WO2021058853A1

WO2021058853A1 - Optical measurement apparatus and method

Info

Publication number: WO2021058853A1
Application number: PCT/FI2019/050697
Authority: WO
Inventors: Kalle BLOMBERG VON DER GEEST; Miisamari JESKANEN; Ari MÄKINEN; Matti Sarén
Original assignee: Sensmet Oy
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-04-01

Abstract

An optical measurement apparatus (100) comprises a measurement chamber (110); a plasma generating equipment (120) to form a microplasma (124) in the measurement chamber; a light source (140); a spectral detector (130); and a light signal collecting arrangement (165) to form a primary optical path (160) for receiving a primary light signal (170), initially emitted by the microplasma (124), from the measurement chamber (110) and transmitting it to the spectral detector (130), and an auxiliary optical path (161) for receiving an auxiliary light signal (171), originating from the light (141) emitted by the light source (140), from the measurement chamber (110) and transmitting it to the spectral detector (130). At least a part of each of the primary and the auxiliary optical paths (160, 161) are formed by an optical fiber (150, 151).

Description

OPTICAL MEASUREMENT APPARATUS AND METHOD TECHNICAL FIELD

The present specification relates generally to analysing liquids such as water by means of light signals received from the liquids to be analyzed. More specifically, the present specification relates to optical measurement apparatuses and methods for determining contents of var ious elements and/or compounds in the liquid to be an alysed. Especially, the present specification discloses embodiments for determining inorganic elements con tained in liquids such as water.

BACKGROUND

Appropriate quality and content of water is important in many applications, such as in various industrial pro cesses, in municipal water treatment and domestic water delivery, as well as in municipal wastewater treatment. There are also numerous applications where some other liquids are to be analysed.

Various techniques are known for analysing the quality and chemical and/or physical composition of water and other liquids. Many analysers utilize light signals re ceived from the liquid as the primary source of infor mation for such analysis. For example, inorganic ele ments contained in a liquid may be analysed by plasma emission spectroscopy. On the other hand, absorption spectra of various organic elements or compounds can be utilized for determining such organic content of a liq uid. In both approaches, the spectral information needed for the determination may be measured by a spectral detector.

Conventionally, when several different parameters, such as inorganic element(s) and organic species content of a liquid is to be measured, several separate analysers or at least several spectral detectors are used. This causes several challenges, such as increased costs and complexity of the analysis equipment.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the De tailed Description. This Summary is not intended to def initely identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

In one aspect, an optical measurement apparatus for an alyzing liquids such as water is disclosed.

The optical measurement apparatus comprises: one or more measurement chambers configured to receive a liquid to be analyzed; a plasma generating equipment configured to excite liquid received in a measurement chamber of the one or more measurement chambers so as to form a microplasma therein; a light source configured to emit light and transmit it to a measurement chamber of the one or more measurement chambers; a spectral detector configured to receive light signals and produce elec trical signal(s) indicative of spectral information thereof; and a light signal collecting arrangement con figured to form a primary optical path for receiving a primary light signal, initially emitted by the micro plasma, from the measurement chamber where the micro plasma is formed and transmitting it to the spectral detector.

The light signal collecting arrangement is further con figured to form at least one auxiliary optical path for receiving an auxiliary light signal, initially origi nating from the light emitted by the light source, from the measurement chamber to which the light was trans mitted, and transmitting it to the spectral detector.

Further, at least a part of each of the primary and the at least one auxiliary optical path is formed by an optical fiber.

The plasma generating equipment may be configured to excite the liquid so as to form the microplasma to have a volume of less than 20 cm³, for example less than 10 cm³, for example less than 5 cm³, for example less than 1 cm³.

The plasma generating equipment may be configured to produce an electrical energy density sufficient to in itiate excitation of the liquid. Such plasma generating apparatus may comprise a power supply and two or more electrodes connected to the power supply and positioned within the measurement chamber in which the microplasma is to be formed, the power supply and the electrodes being configured to supply a current flow through the liquid so as to gasify a portion of the liquid and generate a discharge through the thereby formed gas to initiate the excitation.

The spectral detector may be configured to determine spectral information of the received light signals with a resolution in the range of 0.001 nm to 2.5 nm.

The spectral detector may be configured to determine spectral information of the received light signals in a wavelength range of 100 to 2000 nm, for example 150 to 1100 nm, for example 200 to 900 nm.

The at least one auxiliary optical path may comprise an auxiliary optical path for receiving a first auxiliary light signal, initially emitted by the light source and transmitted to the measurement chamber, from the meas urement chamber and transmitting it to the spectral de tector. Such light signal received from the measurement chamber and therefore propagated through at least a part of it may have attenuated, for example, due to absorp tion. Thereby, the received first auxiliary light signal may enable determination of the absorbance of the liq uid.

The at least one auxiliary optical path may comprise an auxiliary optical path for receiving a second auxiliary light signal, originating from elastic or inelastic scattering of, or fluorescence excited by, light emitted by the light source and transmitted to the measurement chamber, from the measurement chamber and transmitting it to the spectral detector.

The light signal collecting arrangement may be further configured to form an auxiliary optical path for re ceiving a third auxiliary light signal, originating from a chemiluminescent reaction taking place in the liquid, from the measurement chamber to which the light was transmitted and transmitting it to the spectral detec tor.

The optical measurement apparatus may further comprise a camera for imaging the measurement chamber and the liquid received therein. The camera may be a spectral camera configured to provide image data for a plurality of different wavelength bands.

The optical measurement apparatus may further comprise a computing unit connected to the spectral detector for receiving the electrical signal(s) produced by the spec tral detector, and configured to determine, on the basis of spectral information of at least the primary light signal, at least one inorganic element content of the liquid. The computing unit may be configured to deter mine the at least one inorganic element content of the liquid on the basis of spectral information of the pri mary light signal and at least one of the first to third auxiliary light signal.

The computing unit may be further configured to deter mine, on the basis of spectral information of at least one auxiliary light signal, at least one organic species content of the liquid.

In another aspect, a method for analyzing liquids is disclosed. The method comprises collecting, by an appa ratus in accordance with the aspect discussed above, electrical signal(s) indicative of spectral information of the primary light signal and at least one auxiliary light signal.

The method may further comprise determining, on the ba sis of spectral information of the primary light signal, at least one inorganic element content of the liquid. The at least one inorganic element content of the liquid may be determined on the basis of spectral information of the primary light signal and one or more of the at least one auxiliary light signals.

The method may further comprise determining, on the ba sis of spectral information of one or more of the least one auxiliary light signals, at least one organic spe cies content in the liquid.

Many of the attendant features will be more readily appreciated as the same becomes better understood by reference to the following detailed description consid ered in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The present description may be better understood from the following detailed description read in light of the accompanying drawings, wherein:

FIG. 1 illustrates schematically an optical measurement apparatus,

FIG. 2 illustrates schematically another opti cal measurement apparatus, and

FIG. 3 illustrates a flow chart of a method.

The drawings of FIGs. 1 and 2, illustrating the meas urement apparatuses only schematically, are not to scale. Different parts and elements of the apparatuses may be illustrated unrealistically as to the sizes and/or the shapes thereof.

DETAILED DESCRIPTION

The detailed description provided below in connection with the appended drawings is intended as a description of a number of embodiments and is not intended to rep resent the only forms in which the embodiments may be constructed, implemented, or utilized.

One or more of the embodiments and examples discussed below may advantageously enable, for example, reliable determination of inorganic element (s) content of a liq uid such as water. Further, one or more of those embod iments and examples may especially advantageously ena ble, cost efficient and reliable determination of both inorganic element(s) and organic element(s) or species content of the liquid.

The optical measurement apparatus 100 of FIG. 1 may be used for analyzing liquids such as water. The apparatus comprises a measurement chamber 110 for receiving a liquid to be analyzed into the measurement chamber.

In the example of FIG. 1, the measurement chamber is formed by a cylindrical quartz tube into the inner vol ume 111 of which the liquid can be received. In other embodiments, different types and shapes of measurement chambers, possibly made of different materials, may be used as far as they are suitable for receiving a liquid and allowing light signals to be transmitted to and from the liquid.

A measurement chamber such as that of FIG. 1 may have a size, for example, so as to define an inner volume of a couple of or some tens of or hundreds of cubic centime ters. A cylindrical measurement chamber may have, for example, a length/height of 1 to 15 cm, e.g. about 10 cm, and a diameter of 0.5 to 5 cm, e.g. about 2 or 3 cm. On the other hand, the size of a measurement chamber is not limited to those example values.

Although not illustrated in FIG. 1, a measurement cham ber may have any appropriate type of support structure, such as a housing or a frame surrounding the actual measurement chamber. Such support structure may enable coupling or mounting of various other elements and parts of the measurement apparatus to the measurement chamber.

The measurement chamber 100 of the apparatus of FIG. 1 comprises an inlet 112 and an outlet 113 for introducing a fluid 114 to the inner volume 111 of the measurement chamber 110 and removing it therefrom, respectively.

A measurement chamber such as that of the apparatus of FIG. 1 may be configured to receive a discrete sample volume of a liquid at a time, serving thereby as a sampling type measurement chamber. Such measurement chamber may comprise closing means configured to close the sample volume after receiving the sample therein. Closing means may comprise any appropriate members and actuators such as one or more valves or pumps such as a peristaltic pump.

Alternatively, a measurement chamber may be implemented as a flow-through type measurement chamber where the liquid to be analyzed can be led through the measurement chamber as a continuous flow. In such measurement cham ber, the sample of the liquid within the chamber may change continuously. A measurement chamber may also be configured so as to enable serving alternatively as a sampling type measurement chamber or a flow-through measurement chamber. The liquid to be analyzed can be led into or through the measurement chamber automati cally using one or more pumps. The apparatus 100 of FIG. 1 comprises one measurement chamber 110. In other embodiments, an optical measure ment apparatus may comprise two or more measurement chambers. Two or more measurement chambers may be ar ranged in series, wherein the same sample volume of the liquid can be led sequentially from one measurement chamber to another. Alternatively, two or more measure ment chambers may be arranged in parallel, wherein dif ferent sample volumes of the liquid are received in different measurement chambers. In any of such multi- chamber configurations, each of the chambers of an ap paratus may be of any of those types discussed above with reference to FIG. 1.

The apparatus 100 of FIG. 1 further comprises a power supply 121 and two electrodes 122, 123 positioned within the measurement chamber and electrically connected to the power supply so that current may be supplied between the electrodes. The electrical connections between the electrodes and the power supply, marked only schemati cally in FIG. 1, may be implemented in any appropriate manner. The connections may comprise any appropriate types and number of connectors, electrical cables or wires, etc.

In other embodiments, more than two electrodes or elec trode elements positioned within a measurement chamber and electrically connected to a power supply may be used. For example, an electrode may comprise, or be divided into, a plurality of discrete or separate sub electrodes.

The purpose of the power supply and the electrodes is to serve for producing an electrical energy density in a liquid received in the measurement chamber which is sufficient to initiate excitation of the liquid. In re sult of the excitation, a microplasma 124 may be formed in the measurement chamber. For this purpose, the power supply and the electrodes are configured to supply a current flow through an electrically conductive liquid received in the measurement chamber. Gasification of a portion of the liquid may result from the electrical current heating the liquid. Due to the gasification, a bubble of gas may be formed within the liquid. Thereaf ter, electrical breakdown in the bubble may initiate the excitation and plasma formation. Thereby, the power sup ply and the electrodes may gasify a portion of the liquid and generate a discharge through the thereby formed gas to initiate the excitation and plasma formation.

"Excitation" of a liquid refers to excitation of atoms or molecule fragments of the liquid into higher energy states by means of external energy introduced into the liquid. Excitation may result in, or comprise, ioniza tion of the liquid. In some embodiments excitation of a liquid may also refer to excitation of fragments of molecules of the liquid or of molecules contained in the liquid into higher energy states without dissociating the molecules into atoms.

"Microplasma" may refer to a plasma having a relatively small volume. A micro"plasma" may also refer to a mi crodischarge. The microplasma formed in the measurement chamber may have a volume of less than 20 cm³, for ex ample less than 10 cm³. A microplasma may have even smaller size, such as a volume of less than 5 cm³, or even less than 1 cm³.

To serve for the gasification and discharge, the elec trodes and the power supply may be implemented in ac cordance with principles known as such. For example, they may be implemented in accordance with the examples and principles disclosed in WO 2017/103341 A3. As dis closed in said publication, the electrodes may comprise a first electrode and a second electrode, each having an electrically conductive contact area, wherein the electrically conductive contact area of the first elec trode may be configured to be smaller than the electri cally conductive contact area of the second electrode. The smaller contact area of the first electrode may enable producing said sufficiently high electrical en ergy density in a controllable manner within a small volume to form the microplasma. As disclosed in WO 2017/103341 A3, the contact area of the first electrode may be adjustable.

In the example of FIG. 1, the electrode 122 marked in the drawing on the left side of the microplasma 124 may be in accordance with such first electrode. The elec trode 123 marked in the drawing on the right side of the microplasma 124 may be in accordance with such second electrode. To summarize, the power supply 121 and the electrodes 122, 123 connected to it form an example of at least part of, or serve as at least a part of, a plasma gen- erating equipment 120 configured to produce an electri cal energy density sufficient to initiate excitation of the liquid received in the measurement chamber.

In other embodiments, any other appropriate types of plasma generating equipment, configured to produce an electrical energy density sufficient to initiate exci tation of the liquid, may be used. Such other plasma generating equipment may be based on e.g. capacitive techniques comprising producing high electrical energy by means of a high frequency voltage coupled between two electrodes. Yet other examples comprise various break down techniques such as those used in spark induced breakdown spectroscopy (SIBS) and in laser induced breakdown spectroscopy (LIBS).

On the other hand, also plasma generating equipment may be used which are configured to form a microplasma at a liquid-gas interface instead of forming it within the liquid. The gas may comprise, for example, air, argon, and/or nitrogen. Such equipment may be based on various techniques, such as liquid electrode discharge wherein an atmospheric pressure glow discharge is created with one or both of the electrodes being the liquid. The elements to be analyzed are contained in the liquid which is either fed to the proximity of one of the electrodes via a capillary or, alternatively, sprayed to the glow discharge. Variations of liquid electrode discharge techniques comprise electrolyte cathode at mospheric pressure glow discharge (ELCAD) and solution cathode glow discharge (SCGD). In embodiments where an optical measurement apparatus comprises several measurement chambers, one single plasma generating equipment of any appropriate type may be configured to excite a liquid received in one or several of the measurement chambers of the apparatus. It is also possible that in the case of several meas urement chambers, there is a separate plasma generating equipment of any appropriate type for each of them. On the other hand, two or more measurement chambers may share at least a part of a plasma generating equipment.

The high temperature of a microplasma formed within a liquid or at a liquid-air interface decomposes the liq uid molecules and excites the atoms to elevated energy states. When the atoms return to lower energy states, light is emitted. Each element has its specific energy states and consequently, a specific spectrum of the mit- ted light.

Thereby, the optical measurement apparatus may be used for analyzing the liquid by means of plasma emission spectroscopy, i.e. on the basis of the emission spectrum of the microplasma. Plasma emission spectroscopy enables especially analysis or determination of the inorganic elements contained in the liquid.

Analysis or determination of an element, compound, or species contained in a liquid may refer to analyzing or determining the presence and/or amount, such as concen tration, of the element, compound, or species in the liquid. From a terminological point of view, such anal ysis or determination may thus refer to analysis or determination of the element, compound, or species con tent of the liquid. Vice versa, an element, compound, or species "content" of a liquid may refer to the pres ence and/or amount of the element, compound, or species contained in the liquid. Said analysis may refer, for example, to determination of the presence as well as the concentration of one or more inorganic elements in the liquid to be analyzed. Examples of such inorganic elements include, for exam ple, Na, K, Ca, Pb, Hg, Zn, Cu, Ni, Al, Mg, Mn, Fe, Co, Cu, P, Ag, Au, Li, Sc, Ti, Y, Tl, Ga, Ir, Cd, Cr, etc.

For carrying out the actual emission spectrum determi- nation forming the key part of the plasma emission spec troscopy, the apparatus comprises a spectral detector 130 which is configured to receive light signals and produce electrical signal(s) indicative of spectral in formation thereof.

A spectral detector may be implemented in accordance with principles known as such. A spectral detector may comprise any appropriate optical elements such as prisms, gratings, optical fibers, etalons, filters, and other spectrally dispersive components, reflectors, lenses, and one or more sensing elements for converting the incident light energy into electrical signal(s). A spectral detector may provide the spectral information in the form of electrical signal(s) of any appropriate type.

A spectral detector may be formed as a modular config uration comprising several detector modules. For exam ple, there may be several modules, each configured to determine spectral information and produce correspond ing electrical signal(s) for a specific sub-range of the operational wavelength range of the spectral detector. Each "detector module" of a modular spectral detector may be in the form of a stand-alone, fully operable spectral detector. The spectral detector 130 may be configured to determine spectral information of the received light signals with a resolution which lies in the range of 0.001 nm to 2.5 nm. Such high resolution may enable separation of emis sion peaks of different inorganic elements, and thereby reliable analysis of the inorganic elements contained in the liquid.

Resolution refers to the wavelength separation capabil ity of the spectrometer. It thus defines the narrowest wavelength band, the light signal intensity within which band can be determined separately. The resolution may refer to resolution defined in terms of the Full Width Half Maximum (FWHM) of such narrowest separable wave length band.

Examples of commercially available spectral detectors capable of determining spectral information with a suit ably high resolution include Avantec AvaSpec-ULS2048CL- EVO, Ocean Optics HR 4000, and Light Machinery HyperFine Spectrometer.

The spectral detector may be configured to determine the spectral information of the received light signals in a wavelength range of 100 to 2000 nm or in a narrower range such as 150 to 1100 nm or 200 to 900 nm. The emission peaks of the inorganic elements typically lie in the ultraviolet and/or visible portion of the spec trum. However, such operational wavelength range of the spectral detector may enable utilization thereof for other purposes also, as discussed further below.

For collecting the light emitted by microplasma formed in the measurement chamber and thereby enabling the analysis of the liquid by plasma emission spectroscopy, the optical measurement apparatus comprises a primary optical fiber 150. The primary optical fiber 150 serves for forming a primary optical path 160 between the meas urement chamber 110 and the spectral detector 130. The primary optical path 160 is configured to receive a primary light signal 170, which is initially emitted by the microplasma 124 formed in the measurement chamber 110, from the measurement chamber and transmit it to the spectral detector 130.

The primary optical path 160 is arranged so that the primary light signal is received from the measurement chamber at a location close to the microplasma to be formed in the measurement chamber. Such close position ing may advantageously provide high intensity level of the primary light signal. In the example of FIG. 1, the first and the second electrodes 122, 123 are positioned close to one end of the measurement chamber, and the primary optical path is arranged to receive the primary light signal from this same end. In other embodiments, such close positioning may be implemented in any other appropriate manner.

The optical measurement apparatus 100 of FIG. 1 further comprises a light source 140 configured to emit light 141 and transmit it to the measurement chamber 110.

In the example of FIG. 1, the schematically illustrated light source 140 is mounted to the measurement chamber or to its support structure (not illustrated) so that the light source is in contact with, or close to, the wall of the measurement chamber. It may then be possible to transmit the light initially emitted by the light source to the measurement chamber without any additional light transmission means.

In other embodiments, a light source may be positioned at a distance from a measurement chamber. An optical measurement apparatus may then comprise any appropriate light transmission means or system for transmitting the light emitted by the light source to the measurement chamber. Such means or system may comprise any appro priate optical means, such as lenses, reflectors, opti cal fibers or other types of light guides, optical shut ters, and/or optical switches. On the other hand, a light source positioned at a distance from a measurement chamber may be directed towards a measurement chamber for transmitting the emitted light to it without any specific light transmission means or system.

In the case of an optical measurement apparatus com prising several measurement chambers, light from one single light source may be transmitted to two or more measurement chambers. Alternatively, there may be a plu rality of light sources, light from each being trans mitted to one measurement chamber only.

A light source of an optical measurement apparatus such as that of FIG. 1 may comprise any appropriate type of light emitting element(s) capable of emitting light. Examples of such light emitting elements comprise light emitting diode LED, laser diode, other types of laser sources, filament lamp, halogen lamp, hollow-cathode lamp, xenon lamp, deuterium lamp, mercury lamp, and ar gon lamp.

A light source of an optical measurement apparatus such as that of FIG. 1 may be configured to emit light at a broad wavelength band. The light may comprise all wave lengths within such band. Alternatively, the light may be emitted at several separate sub-bands within the broad wavelength band.

A broad wavelength band may range, for example, from the ultraviolet to the near-infrared or mid-infrared regions of the electromagnetic spectrum. In terms of wavelength, such broad wavelength band may range, for example, from 100 nm to 2000 nm or 150 tO 1100 nm.

Light 141 initially emitted by the light source 140 and transmitted to the measurement chamber may interact with the molecules of and/or possible particles contained in a liquid present in the measurement chamber, for exam ple, via absorption, elastic or inelastic (Raman) scat tering, or fluorescence. Such interaction may attenuate, re-direct, and/or change the spectral distribution of, the light propagating in the liquid. The change of spec tral distribution of the light may result, in particular from the spectral absorption of the liquid and the el ements and molecules contained therein. Therefore, anal ysis of light initially emitted by the light source and transmitted to the measurement chamber may enable de termining additional information about the liquid to be analyzed by means of the optical measurement apparatus.

For such analysis purpose, the apparatus 100 comprises a first auxiliary optical fiber 151. The first auxiliary optical fiber 151 serves for forming a first auxiliary optical path 161 between the measurement chamber 110 and the spectral detector 130. The first auxiliary optical path 161 is configured to receive a first auxiliary light signal 171, which is initially emitted by the light source, transmitted to the measurement chamber, and propagated through it, from the measurement chamber and transmit it to the spectral detector 130.

Having been "propagated through" the measurement chamber refers to the first auxiliary light signal having trans mitted straightforwardly through the inner volume of the measurement chamber between an enter point and an exit point. During such propagation, the light signal inter acts with the liquid and may become, for example, par tially absorbed. An optical path being configured to receive a light signal refers to the optical path and the corresponding optical fiber being positioned appropriately so that the optical fiber may form at least partially the optical path.

The first auxiliary optical path is arranged so that, relative to the light source, the exit point lies, and thus the first auxiliary light signal is received from the measurement chamber, in the direction of maximum intensity of the light emitted by the light source. This may provide advantageously high intensity level of the first auxiliary signal. In the example of FIG. 1, said direction is aimed towards the center of the measurement chamber. So, the first optical fiber is positioned so to as to receive the primary light signal at a location of the measurement chamber wall which lies opposite to the light source. In other embodiments, a first optical fiber may be positioned to receive the first auxiliary light signal in a direction deviating from the maximum intensity of the light emitted by the light source.

When the light of the first auxiliary light signal prop- agates in the measurement chamber filled with a liquid, the light may be, for example, partially absorbed or scattered so that its intensity decreases. To optimize such attenuation, the length of the path the light through the measurement chamber may be changed. For ex- ample, in a measurement chamber in accordance with that of FIG. 1, a light source and the exit point from which the first auxiliary light signal is received from the measurement chamber could be positioned at the opposite ends of the elongated cylindrical measurement chamber.

The additional information about the liquid determinable on the basis of the first auxiliary light signal may be used, for example, to estimate the attenuation, and/or change of the spectral distribution, of the primary light signal during its propagation in the liquid. Such estimated attenuation and/or change of spectral distri bution may enable, determination of the absorbance of the liquid and therefore correction or compensation of the intensity and/or spectral distribution of the pri mary light signal received from the measurement chamber. Thereby, the reliability of the analysis of the primary light signal and, consequently, the determination of the inorganic elements contained in the liquid may be im proved.

The fist auxiliary optical path may also be used for colorimetry type absorption measurements where a color agent adherable to a target compound is added to the liquid. Then, the presence of the target compound may be determined on the basis of absorption of the light signal by the color agent.

On the other hand, additional information about the liq uid determinable on the basis of the any auxiliary light signal may be used to determine, for example, particles and/or one or more organic elements contained in the liquid. Especially, change of the spectral distribution of the light initially emitted by the light source due to wavelength-dependent or spectral absorption of the liquid may enable determination of organic species con tained in the liquid. This may be based on the fact that each organic element possibly present in the liquid has a unique absorption spectrum. Also some inorganic ele ments may show wavelength-dependent absorption when dis solved in liquids and thus absorption measurement may be used to determine the content of such elements in the liquid. Thus, the optical measurement apparatus of FIG. 1 may advantageously enable reliable determination of both inorganic and organic elements contained in the liquid.

Utilization of one single spectral detector for spectral analysis of both the primary light signal and the first auxiliary light signal enables a cost-efficient imple mentation of the apparatus. Further, as the different light signals are received and analyzed by the same spectral detector, the reliability of the spectral in formation of the light signals may be improved in com parison to implementations utilizing different spectral detectors for different light signals. For example, ef fects of possibly different drifting properties, or dif ferent responses to various environmental factors such as temperature, pressure, humidity and electrical dis turbances of different spectral detectors can be avoided.

For determining even further additional information about the liquid, the optical measurement apparatus 100 of FIG. 1 comprises further a second auxiliary optical fiber 152. The second auxiliary optical fiber 152 serves for forming a second auxiliary optical path 162 between the measurement chamber 110 and the spectral detector 130.

The second auxiliary optical path 162 is configured to receive a second auxiliary light signal 172 which orig inates from elastic or inelastic (Raman) scattering of, or fluorescence excited by, light emitted by the light source and transmitted to the measurement chamber, from the measurement chamber and transmit it to the spectral detector.

Originating from scattering of light emitted by a light source refers to light resulting from a scattering event where light changes its direction of propagation and, in the case of Raman scattering, also its wave length/frequency. Originating from fluorescence refers to light resulting from excitation, by incident light, of an atom or a molecule present in a liquid received in the measurement chamber. When the excitation returns to some lower energy level(s), light with wavelength (s) different from that of the excitation light may then be emitted.

The second auxiliary optical path 162 is arranged so that it receives light from a direction different from the direction from which the light initially emitted by the light source 140 is received to the first auxiliary optical path. In the example of FIG. 1, these directions are substantially perpendicular to each other. In other embodiment, any other appropriate difference in the di rections may be used. As the direction of scattered light typically depends on the size and/or shape of the scattered object such as a particle, different infor mation about the scattering objects may be determined on the basis of the direction from which the second auxiliary light signal is received. For maximizing the determinable information, an optical apparatus may com prise several auxiliary optical paths configured to re ceive auxiliary light signals, originating from scat tering or fluorescence, from different directions and transmit such auxiliary light signals to the spectral detector.

The further additional information about the liquid de terminable on the basis of the second auxiliary light signal may be used for different purposes. First, it may be used to correct the measurements of the primary light signal or the first auxiliary light signal. For example, information about the scattering properties of the liq uid may be used to compensate the effect of scattering in the primary light signal or the first auxiliary light signal. Thereby, the reliability of the analysis of the primary light signal and the inorganic elements con tained in the liquid may be improved. In other embodi ments the reliability of the analysis of the first aux iliary light signal and the organic species contained in the liquid may be improved by using the information about the scattering properties of the liquid.

On the other hand, information about the scattering properties of the liquid may be used to determine the amount, sizes, and/or shapes of scattering particles contained in the liquid.

Further, information of the fluorescence properties of the liquid may enable determination, on the basis of spectral information of the second auxiliary light sig nal 172, of some organic elements contained in the liq uid.

In the examples of FIGs. 1 and 2, both the first auxil iary light signal and the second auxiliary light signal are basically caused by or initiated by the light emit ted by the light sources. They are thus examples of auxiliary light signals initially originating from the light emitted by the light source. In other embodiments, optical measurement apparatuses may be implemented with one auxiliary optical fiber and correspondingly one aux iliary optical path only for receiving such an auxiliary light signal initially originating from the light emit ted by the light source. Such single auxiliary light signal may be in accordance with any of the first and the second auxiliary light signals discussed above.

In the example of FIG. 1 and in other embodiments, an optical fiber forming at least partially a primary or an auxiliary optical path may be of any appropriate type. For example, such optical fiber may be a single mode optical fiber or a multi-mode optical fiber. The diameter of an optical fiber may range, for example, from lym to 2000 ym.

To enable analysis of different light signals by the same spectral detector, for example, multiplexing, fre quency modulation, or chopping of light signals may be utilized. In addition or alternatively, the light source and/or the plasma generating equipment may be pulsed for appropriate timing of the different light signals.

In the example of FIG. 1, the primary optical fiber 150 and the auxiliary optical fibers 151, 152 are coupled to the measurement chamber 110 and to the spectral de tector 130 by means of fiber heads. At the end of the measurement chamber, the light signals are received to the optical paths via receiving fiber ends 155¹. At the end of the spectral detector, the light signals are distributed out of the optical paths via delivering fi ber ends 155².

A "fiber head" refers to an optical connector element or module to which an optical fiber may be connected to form, in a controlled way, an optical interface between the optical fiber and the ambient or other optical el ements such and another optical fiber. An optical fiber may be mounted to a fiber head integrally or releasably.

A fiber head may comprise any appropriate optical and mechanical components and elements such as lenses, po larizing components, spectral or attenuating filters, shutters, optical switches, optical beam steering units, reflective surfaces, diffractive optical components, spectrally dispersive components and/or mechanically moving components such as translation, rotation of flip- ping stages. Optical switches, shutters and/or mechan ically moving stages may be used, for example, to carry out timing and/or multiplexing of light signals to be transmitted to the spectral detector. The frequency of multiplexing and/or timing may be, for example, from millihertz to several gigahertz.

The optical fibers and the fiber heads, as well as pos sible other optical elements for forming light signal paths discussed above serve for forming at least part of a light signal collecting arrangement 165. The light signal collecting arrangement is configured to form the primary and auxiliary optical paths for receiving the primary and auxiliary light signals from the measurement chamber and transmitting them to the spectral detector.

In the example of FIG. 1, the light signal collecting arrangement 165 is thus configured to form a primary optical path and the first and the second auxiliary optical paths. In other embodiments, a light signal col lecting arrangement may comprise a primary optical path and one or more auxiliary optical paths.

In the example of FIG. 1, the primary optical fiber 150 and the auxiliary optical fibers 151, 152 form practi cally entirely the primary and auxiliary optical paths of the light signal collecting arrangement. In other embodiments, light signal collecting arrangements may be used where one or more optical fibers may form an optical path only partially. The rest of such optical path may be formed by free-air transmission paths, var ious optical elements to guide the light signal, and/or one or more other optical fibers. For example, it is possible to combine several optical paths into one sin gle common optical path. Such combination may allow, for example, transmission of a plurality of light signals to the spectral detector via a single common optical fiber. One example of this is illustrated in FIG. 2. Such combination may be implemented, for example, by a fiber to fiber coupling unit capable of transmitting light signals from several optical fibers to one or more different optical fibers, or vice versa. In some embod iments, alternatively or in addition, coupling units capable of coupling light signals from one or more fi bers to free space, or vice versa, may be used.

Basically, a light signal collecting arrangement com prising optical fibers forming at least partially one or more primary or auxiliary optical paths light may comprise any appropriate number of coupling units. A coupling unit may be capable of performing signal cou pling, switching and/or selection operations. A coupling unit may comprise any appropriate optical and mechanical components such as lenses, polarizing components, spec tral or attenuating filters, shutters, optical switches, optical beam steering units, reflective surfaces, dif fractive optical components, spectrally dispersive com ponents and/or mechanically moving components such as translation, rotation of flipping stages. Said optical switches, shutters and/or mechanically moving compo nents may be used to carry out timing and/or multiplex ing of different light signals so as to enable proper determination of the spectral information thereof by the spectral detector.

Advantageously, forming the optical paths of a light signal collecting arrangement at least partially by op tical fibers provide a reliable, space-saving, and cost- efficient way to collect the light signals to the spec tral detector. The flexibility of optical fibers enables adaptive implementation of various designs of light sig nal collecting arrangements in different optical meas urement apparatus configurations. As illustrated in FIG. 1, the optical apparatus 100 comprises also a camera 180 mounted to the support structure (not illustrated) of the measurement chamber. The camera is directed towards the inner volume 111 of the measurement chamber 110 for imaging the liquid 114 received therein. More specifically, it is directed to wards the electrodes 122, 123 of the plasma generating equipment 120.

The camera may be used to monitor the initiation of formation, status, and/or maintaining of the micro plasma. The information provided thereby may then be used to control, and/or improve the performance of, the plasma generating means.

The camera 180 may be a spectral camera configured to provide image data for a plurality of different wave length bands. A spectral camera may enable monitoring the spectral information of the light emitted by the microplasma. Thereby, the reliability of the determina tion of one or more inorganic elements contained in the liquid may be further improved. It may also be possible to determine inorganic element and/or organic species content in the liquid on the basis of image data produced by the camera.

In other embodiments, a camera may be directed towards elsewhere the inner volume of the measurement chamber. Such camera may be used for other purposes than moni toring the microplasma.

In other embodiments, optical measurement apparatuses may be implemented without any camera.

The optical measurement apparatus 200 of FIG. 2 is ba sically in accordance with that of FIG. 1. It differs from the optical measurement apparatus 100 of FIG. 1 in that it further comprises a third auxiliary optical fi ber 253. The third auxiliary optical fiber 253 serves for forming a third auxiliary optical path 263 between the measurement chamber 210 and the spectral detector 230.

In other embodiments, an auxiliary optical path in ac cordance with the third auxiliary optical path 263 of the example of FIG. 2 may also be present in an optical measurement apparatus basically in accordance with any of those examples and embodiments discussed above with reference to FIG. 1.

The third auxiliary optical path 263 is configured to receive a third auxiliary light signal 273 which orig inates from a chemiluminescent reaction, marked by ref erence number 215, taking place in the liquid, from the measurement chamber and transmitting it to the spectral detector 230.

Originating from a chemiluminescent reaction refers to light resulting from a chemiluminescent reaction taking place in a liquid received in the measurement chamber.

The chemiluminescent reaction 215 may be a biolumines- cent reaction catalyzed by an enzyme. In such embodi ments, an optical measurement apparatus may comprise any appropriate means (not illustrated) for introducing suitable catalyzing enzymes into the measurement cham ber.

The third auxiliary optical path 263 is arranged so that it receives light out of the measurement chamber from a direction different from the direction from which the light initially emitted by the light source is received to the first auxiliary optical path. It also differs from the direction from which the second auxiliary light signal is received to the second auxiliary optical path. In the example of FIG. 2, the third auxiliary optical path is arranged to receive the third auxiliary light signal from a direction directed obliquely backwards relative to the emission direction of the light source. This may allow reducing reception of scattered light initially emitted by the light source to the third aux iliary optical path. This may decrease disturbances, caused by stray light originating from the light ini tially emitted by the light source, in the received third auxiliary light signal. In other embodiments, any other appropriate directions may be used. Said disturb ances may then be avoided, for example, by having the light source shut off during the measurement of a third auxiliary light signal.

Further additional information about the liquid may be determined on the basis of the third auxiliary light signal. Each chemiluminescent reaction emits light with a specific spectrum dependent on the element(s) or com pound (s) participating the reaction. Therefore, addi tional information determinable on the basis of the third auxiliary light signal may be used to determine organic species and/or compound (s) and/or living cells contained in the liquid.

Alternative embodiments are possible where a light sig nal collecting arrangement does not comprise a second auxiliary optical path but auxiliary paths in accordance with the first and the third auxiliary optical paths discussed above. On the other hand, in yet other embod iments, one single appropriately arranged auxiliary op tical path may be possible to be utilized for receiving different auxiliary light signals, such as light signals in accordance with the second and third auxiliary light signals discussed above. In embodiments basically in accordance with any of the examples and embodiments discussed above, a light signal collecting arrangement may comprise any appropriate ad ditional auxiliary optical paths. One example of such possible additional auxiliary optical paths is an aux iliary optical path for receiving a fourth auxiliary light signal, initially emitted by the microplasma and propagating to a direction differing from the propaga tion direction of the primary light signal, from the measurement chamber where the microplasma is formed and transmitting it to the spectral detector. This may en able, for example, analyzing the absorbance of the liq uid on the basis of the light emitted by the microplasma. Another example is an auxiliary optical path for re ceiving a fifth auxiliary light signal, originating from elastic or inelastic scattering of, or fluorescence ex cited by, light emitted by the microplasma, from the measurement chamber where the microplasma is formed and transmitting it to the spectral detector.

The apparatus 200 of FIG. 2 differs from that of FIG. 1 also in that the primary and the auxiliary optical paths 260, 261, 262, 263 of the light signal collecting ar rangement 265 are combined, at the end of the spectral detector 230, by a fiber coupling unit 256, into a common optical path 264 formed by a common optical fiber 254. The fiber coupling unit 256 may serve, in addition to coupling all the light signals into the common optical path, also for carrying out multiplexing of the light signals for enabling separation them at the spectral detector.

In other embodiments, a fiber coupling unit and a common optical path in accordance with those of the example of FIG. 2 may also be present in an optical measurement apparatus basically in accordance with any of those ex amples and embodiments discussed above with reference to FIG. 1.

In the examples of FIGs. 1 and 2, the receiving fiber heads 155¹, 255¹ of the auxiliary optical paths are po sitioned so as to receive all the auxiliary light sig nals from a single horizontal plane 116, 216, lying substantially at the middle level of the measurement chamber 110, 210. The plane is marked in the drawings by a dashed line. This positioning is for illustrative purposes only. Basically, the primary as well as the auxiliary light signals may be received at any appro priate, different planes or levels of the measurement chamber.

The light signal measurement configuration and arrange ment of any of the examples and embodiments discussed above may be controlled by, and the spectral information of the light signals in the form of electrical signals provided by the spectral detector may be received by control unit. Such electrical control unit, which may be an integral part of the optical measurement appa ratus, may be connected to the plasma generation equip ment, the light source, the spectral detector, and one or more of the fiber coupling units and possible other controllable elements of the light signal collecting arrangement.

To carry out the control operations of an optical meas urement apparatus, a control unit may comprise one or more processors coupled with at least one memory. The at least one memory may comprise computer-readable pro gram code instructions which, when executed by the at least one processor, cause the control unit to carry out the control operation (s) at issue at least partially automatically. Alternatively, or in addition, at least some of those operations may be carried out, at least partially, by means of some hardware logic elements or components, such as Application-specific Integrated Circuits (ASICs), Application-specific Standard Prod ucts (ASSPs), or System-on-a-chip systems (SOCs), with out being limited to those examples.

In the above, optical measurement apparatuses are dis cussed with the main focus on the actual light signal measurement configurations and arrangements for col lecting and analyzing, by the spectral detector, the light signals.

Referring back to FIGs. 1 and 2, each of the optical measurement apparatuses 100, 200 comprises further a computing unit 190, 290. The computing unit is connected to the spectral detector 130, 230 for receiving the electrical signal(s) 131, 231 produced by the spectral detector. It is further configured to determine, on the basis of spectral information of the primary light sig nal 170, 270 and at least one of the first and second auxiliary light signals 171, 271, 172, 272, 173, 273, at least one inorganic element content of the liquid. In other embodiments with even more auxiliary light sig nals measurable by an optical measurement apparatus, spectral information of at least one of all the avail able auxiliary light signals may be utilized in deter mination of the at least one inorganic element content of the liquid.

In other embodiments, it may be possible to determine at least one inorganic element content of the liquid on the basis of spectral information of the primary light signal only.

The computing unit 190, 290 is further configured to determine, on the basis of spectral information of at least one of the first to third auxiliary light signals 171, 271, 172, 272, 173, 273, at least one organic spe cies content of the liquid.

Any computing unit such as those of the apparatuses of FIGs. 1 and 2 may further be configured to determine any other information about the liquid to be analyzed. For example, it may be possible to determine the amount of and size distribution of particles contained in the liq uid on the basis of any appropriate auxiliary light signal originating from scattering of light initially emitted by the light source of an optical measurement apparatus. On the other hand, it may be possible to determine the turbidity of the liquid, for example, on the basis of an auxiliary light signal in accordance with the first auxiliary light signal discussed above.

A computing unit may be a sub-unit within, or an integral part of the possible control unit of an optical meas urement apparatus. In other embodiments, an optical measurement apparatus may comprise a separate computing unit.

From another terminology point of view, a computing sys tem or a part thereof "configured to" perform a specific method operation means actually that the computing sys tem comprises "means for" performing that operation. The computing system may comprise separate means for dif ferent operations. Alternatively, any of such means for performing those various operations specified below may be combined so that more than one operation is carried out by the same means. It is even possible that all those operations are carried out by the same means, e.g. by a single data processing apparatus.

Any means for performing any of such operations may comprise one or more computer or other computing and/or data processing components, units and/or sub-units, de vices, or apparatuses. In addition to actual computing and/or data processing means, the means for performing said operations may naturally also comprise any appro priate data or signal communication and connecting means, as well as memory or storage means for storing generated and/or received data.

Computing and/or data processing means serving as means for performing one or more of the operations of the electrical property of interest determination may com prise, for example, at least one memory and at least one processor coupled with the at least one memory. Then, the at least one memory may comprise computer-readable program code instructions which, when executed by the at least one processor, cause the apparatus to perform the operation (s) at issue. Alternatively, or in addi tion, at least some of those operations may be carried out, at least partially, by means of some hardware logic elements or components, such as Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), or System-on-a-chip systems (SOCs), without being limited to those examples.

In other embodiments, optical measurement apparatuses may be implemented without any computing unit integrated to the measurement arrangement. Then, the actual deter mination of the at least inorganic element and/or or ganic species content of the liquid may be carried out by any appropriate external computing system or unit such as a computer.

The signals from a spectral detector may be transferred to an external computing unit by any appropriate wired or wireless means. Instead of directly transmitting the measurement data to a computing unit, the measurement data may alternatively be transmitted from the measure ment apparatus to an intermediate data storage, such as an external data server or a cloud service, for being transmitted therefrom to a computing unit.

The apparatuses discussed above may be configured to carry out the methods discussed below with reference to FIG. 3.

The method 300 of FIG. 3 may be used for analyzing a liquid received in a measurement chamber of an optical measurement apparatus in accordance with any of those discussed above.

The method 300 of Fig. 3 comprises collecting, in oper ation 301, by an optical measurement apparatus one or more electrical signals indicative spectral information of the primary light signal and at least one auxiliary light signal. The optical measurement apparatus may be in accordance with any of those discussed above with reference to FIGs. 1 and 2. An auxiliary light signal may be in accordance with any of the first to fifth auxiliary light signals discussed above.

"Collecting" refers to receiving the light signals from the measurement chamber, transmitting them to the spec tral detector, and measuring the light signals by the spectral detector. Said actual measuring comprises de termining electrical signal(s) indicative of spectral information of the measured light signals. Thus, col lecting refers to operations or steps resulting in providing available the electrical signals for further processing or storing.

Embodiments are possible comprising this first operation only. In the example of FIG. 3, the method however further comprises, in optional operation 302, determining, on the basis of spectral information of the primary light signal and one or more of the at least one auxiliary light signal, at least one inorganic element content of the liquid. Such determination may be carried out by any appropriate computing unit. The computing unit may be in accordance with any of those discussed above with reference to the apparatus aspect. The computing unit may be a part of the optical measurement apparatus or a separate from that.

Said determination being based on also the spectral in formation of one or more auxiliary light signals may improve the reliability of the determination as dis cussed above with reference to the apparatus aspect.

Embodiments are possible comprising the first operation and the second operation only.

The method 300 of FIG. 3 however further comprises, in optional operation 303, determining, on the basis of spectral information of one or more of the least one auxiliary light signals, at least one organic species content of the liquid. Determination of one organic spe cies content on the basis of spectral information of more than one auxiliary light signal may refer to, for example, correcting or compensating the measurement of one auxiliary light signal on the basis of measurement of another auxiliary light signal. The order of the method operations is not limited to that illustrated in Figure 3 and explained above. The order of the operations may be any appropriate one. Two or more operations may be carried out at least partially simultaneously .

Although the subject matter has been described in lan guage specific to structural features and/or methodo logical acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items.

The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed there after, without excluding the presence of one or more additional features or acts.

It is to be noted that the embodiments of the claims are not limited to those discussed above, but further em bodiments may exist within the scope of the claims.

Claims

1. An optical measurement apparatus (100) for analyzing liquids, comprising: one or more measurement chambers (110) config- ured to receive a liquid (114) to be analyzed; a plasma generating equipment (120) configured to excite liquid received in a measurement chamber of the one or more measurement chambers so as to form a microplasma (124) therein; a light source (140) configured to emit light

(141) and transmit it to a measurement chamber (110) of the one or more measurement chambers; a spectral detector (130) configured to receive light signals (170, 171, 172) and produce electrical signal (s) (131) indicative of spectral information thereof; and a light signal collecting arrangement (165) configured to form a primary optical path (160) for receiving a primary light signal (170), initially emit- ted by the microplasma (124), from the measurement cham ber (110) where the microplasma is formed and transmit ting it to the spectral detector (130); the light signal collecting arrangement (165) being further configured to form at least one auxiliary optical path (161) for receiving an auxiliary light sig nal (171), initially originating from the light (141) emitted by the light source (140), from the measurement chamber (110) to which the light was transmitted, and transmitting it to the spectral detector (130); at least a part of each of the primary and the at least one auxiliary optical paths (160, 161) being formed by an optical fiber (150, 151).

2. An optical measurement apparatus (100) as defined in claim 1, wherein the plasma generating equipment (120) is configured to excite the liquid (114) so as to form the microplasma (124) to have a volume of less than 20 cm³, for example less than 10 cm³, for example less than 5 cm³, for example less than 1 cm³.

3. An optical measurement apparatus (100) as defined in claim 1 or 2, wherein the plasma generating equipment (120) comprises a power supply (121) and two or more electrodes (122, 123) connected to the power supply and positioned within the measurement chamber (110) in which the microplasma is to be formed, the power supply and the electrodes being configured to supply a current flow through the liquid so as to gasify a portion of the liquid and generate a discharge through the thereby formed gas to initiate the excitation.

4. An optical measurement apparatus (100) as defined in any of claims 1 to 3, wherein the spectral detector (130) is configured to determine spectral information of the received light signals with a resolution in the range of 0.001 nm to 2.5 nm.

5. An optical measurement apparatus (100) as defined in any of claims 1 to 4, wherein the spectral detector (130) is configured to determine spectral information of the received light signals in a wavelength range of 100 to 2000 nm, for example 150 to 1100 nm, for example 200 to 900 nm.

6. An optical measurement apparatus (100) as defined in any of claims 1 to 5, wherein the at least one auxiliary optical path comprises an auxiliary optical path (161) for receiving a first auxiliary light signal (171), in itially emitted by the light source (140) and transmit ted to the measurement chamber (110), from the meas urement chamber and transmitting it to the spectral de tector (130).

7. An optical measurement apparatus (100) as defined in any of claims 1 to 6, wherein the at least one auxiliary optical path comprises an auxiliary optical path (162) for receiving a second auxiliary light signal (172), originating from elastic or inelastic scattering of, or fluorescence excited by, light (141) emitted by the light source (140) and transmitted to the measurement chamber (110), from the measurement chamber and trans mitting it to the spectral detector (130).

8. An optical measurement apparatus (200) as defined in any of claims 1 to 7, wherein the light signal collecting arrangement (265) is further configured to form an aux iliary optical path (263) for receiving a third auxil iary light signal (273), originating from a chemilumi nescent reaction (215) taking place in the liquid, from the measurement chamber (210) to which the light was transmitted and transmitting it to the spectral detector (230).

9. An optical measurement apparatus (100) as defined in any of claims 1 to 8, further comprising a camera (180) for imaging the measurement chamber (110) and the liquid (114) received therein.

10. An optical measurement apparatus (100) as defined in claim 9, wherein the camera (180) is a spectral camera configured to provide image data for a plurality of different wavelength bands.

11. An optical measurement apparatus (100) as defined in any of claims 1 to 10, further comprising a computing unit (190) connected to the spectral detector (130) for receiving the electrical signal(s) (131) produced by the spectral detector, and configured to determine, on the basis of spectral information of at least the primary light signal (170), at least one inorganic element con tent of the liquid.

12. An optical measurement apparatus (100) as defined in claim 11 and any of claims 6 to 8, wherein the com puting unit (190) is configured to determine the at least one inorganic element content of the liquid on the basis of spectral information of the primary light sig nal (170) and at least one auxiliary light signal (171, 172).

13. An optical measurement apparatus (100) as defined in claim 11 or 12 and any of claims 6 to 8, wherein the computing unit (190) is further configured to determine, on the basis of spectral information of at least one auxiliary light signal (171, 172), at least one organic species content of the liquid.

14. A method (300) for analyzing liquids, comprising collecting, by an apparatus as defined in any of claims 1 to 10, electrical signal(s) indicative of spectral information of the primary light signal and at least one auxiliary light signal (301).

15. A method (300) as defined in claim 14, further com prising determining, on the basis of spectral infor mation of the primary light signal, at least one inor ganic element content of the liquid (302).

16. A method (300) as defined in claim 15, wherein the at least one inorganic element content of the liquid is determined on the basis of spectral information of the primary light signal and one or more of the at least one auxiliary light signals (302).

17. A method (300) as defined in claim 15 or 16, the method further comprising determining, on the basis of spectral information of one or more of the least one auxiliary light signals, at least one organic species content in the liquid (303).