sampling tip 20 from the corresponding well 54. A
quantity of solvent sufficient to completely soak the filling material 30 and cover the sample 40 should preferably be used.
Advantageously, it is believed that for some embodiments of the invention, the contact period 56 may be very short, for example of the order of few seconds.
Of course, the actual length of the contact period may vary with a number of factors from one embodiment to the next. Preferably, the contact period is between a few seconds and a few hours. The contact period should be determined in order for the sample to contact sufficiently well with the solvent to allow its subsequent extraction, as shown in FIG. 2C.
The extraction solvent should be in contact with the filling material as well as with the dry samples. In some embodiments of the invention, it may be advtageous to aspirate a volume of air following the extraction solvent aspiration in order for the extraction solvent to reach the region of the cavity where the filling material and the dry sample are provided.
The extracting method finally includes expelling the sample and solvent mix out of the cavity from the output end of the body of each sampling tip. The sample and solvent mix is transferred to a location appropriate for the subsequent analysis of the sample.

In the illustrated embodiment (FIG. 1E), this is accomplished by positioning the sampler robot 42 over an analysis support 58 provided with an appropriate number of wells 60, and reversing the pump mechanism to push out the liquid contents of the sampling tip into the wells.

One skilled in the art will readily understand that a wide number of systems and configurations could be used to accomplish the collecting and the extracting methods in an automated manner, using for example a system similar to the Liquid Handling Workstation from Hamilton (corporate name) or the Direct Drive Robot from Agilent

10 (corporate name).
Experimental results Human blood was spiked with Dextrorphan at concentrations from 1 to 500 ng/mL.
15pL of blood were spotted onto a FTA DMPK-C card and 3 pl were deposited onto is the paper fibers filled into a tip. Blood was dried at room temperature for 2 hours.
The 3mm punches were extracted with 50pL of methanol ¨water (75/25) containing deuterated IS (vortex and centrifuged for 2 minutes). 4 pl of the extract were deposited into the well. The DBS in tips were extracted by aspiration of 10 pl of the methanol/water solution with a contact time of 10 seconds and by expulsing the extract directly into Lazwell. This process was performed on a Hamilton Nimbus.
After drying, plates were analyzed in LDTD-MS/MS.
The traditional DBS card extracts analyzed in LDTD-MS/MS gave an excellent linearity over the calibration range (r2 = 0.99). With the criteria of 5 times the analyte signal over the blank, we got a limit of quantification (LLOQ) of 5 ng/mL. The accuracy at the LLOQ was higher than 90 % and varies between 5 % for the other calibration points. The precision was evaluated by running the same batch within the same day (intra-day) and on different days within the same week (inter-batch).
The

11 average precision at the LLOQ was below 15% while it's below 10% at the other calibration points.
Analyzing the extracts from the DBS in tips gives similar results as compared to traditional DBS cards in term of LLOQ, linearity and accuracy. The reproducibility (%CVs) of 12 extractions of the same blood set as QC at 100 ng/mL gives 8.5%
in ratio and 13.7% in total area count. Variation of the internal standard area over all samples extracted in the experiment showed 15.3 %. Sample volume deposition on the tip was optimized in conjunction with the extraction solvent volume. The optimal sampling volume is 3 pl of blood and the optimal extraction volume is 10p1 of methanol-water (75-25). The extraction time reach a maximum at 10 seconds contact time and the fiber amount of 2 mg filled a volume of 6 pl. The volume expulsed from the tip is 8pL and this volume is directly deposited into the well. Using a commercial robot to performed the extraction-spotting process in a 96 tips configuration lead to 21 seconds effective extraction which represents 0.2 second per sample.
Of course, numerous modifications could be made to the embodiments above without departing from the scope of the present invention.

Claims (6)

Claims

1. A method for preparing a sample for analysis, including the steps of:
a) collecting said sample, said collecting including the substeps of:
i. providing a sampling tip including a hollow body having opposite open extremities respectively defining an input end and an output end, the body defining a cavity between said open extremities, the sampling tip further including a filling material provided within the cavity;
ii. depositing the sample on the filling material from the input end of the body;
and iii. allowing the sample to dry on the filling material for a sufficient drying period; and b) extracting the sample from the cavity, said extracting including the substeps of:
i. inserting a solvent within the cavity from the output end of the hollow body and allowing the solvent to contact the sample for a contact period; and ii. expelling the sample and solvent mix out of the cavity from the output end of the hollow body.

2. A sampling tip for receiving a sample, including:
a hollow body having opposite open extremities respectively defining an input end and an output end, the body defining a cavity between said open extremities;
a filling material provided within the cavity for receiving the sample from the input end of the body, wherein the output end of the body is designed to allow an extraction of the sample therefrom.

3. The sampling tip according to claim 2, wherein the input end of the body is adapted for connection to an automated system.

4. The sampling tip according to claim 2, wherein the hollow body is conical or pyramidal-shaped.

5. A collecting method for collecting an analyte sample for analysis, the collecting method including the steps of:
i. providing a sampling tip including a hollow body having opposite open extremities respectively defining a sample input end and a sample output end, the body defining a cavity between said open extremities, the sampling tip further including a filling material provided within the cavity;
ii. depositing the sample on the filling material from the input end of the body;
and iii. allowing the sample to dry on the filling material for a sufficient drying period.

6. An extracting method for extracting a sample from the cavity of a sampling tip in which it has been collected according to the collecting method of claim 5, the extracting method including the steps of:
i. inserting a solvent within the cavity from the output end of the hollow body and allowing the solvent to contact the sample for a contact period; and ii. expelling the sample and solvent mix out of the cavity from the output end of the hollow body of the sampling tip.