WO2014072503A1

WO2014072503A1 - A method for analyzing a solution, a device for analyzing a solution as well as a system for analyzing a solution

Info

Publication number: WO2014072503A1
Application number: PCT/EP2013/073494
Authority: WO
Inventors: Ynze Mengerink; Roland Antoon Hubertina Peters
Original assignee: Dsm Ip Assets B.V.
Priority date: 2012-11-09
Filing date: 2013-11-11
Publication date: 2014-05-15

Abstract

Method for analyzing a solution comprising at least one solvent and at least one compound of interest. The mass of at least one compound of interest is being determined. The method comprising using a nano-weighing device with a fluid channel,characterized in that the fluid channel comprises a stationary phase, and in that the method further comprising the steps of flowing the solution through the stationary phase, trapping during at least a predetermined time the compound of interest in the stationary phase, and determining the mass of the at least one compound of interest with the nano-weighing device.

Description

A METHOD FOR ANALYZING A SOLUTION, A DEVICE FOR ANALYZING A SOLUTION AS WELL AS A SYSTEM FOR ANALYZING A SOLUTION

FIELD OF THE INVENTION

The invention relates to a method for analyzing a solution comprising at least one solvent and at least one compound of interest, whereby at least one physical property of the compound of interest (mass or mass increase due to interaction) is being determined.

The invention also relates to a device for analyzing a solution comprising a solvent and a compound of interest, whereby at least one physical property of the compound of interest (mass or mass increase due to interaction) is being determined.

The invention further relates to a system for analyzing a solution, which system comprises a liquid chromatography device for providing the flow of solution and at least one device for analyzing a solution comprising a solvent and a compound of interest, whereby at least one physical property of the compound (mass or mass increase due to interaction) of interest is being determined.

BACKGROUND OF THE INVENTION

With such a method being known from US2008/001 1058A1 several physical properties e.g., electric field, magnetic field, viscoelastic properties, fluid mechanics, flow rate or viscosity of a fluid, physical dimensions of the solutes, long range forces, e.g., electrostatic and Van der Waals, and/or chemical properties e.g., chemical nature of the solvents and solutes, chemisorption, are being measured at a nanoscale by means of a piezoresistive microcantilever.

For determining a number of these physical properties, it is necessary to know in advance other physical properties of the solution and the solutes in the fluid.

However, very often only relevant physical properties of the main solvent in the fluid are known but no or nearly none information at all is available about the physical properties of the solutes in the fluid. Furthermore, by the method as described in US2008/001 1058A1 the kind of micro-cantilever and the sensing tip of the micro-cantilever that is being used need to be determined for each specific kind of fluid, solvent and solutes.

US 2004/0038426A1 discloses a microfluidic channel for transport and analysis of molecules of interest. Inside the channel different capture moieties are bound, each capture moiety is designed to capture a specific molecule. Thereafter, the mass of a specific molecule can be measured. In other words, US 2004/0038426 is hence limited to samples where the possible content is known before prior to the analysis.

US 2010/277722A1 discloses a fluid channel with a stationary phase used for separating the compound and not for retaining it so the mass can be measured.

SUMMARY OF THE INVENTION

In view of the above-mentioned and other drawbacks of the prior art, a general object of the present invention is to provide a universal method for analyzing different kind of solutions with different kind of compounds of interest, wherein at least one physical property of a compound of interest (mass or mass increase due to interaction) in the solution can be measured, whilst no or nearly none information about the compound of interest needs to be known in advance.

This object is accomplished with the method according to the invention for determining the mass of at least one compound of interest in a solution comprising at least one solvent and at least one compound of interest, the method comprising using a nano-weighing device with a fluid channel, characterized in that the fluid channel comprises a stationary phase, and in that the method further comprising the steps of flowing the solution through the stationary phase, trapping during at least a predetermined time the compound of interest in the stationary phase, and determining the mass of the at least one compound of interest with the nano-weighing device. By during at least a predetermined time is herein meant that the compound is trapped permanently or temporary and that the operator may determine the time of the trapping by adjusting the conditions (like for example changing the temperature or the solvent (during the method) or changing the trapping material or solvent (before the method).. By nano-weighing device is herein meant a device that can determine the mass of the at least one compound of interest when trapped in the stationary phase or the change in mass in the nano range (that is at least a part of the range of 1 to 1000 x10^"9 g), when the at least one compound is trapped in the stationary phase. Examples of nano- weighing devices are quartz crystal microbalance and other surface acoustic wave sensors and cantilever based systems. The nano-weight utilized in the present invention has a fluid channel where a stationary phase inside. The fluid channel can be integrated into the nano-weighing device or it may be connected to it so the solution can flow through the fluid channel and the mass of the at least one compound of interest can be determined with the nano-weight device.

The mass of a compound of interest is a physical property which can be measured for all different kind of compounds. The present invention is hence not limited to a specific molecule, but allows for a generic measurement of mass of the compound(s) of interest. Particularly, it is possible with the present invention to establish the mass of a compound of interest without knowing the compound of interest beforehand. In some embodiments, the mass of several individual (different) compounds of interest in solution with several compounds of a sample can be established without knowing the ratio or the type of compounds. Since often the mass of the compound of interest is relatively small with respect to the mass of the solvent, for example because the concentration of the compound of interest is only in the order of parts per million, the compound of interest is being trapped from the solvent in a generic way, meaning a kind of separation of the compound of interest from the solvent or the collection of the compound of interest from the solution to be able to measure the mass of the compound of interest with a relatively high accuracy. The flow of solution will flow through the nano-weighing device, wherein during passing the nano- weighing device, the compound of interest is trapped from the solution in the nano- weighing device so that the total mass of all the compound of interest in the flow of solution is being measured. The predetermined time can be the time needed to let a part of the flow of solution pass the nano-weighing device, which part comprises part or all the amount of the compound of interest. However, the predetermined time can also be the time needed to let the complete flow of solution pass the nano-weighing device.

Frequently, the composition of the solution flowing through the stationary phase changes with time. This is for example realized by feeding the solution through a liquid chromatography column where one or more of the compounds of interest are delayed as compared to the at least one solvent and particularly various compounds forming the one or more compounds of interest are delayed relative to other compound. It is important to realize that the nano-weighing device according to the present invention does not provide for separation of various compounds of interest but rather measures the total weight of a compound of interest trapped (temporarily) in the stationary phase or nanofilter. It is also important to recognize that changes in solvent over time typically takes place gradually (for example resulting from addition of a second solvent to a liquid chromatography column, whereas changes of content of a compound of interest is rather rapid and typically follows a Gaussian curve. An embodiment of the method according to the invention is characterized in that a composition of the solution flowing through the stationary phase change with time, and further comprising the step of after determining the mass of at least one compound of interest, trapping at least temporary at least a second compound of interest in the stationary phase and determining the mass of the at least second compound of interest.

In time the complete solution will pass the nano-weighing device so that all the compounds of interest in the solution will be trapped in the nano-weighing device, whilst all or at least a relatively large amount of the solvent will pass through the nano-weighing device. If the different kinds of compounds of interest are located in different parts of the flow of solution, the different kind of compounds of interest will be collected in and interact with the nano-weighing device one after the other. In time the determined mass will first increase due to trapping a first compound of interest. If the following part of the flow of solution does not comprise a solute or compounds of interest, the total determined mass will remain constant. As soon as a part of the flow of solution comprising a solute with one or more compounds of interest, the total determined mass will increase again. At a constant solvent composition, each increase of the determined mass indicates that a compound or compounds of interest is/are being trapped in the nano-weighing device. Each time the total determined mass remains constant, indicates that no compound or compounds of interest is/are being trapped within the measuring range of the nano-weighing device. The increase of response of the nano-weighing device provides information about the total mass of all compounds of interest that have been trapped in the nano-weighing device so far. The trapped compound can leave the trap, e.g. when the solvent composition changes, which has to be taken into account by calculating the mass of the compounds.

An advantage of this method is that between measuring different kind of compounds, the nano-weighing device needs not to be cleaned.

Another embodiment of the method according to the invention is characterised in that after the mass has been determined, the trapped compound of interest is being removed from the nano-weighing device, after which another kind of compound of interest from another predetermined part of the flow of the solution is being trapped and determined in the nano-weighing device.

An advantage of removing a first compound of interest from the nano- weighing device, before collecting or trapping another compound of interest in the nano-weighing device, is that the nano-weighing device only needs to determine the mass of the specific compound of interest due to which a higher accuracy can be obtained, especially if the mass of the first trapped compound is significant higher than the consecutive compounds.

Another embodiment of the method according to the invention is characterised in that the nano-weighing device comprises a trapping material, wherein due to the retention factor of the compound of interest in the nano-weighing device the compound of interest is trapped in the nano-weighing device at least during said predetermined time.

The trapping material forms a stationary phase whilst the solvent in the solution forms a mobile phase which flows through the stationary phase. Herein, the stationary phase is referred to as trapping material as well as stationary phase interchangeably. The retention factor is a well-known chromatographic parameter giving information about the period of time that the compound of interest will remain in the trapping material, also referred to as stationary phase. The retention factor depends amongst others on the elements of the stationary phase and the elements of the mobile phase. So a desired retention factor can be obtained by changing the elements of both phases, for example.

The retention factor is defined as the ratio of the net-time that the compound of interest is in the stationary phase or trap (time in the stationary phase of the compound of interest minus the time an unretained compound would use for passing the stationary phase) and the time an unretained compound would use for passing the stationary phase.

k=tn/to=(tr-to)/to k=retention factor

tr=time of compound of interest in stationary phase or trap

to=time of unretained compound in stationary phase or trap

tn=net retention time of compound in trap = tr-to The stationary phase (also referred to as trapping material) is arranged in a fluid channel of the nano-weighing device and interacts physically, chemically, mechanically with the at least one compound or particle of interest of the solution to effect an at least temporary bonding to the stationary phase. Preferably, the solvent is a liquid during the interaction with the stationary phase and the stationary phase is arranged in a cantilever with a fluid channel of the nano-weighing device. However, the solution may also be a gas comprising vapourised solvent with solid or liquid particles of the at least one compounds of interest where the nano-weighing device is equipped with a solid phase for trapping the at least one compound of interest from a gas.

Examples of stationary phases useful for the embodiment where the solution is liquid are materials used in liquid chromatography or solid phase extraction and may for example be particles, monoliths, etc. Preferred materials are Tenax, silica, reversed phase modified stationary phases e.g. C18, PolyStyreenDiVinylBenzene, carbon, ion exchangers, etc. Examples of stationary phases useful for the embodiment where the solvent of the solution has been vaporized are materials used in Gas

Chromatography (where interaction between the stationary phase and the at least one compound of interest takes place on molecular level). Preferred materials are

Poly(phenyl methyl) siloxane, DiMethylPolysiloxanes, Carbowax, etc. Another type of stationary phase useful where the solvent of the solution has been vaporized are nano particle filters and smoke filters (where interaction is on particle level). Preferred examples are polymeric membranes and electrostatic precipitators, which both can be arranged inside the fluid channel of a nano-weighing device.

When the flow of solution goes through the nano-weighing device, the compound of interest interacts with the trapping material (also referred to as stationary phase) of the nano-weighing device, due to which compound of interest is trapped and remains in the nano-weighing device. The solvent flows through the nano-weighing device and at each moment only a relatively small part of the solvent will be in the nano-weighing device together with the trapping material and the collected and trapped compound of interest.

Another embodiment of the method according to the invention is characterised in that before entering the nano-weighing device, an additional solvent is added to the solution to adjust the retention factor of the compound of interest in the nano-weighing device. The adjustment of the retention factor may be an increase (for trapping) or a decrease (cleaning).

By adding the additional solvent to the solvent, a combined solvent forming a new mobile phase is obtained. By choosing the quantity and kind of additional solvent, the retention factor can be increased to the desired value or range to retain the compound or compounds of interest in the stationary phase of the nano- weighing device at least during the predetermined time. This is particularly

advantageous when the compound of interest is otherwise difficult to trap. By choosing the quantity and kind of additional solvent, the retention factor can alternatively be decreased to a desired value or range. Decreasing the retention factor is for example useful for releasing or removing a compound of interest from the nano-weighing device, which is particularly advantageous to do inline when the solution contains more than one compounds of interest arriving separately to the nano-weighing device or for cleaning the nano-weighing device after use.

Another embodiment of the method according to the invention is characterised in that before or in the nano-weighing device, the temperature of the solution is being changed to increase or decrease the retention factor of the compound of interest in the nano-weighing device.

By changing the temperature, the retention factor can be increased to the desired value or range to maintain the compound or compounds of interest in the stationary phase at least during the predetermined time. This is particularly

advantageous when the compound of interest is otherwise difficult to trap. By changing the temperature, the retention factor can alternatively be decreased to a desired value or range. Decreasing the retention factor is for example useful for releasing or removing a compound of interest from the nano-weighing device, which is particularly advantageous to do inline when the solution contains more than one compounds of interest arriving separately to the nano-weighing device or for cleaning the nano- weighing device after use.

Another embodiment of the method according to the invention is characterised in that at least during said predetermined time the solvent is being evaporated from the solution, whilst the compound of interest is being trapped in the nano-weighing device.

After evaporation of the solvent, a compound of interest having a higher evaporation temperature than the solvent, will remain liquid or solid and can be collected by depositing in or trapped in the fluid channel of the the nano-weighing device. After all the solvent from a part of the flow of solution or the complete flow of solution has been evaporated, all the compound or compounds of interest in the part of the flow of solution or the complete flow of solution, have been collected and the mass thereof can be measured by means of the nano-weighing device.

The evaporation temperature is defined as a relative temperature at which a defined part of the solution or compound of interest is evaporated in a defined time in a defined system. Another embodiment of the method according to the invention is characterised in that the solution is being nebulized in a chamber, wherein the temperature of the solution is being changed to at least the evaporation temperature of the solvent to evaporate in the chamber the solvent from the solution.

By nebulizing the solution into the chamber relatively small droplets of the solution are obtained in the chamber for example of a size in the range of pL to μΙ_ for each droplet. Preferably the droplets have a uniform size with a so called RSD (relative standard deviation) of less than 25%, preferably less than 10%. The evaporation temperature of the solvent is lower than the evaporation temperature of the compounds. Due to the relatively small size of the droplets, the amount of energy needed to evaporate the solvent from each droplet is relatively low. Furthermore, due to the uniform size of the droplets, the amount of solvent that needs to be evaporated from each droplet is about the same and the solvent of the droplets will be evaporated in about the same time, minimizing the evaporation of the compounds with the higher evaporation temperature.

It is preferred that the evaporation of the at least one solvent is conducted by nebulizing the solvent into uniformly sized droplets by a microfluidic device or inkjet-type device to enhance controlled evaporation in a defined time for all solvent droplet. Predefined time here refers to that the evaporation time depends on the droplet size and that the evaporation time hence can be adjusted by changing the size of the droplets.

Another embodiment of the method according to the invention is characterised in that the solution is obtained from a liquid chromatography device, preferably a high performance liquid chromatography device, wherein at least from a predetermined part of the flow of solution leaving the liquid chromatography device, the compound of interest is being trapped and the mass is being determined by means of the nano-weighing device.

With a liquid chromatography device it is relatively easy to obtain a flow of solution wherein successive different parts of the flow comprise different compounds of interest. By guiding the flow of solution obtained from the liquid chromatography device through the nano-weighing device, the mass of each compound of interest can readily be determined.

Another embodiment of the method according to the invention is characterised in that a resonance frequency of the nano-weighing device is measured, whereafter the mass of the compound of interest that has been trapped in the nano- weighing device is being calculated based on the measured resonance frequency of the nano-weighing device.

The nano-weighing device can comprise a cantilever which will have a known resonance frequency if no compound of interest is trapped in the nano- weighing device. However, the collected and trapped compound or compounds of interest will be located in, the stationary phase in the fluid channel of the cantilever and will change the resonance frequency of the cantilever. The resonance frequency can be measured and from the measured resonance frequency the mass of the

compound(s) can be calculated. Preferably the nano-weighing device is being calibrated with regular intervals so that accurate measurements of the mass of the compounds will be obtained.

The invention also relates to a device for analyzing a solution comprising a solvent and a compound of interest, whereby at least one physical property of the compound of interest is being determined.

The device according to the invention is a device for determining the mass of at least one compound of interest in a solution comprising at least one solvent and at least one compound of interest, the device comprises a nano-weighing device with a fluid channel, characterized in that the fluid channel comprises a stationary phase through which the solution can be flown and in which stationary phase the at least one compound of interest can be at least temporarily trapped, and the nano- weighing device being arranged so it can determine the mass of the compound of interest trapped within the fluid channel.

The device according to another aspect of the invention is characterized in that the device comprises a nano-weighing device, means to trap during at least a predetermined time the compound of interest from the flow of solution in the nano-weighing device and means to determine the mass of the trapped compound of interest by the nano-weighing device.

With such a device the mass of a number of compounds of interest in the flow of solution can be determined.

Another embodiment of the device according to the invention is characterised in that the nano-weighing device is provided with a trapping material also referred to as stationary phase, wherein due to the retention factor of the compound of interest in the nano-weighing device the compound of interest is trapped in the nano- weighing device at least during said predetermined time. The resulting retention factor can be established experimentally or by means of calculations of the amount and kind of trapping material in relation to amongst others the solvent in the solution. By changing for example the kind of trapping material the resulting retention factor can be increased or decreased as desired.

Another embodiment of the device according to the invention is characterised in that the device comprises means to add an additional solvent to the solution to change the retention factor of the compound of interest in the nano-weighing device.

By adding an additional solvent the retention factor can readily be changed without changing the trapping material (also referred to as stationary phase) amongst others allowing for changing of the retention factor inline, i.e. during an experiment, or after an experiment to facilitate cleaning.

Another embodiment of the device according to the invention is characterised in that the device comprises means to change the temperature of the solution in the nano-weighing device to increase or decrease the retention factor of the compound of interest in the nano-weighing device.

By changing the temperature of the solvent the retention factor can readily be changed without changing the trapping material amongst others allowing for changing of the retention factor inline, i.e. during an experiment, or after an experiment to facilitate cleaning.

An embodiment of the device according to the invention is

characterised in that the device comprises means to evaporate the solvent from the solution and to deposit and trap the compound of interest on the nano-weighing device.

By evaporating the solvent only the remaining compound of interest will be collected on the nano-weighing device and the mass of the compound of interest can readily be determined.

Another embodiment of the device according to the invention is characterised in that the device comprises a chamber, a nebulizing device to nebulize the solution in the chamber and means to change the temperature of the solution to at least the evaporation temperature of the solvent.

Such a nebulizing device can be a kind of inkjet-device or a microfluidic device being able to generate a constant and continuous spray of about the same size droplets. The means to change the temperature of the solution can be provided in the nebulizing device or the chamber or in both the nebulizing device and the chamber. The means can be heating or cooling elements to change the temperature to above the evaporation temperature of the solvent but below the evaporation temperature of the compound of interest. As the solvent droplets are uniformly sized, the energy needed in the predetermined time to evaporate a solvent droplet is constant for all droplets and as a consequence, the evaporation of the compound of interest is minimized.

Another embodiment of the device according to the invention is characterised in that by means of the nebulizing device the solution is nebulized into droplets with about the same size.

By means of for example a kind of inkjet-device droplets with about the same size can easily be obtained. Also microfluidic devices can be used to generate uniformly sized droplets.

Another embodiment of the device according to the invention is characterised in that the device comprises means to remove the compound of interest that is trapped in the nano-weighing device from the nano-weighing device.

After measuring the mass of one single compound of interest or a number of compounds of interest, the compounds of interest are removed from the nano-weighing device so that the nano-weighing device can be used again for another kind of measurement. It is also possible that the trapping material (also referred to as stationary phase) of the nano-weighing device is removed as well to replace it with another kind of trapping material being more suitable for the trapping compounds from another kind of solution. The trapping material may also be replaced with the same kind of trapping material for example to allow for cleaning of the trapping material offline and/or in an area more suited for cleaning of the trapping material for example due to (working) environmental considerations.

In a particularly preferred embodiment, the trapping material (also referred to as stationary phase) is arranged in a cartridge detachably connected to the nano-weighing device. Such an arrangement of the trapping material facilitate rapid replacement of trapping material to different type of trapping material or for separate cleaning of (multiple) cartridge leading to increase efficiency of operating the device or system (as discussed below) according to the invention. It furthermore facilitate a cleaner and safer working environment as cleaning (which may involve aggressive solvents, high temperature and/or working with unknown compounds recently trapped in the trapping material) can be conducted in a separated area or even in a dedicated cartridge cleaning device. In one embodiment, the cartridge is a disposable cartridge. This eliminates the need for removing of the (unknown) compound of interest from the trapping material thereby allowing for one or more of a safer working environment, faster preparation / maintenance of the device or system, and reduced environmental impact due to no need for cleaning of the trapping material.

The invention also relates to a system for analyzing a solution, which system comprises a liquid chromatography device for providing the flow of solution and at least one device according to the invention to analyze the flow of solution obtained from the liquid chromatography device.

With such a system it is possible to introduce a solution comprising a number of compounds of interest into the liquid chromatography device. In the solution leaving the liquid chromatography device the different compounds of interest are located in different parts of the flow of solution. By means of the device according to the invention the total mass of each compounds of interest is subsequently measured.

An embodiment of the system according to the invention is

characterised in that the system comprises a number of devices for analyzing the flow of solution obtained from the liquid chromatography device, wherein the devices are in parallel or serial connection.

With such a system preferably each compound of interest is introduced to its own device for measuring the mass of the compound. Due to the number of devices, which might be all identical, the time needed to measure the mass of all the compounds can be reduced.

Another embodiment of the system according to the invention is characterised in that the system comprises a detector to detect another physical property of the compound of interest, wherein the device for analyzing the flow of solution obtained from the liquid chromatography device and the detector are in parallel or serial connection.

With such a detector, for example the ultraviolet absorption can be measured so that it is easily known in which parts of the flow of solution a compound of interest can be found.

Another embodiment of the system according to the invention is characterised in that the system comprises a controlling device to control the liquid chromatography device and the device for analyzing the solution. By means of the controlling device the flow of solution through the whole system can be controlled and the determined masss of the different compounds of interest can be calculated based on input from the nano-weighing device, for example via the resonance frequencies of the nano-weighing device. Such calculations may also involve establishing amounts of compounds of interest where peaks from compounds of interest measured by the nano-weighing device are (partially) overlapping. Methods of separating such peaks are well known in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the inventions, wherein:

Figure 1 is a schematic view of an embodiment of a system according to the invention comprising a first embodiment of a device according to the invention,

Figure 2 is a chromatogram of a solution flowing through the system as shown in figure 1 ,

Figure 3 is a schematic view of a second embodiment of a device according to the invention.

All figures are highly schematic and not necessarily to scale, and they show only parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested. Like parts are indicated by the same numerals in the figures.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows a schematic view of a system 1 according to an embodiment of the invention, the system comprising a liquid chromatography device 2 and a device 3 according to the invention to analyze the flow of solution obtained from the liquid chromatography device 2.

Such a liquid chromatography device 2 is known as such and comprises at least a column comprising a stationary phase and an injector for injecting a solution comprising a solvent and a number of compounds of interest into and the column. The solvent forms a mobile phase. The solution is introduced into the liquid chromatography device 2 in the direction indicated by arrow P1 and is leaving the liquid chromatography device 2 in the direction indicated by arrow P2. When leaving the liquid chromatography device 2, the different compounds of interest are preferably located in a different part of the flow of solution, so that each part of the flow comprises one compound of interest only, for example due to different retention time in a coil of the liquid chromatography device 2.

In this embodiment, the device 3 comprises a fluid entrance 5, a nano-weighing device 4 with a fluid channel and a stationary phase, and a fluid exit 8. The nano-weighing device 4 is provided with a cantilever 6 and a fluid channel 7 inside the cantilever 6. The nano-weighing device 4 is connected to the fluid entrance 5 and to the fluid exit 8. The fluid entrance 5 is connected to a fluid exit of the liquid chromatography device 2 so that the flow of solution leaving the liquid chromatography device 2 will directly be introduced into the nano-weighing device 4. At least the fluid channel 7 surrounding the cantilever 6 is provided with a trapping material forming a stationary phase.

In one embodiment, an adjustable flow splitter is provided between the liquid chromatography device 2 and the nano-weighing device 4 for directing all, a part or no flow of solution to device 3. The flow P5 of solution not directed to device 3 may be directed to devices or detectors arranged in parallel to device 3. Detectors may be identical to the nano-weighing device 4 or a different type of detector, such as UV- detector or other detectors described elsewhere herein. If both a flow splitter and an inlet for inserting an additional solvent are arranged between device 2 and device 4, then it is highly preferred that the flow splitter is arranged in the flow direction indicated by arrow P2 before the inlet for inserting an additional solvent, as this allows for analysis in parallel detectors without the additional solvent and less additional solvent will be needed to achieve the desired change in retention factor of the compound.

In one embodiment, the optional device 13 for converting the solution into a mixture of vaporised solvent and liquid or solid compound of interest is included in the device 1 according to the invention.

In a particular preferred embodiment, an inlet is provided between the liquid chromatography device 2 and the nano-weighing device 4 for inserting an additional solvent in the direction indicated by arrow P3 in the flow of solution leaving the liquid chromatography device 2. The device 3 may also be provided with means to control the temperature of the solution entering the nano-weighing device 4.

The solution, combined - if desired - with the additional solvent, is introduced into the device 3 and will flow through the fluid entrance 5 into the fluid channel 7. In the fluid channel 7 the compound of interest will be trapped by the trapping material in the fluid channel 7 and onto the cantilever 6, whilst the solvent and the optional additional solvent will leave the device 3 via fluid exit 8 in the direction indicated by arrow P4. The retention factor in the device 3 is preferably such that during a predetermined time the compound of interest remains in the fluid channel 7 and into the fluid channel 7 of cantilever 6. When leaving device 3, the solvent, optional solvent and compound (if released from the trapping material) may be discharged or may be directed to further serially arranged detectors or devices (not shown). Serially arranged detectors and devices (particularly a UV detector as described elsewhere) may also be arranged in the flow stream between device 2 and device 3 (not shown).

The operation of system 1 according to a preferred embodiment of the invention will be explained with reference to figure 2 showing a simulated chromatogram. To a solvent six different compounds of interest are added, each having a mass of 1 nano-gram. In a well-known manner this solvent with the mixture of the six compounds is introduced through the liquid chromatography device 2. When leaving the liquid chromatography device 2, the six different compounds of interest are each located in a different part of the flow of solution, so that each part of the flow comprises one compound of interest only.

Right after the liquid chromatography device 2 a UV-detector (not shown) is mounted, by means of which the six compounds C1 -C6 can be detected one after the other. As can be seen in the line 9 of the chromatogram, the height of the top and shape of the curve of each compounds C1 -C6 differ from the curves of the other compounds C1 -C6. So from the information obtained by means of the UV-detector (not shown) without using known standard solutions of identical compounds, nothing can be said about the mass of each compound or even the mass ratios of the compounds. The operation of the liquid chromatography device 2 as well as such a UV-detector are well known in the art and will not further be explained.

To the solution leaving the liquid chromatography device 2, an additional solvent may be added to amend the retention factor in the device 3 as desired. The solution together with the additional solvent will then enter the device 3 via fluid entrance 5.

In the trapping material of the nano-weighing device 3 firstly, the first compound C1 of interest will be trapped. Whilst trapping the compound C1 of interest, the resonance frequency of the cantilever 6 will change. From the measured resonance frequency of the cantilever 6, the mass of the first compound of interest can be calculated. This is plotted as line 10 in the chromatogram. As can be seen the curve indicating the mass M1 starts at 0.0 and then increases to 1 .0 nano-gram, being exactly the amount added to the solution before entering the liquid chromatography device 2. The line 1 1 in the chromatogram shows the first derivative of line 10.

The compound C1 remains in the nano-weighing device 3, whilst the solvent that carried the compound C1 will leave the nano-weighing device 3 through fluid exit 8. As soon as the part of the flow of solution comprising the second compound C2 enters the trapping material, the second compound C2 will be trapped as well. From the measured resonance frequency of the cantilever 6, the total mass M2 of the first and second compound of interest can be calculated.

In this way one after the other the compounds C3, C4, C5 and C6 will be trapped and the total mass M3-M6 of all the compounds trapped so far can be calculated. To know the mass of a specific compound, for example compound C4, the total mass M3 needs to be subtracted from the total weigh M4.

Figure 3 shows a schematic view of of an optional device 13 for converting the liquid solution into a mixture of solvent vapour and solid or liquid particles of the at least one compound of interest, which optional device may be included or omitted in the position shown in Fig. 1 of the device according to the invention.

The device 13 also comprises nozzle 20 for preparing droplets of the solution provided via fluid entrence 15. The nozzle may be part of a nebulizing device 19 By nebulizing the solution into the chamber 21 relatively small droplets 22 of the solution are obtained in the chamber 21 , for example of a size in the range of pL tot μΙ_ for each droplet 22. Preferably the droplets 22 have a uniform size with a so called RSD (relative standard deviation) of less than 25%, preferably less than 10%.

The nebulizing device 19 and/or the chamber 21 are provided with means to control the temperature of the droplets 22 that are ejected by nebulizing device 19 into the chamber 21. The temperature is controlled so that from each droplet 22 all the solvent of the solution is being evaporated during the time that the droplet 22 needs to travel from the nozzle 20 to the solvent exit 24. At the solvent exit 24 the solvent is evaporated and the at least one compound of interest remains as a particle or droplet 23. This particle or droplet 23 flows with the evaporated solvent from the solvent exit 24 and into the fluid entrance 5 of Fig. 1 .

It is also possible to change other physical parameters than the temperature in the chamber, like gas flow, currents for charging compounds etc to control the evaporation of the solvent. The kind of solvent and the optional additional solvent to be used can be any kind of aqueous solvent or organic solvent ranging from water or carbon dioxide to methanol to acetonitrile to hexane. The kind of compound can be any kind of inorganic or organic compound.

The trapping material nano-weighing device can be any kind of trapping material in the known for liquid chromatography device.

It is also possible to arrange a number of nano-weighing devices in serial or parallel connection wherein each nano-weighing device is being used to trap another kind of compound.

The device can be provided with means to remove the compound of interest that is trapped in the nano-weighing device from the nano-weighing device. Such means to remove the compound of interest can be means to introduce a solvent or gas to the nano-weighing device to which the compounds adhere, or heating means to heat the temperature of the nano-weighing device to 450 - 900 degrees Celsius whereby the compound of interest is evaporated, decomposed or combusted. This means to remove the compound of interest that is trapped in the nano-weighing device may be an integral part of the device or may be a separate (sub)device arranged apart from the main device for example allowing removing of the compound offline or in a protected environment.

The device can be provided with one or more detectors to detect another physical property of the compound of interest. Such a detector can be a Mass Spectrometric detector (MS), a Ultra Violet detector (UV), a Fluorescence detector (FLU), an Infra Red detector (IR), a Refractive Index detector (RID), a Electrochemical detector (EC), an Evaporative Light Scattering Detector (ELSD), a

Charged Aerosol Detector (CAD), a Nano Quantitative Analyte Detector (NQAD).

The means to calculate the mass of the compound of interest that has been trapped in the nano-weighing device can be any calculator or computer.

The means to changing the temperature of the solution in the nano- weighing device to increase or decrease the retention factor of the compound of interest in the nano-weighing device can be thermal heating with gas, Curie-Point- heating, microwave heating, resistive heating etc.

An individual feature or combination of features from an embodiment of the invention described herein, as well as obvious variations thereof, are combinable with or exchangeable for features of the other embodiments described herein, unless the person skilled in the art would immediately realize that the resulting embodiment is not physically feasible.

REFERENCE LIST

1 system

2 device

3 device

4 device

5 fluid entrance

6 cantilever

7 fluid channel

8 fluid exit

9 line

10 line

1 1 line

13 device

14 device

15 fluid entrance

16 cantilever

19 device

20 nozzle

21 chamber

22 droplet

23 droplet

24 solvent exit

Method for analyzing a solution comprising a solvent and at least one compound of interest, whereby at least one physical property (mass or mass increase due to interaction) of the compound of interest is being determined, characterized in that during at least a predetermined time the compound of interest is being trapped from a flow of solution in a nano-weighing device, whereby in the nano-weighing device different kind of compounds of interest can be trapped and the mass of the compound of interest can be determined.

Method according to item 1 , characterized in that after the mass of a first compound of interest has been determined, at least a second compound of interest from another predetermined part of the flow of the solution is also being trapped from the flow of solution in the nano-weighing device, and the total mass of the trapped first compound of interest and the at least second compound of interest is being determined by means of the nano-weighing device.

Method according to item 1 , characterized in that after the mass has been determined, the trapped compound of interest is being removed from the nano- weighing device, after which another kind of compound of interest from another predetermined part of the flow of the solution is being trapped and determined in the nano-weighing device.

Method according to one of the preceding items, characterized in that the nano- weighing device comprises a trapping material, wherein due to the retention factor of the compound of interest in the nano-weighing device the compound of interest is trapped in the nano-weighing device at least during said predetermined time.

Method according to item 4, characterized in that before entering the nano- weighing device, an additional solvent is added to the solution to change the retention factor of the compound of interest in the nano-weighing device.

Method according to item 4 or 5, characterized in that before or in the nano- weighing device, the temperature of the solution is being changed to change the retention factor of the compound of interest in the nano-weighing device.

Method according to any one of items 1 -3, characterized in that at least during said predetermined time the solvent is being evaporated from the solution, whilst the compound of interest is being trapped in the nano-weighing device.

Method according to item 7, characterized in that the solution is being nebulized in a chamber, wherein the temperature of the solution is being changed to at least the evaporation temperature of the solvent to evaporate in the chamber the solvent from the solution.

9. Method according to one of the preceding items, characterized in that the

solution is obtained from a liquid chromatography device, preferably a high performance liquid chromatography device, wherein at least from a

predetermined part of the flow of solution leaving the liquid chromatography device, the compound of interest is being trapped and the mass is being determined by means of the nano-weighing device.

10. Method according to one of the preceding items, characterized in that a

resonance frequency of the nano-weighing device is measured, whereafter the mass of the compound of interest that has been trapped in the nano-weighing device is being calculated based on the measured resonance frequency of the nano-weighing device.

1 1. Device for analyzing a solution comprising a solvent and a compound of interest, whereby at least one physical property of the compound of interest is being determined, characterized in that the device comprises a nano-weighing device, means to trap during at least a predetermined time the compound of interest from the flow of solution in the nano-weighing device and means to determine the mass of the trapped compound of interest by the nano-weighing device.

12. Device according to item 1 1 , characterized in that the nano-weighing device is provided with a trapping material, wherein due to the retention factor of the compound of interest in the trapping material the compound of interest is trapped in the nano-weighing device at least during said predetermined time.

13. Device according to item 12, characterized in that the trapping material is

arranged in a cartridge detachably connected to the nano-weighing device.

14. Device according to item 12 or 13, characterized in that the device comprises means to add an additional solvent to the solution to change the retention factor of the compound of interest in the nano-weighing device.

15. Device according to any one of the items 12-14, characterized in that the device comprises means to change the temperature of the solution in the nano-weighing device to change the retention factor of the compound of interest in the nano- weighing device.

16. Device according to item 1 1 , characterized in that the device comprises means to evaporate the solvent from the solution and to deposit and trap the compound of interest on the nano-weighing device. Device according to item 16, characterized in that the device comprises a chamber, a nebulizing device to nebulize the solution in the chamber and means to change the temperature of the solution to at least the evaporation temperature of the solvent.

Device according to item 17, characterized in that by means of the nebulizing device the solution is nebulized into droplets with about the same size.

Device according to one of the items 1 1 -18, characterized in that the device comprises means to remove the compound of interest that is trapped in the nano- weighing device from the nano-weighing device.

System for analyzing a solution, which system comprises a liquid

chromatography device for providing the flow of solution and at least one device according to one of the preceding items 1 1 -18 to analyze the flow of solution obtained from the liquid chromatography device.

System according to item 20, characterized in that the system comprises a number of devices for analyzing the flow of solution obtained from the liquid chromatography device, wherein the devices are in parallel or serial connection. System according to item 20 or 21 , characterized in that the system comprises a detector to detect another physical property of the compound of interest, wherein the device for analyzing the flow of solution obtained from the liquid

chromatography device and the detector are in parallel or serial connection. System according to any one of the items 20-22, characterized in that the system comprises a controlling device to control the liquid chromatography device and the device for analyzing the solution.

Claims

A method for determining the mass of at least one compound of interest in a solution comprising at least one solvent and at least one compound of interest, the method comprising

- using a nano-weighing device with a fluid channel,

characterized in that the fluid channel comprises a stationary phase, and in that the method further comprising the steps of

- flowing the solution through the stationary phase,

- trapping during at least a predetermined time the compound of interest in the stationary phase, and

- determining the mass of the at least one compound of interest with the nano- weighing device.

Method according to claim 1 , characterized in that a composition of the solution flowing through the stationary phase change with time, and further comprising the step of

- after determining the mass of at least one compound of interest, trapping at least temporary at least a second compound of interest in the stationary phase and determining the mass of the at least second compound of interest.

Method according to claim 1 or 2, further comprising the step of changing a retention factor of the compound of interest in the stationary phase by adding an additional solvent to the solution before flowing the solution through the stationary phase, preferably to release the at least one compound of interest from the stationary phase.

Method according to any one of the claims 1 to 3, further comprising the step of changing a retention factor of the at least one compound of interest in the stationary phase by changing the temperature of the solution in the fluid channel, preferably to release the at least one compound of interest from the stationary phase.

Method according to any one of the claims 1 , 2 or 4, further comprising the step of evaporating the at least one solvent before flowing the solution through the stationary phase.

Method according to claim 5, characterized in that the step of evaporating the at least one solvent involves nebulizing the solution in a chamber, wherein the temperature of the solution is being changed to at least the evaporation temperature of the solvent to evaporate in the chamber the solvent from the solution.

Method according to claim 5 or 6, characterized in that the step of evaporating the at least one solvent by nebulizing the solvent into uniformly sized droplets by a microfluidic device or inkjet-type device to enhance controlled

evaporation in a defined time for all solvent droplet.

Method according to any one of the preceding claims, further comprising the step of obtaining the solution from a liquid chromatography device, preferably a high performance liquid chromatography device, wherein at least from a part of the flow of solution leaving the liquid chromatography device, the compound of interest is being trapped and the mass is being determined by means of the nano-weighing device, and optionally the step of providing at least a part of the flow of solution leaving the liquid chromatography device inline to the nano-weighing device.

A device for determining the mass of at least one compound of interest in a solution comprising at least one solvent and at least one compound of interest, the device comprises a nano-weighing device with a fluid channel,

characterized in that the fluid channel comprises a stationary phase through which the solution can be flown and in which stationary phase the at least one compound of interest can be at least temporarily trapped, and the nano- weighing device being arranged so it can determine the mass of the compound of interest trapped within the fluid channel.

Device according to claim 9, characterized in that the stationary phase is in a fluid channel, which fluid channel is arranged in a cartridge detachably connected to the nano-weighing device.

Device according to claim 9 or 10, characterized in that the device comprises means to evaporate the at least one solvent from the solution before the fluid channel and means to direct the evaporated at least one solvent and the at least one compound of interest to the fluid channel of the nano-weighing device.

Device according to claim 1 1 , characterized in that the device comprises a chamber arranged before the fluid channel in the flow path of the solvent, said chamber comprises a nebulizing device to nebulize the solution in the chamber and means to change the temperature of the solution to at least the evaporation temperature of the solvent, and a metering device for providing solvent to the nebulizing device.

System for analyzing a solution, which system comprises a liquid

chromatography device for providing the flow of solution and at least one device according to one of the claims 9-12 to determine the mass of at least one component of interest in the solution the flow of solution obtained from the liquid chromatography device.

System according to claim 13, characterized in that the system comprises a number of devices to determine the mass of at least one component of interest in the solution, wherein the devices are in parallel or serial connection. System according to claim 13 or 14, characterized in that the system comprises a detector to detect another physical property of the compound of interest, wherein the device to determine the mass of at least one component of interest in the solution and the detector are in parallel or serial connection.