WO2013091118A1

WO2013091118A1 - Method and apparatus for analysis of samples containing small particles

Info

Publication number: WO2013091118A1
Application number: PCT/CH2012/000274
Authority: WO
Inventors: Markus Michler; David Bischof; André Bernard; Andres HELDSTAB; Ruedi OBERHOLZER; Klaus Dietrich
Original assignee: Nanotion Ag
Priority date: 2011-12-22
Filing date: 2012-12-17
Publication date: 2013-06-27

Abstract

The nozzle can be used in an apparatus for determining a characteristic of a sample liquid comprising particles by irradiating sample liquid in an open jet of said sample liquid by means of a pulsed light beam focused into said open jet and obtaining a signal by detecting a breakdown of at least one of said particles, wherein said characteristic is obtainable from said signal. The nozzle comprises a first member and a second member, wherein said first and second members are fixed to each other, and a channel is formed at an interface between said first and second members. The channel has an open end for letting emerge said open jet. The arrangement comprises a top portion in which the nozzle is inserted and a base portion. A gas sheath is provided surrounding the open jet.

Description

METHOD AND APPARATUS FOR ANALYSIS OF SAMPLES CONTAINING SMALL PARTICLES

Technical Field

The invention relates to the analysis of liquids containing small particles, more particularly to the detection of small particles in liquids by laser-induced breakdown detection (LIBD). It relates more specifically to the determination of sizes and/or concentrations of nanoparticles in solutions. The invention relates to methods and apparatuses according to the opening clauses of the claims. Such methods and apparatuses find application, e.g., in potable water analysis and in contamination detection.

Background of the Invention

From WO 00/106993 Al is known a method for determining the size of particles in a solution. The method is based on the principle of laser-induced breakdown detection (LIBD) and allows to determine particle sizes. This is achieved by generating plasma emissions and detecting the plasma emissions in a spatially resolved manner and representing the plasma emissions in a location-frequency diagram which is a function of particle size, and comparing the location-frequency diagram with location-frequency diagrams of solutions containing particles of known size. From this, particles sizes can be determined. In US 7,679,743 Al , an apparatus and method for measuring the size of nanoparticles present in an aqueous solution based on laser-induced breakdown is presented. Using calibration curves, the size of the nanoparticles can be determined.

EP 1 918 694 Al relates to the detection of changes in a population of particles in a solution, based on laser-induced breakdown detection. In "Determination of colloidal iron in water by laserinduced breakdown spectroscopy" by Y. Ito, O. Ueki, S. Nakamura, in Analytica Chemica Acta 299 (1995) p.401-405, laser-induced breakdown spectroscopy is applied to the determination of FeO(OH) in water. Therein, plasma light is detected in a direction perpendicular to the direction of incidence of an exciting laser beam, and the sample solution is provided in an open jet, a sheath of gas surrounding this open jet.

"Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength" by W.F. Ho, C.W. Ng, N.H. Cheung, in Applied Spectroscopy 51 (1997) p.87-91 discloses a spectroscopic study of the plasma plume produced by ablation of liquid samples using lasers of 532 and 193 nm. Therein, a flow cell produces a vertical sample jet, laser pulses being focused on that sample jet about 12 mm downstream from the flow cell and plasma light detection taking place at an angle with respect to the incidence of the laser pulses.

A method frequently used for characterizing sample liquids comprising particles is known as dynamic light scattering (DLS). DLS is described, e.g., in the "DLS technical note MRK656-01 " with the title "Dynamic Light Scattering: An Introduction in 30 Minutes" available at

http://www.malvem.com/common/downloads/campaign/MRK656-01.pdf. A spectial way of carrying out LIBD is known as laser-induced breakdown

spectroscopy (LIBS). In this case, the light emitted at a breakdown of a particle is spectroscopically analyzed. This way, different elemental compositions of particles in a sample liquid can be investigated.

Summary of the Invention

One object of the invention is to create an improved way of providing a sample liquid to be examined. Even more specifically, an improved way of creating an open jet suitable for use in a method for determining a characteristic of a sample liquid comprising particles shall be provided, and in second aspect of the invention, an improved way of creating an air curtain (or more generally a gas sheath) shall be be provided.

A nozzle and a nozzle device and an arrangement shall be provided, as well as a method for manufacturing a nozzle. Futhermore shall be provided a method for determining a characteristic of a sample liquid comprising particles and an apparatus for determining a characteristic of a sample liquid comprising particles and a use of a nozzle. In said second aspect of the invention, a method for determining a characteristic of a sample liquid comprising particles and an apparatus for determining a characteristic of a sample liquid comprising particles and an arrangement for use in such an apparatus or method shall be provided.

Another object of the invention is to create an improved way of carrying out LIBD and more particularly to create an improved way of providing a sample liquid to be examined by means of LIBD. Another object of the invention is to create an improved way of carrying out LIBS and more particularly to create an improved way of providing a sample liquid to be examined by means of LIBS.

Another object of the invention is to create an improved way of carrying out DLS and more particularly to create an improved way of providing a sample liquid to be examined by means of DLS.

Another object of the invention is to provide a way of producing a well-defined open jet.

Another object of the invention is to provide a way of producing a particularly small open jet.

Another object of the invention is to provide a way of producing a particularly stable open jet.

Another object of the invention is to provide a nozzle being well manufacturable.

Another object of the invention is to provide a nozzle manufacturable with excellent reproducibility.

Another object of the invention is to provide a way of carrying out with high precision a method for determining a characteristic of a sample liquid comprising particles, in particular dynamic light scattering (DLS) or laser-induced breakdown detection (LIBD), or more particularly laser-induced breakdown spectroscopy (LIBS). Another object of the invention is to provide a way of carrying out with high sensitivity for the detection small particles a method for determining a characteristic of a sample liquid comprising particles, in particular DLS or LIBD, or more particularly LIBS.

Another object of the invention is to provide an improved way of carrying out in an inline mode a method for determining a characteristic of a sample liquid comprising particles, in particular DLS or LIBD, or more particularly LIBS. Another object of the invention is to provide a way of carrying out in a particularly stable way a method for determining a characteristic of a sample liquid comprising particles, in particular DLS or LIBD, or more particularly LIBS.

Another object of the invention is to provide a way of carrying out a method for determining a characteristic of a sample liquid comprising particles, in particular DLS or LIBD, or more particularly LIBS, in such a way that it requires little maintenance.

Another object of the invention is to provide a way of simply and/or quickly adjusting an apparatus for determining a characteristic of a sample liquid comprising particles, in particular an DLS or LIBD or, more specifically an LIBS apparatus, to different kinds of sample liquid.

Another object of the invention is to provide a way of simply and/or quickly exchanging a nozzle for producing an open jet of a sample liquid.

Further objects emerge from the description and embodiments below.

At least one of these objects is at least partially achieved by apparatuses and methods according to the patent claims.

The method for determining a characteristic of a sample liquid comprising particles comprises the steps of a) producing an open jet of said sample liquid; wherein step a) is carried out using a nozzle according to the invention. In particular, e.g., in case if LIBD or LIBS, the method can comprise the steps of c) irradiating said sample liquid in said open jet by means of a pulsed light beam focused into said open jet; and d) obtaining a signal by detecting a breakdown of at least one of said particles; wherein said characteristic is obtainable from said signal. The nozzle is a nozzle suitable for use in a method or an apparatus for determining a characteristic of a sample liquid comprising particles, and the nozzle comprises

— a first member;

— a second member;

5 said first and second members being fixed to each other, a channel being formed at an interface between said first and second members, said channel having an open end for letting emerge said open jet. In particular, it can be provided that said method or apparatus is a method or apparatus for determining a characteristic of a sample liquid comprising particles by irradiating sample liquid in an open jet of said sample liquid by l o means of a pulsed light beam focused into said open jet and obtaining a signal by

detecting a breakdown of at least one of said particles, said characteristic being obtainable from said signal.

Said characteristic usually is a characteristic relating to said particles. More particularly, said characteristic comprises at least one of a size of said particles and a concentration 15 of said particles; e.g., a mean size of the particles; a concentration of said particles; a size distribution of said particles; and/or a concentration of those of said particles having a size in a pre-determined size range.

Said sample liquid usually either is a specimen to be examined or is a liquid containing specimen to be examined, e.g., a solution of specimen to be examined, e.g., based on 20 water or on another solvent.

Said particles are usually nanoparticles. Generally, this designates particles having a volume of at most 1 μιη , and in particular of at least 1 nm . More specifically, nanoparticles are particles having a maximum linear extension of at most 1 μηι, and in particular at least 1 nm. Another way of interpreting the term nanoparticles is to let it 5 designate particles measuring in at least one dimension at most 100 nm, and more

particularly particles measuring in at least two dimensions at most 100 nm. Under "light", we understand most generally electromagnetic radiation; and more particularly electromagnetic radiation of the infrared, visible or ultraviolet portion of the electromagnetic spectrum.

Typically, said light is laser light. Laser light can readily provide energy densities large 5 enough for creating a breakdown of nanoparticles. The breakdown generates a plasma.

And the plasma can be detected, e.g., photosensitively, acoustically or otherwise. Or, the plasma is detected by detecting the absorption of light of a light pulse of said pulsed light beam. Therein, the absorption takes place because inducing a plasma absorbs energy. For accomplishing this way of detecting a particle breakdown, a detector, e.g., a i o pyroelectrical detector, can be used which is positioned for the detection of radiation propagating in the direction of the light pulses.

Usually, an apparatus is set-up in such a way that the center of the focus of the pulsed light beam is inside the open jet.

In one embodiment, there is a laminar flow in said open jet in the range where said 15 pulsed light beam is focused.

In a method according to said second aspect, which, however, can be combined with the other aspects of the invention, the method comprises the step of b) producing a sheath of a gas surrounding said open jet.

In this second aspect of the invention, it is generally not necessary to use a nozzle 20 according to the invention, but it can be of advantage to do so.

In this second aspect of the invention, step b) can in particular comprise the step of bl) guiding said gas along a gas path to a gas outlet at which said sheath of said gas emerges, wherein an area of a cross-section experienced by said gas flowing along said gas path reduces along said gas path.

25 A sheath of gas can protect equipment close to the location where the breakdown takes place (and the plasma is formed) from contamination. E.g., a lens for focusing the pulsed light beam into the open jet and/or a lens for collecting radiation propagating from the open jet can be protected from spillings caused by the plasma. Furthermore, a gas sheath can contribute to avoiding or minimizing contamination of sample fluid in the open jet and to stabilizing the open jet.

5 The described particular way of generating the sheath of gas can make possible to create a particularly homogeneous and a particularly stable sheath of gas. E.g., said gas can flow along said gas path along which it enters a first section having a first cross- sectional area and, subsequently thereto, enters a second section having a second cross- sectional area, wherein said first cross-sectional area is larger than said second cross- i o sectional area.

In one embodiment, said gas outlet describes, in cross-section, a closed shape, e.g., a ring shape, wherein elliptic or rectangular shapes or also other shapes are generally possible, too.

In one embodiment which may be combined with one or more of the before-addressed 15 embodiments comprising step c), an extension of said channel in a direction parallel to a propagation direction of said pulsed light beam is, at said open end, at most 3 mm, more particularly at most 1 mm, even more particularly at most 500 μηι, but it can even be provided that said extension of said channel in a direction parallel to a propagation direction of said pulsed light beam is, at said open end, at most 200 μηι, more

2.0 particularly at most 100 μηι, even more particularly at most 50 μιη. This can make the method and a corresponding apparatus particularly sensitive to exciting (and detecting) particularly small particles. More particularly, this way, the excitation (and detection) of large particles can be reduced. Usually, a lower limit for said extension of said channel in a direction parallel to a propagation direction of said pulsed light beam is 1 μηι.

25 In one embodiment which may be combined with one or more of the before-addressed embodiments comprising step c), an extension of said channel in a direction parallel to a propagation direction of said pulsed light beam is, at said open end, at most two times, more particularly at most 1.2 times a confocal parameter b of said focused pulsed light - Si -

beam, and, optionally, an extension of said channel in a direction parallel to a propagation direction of said pulsed light beam is, at said open end, at least 0.05 times, more particularly at least 0.2 times a confocal parameter b of said focused pulsed light beam. This can enhance the sensitivity for producing a breakdown of smaller particles 5 relatively to the sensitivity for producing a breakdown of larger particles.

In one embodiment which may be combined with one or more of the before-addressed embodiments comprising step c), an extension of said channel at said open end is, in a direction perpendicular to a propagation direction of said pulsed light beam and perpendicular to a direction of flow of said sample liquid in said open jet, at most 3 mm, l o more particularly at most 1 mm, even more particularly at most 500 μπι, but it can even be provided that an extension of said channel at said open end is, in a direction perpendicular to a propagation direction of said pulsed light beam and perpendicular to a direction of flow of said sample liquid in said open jet, at most 200 μηι, more particularly at most 100 μηι, even more particularly at most 50 μπι. Vibrations and

25 turbulences in the open jet can be minimized by choosing said extension of said channel sufficiently small.

In one embodiment which may be combined with one or more of the before-addressed embodiments, for any first and second directions perpendicular to a direction of flow of said sample liquid in said open jet which are perpendicular with respect to each other 20 applies that an extension of said channel at said open end along said first direction is between 0.5 times and 2 times, more particularly between 0.7 and 1.5 times an extension of said channel at said open end along said second direction.

In one embodiment which may be combined with one or more of the before-addressed embodiments comprising step d), step d) is replaced by the step of

25 d') obtaining a signal by detecting for each of a multitude of said particles a

breakdown of the respective particle.

This is a particularly good way of particularly precisely determining said characteristic. E.g., it is possible to irradiate said sample liquid with pulses of varying energy, thus providing varying energy densities in the sample liquid and, consequently, creating breakdown of particles of varying size (more precisely varying the probabilities for creating a breakdown of particles of different particle sizes). It is to be noted that usually, a minimum energy density (provided by a light pulse) required for creating a 5 breakdown of a smaller nanoparticle is larger than a minimum energy density (provided by a light pulse) required for creating a breakdown of a larger nanoparticle.

In one embodiment which may be combined with one or more of the before-addressed embodiments, said channel comprises a trench in said first member. It is optionally also possible to provide a trench in said second member contributing to said channel. The i o latter way of forming the channel, however, requires a precise alignment of the first and second members in order to obtain a properly shaped channel. A way of precisely and reproduceably manufacturing said trench is to make use of etching, in particular using a lithographic process. In particular if said first member - at least in the region where said trench is formed - is made of a crystalline semiconductor material, this can allow to

15 facilitate a precise etching, even forming structures of high aspect ratios, but other materials, e.g., glass, could be used, too.

In one embodiment which may be combined with one or more of the before-addressed embodiments, said channel is of substantially rectangular cross-section, at least in the region of said open end. Alternatively, elliptic, circular, triangular or other cross- 20 sectional shapes are possible.

The method for manufacturing a nozzle can be a method for manufacturing a nozzle suitable for use in an apparatus for determining a characteristic of a sample liquid comprising particles and in particular is a method for manufacturing a nozzle according to the invention. The method comprises the steps of

25 A) providing a first member, e.g., a first wafer;

B) providing a second member, e.g., a second wafer;

C) forming a trench in said first member, e.g., by etching; D) fixing said first and said second members to each other such that a channel is formed at an interface between said first and second members, said trench contributing to said channel.

Therein, said method can, more specifically be a method for manufacturing a nozzle suitable for use in an apparatus for determining a characteristic of a sample liquid comprising particles by irradiating a sample liquid in an open jet of said sample liquid by means of a pulsed light beam focused into said open jet and obtaining a signal by detecting a breakdown of at least one of said particles.

The fixing addressed in step D) can be accomplished, e.g., using a bonding technique, e.g., gluing.

The first and second members are usually substantially plate-shaped, e.g., wafers, wherein wafer materials are not limited to semiconductor materials, e.g., also glass materials and other materials are possible.

In one embodiment of this method, step C) is replaced by the step of C) forming a multitude of trenches in said first member; and step D) is replaced by the step of

D') forming a stack by fixing said first and said second members to each other such that a multitude of channels is formed at an interface between said first and second members, each of said trenches contributing to at least one of said channels.

This can be a very efficient way of manufacturing a multitude of nozzles and to do so with high precision. Therein, it is furthermore possible to provide the step of

E) separating said stack into at least two parts and thereby separating each of said multitude of channels into two separate channels. and/or the step of F) separating said stack into a multitude of nozzles each comprising one channel; in particular, and if step E) is carried out, each comprising one of said channels obtained in step E).

This way, nozzles can be produced in high quality in large numbers. In particular by 5 step E), it can be possible to obtain high-precision nozzles, more precisely nozzles having well-defined open ends.

The separating addressed in step E) and/or step F) may be accomplished, e.g., by laser cutting or using a wafer saw or otherwise.

The nozzle device according to the invention comprises a nozzle according to the i o invention and at least one plug part attached to said nozzle, in particular a first and a second plug part, said first plug part attached to said first member and said second plug part attached to said second member. The nozzle device can form a plug, in particular a plug-in connector. This can facilitate replacing nozzles. Adjusting an apparatus such as an LIBD, DLS or LIBS apparatus to sample liquids of different properties such as 15 different viscosity, is thus greatly facilitated.

In one embodiment, the nozzle device describes, in a plane parallel to said interface between said first and second members, a silhouette describing a waist. This can contribute to producing a sheath of gas of particularly good quality. In particular, it can be provided that a width of a portion of said silhouette adjacent to said waist and located 20 between said waist and the location of said open end is smaller than a width of another portion of said silhouette adjacent to said waist and located on a side of said waist opposite to that side where said open end is located. This way, a stable and

homogeneous gas sheath can be obtained.

The arrangement according to the invention comprises a nozzle according to the 25 invention and a top portion and a base portion, said top portion and said base portion being fixed with respect to each other in a distance from each other. In particular, said top portion forms a socket for accepting a nozzle device according to the invention. In the bottom portion, sample liquid having passed the region where the irradiation with light pulses takes place can be drawn off and, if a gas sheath is provided, also gas of a sheath of gas can be drawn off there. In the top part, the nozzle can be held in a well- defined position. And in an open space between top and bottom part, sample liquid in the open jet can be irradiated by the pulsed light beam. All required inlets and outlets 5 can be provided by the arrangement.

The apparatus for determining a characteristic of a sample liquid comprising particles comprises

— a nozzle according to the invention.

In particular, it can furthermore comprise i o — a light source unit for irradiating a sample liquid in an open jet of said sample liquid emerging from said open end of said nozzle by means of a pulsed light beam focused into said open jet; and

— a detecting unit for detecting a breakdown of at least one of said particles.

In the above-addressed second aspect of the invention, the apparatus comprises

15 alternatively to or in addition to said nozzle means for producing the above-addressed sheath of gas, e.g., comprising an arrangement according to the invention.

The light source unit usually comprises a light source, e.g., a laser operable in pulsed mode. And in addition, it usually also comprises at least one lens for focusing a light beam produced by said light source. Futhermore, it usually comprises means of

20 controlling the energy of light pulses produced by the light source unit, or more

particularly for adjusting an energy density produced by the light source unit in a focus region.

In one embodiment, the apparatus comprises an evaluation unit for obtaining said characteristic from said signal produced by said detecting unit. Said detecting unit can 25 be or comprise, e.g., a pyroelectric detector or a photosensitive detector such as, e.g., a photo diode, a photo element, a photomultiplier tube, an amplified photomultiplier tube. If breakdowns are detected by detection of light emitted as a result of the breakdown, the detected light usually is of a wavelength range not including a wavelength range of said pulsed light beam.

It is possible to carry out the invention without making use of a spatially resolving 5 detector such as an image detector or a pixel array detector. It is possible to obtain

information mainly or solely from radiation propagating from the region in which the light pulses interact with said sample fluid in the open jet.

It is readily understood that features mentioned with respect to a certain portion of the invention, e.g., for a method, can be provided - at least in analogy - in other portions of l o the invention, e.g., in a device or apparatus, as far as logically meaningful. The

achievable effects correspond to each other.

When methods and/or apparatuses for determining a characteristic of a sample liquid comprising particles are mentioned, this can specifically refer to LIBD or more specifically to LIBS, but also to DLS or other methods and corresponding apparatuses.

15 Further embodiments and advantages emerge from the dependent claims and the

figures.

Brief Description of the Drawings

20

Below, the invention is described in more detail by means of examples and the included drawings. The figures show:

Fig. 1 a schematic illustration of an LIBD apparatus;

Fig. 2 a schematic illustration of a detail of an LIBD apparatus;

25 Fig. 3 a schematized cross-section through a nozzle; Fig. 4 a schematized cross-section through a nozzle;

Fig. 5 a semi-transparent perspective view a nozzle with attached sample inlet;

Fig. 6 an illustration of a top view onto a channel;

Fig. 7 a schematic illustration of top view onto a wafer for manufacturing nozzles;

Fig. 8 a side view a constituent of a nozzle device;

Fig. 9 a side view two constituents of a nozzle device;

Fig. 10 a schematic cross-section through a nozzle device;

Fig. 11 a schematic cross-section through a nozzle device;

Fig. 12 a front view of an arrangement;

Fig. 13 a side view of a cross-section through an arrangement;

Fig. 14 a perspective view of a cross-section through an arrangement.

Detailed Description of the Invention

Fig. 1 shows schematic illustration of an LIBD apparatus. LIBD stands for laser- induced breakdown detection. In LIBD, a breakdown of a small particle, usually a nanoparticle, is detected, and this is usually carried out for a multitude of particles in a liquid sample. In a specific way of carrying out LIBD, light emitted because of the breakdown of a particle is spectrometrically analyzed. Such methods are referred to as LIBS. The LIBD apparatus illustrated in Fig. 1 comprises a light source LQ capable of producing light pulses (the produced light being referenced as 5), typically a pulsed laser, and two lenses LI, L2 each of which, of course, may comprises more than one lens elements, and a detector D. One or more of various possible detection principles 5 known in the art can be implemented in detector D. An evaluation unit 8 is

operationally connected to detector D, receiving signals from detector D from which information about a sample liquid S to be examined is determined and outputted, in particular information concerning the concentration and/or the size of particles present in sample liquid S. Sample liquid may contain a specimen to be investigated, e.g., in an 1 o aqueous solution.

By means of an arrangement comprising a top portion 1 and a bottom portion 2 and a nozzle N, an open jet J (also referred to as "free jet") of sample liquid S is produced which furthermore is surrounded by a sheath V of a gas G.

The light beam produced in light source LQ is focused by lens LI into open jet J. In a l 5 region in which a sufficiently high energy density provided by the light pulses is present in sample liquid S in open jet J, particles in sample liquid S can be subject to breakdown and thus convert into a plasma and, accordingly emit light and also sound waves. If the breakdown shall be detected by detecting the light or the sound waves originating from the plasma, detector D would usually not have to be arranged in the light path described 20 by the light emitted by light source LQ. But another way of detecting a breakdown of a particle in an arrangement as illustrated in Fig. 1 is to detect a drop in intensity of light produced in light source LQ and having passed open jet J. A light pulse having induced a breakdown of a particle in open jet J will comprise less energy than a light pulse having traversed open jet J without doing so. This way of detecting breakdowns of 25 particles does not require the presence of a spatially resolving detector such as an array (image) detector. Detector D will, accordingly, be positioned in the light path of the light 5 emitted by light source LQ having traversed lens L2, as illustrated in Fig. 1. Fig. 2 is a schematic illustration of a detail of an LIBD apparatus. Like in Fig. 1 and in other Figures of the present patent application, a coordinate system is sketched for showing the orientation of the respective Figure. The pulses of light 5 propagate in the direction of the (positive) x axis, and the sample liquid S in open jet J flows in the

5 direction of the (positive) z axis. Between lenses LI and L2, the beam of light 5 has its focus. A region in which the energy density of light 5 is sufficiently high for inducing a breakdown of nanoparticles in open jet J is referenced 5 and known as effective focus volume E. The length of the effective focus volume E is referenced F. At least for focused laser light beams (generally for Gaussian beams), a magnitude referred to as i o depth of focus b is also known as "confocal parameter b" and defined as b = 2zR,

wherein zR is the Rayleigh range. Although schematically illustrated in Fig. 2 that way, length F is not necessarily larger than depth of focus b. The energy density required for inducing a breakdown in a smaller particle (having a smaller volume) is, at least usually, larger than the energy density required for inducing a breakdown in a larger

1 5 (higher volume) particle. Thus, effective focus volumes E are preferably defined for particles of a certain size or volume. The effective volume E (and the corresponding length F thereof) for a smaller particle therefore is smaller than for a larger particle. Thus, if it can be achieved to produce a very small or very thin open jet (in x-direction), e.g., smaller than four times or thinner than two times the confocal parameter b or even

20 smaller than confocal parameter b or even smaller than 0.5 times the confocal parameter b, this can allow to achieve a sensitivity for very small particles which is relatively increased with respect to a sensitivity for larger particles. But usually, said thickness of the open jet in x-direction is at least 0.2 times or rather 0.4 times the confocal parameter b.

25 Fig. 3 shows a cross-section through a nozzle N which can be used for creating open jets in LIBD apparatuses, e.g., like described in conjunction with Figs. 1 and 2. The nozzle N comprises or even substantially consists of two members Ml, M2 which form an interface 4 at which a channel C is present. Members Ml , M2 are, e.g., of plate shape, and are usually, at least at their surfaces contributing to interface 4, substantially flat. A trench T contributes to channel C, trench T being formed in member Ml .

Channel C can be, as illustrated in Fig. 3, of rectangular cross-section with a depth t (usually in x-direction) and width B (usually in y-direction). Other cross-sectional shapes are possible. Depths t are typically below 200 μπι, more particularly at most 5 100 μπι and in many cases at most 50 μπι or even below at most 30 μπι. Such small dimensions in the direction of the propagation of the exciting light 5 can result in a particulary high sensitivity to particularly small particles.

Fig. 4 shows, in the same manner as Fig. 3, a cross-section through another nozzle N which can be used for creating open jets in LIBD apparatuses, e.g., like described in l o conjunction with Figs. 1 and 2. This is to illustrate another possible cross-sectional shape (elliptic, which could also be round) and to show that it is possible to provide that a trench Tl in member Ml and, in addition, a trench T2 in member M2 can contribute to channel C.

Providing a trench in one member only, e.g., like shown in Fig. 3, renders superfluous 15 the need to precisely align the members M 1 , M2 when fixing them to each other at interface 4, e.g., by bonding, such as by gluing or fusing.

For each member Ml , M2, e.g., glass, a polymer material or a semiconductor material can be used. For members in which a trench has to be manufactured, a semiconductor material or glass can be particularly suitable, whereas for a member in which no trench 20 contributing to channel C shall be present, glass can be a particularly good choice.

Fig. 5 is a semi-transparent perspective view a nozzle N with attached sample inlet 1 1. The drawing is to scale. Channel C can be formed, e.g., like illustrated in Fig. 3 and has open end El at which a fine (thin) open jet can emerge when sample liquid is injected at sample inlet 1 1 at a closed end E2. In the region of closed end E2, a through-hole can be 25 provided in member M2 which allows sample liquid to traverse member M2 and enter channel C. Open end El is located at an edge face of nozzle N. Open end El is located at a side face of first member M 1 and, at least possibly, at a side face of second member M2. Providing sample liquid in an open jet avoids problems that may occur when sample liquid is present in a container, e.g., plasmas emerging at container walls, contamination of container walls and the like. Using an open jet can make it possible to carry out LIBD in-line measurements in an elegant and stable, reproduceable way, e.g., for in-line 5 quality control.

Fig. 6 illustrates a top view onto a channel C, the small insert in Fig. 6 illustrating a cross-section through channel C at line A-A. In the region of closed end E2, a through- hole in one member (typically the one not having a trench contributing to channel C) is illustrated, too, in Fig. 6. Between closed end E2 and open end El , the cross-sectional i o area of channel C reduces. In the region of open end El , the cross-sectional area of channel C remains at least substantially constant. The depth of the trench T can remain constant, such that a variation of the cross-sectional area of channel C can be accomplished by varying the width B of channel C.

Fig. 7 is a schematic illustration of top view onto a wafer or member Ml ' for

1 5 manufacturing nozzles, e.g., nozzles of the above-described kind. In particular, several members Ml like described above may be manufactured using one semiconductor wafer, e.g., a silicon wafer or a glass wafer. Trenches T for a plurality of nozzles can be etched into member Μ , e.g., using processes such as lithographic processes well- known in semiconductor industry. Separating member M 1 ' into a plurality of members 20 Ml each comprising one trench can take place along the directions indicated by the dashed arrows, e.g., using a wafer saw or by laser cutting. At El ', the locations where open ends El will be located are indicated. The manufacture of an open end El at which an open jet shall emerge is crucial, because burrs present there might degrade the quality and in particular the shape and stability of an open jet to be produced. It turned 25 out that a separating as addressed above by means of which one trench is transformed into two trenches is very well suitable for reproducibly manufacturing well-defined trenches and channels. It is suggested to form trenches in a member Ml ' like illustrated in Fig. 7 and then attach thereto another member (which finally will form members M2) such as a glass plate, so as to form a plurality of channels, e.g., having a cross-section as illustrated in Fig. 3 and a shape, e.g., as illustrated in Fig. 6. With these two members attached to each other, e.g., by gluing, separation takes place, creating a plurality of nozzles preferably with open ends manufactured by a separation step as described above.

It is possible to manufacture using one (wafer) member ΜΓ nozzles having different channel geometries like visualized in Fig. 7, having different widths and different lengths of constant width before the open end. But it is also possible to manufacture only one or maybe two types of nozzles using one (wafer) member Ml '.

Figs. 8 and 9 show in a side view constituents of a nozzle device. The drawings are to scale. In addition to parts PI and P2, the nozzle device comprises a nozzle, in particular a nozzle of the above-described kind. In the space between parts PI and P2 visible in Fig. 9, such a nozzle can be provided, e.g., by gluing parts PI , P2 onto the outer sides of the nozzle.

Such a nozzle device can function as a plug facilitating changing nozzles in an apparatus for LIBD. And, in addition, it can contribute to producing a gas sheath around the open jet, e.g., an air curtain. The gas can be air, in particular ambient air. Along the z-direction, the nozzle device has sections si , s2, s3 which, in case of the prevailingly rotationally symmetric geometry, have different diameters dl , d2, d3. A plug-like nozzle device can be inserted (plugged) into a top portion 1 of a arrangement shown in Figs. 12 to 14, that top portion 1 functioning a socket for the nozzle device 10.

Figs. 10 and 1 1 show a schematic cross-section through a nozzle device 10 at least similar to the one illustrated in Figs. 8 and 9. Figs. 12 to 14 illustrate an arrangement for use in an LIBD apparatus, e.g., like described above, with inserted nozzle member 10. Fig. 12 is a front view, Fig. 13 a side view of a cross-section, Fig. 14 a perspective view of a cross-section. The drawings are to scale. Nozzle device 10 comprising nozzle N is plugged into top portion 1 having an inner diameter d4 (cf. Figs 10, 11) substantially identical to and possibly smaller (by play) than outer diameter d3 (cf. Fig. 9) of nozzle device 10 in section s3 (cf. Fig. 8).

Diameter d2 is smaller than d3, and diameter dl is even smaller than d2, thus presenting 5 for gas injected into gas inlet 14 (cf. Fig. 13), cross-sectional areas along the path along nozzle device 10 to a gas outlet 15 which reduce, as is also visible from Figs. 10 and 1 1. In section s2, nozzle device 10 forms a waist, and farther down in the gas path, at section s2, the cross-section through which the gas flows is smaller than at the waist. A consequence of this is that the distribution of gas in the gas sheath over the

i o circumference of the gas sheath is very homogeneous. Thus, a stable and dense gas sheath can be obtained. This can protect lenses LI and L2 from contamination by avoiding substance sprayed out of the open jet reaching and settling on lenses LI , L2, and it can contribute to minimizing contamination of sample liquids, and it can contribute to stabilizing the open jet. It is also possible to provide that the outer

1 5 diameters in sections si and s2 are at least substantially identical and to design the inner diameters of top portion 1 accordingly, forming a reducing cross-section before gas outlet 15. Of course, other cross-sectional shapes of the gas path, i.e. not ring-shaped ones are generally possible, e.g., elliptic shapes, triangular shapes, rectangular shapes, possibly with rounded corners

20 Sample liquid S is injected in sample liquid inlet 11 , enters channel C through a

through-hole in second member M2 of nozzle N, then flows through channel C, then forms an open jet emerging at open end El, particles in the open jet then interacting - with a certain probability and in a region of sufficiently high energy density - with the pulsed light.

25 The gas of the gas sheath enters base portion 2 of the arrangement (cf. Figs. 12 to 14), usually together with sample liquid having passed the region E' where the effective focus volume is when in operation. Gas G and/or sample liquid S can alternatively or additionally leave through a bottom opening 16 in base portion 2. Top portion 1 and base portion 2 are distanced from each other, e.g., by a mechanical connection 3 like shown in Figs. 12 to 14, so as to provide space in which the focused light beam can interact with the sample liquid S.

Although most aspects of the invention have been described referring to LIBD, it is well possible to make use of the invention (or at least most aspects thereof) in conjunction with DLS or other methods and corresponding apparatuses for characterizing liquids in which particles, in particular nanoparticles, are present. Of course, the invention (or at least most aspects thereof) can also be applied when carrying out LIBS.

Claims

Patent Claims:

1. A nozzle for use in a method or an apparatus for determining a characteristic of a sample liquid comprising particles, said nozzle comprising — a first member;

— a second member; said first and second members being fixed to each other, a channel being formed at an interface between said first and second members, said channel having an open end for letting emerge said open jet, in particular wherein said method or apparatus is a method or apparatus for determining a characteristic of a sample liquid comprising particles by irradiating sample liquid in an open jet of said sample liquid by means of a pulsed light beam focused into said open jet and obtaining a signal by detecting a breakdown of at least one of said particles, said characteristic being obtainable from said signal.

2. The nozzle according to claim 1 , said first and second members each comprising a substantially flat surface facing the respective other member, in particular wherein said first and second members are substantially plate-shaped.

3. The nozzle according to claim 1 or claim 2, said channel comprising a trench in said first member.

4. The nozzle according to claim 3, wherein said trench is formed by etching, in particular using a lithographic process.

5. The nozzle according to one of the preceding claims, wherein said first member is substantially made of a semiconductor material, in particular of a crystalline semiconductor material, more particularly of monocrystalline silicon.

6. The nozzle according to one of the preceding claims, wherein an extension of said channel at said open end in a first direction perpendicular to a direction defined by said channel amounts to at most 200 μπι, more particularly at most 100 μηι, even more particularly at most 50 μπι.

7. The nozzle according to claim 6, wherein an extension of said channel at said open end is in a second direction perpendicular to said first direction and perpendicular to said direction defined by said channel amounts to at most 1000 μπι, more particularly at most 500 μπι, even more particularly at most 250 μπι.

8. The nozzle according to one of the preceding claims, wherein a cross-sectional area of said channel is reducing towards said open end.

9. The nozzle according to one of the preceding claims, wherein said second member comprises a through-hole for forming an inlet for inserting said sample liquid into said channel.

10. A method for determining a characteristic of a sample liquid comprising particles, said method comprising the steps of a) producing an open jet of said sample liquid; wherein step a) is carried out using a nozzle according to one of claims 1 to 9.

1 1. The method according to claim 10, comprising the step of b) producing a sheath of a gas surrounding said open jet; wherein step b) comprises the step of

5 bl) guiding said gas along a gas path to a gas outlet at which said sheath of said gas emerges, wherein an area of a cross-section experienced by said gas flowing along said gas path reduces along said gas path.

12. The method according to claim 10 or claim 1 1, wherein step a) comprises the l o step of al) letting said sample liquid flow through said channel; wherein said open jet emerges at said open end.

13. The method according to one of the claims 10 to 12, wherein an extension of 15 said channel at said open end is, in at least one direction perpendicular to a direction of flow of said sample liquid in said open jet, at most 200 μηι, more particularly at most 100 μιτι, even more particularly at most 50 μηι.

14. The method according to one of the claims 10 to 13, comprising the steps of 0 c) irradiating said sample liquid in said open jet by means of a pulsed light beam focused into said open jet; d) obtaining a signal by detecting a breakdown of at least one of said particles; wherein said characteristic is obtainable from said signal.

15. The method according to claim 14, wherein said detecting said breakdown addressed in step d) comprises detecting light having passed said open jet.

16. The method according to claim 14 or claim 15, wherein step d) is replaced by the step of d') obtaining a signal by detecting for each of a multitude of said particles a

breakdown of the respective particle.

17. The method according to one of claims 14 to 16, comprising the step of e) determining said characteristic from said signal.

18. A nozzle device for use in a method or an apparatus for determining a characteristic of a sample liquid comprising particles, said nozzle device comprising a nozzle according to one of claims 1 to 9 and at least one plug part attached to said nozzle, in particular a first and a second plug part, said first plug part attached to said first member and said second plug part attached to said second member.

19. The nozzle device according to claim 18, a silhouette of said nozzle device in a plane parallel to said interface between said first and second members describing a waist, in particular wherein a width of a portion of said silhouette adjacent to said waist and located between said waist and the location of said open end is smaller than a width of another portion of said silhouette adjacent to said waist and located on a side of said waist opposite to that side where said open end is located.

20. An arrangement for use in a method or an apparatus for determining a characteristic of a sample liquid comprising particles, said arrangement comprising a nozzle according to one of claims 1 to 9 and a top portion and a base portion, said top portion and said base portion being fixed with respect to each other in a distance from each other, in particular wherein said arrangement is an arrangement for use in a method or an apparatus for determining a characteristic of a sample liquid comprising particles by irradiating a sample liquid in an open jet of said sample liquid by means of a pulsed light beam focused into said open jet and obtaining a signal by detecting a breakdown of at least one of said particles, said characteristic being obtainable from said signal.

21. The arrangement according to claim 20, wherein said top portion forms a socket for accepting a nozzle device according to claim 18 or claim 19.

22. An apparatus for determining a characteristic of a sample liquid comprising particles, said apparatus comprising

— a nozzle according to one of claims 1 to 9; and, in particular,

— a light source unit for irradiating a sample liquid in an open jet of said sample liquid emerging from said open end of said nozzle by means of a pulsed light beam focused into said open jet;

23. The apparatus according to claim 22, comprising at least one of

— a nozzle device according to claim 18 or claim 19; and

— an arrangement according to claim 20 or claim 21.

24. A method for manufacturing a nozzle for use in an apparatus for determining a characteristic of a sample liquid comprising particles, in particular a nozzle according to one of claims 1 to 9, the method for manufacturing a nozzle comprising the steps of

A) providing a first member;

B) providing a second member;

C) forming a trench in said first member;

D) fixing said first and said second members to each other such that a channel is formed at an interface between said first and second members, said trench contributing to said channel.

25. The method according to claim 24, wherein step C) is replaced by the step of C) forming a multitude of trenches in said first member; and wherein step D) is replaced by the step of

D') forming a stack by fixing said first and said second members to each other such that a multitude of channels is formed at an interface between said first and second members, each of said trenches contributing to at least one of said channels; and further comprising the step of

E) separating said stack into at least two parts and thereby separating each of said multitude of channels into two separate channels.

26. The method according to claim 25, comprising the step of

F) separating said stack into a multitude of nozzles each comprising one of said channels obtained in step E).

27. Use of a nozzle according to one of claims 1 to 9 in a method and/or in an apparatus for determining a characteristic of a sample liquid comprising particles, in particular in a method and/or in an apparatus for determining a characteristic of a sample liquid comprising particles by irradiating a sample liquid in an open jet of said sample liquid by means of a pulsed light beam focused into said open jet and obtaining a signal by detecting a breakdown of at least one of said particles, said characteristic being obtainable from said signal.