DECRIPTION OF THE PREFERRED EMBODIMENTS

[0021] FIGS. 1,2 and 3 have been described in relation to prior art.

[0022] In this text a term diluter is used, but that is not to be intended as limiting the scope of protection only to the devices called as diluters. It is e.g. possible to manufacture a single device comprising both the sample pre-processing and analysing and call that device an analyser, but still fall under the scope of this application. Thus the actual term used to call the device is not significant. What matters is the device comprising the parts identified in the accomplishing claims or their equivalents.

[0023] In FIG. 4 cross section of an embodiment of the invention is presented. The embodiment carries out the dilution in two phases, first the sample flow 21 is diluted by a first dilution flow 32 a in a construction similar to a porous tube diluter. This produces a first diluted flow 33 a . First diluted flow 33 a is then further diluted by a second dilution flow 32 b directed to a said fist diluted flow 33 a by a construction similar to an ejector. The resulting second diluted flow 33 b is directed to an analyser 14 .

[0024] Carrying out the dilution in two phases gives clear benefits over the prior art solutions. Losses would be low because the first dilution flow 32 a coming from through the walls of the central cavity, would keep the sample flow away from the walls. In the ejector type configuration, which is more prone to losses, the first diluted flow 33 a would already have a low density of the sample to be studied due the dilution done in the porous tube type configuration. Thus if the dilution in the first phase would be e.g. 1:10, then the losses produced by the ejector would by only {fraction (1/10)} nt of the losses compared to an ejector used as a single device according to prior art solution.

[0025] The low losses are, however, achieved without sacrificing accuracy of controlling of the dilution ration and temperature as would be the case if prior art type solution based on a porous tube diluter would be used. As the second dilution is carried out by a ejector type configuration these parameter are easily controlled.

[0026] In one embodiment said two dilution phases are carried out so close to each other that there is no time for significant changes of characteristics like temperature of chemical composition the sample flow to happen. That is to say that the transition delay between two dilution phases is short compared to the uncontrolled transformations happening in the sample. One way of achieving this would be to place the porous tube type configuration and ejector type configuration so close to each other that the means connecting them could be short compared to the velocity of the flow.

[0027] The means carrying out the first and second dilution can be arranged so that the exit opening of the porous tube type construction would be entry opening for a ejector type construction. Said two construction could be build e.g. to a single case forming one combined device.

[0028] As the first and second dilution flows have slightly different objectives, in one embodiment of the invention said first dilution flow 32 a and second dilution flow have separate control means. Said two flows could even have separate sources of dilution medium, so that different mediums and temperatures could be used in the first and second dilution phases.

[0029] If FIGS. 5 a and 5 b two cross section of a porous tube used in one embodiment of the invention are shown. FIG. 5 b presents the cross section of the porous tube construction along the line A-A in FIG. 5 a . The embodiment comprises first flow guide or other similar means for delivering the first dilution flow 32 a to the wall of porous tube known as such to a man skilled in the art. The temperature of the first dilution flow 32 a as well as the temperature of the whole porous tube construction is controlled by a temperature control medium 52 i.e. cooling or heating agent, flowing in a second flow guide around the said first flow guide.

[0030] To improve heat exchange between said first and second flow guides, one or both sides of the wall separating said two flow guides can be equipped with a geometry improving heat exchange, like a serrate shaped structures 57 . In the magnification in FIG. 5 only at the side of said second flow guide is equipped with a cooling serrature 57 , but as stated above similar or different geometry could be applied also to the other side of the wall.

[0031] It is to be understood that although the present invention has been specially disclosed with preferred embodiments and examples, modifications to these may be apparent to a man skilled in the art and such modifications and variations are considered to be within the scope of the invention and the appended claims. It is also intended that all the matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.