SPRAYING DEVICE AND METHOD FOR COATING SAMPLES

Abstract

The spraying device serves for spraying samples with a solution, wherein a liquid feed for the metered feeding of the solution and a gas feed are provided which are connected via supply lines to a nozzle head (10) which has a gas outlet (36) and a liquid outlet (16) in order to spray the solution. In order, after drying, to allow a formation of relatively small crystals of the matrix in a coating which is as homogeneous as possible, it is proposed that the liquid outlet (16) is provided at the end of a capillary line (14) which projects beyond the gas outlet (36).

Claims

1. A spraying device for spraying samples (112) with a solution, wherein a liquid feed, for the metered feeding of the solution, and a gas feed are provided and are attached via supply lines to a nozzle head (10) which has a gas outlet (36) and a liquid outlet (16) in order to atomize the solution, characterized in that the liquid outlet (16) is provided at the end of a capillary line (14) which projects beyond the gas outlet (36).

2. The spraying device as claimed in claim 1, characterized in that the end of the capillary line (14) is tapered at its outer circumference.

3. The spraying device as claimed in claim 1, characterized in that the gas outlet (36) is formed by an annular gap between an outer circumference of the capillary line (14) and a guide hose (34) or guide tube.

4. The spraying device as claimed in claim 1, characterized in that the guide hose (34) and/or the capillary line (14) are held in a gastight manner in a housing (18).

5. The spraying device as claimed in claim 4, characterized in that the housing (18) has a gas port (28) for the gas feed, and a gas passage is provided in an annular gap between the guide hose or tube (34) and the capillary line (14) in the housing.

6. The spraying device as claimed in claim 4, characterized in that the housing (10), at a side directed away from the liquid outlet (16), is provided with a threaded stopper (20) which closes the housing (10) in a gastight manner against the outer wall of the capillary line (14).

7. The spraying device as claimed in claim 4, characterized in that the housing has a shoulder (24) which is arranged at a defined distance from the liquid outlet (16).

8. The spraying device as claimed in claim 1, characterized in that the nozzle head (10) is held on a moving device (100) which allows the position of the nozzle head (10) to be moved in the X, Y and/or Z direction.

9. A method for coating samples (112) by spraying with a solution using a spraying device as claimed in claim 1, characterized in that the sample (112) is sprayed several times in succession, wherein a subsequent spray application is carried out only when the previously applied layer has dried off.

10. The method as claimed in claim 9, characterized in that the first layer applied is sprayed with a relatively small amount of solution per surface area, and the amount is increased in the subsequent layers until a defined amount of solution per surface area is reached, which is applied again for the last layer or applied several times again for several layers.

11. The method as claimed in claim 10, characterized in that a first amount of solution per surface area for the first layer is doubled upon application of the second layer, trebled upon application of the third layer and, if appropriate, further increased up to a maximum in a further layer, which maximum is used in the application for all subsequent layers.

12. The method using a device as claimed in claim 8, characterized in that the sample is sprayed line by line for the application of a respective layer.

Description

[0026] An illustrative embodiment of the invention is discussed in more detail below with reference to the attached drawings, in which:

[0027] FIG. 1 shows an overall view, in cross section, of a spraying head of a spraying device;

[0028] FIG. 2 shows a detailed view of the output regions of the spraying head;

[0029] FIG. 3 shows a schematic view of a spraying device with an adjustable spraying head.

[0030] FIG. 1 shows a nozzle head 10, which can also be designated as a spraying head. The nozzle head 10 is connected, via a rear end 12 of a quartz capillary 14 as capillary line, to a liquid feed (not shown in any detail). This liquid feed can be provided by a constant-delivery syringe pump or by a dispenser with a very high resolution of 24,000 steps per syringe filling, in order to convey very exact amounts of liquid through the capillary line of the quartz capillary 14 to a liquid output 16 (see also FIG. 2).

[0031] The quartz capillary line 14 is routed through a housing 18, which is closed at its rear end with the aid of a union nut 20, wherein the union nut 20 engages in a thread 22 in the housing 18 and seals the housing against the outer circumference of the quartz capillary 14. The housing itself is designed in a stepped shape with a shoulder 24, the function of which is discussed in more detail below.

[0032] The housing is provided internally with a central bore 26, the latter communicating with a radial gas port 28 that is to be connected to a gas feed (not shown). By suitable pumping means, the gas feed ensures the delivery of air or another suitable gas, e.g. nitrogen, at a pressure of usually 2 to 3 bar, which is kept constant during operation, although other pressure values can also be realized.

[0033] At the end of the housing 18 opposite the union nut 20, a first guide hose 32 sits in a widened bore portion 30, said guide hose 32 also being able to be designed as a guide tube inside which a further guide hose 34 is introduced in a pressure-tight manner. The second guide hose 34 encloses the outer circumference of the quartz capillary 14 with an annular gap. That is to say, between the second guide hose 34 and the quartz capillary, there is a gas passage between the bore 26 of the housing 10 and a gas outlet 36 (see FIG. 2) at the end of the second guide hose 34, at the center of which the quartz capillary 14 projects by a defined distance beyond the end of the second guide hose 34.

[0034] As will be clearly seen from FIG. 2, the annular gap 38 is provided to ensure that the gas fed through the gas port 28 is blown out at the end of the second guide hose 34, as is indicated by the arrows. The liquid output 16 is here realized at a distance from the gas output 36 and is depicted by the sketched droplets. As a result of the distance between the gas outlet 36 and the liquid outlet 16, the stream of gas can easily swirl, wherein the end of the glass capillary 14 is provided with a conical taper 40 by which the swirling stream of gas is conveyed in the direction of the metered stream of liquid issuing from the liquid output 16. This conical taper, which can also be convex, permits the formation of particularly fine droplets, wherein the stream of gas conveys the fine liquid droplets farther in the direction of a sample arranged underneath the liquid outlet 16.

[0035] The nozzle head shown in FIGS. 1 and 2 is mounted in a spraying device 100, wherein the shoulder 24 rests in a defined position of a seat, such that the liquid outlet 16 lies at a defined distance from metal targets 110 which are arranged on a table and on which tissue 112 that is to be sprayed is placed in preparation for further tests. The seat 102 of the nozzle head 10 is arranged on a carrier 104 so as to be movable laterally in a Y direction, which carrier 104 is in turn mounted on a rail 106 so as to be movable in an X direction, such that the nozzle head is adjustable in the X and Y directions by movement of the seat 102 on the carrier 104 and movement of the carrier 104 on the rail 106. The seat 102 can be adjustable in the Z direction in order to be able to set the liquid outlet 16 at its distance to the targets 110 or prepared glass supports.

[0036] Generally, however, an adjustment of the distance between the spraying head 10 and the targets 110 is not necessary during the actual spraying procedure.

[0037] Normally, the tissue 112 is sprayed by means of the nozzle head 10 traveling line by line over the surface area to be sprayed, since generally the region covered by the spray jet is smaller than the surface area of the tissue that is to be sprayed. Typically, when traveling line by line, the sprayed matrix solution covers a strip-shaped surface area with a width of approximately 2 mm.

[0038] An illustrative embodiment is described in detail below in which some parameters are stated explicitly, even though these may vary within a wide range in the context of the invention.

[0039] A matrix solution was atomized that had been mixed, in the region of the nozzle head 10, with a stream of air delivered at a constant pressure of 2.5 bar. The external diameter of the selected quartz capillary was 280 m, wherein an annular gap with a height of 60 m was provided between the second guide hose 34 and the external diameter of the quartz capillary 14, i.e. the internal diameter of the second guide hose made of PEEK was 400 m. The quartz capillary 14 had an inner channel 42 with a diameter of 75 m.

[0040] At a fixed distance of 40 mm between the liquid output and the surface of the target 110, the latter was sprayed line by line until a desired surface area had been sprayed completely with the matrix solution. With the chosen nozzle geometry and at the chosen gas pressure, a region of ca. 2 mm is in this case sprayed directly, wherein the line spacings are chosen such that there is only minimal overlapping of adjacent sprayed lines, so as to avoid deviating layer thicknesses in the overlap region.

[0041] When applying a first layer, a liquid feed of 10 l per minute was chosen, wherein the speed of movement was 200 cm per minute.

[0042] After application of the first layer, a second layer was applied by atomization which, with otherwise identical parameters, had been carried out with doubling of the liquid feed to 20 l per minute. A third layer was applied with 30 l per minute, a fourth with 40 l per minute, wherein a total of 8 layers were applied which, starting from the fourth layer, had all been applied with a liquid feed of 40 l per minute.

[0043] An electron microscope test of the layer revealed that matrix crystals of a very constant crystal size in the range of 130 to 140 nm had formed. With such crystal sizes, the sample was eminently suitable for further testing in the context of the latest MALDI technique using a laser with a light beam focused to 1 m. By means of the small crystals, the resolution of the mass spectroscopy test is defined by the extremely small cross section of the laser beam of 1 m, which is below the size of a human cell of up to 10 m, such that in the context of this test the tissue could be analyzed by individual cells.

[0044] The described illustrative embodiment is not restricted in terms of its key data. In particular, the dimensions of the quartz capillary and of the guide hose can differ considerably, and the amount of liquid can also differ considerably from the stated values depending on the nature of the matrix solution to be atomized. As regards the gas feed too, deviations from the chosen pressure are possible in order to be able to apply correspondingly different layers in accordance with the desired test.