Sample block comprising a microsample, method for creating such a sample block and method for surface analysis using mass spectrometry of a microsample in such a sample block

Abstract

The current invention relates to a sample block configured for surface analysis using mass spectrometry of a microsample comprised in the sample block. The sample block comprises an embedding block of a transparent hardened electrically insulating embedding material, having parallel top and lower surfaces, and a side surface extending from the top surface to the lower surfaces. The sample block comprises a microsample in the embedding block. The embedding block comprises a conductive layer extending at least parallel to the top surface of the embedding block, throughout the embedding block, at a distance from the microsample and between the microsample and the lower surface of the embedding block, the conductive layer being connectable to a ground element. The invention also relates to a method of creating such a sample block and to a method for surface analysis using mass spectrometry of a microsample in such a sample block.

Description

[0001] SAMPLE BLOCK COMPRISING A MICROSAMPLE, METHOD FOR CREATING SUCH A SAMPLE BLOCK AND METHOD FOR SURFACE ANALYSIS USING MASS SPECTROMETRY OF A MICROSAMPLE IN SUCH A SAMPLE BLOCK

[0002] Description:

[0003] The present invention is related to a method for surface analysis using mass spectrometry of a microsample comprised in the sample block in general, and especially Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) of an embedded microsample. The microsample can for example be a very small part of an artwork (painting, statue) to be analysed. However, it can also be any sample of solid material that can be microsampled without inhibiting other research methods using diverse analytical instrumentation.

[0004] Methods for surface analysis using mass spectrometry rely on the creation of ions on a surface, their high voltage acceleration and detection. For this purpose, the surface to be examined is bombarded with charged ions. As a result, ions are ejected from the surface. These ejected ions, called secondary ions, are analysed with regard to their mass (surface mass spectrometry).

[0005] Time-of-flight mass spectrometry is a method of mass spectrometry in which an ion's mass-to-charge ratio is determined by a time of flight measurement. Ions are accelerated by an electric field of known strength. This acceleration results in an ion having the same kinetic energy as any other ion that has the same charge. The velocity of the ion depends on the mass-to-charge ratio. Heavier ions of the same charge reach lower speeds, although ions with higher charge will also increase in velocity. The time that it subsequently takes for the ion to reach a detector at a known distance is measured. This time will depend on the velocity of the ion, and therefore is a measure of its mass-to-charge ratio. From this ratio and known experimental parameters, one can identify the ion.

[0006] In ToF-SIMS analysis, elements and molecules can be detected simultaneously. The secondary ions are accelerated by the bombardment to have a kinetic energy for which the instrument is tuned, adapted for electrically conductive surfaces. Where the term conductivity is used in this document, it means electrical conductivity.

[0007] In a known method, a sample block is configured for surface analysis using mass spectrometry of a microsample comprised in the sample block, and comprises an embedding block of a transparent hardened electrically insulating material, having a top surface and a lower surface extending parallel to the top surface, and at least one side surface extending between the top and lower surfaces. The microsample to be analysed is embedded in the embedding block and is exposed at the top surface of the sample block.

[0008] A known method for creating the sample block comprises the staps of: providing a mould; providing a liquid transparent embedding material, which embedding material is electrically insulating once hardened; pouring a first amount of the transparent embedding material in the mould; hardening the first amount of the transparent embedding material in the mould to create a half block (the half block doesn’t necessarily comprise exactly 50% of the entire block once finished; the microsample in the entire block should be located near the centre axis of the sample block as explained hereinbelow); placing the microsample onto the half hardened block; pouring a second amount of the transparent embedding material in the mould, over the microsample on the half hardened block; and hardening the second amount of the embedding material in the mould.

[0009] Before the embedding block can be used for surface analysis using mass spectrometry of the microsample, the top surface of the sample block is polished (partly away), until the microsample is exposed at the top surface of the sample block. Polishing may include sanding or milling redundant embedding material.

[0010] A known method for analysing a microsample comprises the steps of: providing a device for surface analysis using mass spectrometry including a sample block holder, preferably a conventional sample block holder; providing a known sample block as described herein above, the top surface being exposed at the top surface of the sample block; bombarding the exposed microsample with (primary) ions; and analysing the secondary ions with respect to their mass. Whereas satisfactory results of surface analysis using mass spectrometry, and especially of ToF-SIMS, can be reached with the known method, said method suffers some disadvantages. For insulating objects like the embedding block, a potential builds up under high voltage (dielectric) and residual charges accumulate. Thus, ions have altered kinetic energy after acceleration, leading to signal degradation or loss of detection. Electron flood can evacuate some residual charges and the sample holder voltage can be tuned to correct the energy, but that is limited to blocks of a solidifying embedding material thinner than 7-8 mm.

[0011] The current invention aims to improve the quality and / or speed of the known method for surface analysis using mass spectrometry. Therefore, the invention provides a sample block according to claim 1 , and a method for creating a sample block according to claim 10, the sample block thus comprising a microsample to be analysed and a conductive layer (i.e. a layer of electrically conducting material) at a distance of d mm from the microsample. When mounting the embedding block on a regular sample holder for surface analysis using mass spectrometry in general, and especially for ToF SIMS, extremities will act as electrodes, enabling a conduction path at a distance d mm below the sample, reducing the thickness of the electrically insulating area to d mm. The mould allows achieving this design with a reproducible method that is safe for the sample and may provide optimal results for this research method.

[0012] According to a first aspect, the invention aims to provide a sample block with which the mentioned disadvantages of the known sample block or method can be mitigated. Therefore, the invention provides a sample block that is configured for surface analysis using mass spectrometry of a microsample comprised in the sample block. The sample block comprises an embedding block of a transparent hardened electrically insulating embedding material, having a top surface and a lower surface extending parallel to the top surface, and at least one side surface extending from the top surface to the lower surface, and a microsample to be analysed embedded in the embedding block. The embedding block comprises a conductive layer extending at least substantially parallel to the top surface of the embedding block, throughout the embedding block, at a distance d from the microsample and between the microsample and the lower surface of the embedding block, the conductive layer being connectable to a ground element. The last feature provides the opportunity to connect the conductive layer with a ground element, which may be the device for surface analysing using spectrometry, creating a circuit to evacuate charges that in the known sample block as a result of a potential building up under high voltage (dielectric) and residual charges accumulating. Thus, the objective of the current invention is met.

[0013] Clearly, it would be possible to create half blocks including the conductive layer as a semi-product, so one can buy the semi-products and add a microsample and the second amount of resin to finish the sample block. This two-phase creation is comprised in the scope of the invention and offering such semi-products for sale or other commercial uses is considered as infringement of the invention.

[0014] In a preferred embodiment of the invention, the embedding material is a solidified, or at least solidifying embedding material, preferably a resin. Resins are known for their advantageous characteristics for embedding a microsample in mass spectrometry. Typically these may be synthetic resins that comprise either two components (resin + hardener) or UV curing resins. The first are polyester resins, the second are polyacrylic resins. The materiality of the resin does not matter - except that it must be able to be sanded without issue for the sample.

[0015] In preferred sample blocks for mass spectrometry, the embedding block has a cross section, parallel to the top surface, of a cylindrical, or a polygonal, preferably triangular or rectangular shape.

[0016] If the distance d is in the range of 0-5 mm, preferably 0.5-2.5 mm, more preferably 0.8-1.5 mm, a good insulated environment for surface analysis using mass spectrometry of the microsample is provided.

[0017] Before polishing the top surface of the sample holder, the distance from the microsample to the top surface of the sample block is in the range of 0-5 mm, preferably 0-3 mm, more preferably 0-1 mm. The embedding material, amongst which the embedding material between the microsample and the top of surface of the sample block, protects the microsample of being damaged before the surface analysis using mass spectrometry. On the other hand, before the surface can be analysed, the top surface needs to be polished away until the microsample is exposed at the top surface. A function of the resin is thus to encapsulate the sample so that one side can be exposed. During sanding some of the sample material may be removed to create a flat surface with all necessary layers / strata exposed. The resin block allows for handling of these samples which can be smaller than 5mm in width and smaller than 3mm in height. The depth of the sample extends is contained within the resin block.

[0018] Polishing takes time - and care must be taken during polishing to get to the surface and not loosen the sample by polishing too far. Thus, to prevent unnecessary polishing, the preferred distance from the microsample to the top surface of the sample block may be reduced.

[0019] If the distance from the microsample to the lower surface of the sample block is in the range of 3-20 mm, preferably 4-15 mm, more preferably 5-10 mm. The sample block preferably has a total dimension that can be handled, i.e. pinched between fingers for sanding. Too large (with a small sample) will mean using unnecessary amount of embedding resin.

[0020] If the conductive layer extends throughout the embedding block and beyond at opposite sides of the side surfaces, ends of the conductive layer extending beyond the embedding block are easily accessible for connection with ground elements.

[0021] In a preferred embodiment, the conductive layer extends over 20-90%, preferably 40-80% of an horizontal cross section of the embedding block. Here, a trade off can be made between conductivity and use of electrically conducting material.

[0022] The conductive layer may be a strip or a mesh of electrically conducting material. Meshes and strips can easily extend a distance and beyond the embedding block and can be engaged easily for connection with a ground element. A mesh, or a strip comprising through holes, has the advantage that it can extend across an entire cross section of the embedding block, without separating the embedding block at both sides of the strip or mesh.

[0023] In a preferred embodiment, the electrically conducting material is a metal, preferably aluminium, of an alloy comprising metal. Electrically conducting metals are readily available and have a high conductivity.

[0024] To provide sufficient conductivity and efficient use of conducting material, , the conductive layer preferably has a thickness in the range of 1 - 1000 pm, preferably, 50 - 500 pm and more preferably 100 - 250 pm.

[0025] The embedding block preferably has a longitudinal centre axis extending between the top and lower surfaces, the microsample being located nearer to the centre axis than half the distance of the longitudinal centre axis to the topside surface, preferably nearer than half said distance. If the microsample is near the centre axis, the embedding material surrounds and thus facilitate handling and manipulation of the microsample and protects the microsample sufficiently at all sides.

[0026] According to a second aspect, the invention aims to provide a method for creating the sample block with which the mentioned disadvantages of the known sample block or method can be mitigated. For example for creating a sample block according to the first aspect of the invention. Therefore, the invention provides a method for creating the sample block for surface analysis using mass spectrometry of a microsample according one or more of the preceding claims, comprising the staps of: providing a mould; providing a liquid transparent embedding material, which embedding material is an electrically insulating once hardened; pouring a first amount of the embedding material in the mould; hardening the first amount of the embedding material in the mould to create a half block; placing the microsample onto the half hardened block; pouring a second amount of the transparent embedding material in the mould, over the microsample on the half hardened block; and hardening the second amount of transparent embedding material in the mould;

[0027] The method comprises the step of inserting a conductive layer in the mould, in such a way that after hardening of the second amount of transparent embedding material, the conductive layer extends at least substantially parallel to the top surface of the embedding block throughout the embedding block, to opposite sides of the side surface and at a distance d from the microsample, which step is executed before the step of hardening the second amount of transparent embedding material in the mould. The embedding block thus created provides the opportunity to connect the inserted conductive layer to ground elements.

[0028] The embedding material doesn’t have to be inserted immediately before the step of hardening the second amount of transparent embedding material. The embedding material may, for example, be inserted before the step of pouring a first amount of the embedding material in the mould or during the step of hardening the first amount of the embedding material, before the material is entirely hardened. And the orientation of the mould may not correspond to the orientation of the embedding block during surface analysis using mass spectrometry. The embedding block may be created with the longitudinal centre axis oriented horizontally, while during surface analysis using mass spectrometry it can be oriented vertically.

[0029] Preferably, in the step of inserting the conductive layer, the layer is oriented such that after the step of hardening of the second amount of transparent embedding material, the conductive layer extends beyond the opposite sides of the at least one side surface. Opposite ends of the conductive layer are then easily accessible for connection with ground elements.

[0030] For making the sample block ready for surface analysis using mass spectrometry, the microsample can be exposed by polishing the top surface of the embedding block, until the microsample is exposed at the top surface, after the step of hardening the second amount of transparent embedding material. Because polishing removes redundant material only slowly, one can choose for sanding first and then polishing. Sanding may remove the excess resin and expose the surface of the sample. Polishing may then flatten the surface after sanding.

[0031] According to a third aspect, the invention aims to provide a method for surface analysis using mass spectrometry of a microsample with which the mentioned disadvantages of the known method can be mitigated. Therefore, the invention provides a method for surface analysis using mass spectrometry of a microsample comprising the steps of: providing a device for surface analysis using mass spectrometry including a regular sample holder; providing a sample block according to the first aspect of the invention, the top surface being polished until the microsample is exposed; bombarding the exposed microsample with (primary) ions; and analysing the secondary ions with respect to their mass.

[0032] The method comprises the step of connecting the conductive layer with a grounded element, creating a circuit, before the step of bombarding the exposed microsample. Thus, during surface analysis using mass spectrometry, residual charges that tend to accumulate in the embedding material of a known method, can be prevented by the ability of the conductive layer to evacuate a possible electron flood.

[0033] In a preferred embodiment, the device for surface analysis using mass spectrometry is a ToF-SIMS device. The known method can easily be improved if existing protocols for surface analysis using mass spectrometry don’t have to be changed and if large investments can be avoided. This can be realized if the sample holder used in the method is preferably a conventional device for surface analysis using mass spectrometry, that preferably comprises the earthed element.

[0034] The invention will be elucidated in more detail hereinafter, referring to the appended drawing, wherein:

[0035] Figure 1 shows a schematic and simplified picture of only a part of a device for surface analysis using mass spectrometry according to the current invention;

[0036] Figure 2 shows a perspective view on a sample block for use in surface analysis using mass spectrometry according to the current invention; and

[0037] Figures 3a-d schematically show a method of creating a sample block for use in surface analysis using mass spectrometry according to the current invention.

[0038] Now looking at Fig. 1 , a part of a device and a method of surface analysis using mass spectrometry according to the current invention is shown in a simplified schematic view. This will be clear for a person skilled in the art of mass spectrometry. A sample block 1 comprising a solidified or hardened transparent, electrically insulating embedding material, in this case a resin, for example Polypol® or Technovit®, according to the current invention is held in a sample block holder 2. In this exemplary embodiment, the sample block has a length of 10 mm, a width of 10 mm and a height of 10 mm. At the top surface 3p (p stands for polished) of the sample block 1 , a microsample, also called sample 4, having length, width and height dimensions each smaller than 500 pm, of a painting to be analysed and which is further surrounded by the resin of the sample block 1.

[0039] For surface analysis, an ion beam 5 generated by an ion beam generator 6 (schematically shown as a square) is directed to the sample 4, resulting in the sample 4 being bombarded with primary ions. As a result of the bombardment, ions at the exposed surface of the sample 4, so-called secondary ions, are freed from the sample 4. The secondary ions are accelerated (see arrow A) to a ToF SIMS device, in which the secondary ions and thus the surface of the sample 4 are analysed. A conductive layer embodied as an aluminium strip 7 extends throughout the sample block 1 , parallel to the top surface 3p of the sample block 1 and at a distance d of 1 mm from the sample 4. The aluminium strip 7 in this example is aluminium foil having a thickness of 150 m and is connected at both ends 7a, 7b to the sample block holder 2, which also acts as a grounded element. Whereas the method of mass analysis is explained in a very simplified way, the explanation is considered to be sufficient for understanding the current invention.

[0040] As explained in the introduction, as a result of the ion beam, bombarding the sample 4 with primary ions, in a conventional sample block a potential builds up builds up under high voltage (dielectric) and residual charges accumulate in the sample block, which affects the analysis. The area in which the potential would build up in a conventional sample block (without conductive layer) is depicted in dotted lines as a cloud C in Fig. Uf a potential builds up in the sample block 1 according to the current invention, however, charges will not accumulate, or at least accumulate to a lesser extent. Instead, the charges will be guided through the aluminium strip 7 and to the sample block holder 2 (see arrows G). This results in a much better analysis result than when a conventional sample block would have been used.

[0041] The sample block 1 shown schematically and in 2D in Fig 1 is shown in a perspective 3D view in Fig 2. However, Fig. 1 shows the sample block 1 in use in a ToF SIMS device, while Fig 2 shows the sample block 1 in a different orientation, with the top (polished) surface 3p directed to the viewer. The orientation of the sample block 1 in Fig 2 corresponds to that during creation of the sample block 1 , as discussed later. Because the sample block 1 is created from a solidifying transparent (once hardened, electrically insulating) embedding material, in this exemplary example embodied as the resin, it’s possible to look through the sample block 1. The transparency is important, because the microsample, or sample 4, is visible from outside the sample block 1. When polishing the top surface, one can see how much resin needs to be polished away to expose the sample 4 and determined how much of the sample needs to be removed.

[0042] The sample block 1 in Fig 2 has the top surface 3p oriented vertically in this view, a bottom surface 8 and four side surfaces, 9, 10, 11 , 12. When the cross section of a sample block is cylindrical, the sample block will have only one side surface. The bottom surface 8 extends parallel to the top surface 3p, so that the top surface 3p will be horizontal when the sample block 1 is put upright in a sample holder 2 for surface analysis using mass spectrography. The sample 4 is located close to an imaginary longitudinal centre axis I that extends through the sample block 1 from the top to the bottom.

[0043] The sample 4 is exposed at the top surface 3p and thus ready for use in mass spectrography. The electrically conductive aluminium strip 7 extends parallel to the top 3p and bottom 8 surfaces of the sample block, at the distance d from the sample 4. The distance d may be determined taking into account not to impede observations if the sample also has to undergo optical microscopy. The electrically conductive aluminium strip 7 extends from side surface 10 to opposite side surface 12, with its ends 7a, 7d extending to beyond the embedding block (the embedding block consisting of resin only, in this exemplary embodiment). The aluminium strip 7 also extends over a little bit more than half the distance from side surface 9 to side surface 11 .

[0044] In Fig 2, a plane P is depicted, which plane P may or may not be visible in a finished sample block 1. The imaginary plane P indicates that the embedding block 13 is created in two steps and thus is made of two halves 13a, 13b that are integrally connected. This is discussed more in detail with reference to Figs 3a-d below.

[0045] Figures 3a-d schematically show a method of creating the sample block 1 for use in surface analysis using mass spectrometry shown in Fig, 2. The sample block 1 is created in a mould, which is not visible in Figs. 3a-d, to have a clear view on the creation of the sample block 1.

[0046] Fig 3a shows a half embedding block 13a and the aluminium strip 7. This is a result of the steps of providing a mould (not visible); inserting the electrically conductive aluminium strip 7 in the mould; pouring a first amount of a liquid transparent embedding material, embodied as a resin in this example, which resin is electrically insulating once hardened, in the mould; and hardening the first amount of resin in the mould to create a half block corresponding to the first half 13a of an embedding block. The aluminium strip 7 is held vertically by the mould, so that the aluminium strip 7 maintains its orientation during pouring the first amount of liquid resin in the mould and before the resin is hardened. The aluminium strip 7 will thus extend parallel to the top surface 3p of the finished sample block 1 .

[0047] Fig 3b shows the half hardened embedding block 13a of Fig 3a after placing a microsample embodied as a sample 4 onto the half hardened embedding block 13a. The sample 4 is placed near or at an imaginary longitudinal centre axis of the surface on which the sample 4 is placed, and at a distance d from the aluminium strip 7. Fig 3c shows the half hardened embedding block 13a carrying the sample 4 after pouring a second amount of the resin in the mould, over the sample 4 on the half-hardened block. Plane P is visible in Fig 3c, however it is not necessarily visible in the finished sample block 1. During pouring, or at least before hardening of the second amount of resin, care should be taken that the sample 4 is maintained, or relocated to, near the longitudinal centre axis. After the second amount of resin is hardened, the sample block 1 has its semi-final embodiment. This is the embodiment in which the sample 4 is surrounded by the resin and protected by the hardened resin at all sides of the sample 4. The sample 4 is located at a distance from the top surface 3n which has not been polished. The sample must be placed at a distance from the future sanded surface so as not to be placed on a meniscus incline created when pouring the resin for the first half block. The sample may have a flat top surface. This side is placed onto the hardened surface of the first half block - allowing for the sample to be orientated perpendicular to the edge of the block. This way the strata of the sample can be exposed parallel to the viewing plane, i.e. exposed surface

[0048] Fig 3d, finally, shows the sample block 1 after polishing away the top surface 3n to become top surface 3p to expose the sample 4 and thus the top surface 3p of the sample block 1. Polishing is done just before the surface analysis.

[0049] The invention is elucidated referring to only one embodiment thereof, shown in the appended figures and described in the description hereinabove. However, it will be clear that many changes, which are or aren’t obvious to a person of ordinary skill in the art of mass spectrometry, may be made within the scope of the invention as defined in the appended claims. As already mentioned, the cross section of a sample block may differ from rectangular and may be circular, for example. The order of steps for creating a sample block may differ. For example, a electrically conductive strip may be inserted in the mould after the first amount of resin is poured in the mould, before the first amount of resin is hardened. An electrically conductive strip may also be inserted in the mould after the first amount of resin is hardened. In that case the electrically conductive strip will be embedded in the second amount of resin. The sample block may be created from bottom to top, with the electrically conductive layer oriented horizontally, and the last amount of resin being only a relatively small amount, the major part of which will be polished away later on to expose the microsample. The invention is described with respect to analysis of a sample of a painting, however samples of other pieces of art or pieces of historical items may be analysed with the method and in a sample block according the invention. Also mass spectrography for commercial products of processes may be considered, like geographical samples or coatings to be analysed.

[0050] Reference sign list

[0051] Sample block

[0052] 2 sample block holder

[0053] 3 top surface sample block

[0054] 3p polished top surface

[0055] 3n non yet polished top surface

[0056] 4 (micro)sample

[0057] 5 ion beam

[0058] 6 ion beam generator

[0059] 7 electrically conductive aluminium strip

[0060] 7a, b end of aluminium strip

[0061] 8 bottom surface

[0062] 9 side surface

[0063] 10 side surface

[0064] 11 side surface\

[0065] 12 side surface

[0066] 13 embedding block

[0067] 13a first half block

[0068] 13b second half block

[0069] A arrow

[0070] C cloud

[0071] D distance

[0072] L longitudinal centre axis

Claims

1. CLAIMS1. Sample block configured for surface analysis using mass spectrometry of a microsample comprised in the sample block, the sample block comprising:- An embedding block of a transparent hardened electrically insulating embedding material, having a top surface and a lower surface extending parallel to the top surface, and at least one side surface extending from the top surface to the lower surfaces; and a microsample to be analysed embedded in the embedding block, characterized in that the embedding block comprises a conductive layer of electrically conducting material extending at least substantially parallel to the top surface of the embedding block, throughout the embedding block, at a distance d from the microsample and between the microsample and the lower surface of the embedding block, the conductive layer being connectable to a ground element.

2. Sample block according to claim 1 , wherein the embedding material is a resin.

3. Sample block according to claim 1 or 2, wherein the embedding block has a cross section, parallel to the top surface, of a cylindrical, or a polygonal, preferably triangular or rectangular shape.

4. Sample block according to one or more of the preceding claims, wherein the distance d is in the range of 0.3-5 mm, preferably 0.5-2.5 mm, more preferably 0.8-1.5 mm.5 . Sample block according to one or more of the preceding claims, wherein the distance from the microsample to the top surface of the sample block is in the range of 0-5 mm, preferably 0-3 mm, more preferably 0-1 mm and / or wherein the distance from the microsample to the lower surface of the sample block is in the range of 3-20 mm, preferably 4-15 mm, more preferably 5-10 mm.

6. Sample block according to one or more of the preceding claims, wherein the conductive layer extends throughout the embedding block to beyond at opposite sides of the side surfaces, and / or wherein the conductive layer extends over 20-90%, preferably 40-80% of an horizontal cross section of the embedding block.

7. Sample block according to one or more of the preceding claims, wherein the conductive layer is a strip or a mesh of electrically conducting material, and / or whereinthe electrically conducting material is a metal, preferably aluminium, of an alloy comprising metal.

8. Sample block according to one or more of the preceding claims, wherein the conductive layer has a thickness in the range of 1 - 1000 pm, preferably, 50 - 500 pm and more preferably 100-250 pm.

9. Sample block according to one or more of the preceding claims, wherein the embedding block has a longitudinal centre axis extending between the top and lower surfaces, the microsample being located nearer to the centre axis than half the distance of the longitudinal centre axis to the topside surface, preferably nearer than half said distance.

10. Method for creating the sample block for surface analysis using mass spectrometry of a microsample according one or more of the preceding claims, comprising the staps of: providing a mould; providing a liquid transparent embedding material, which embedding material is electrically insulating once hardened; pouring a first amount of the embedding material in the mould; hardening the first amount of the embedding material in the mould to create a half block; placing the microsample onto the half hardened block; pouring a second amount of the transparent embedding material in the mould, over the microsample on the half-hardened block; and hardening the second amount of transparent embedding material in the mould; characterised in that the method further comprises the stap of inserting a conductive layer in the mould, in such a way that after hardening of the second amount of transparent embedding material, the conductive layer extends at least substantially parallel to the top surface of the embedding block throughout the embedding block, to opposite sides of the side surface and at a distance d from the microsample, which step is executed before the step of hardening the second amount of transparent embedding material in the mould.

11. A method according to claim 10, wherein in the step of inserting the conductive layer, the layer is oriented such that after the step of hardening of the second amountof transparent embedding material, the conductive layer extends beyond the opposite sides of the at least one side surface.

12. A method according to claim 10 or 11 , wherein after the step of hardening the second amount of transparent embedding material, the top surface of the embedding block is polished, until the microsample is exposed at the top surface.

13. Method for surface analysis using mass spectrometry of a microsample comprising the steps of: providing a device for surface analysis using mass spectrometry including a regular sample holder; providing a sample block according to one or more of claims 1-15, the top surface being polished until the microsample is exposed; bombarding the exposed microsample with (primary) ions; and analysing the secondary ions with respect to their mass. characterised in that the method comprises the step of connecting the conductive layer with an grounded element, creating a circuit, before the step of bombarding the exposed microsample.

14. Method according to claim 12, wherein the device for surface analysis using mass spectrometry is a ToF-SIMS device.

15. Method according to claim 13 or 14, wherein the sample holder if the device for surface analysis using mass spectrometry comprises the ground element.

Images