WO2023195506A1

WO2023195506A1 - Monitoring system and method

Info

Publication number: WO2023195506A1
Application number: PCT/JP2023/014166
Authority: WO
Inventors: Christian GOUEGUEL; Lukas Brueckner; Prakash Sreedhar Murthy
Original assignee: Atonarp Inc.
Priority date: 2022-04-08
Filing date: 2023-04-06
Publication date: 2023-10-12

Abstract

A LIBS analyzing system (20) for monitoring substances in a liquid that includes: a light source (21) configured to provide an excitation light (51); an optical head (24) configured to focus the excitation light on a liquid body (5) through a transparent wall (13) of a holder (11) that makes a surface (15) of the liquid body and in a vicinity of the transparent wall to generate a plasma (55) under the liquid body; and an optical path (26) configured to convey an emitted light (52) due to the plasma received through the transparent wall to a detector (22).

Description

MONITORING SYSTEM AND METHOD

The invention generally relates to a system and method that uses Laser-induced breakdown spectroscopy (LIBS).

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique based on atomic emission spectroscopy (AES) of laser-produced plasma. Essentially, a focused laser beam results in the plasma leading to the formation of excited atomic and ionic species, from which multiple species can be identified and quantified simultaneously based on their characteristic emission lines in optical spectra. Indeed, by plotting the emission intensity of a given spectral line from a series of certified samples (calibration curve), it is possible by interpolation to obtain the concentration of the element of interest.

LIBS is one of the tools for exploring of liquid (liquid body, liquid means, solutions). Zhang et al. (Zhang DC, Hu ZQ, Su YB, Hai B, Zhu XL, Zhu JF, et al. Simple method for liquid analysis by laser-induced breakdown spectroscopy (LIBS). Opt Express. (2018) 6:18794-02. doi: 10.1364/OE.26.018794) have proposed a capillary mode LIBS method to detect the elemental concentrations in solution. Their experimental results have shown that the accuracy of quantitative element analysis in liquids can be improved by the capillary mode LIBS. Their experimental results show that the splashing of liquid induced by laser pulses is decreased significantly and the pollution of mirrors is avoided effectively using liquid capillary mode. But the splashing is occurred, and pollution of the optical elements might be happened in the capillary mode LIBS. That is, in the capillary mode LIBS, a stainless-steel capillary is positioned with an angle less than 45 degree between the laser beam and the axis of capillary. The laser pulses will be interacted with liquid sample on a small hole in the wall of capillary. A shield cover with a hole larger than laser beam spot is positioned between focus lens and capillary, which can avoid the pollution of lens by residual splashing. Finally, the liquid sample ejects from the capillary and returns to the container.

New applications of LIBS, driven by various needs in various fields, are continuously in development worldwide. One of the challenges is static or continuous monitoring of solutes in a liquid with enabling accurate measurements by capturing light excited by the plasma in the vicinity while minimizing or eliminating the effects of splashing or bubbling. One of the target applications is monitoring of solutes (materials, substances) in liquids relating to living body such as blood, dialysate, etc.

One of aspects of this invention is a system for monitoring substances in a liquid. The system includes: a light source configured to provide an excitation light; an optical head configured to focus the excitation light on a liquid body through a transparent wall that makes a surface of the liquid body and in a vicinity of the transparent wall to generate a plasma under the liquid body; and an optical path configured to convey an emitted light due to the plasma received through the transparent wall to one or more detectors. The transparent wall may be a part of a holder and the optical head may be configured to focus the excitation light on the liquid body held in or flowing in the holder. When plasma is generated at a surface or a boundary (interface), the phenomena caused by it are complex and difficult to measure with high accuracy. On the other hand, to generate plasma deep under the liquid, it is necessary to irradiate a high-energy laser, which causes a lot of damage to the target, and increases the attenuation of the excited light for detecting. By forming a plasma by focusing (collecting) the excitation light just below the surface (subsurface, near the surface) but in the liquid (under the liquid), these problems are solved. In addition, the transparent wall for making the liquid surface prevents the effect of splashing or bubbling such as the pollution of lens even if the splashing and/or bubbling are occurred in the liquid body due to the plasma. The subsurface region may be within 10 mm from the surface, within 5 mm from the surface, or within 1 mm from the surface. That is, the optical probe may include one or more optical lenses for focusing the excitation light within 10 mm from the transparent wall (inner surface of the transparent wall). The distance between the transparent wall and the plasma may be within 5 mm. The optical head may receive the emitted light from the plasma generated in the vicinity of the transparent wall using the lenses for focusing the excitation light that may be located closest to the generated plasma.

The excitation light may be a pulsed light with a high repetition rate and a low energy. The light pulses with high repetition rate and low energy may not affect the transparent wall but may energize the plasm in liquid by focusing them close to the wall. In addition, by using the high repetition rate and low-energy pulses, the plasma may be generated under the liquid body without visible bubbles or cavitations. The light source may include a pulsed laser light source that provides the excitation light with a repetition rate at least 100 Hz, an energy at most 10 mJ per each, and a duration at most 5 ns per each. The pulsed laser light may have higher repetition rate such as greater than or equal to 1 kHz or 1 MHz, have lower energy such as below 1 mJ per each or 0.5 mJ per each and over 0.1 mJ and have lower pulse duration below 1 ns per each and may be provided by a fiber laser system.

The optical path for conveying the emitted light (emission light) may include one or more filters for dividing the emitted light into a plurality of wavelength bands and one or more paths for conveying divided lights to corresponding detectors (spectrometer devices). The filters may divide the emitted light into a plurality of wavelengths corresponding to the materials such as Na, K, Mg, Ca, Cl, P, etc. The one or more filters may include one or more diffract gratings and/or dichroic optical elements.

The system may include a non-plasma type optical analyzer that includes a laser irradiation apparatus for irradiating the liquid body with one or more laser lights through the transparent wall and a detector for detecting a generated light from the liquid body. The non-plasma type optical analyzer may include an infrared spectroscopy (IR, infrared absorption), a Raman spectroscopy, and others. Raman spectroscopy may include a CARS (Coherent Anti-Stokes Raman Scattering) spectroscopy, an SRS (Stimulated Raman Scattering) spectroscopy, a time-resolved CARS spectroscopy, and others. The excitation light is commonly used, not only LIBS, in multiple optical modalities such as CARS.

The transparent wall for making the surface of the liquid body may be a part of a holder and the optical head may be configured to focus the excitation light on the liquid body held in or flowing in the holder. The holder may include a transparent vessel and a transparent pipe through which a target fluid is allowed to pass as the liquid body. The target fluid may include a fluid of a human body, a dialysate to/from the human body, and a drainage from a dialysis apparatus (equipment).

Another aspect of this invention is a method including monitoring substances in a liquid. The monitoring comprises: holding or flowing a liquid body to be monitored in a holder having a transparent wall; focusing an excitation light on the liquid body in the holder through the transparent wall in a vicinity of the transparent wall to generate a plasma under the liquid body; and detecting an emitted light due to the plasma received through the transparent wall.

The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
Fig. 1 depicts an embodiment of a system of this invention; Fig. 2 depicts an example of an arrangement of a LIBS analyzing system; Fig. 3 depicts an example of plasma generated in the LIBS analyzing system; Fig. 4 depicts an example of LIBS spectra for Mg (Mg II, bivalent magnesium); Fig. 5 depicts an example of LIBS spectra for Ca (Ca II, bivalent calcium); Fig. 6 depicts an example of LIBS spectra for Na (Na I, monovalent sodium); Fig. 7 depicts an example of LIBS spectra for K (K I, monovalent potassium); Fig. 8 depicts an example of LIBS spectra for Cl (Cl I, monovalent chlorine); Fig. 9 depicts LIBS spectra for Na with concentrations 100 mg/dL, 50 mg/dL, 25 mg/dL, 12.5 mg/dL, 6 mg/dL, 3 mg/dL, and 1.5 mg/dL; Fig. 10 depicts results of pseudo-Voigt profile (function) fittings; Fig. 11 depicts the calibration curve between the Na concentrations and the Na I peak area; Fig. 12 depicts a block diagram of another type of detection system; and Fig. 13 depicts a flow diagram of an embodiment of measuring method of this invention.

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

Fig. 1 illustrates a system 1 according to an embodiment of this invention. The system 1 is a dialysis system that includes dialysis equipment 2 with a dialyzer 2a and a monitoring system 10 for monitoring a drainage (waste liquid, discharge fluid) from the dialysis equipment 2. The monitoring system 10 includes a transparent pipe (transparent (translucent) vessel, holder) 11 through which a part of the drainage (target fluid) 5 is to pass as a liquid body to be measured or monitored by the monitoring system 10. The liquid 5 supplied to the transparent pipe 11 is a part of the drainage discharged from the dialysis equipment 2 to a discharge header 8 via a discharge pipe 3 sampled by the sampling pipe 6 branched from the discharge pipe 3. The transparent pipe 11 includes a transparent (translucent) wall 13 through which lasers for monitoring the liquid body 5 in the transparent pipe 11 are irradiated. The liquid 5 introduced in the transparent pipe 11 is discharged to the wastewater system (drainage system) 9 as well as the drainage from the discharge header 8.

The monitoring system 10 includes a LIBS (Laser-induced breakdown spectroscopy) analyzer (analyzing system) 20 and CARS (Coherent Anti-Stokes Raman Scattering) analyzer (analyzing system) 30 for monitoring substances (materials, solutes, components, elements, compositions) in the liquid (liquid body, liquid sample, sample fluid) 5. Raman spectroscopy including CARS is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Therefore, Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. On the other hand, as described above LIBS is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. Therefore, LIBS is commonly used to monitor or analyze the atoms of a target. By analyzing the liquid using the LIBS analyzer 20 and the CARS analyzer 30, molecules and atoms (ions) existed or dissolved in the liquid body 5 can be analyzed and monitored. The CARS analyzer 30 is one of examples of the non-plasma type and the non-plasma type analyzer may be another type of Raman spectroscopy analyzer, an infrared absorption analyzer and others.

The CARS analyzer 30 includes a laser unit (laser irradiation apparatus) 31, which irradiates the liquid body 5 with laser lights 61 through the transparent wall 13 of the holder 11 (transparent pipe), and a detector 32 that detects generated light (CARS light) 62 by the laser lights 61 from the liquid body 5 through the transparent wall 13. The irradiation apparatus 31 includes is a focusing apparatus 34, as one example, one or more objective lenses, which focuses (concentrate, condenses) at least two laser beams 61, in the present embodiment, Stokes light and pump light for generating Raman scattered light (CARS light) 62 into a common spot in the liquid body 5. The irradiation apparatus 31 may be an apparatus that emits, as the laser lights 61, probe light in addition to the Stokes light and the pump light. The irradiation apparatus 31 may include one or more dichroic mirrors and/or prisms 35 and other optical element for constructing appropriate optical paths. The irradiation apparatus 31 includes CARS controller 33 for controlling the CARS analyzer 30 and outputting the detection results to an analyzer 19 of the monitoring system 10.

Among the irradiating laser lights, the Stokes light pulses may have the first range of wavelengths 1085 - 1230 nm, the pump light pulses may have the second range of wavelengths 1040 nm, and the probe light pulses may have the third range of the wavelengths 780 nm. CARS light (TD-CARS light) pulses 62 may have the range of the wavelengths 680 - 760 nm. The Stokes light pulses and the pump light pulses may include one to several hundred fS (femto second)-order pulse widths with tens to hundreds of mW. The probe light pulses may include one to several tens pS (pico second)-order pulse widths with tens to hundreds of mW.

Fig. 2 shows a typical arrangement of the LIBS analyzer (analyzing system) 20 for monitoring a material or materials (substances, solutes) contained in a subject that includes the liquid body (liquid medium) 5 such as an aqueous solution in the transparent vessel (holder, cuvette) 11. As shown in Fig. 1, the LIBS analyzer 20 includes a light source 21 configured to provide an excitation light 51; an optical head (optical probe) 24 configured to focus (concentrate) the excitation light 51 on the liquid body 5 through the transparent wall 13 that makes a surface 15 of the liquid body 5 and in a vicinity of the transparent wall 13 to generate a plasma 55 under the liquid body 5; an optical path 26 configured to convey an emitted light 52 due to the plasma 55 received through the transparent wall 13 to a detector block 22; and a LIBS controller 23 for controlling the LIBS analyzer 20 and outputting the detection results to the analyzer 19 of the monitoring system 10.

The optical head 24 may include one or more optical lenses 24a for focusing the excitation light (irradiation light) 51 close to the internal surface 14 of the transparent wall 13. The lenses may include an aspheric lens and the focal length of the lenses 24a may be 50 mm or less, 30 mm or less, and even 20 mm or less. The distance (gap) d1 between the internal surface 14 of the transparent wall 13 and the plasma 55 may be 10 mm or less, 5 mm or less, and even around 1 mm from the transparent wall. The lenses 24a of the optical head 24 may receive the emitted light (emission light, generated light) 52 from the plasma 55 to convey the emitted light 52 to the optical path 26. The optical head 24 and the optical path 26 may include optical elements such as a dichroic mirror 25, dichroic prism, achromatic doublet 26a, optical fiber interface 27, optical fiber bundles 28 and others for configuring appropriate optical routes for the excitation light 51 and the emitted light 52.

The light source 21 may include a pulsed laser light source 21a. The laser light source 21a may be a fiber laser system that provides the excitation light 51 with pulses having high repetition rate and low energy. The typical pulsed excitation light 51 may have a repetition rate at least 100 Hz, an energy at most 10 mJ per each, and a duration at most 5 ns per each. The pulsed laser light as the excitation light 51 may have higher repetition rate such as greater than or equal to 1 kHz or 1 MHz, have lower energy such as below 1 mJ per each or 0.5 mJ per each and over 0.1 mJ and have lower pulse duration such as below 1 ns per each. An example of specification of laser light source 21a is the following.
Repetition rate: 1 - 10 kHz,
Energy: ~ 160 μJ/pulse max,
Wavelength: 1064 nm, and
Pulse duration: ~ 600 pS.

LIBS analysis of liquids can be performed by volume (i.e., a plasma is created in the liquid volume) or at the surface of the liquid. The analysis carried out in volume produces a plasma with a very short lifetime (~ 1 μs) compared to those generated at the liquid-air interface (> 10 μs). The major disadvantage of bulk analysis is the reduced plasma emission intensity in comparison with that obtained from the liquid surface. The plasma emission typically exhibits broad emission lines at the initial phase of plasma ignition, due to the high density of electrons in the plasma, then gradually becomes thinner, allowing quantitative analysis. Although easier to be carried out in principle, the LIBS measurements carried out on the surface of liquids lead to other experimental difficulties, which are not encountered for solid samples, such as the splashes caused by the impact of the laser, which might alter the optical components. Also, generation of surface waves and volume bubbles, as well as aerosols disturb the measurements from one laser shot to another. It is therefore necessary to define specific procedures in the case of liquids to minimize the impact of these factors on the analytical performance of LIBS. In this invention, most of these issues have been avoided or significantly reduced by making a liquid surface with the transparent wall 13 that separates the optical components for generating the plasma 55 and measuring the emission of the plasma 55, but by irradiating the liquid 5 through the transparent wall 13, the plasma 55 can be generated and the emission of the plasma 55 can be observed through the transparent wall 13. In one of the embodiments of this invention, these issues have been avoided by using a vertical, or horizontal laminar flow of the liquid 5 in the transparent (translucent) holder 11. The robustness and simplicity of a LIBS system make it a promising candidate for in-situ elemental analysis in water.

Single-pulse LIBS is the common configuration used. In these systems, the several nanosecond lasers deliver several tens of mJ of pulse energy. Meanwhile, it has been shown that a long pulse duration, in order of 100 ns, can improve the SNR of spectral lines. In terms of laser irradiance, previous studies showed that the highest spectral emission could be observed at low laser irradiances if they exceed the plasma formation threshold. Furthermore, laser wavelength at 1064 nm is commonly used for igniting the plasma, which relied on the avalanche (also named cascade) ionization absorption. This process requires free electrons in the focal volume to seed the cascade ionization. These seed electrons are usually generated by heating the impurities in liquid or by multiphoton ionization. Thus, sufficient pulse energy of a laser is critical to initialize optical breakdown in liquids.

The lasers that are commonly used in conventional LIBS often operate at several Hz or several tens of Hz. Acquisitions of statistically valid results, e.g., minimizing influences from random fluctuations, are achieved through signal accumulation and averaging. Meanwhile, the extent of the spectral range is commonly achieved by scanning the diffraction grating or using parallel optical detectors. The various advantages offered by diode-pumped lasers, e.g. the excellent beam quality, high energy-conversion efficiency, low pulse-to-pulse variations, and high repetition rate (RR), enable the development of robust and efficient LIBS-based analyzers. Especially, the operating RR up to hundreds of kHz or MHz can significantly improve the throughput compared to conventional LIBS through increasing the number of plasma events per unit time by several orders.

The typical output energy of this compact and high repetition rate (RR) lasers may be less than 10 mJ, more desirably less than one mJ per pulse. Indeed, contrary to liquid surface analysis, such low output energy can be detrimental to maintaining stable breakdowns in the bulk liquid. One of the objectives of this project is to address the applicability of low-energy diode-pumped lasers for high-throughput underwater elemental analysis. To overcome the necessary plasma formation threshold, the focusing lenses 24a with short focal lengths are used in this system 20, thus achieving high irradiances despite the low pulse energies. The focusing lenses 24a with short focal lengths can generate the plasmas 55 in the subsurface region of the target liquid 5.

In underwater applications, the accompanying short working distances of only several mm between the transparent wall 13 and the plasma 55 additionally minimize the fraction of the laser pulse 51 that is absorbed while propagating through the liquid such as water. It has been found that the duration of the line and continuum emission along with the relative amount of continuum radiation decreases as one goes below 10 mJ, more desirably below 1 mJ excitation energy. In addition, by using high PP low energy laser pulses 51, the plasma 55 can be generated under the liquid without visible bubbles or cavitations. In many cases, the SNR is a weak function of energy, but it is possible to obtain good sensitivity by acquiring the emitted lights (emission lights) 52 via the optical head 24 that is located at the closest position to the plasma 55 through the transparent wall 13. This means that working with ungated detectors becomes possible which greatly simplifies the detector 22 requirements and reduces system cost. However, the highest sensitivities may be achieved using gated systems. In addition, the ability to generate or form plasma 55, at least visually, in continuous (uninterrupted, succession) without bubbles not only suppresses the effects of fluctuations and others that degrade the accuracy of LIBS measurements, but also minimizes the effects for the measurements with other methods such as CARS spectroscopy by the CARS analyzer 30 performed on the common sample (liquid) 5 in the common holder 11 at the same time.

Fig. 3 depicts a photo showing the plasma 55 continuously generated under the water 5 near the transparent wall 13 without visible bubbling and cavitation. The excitation light 51 used for generating the plasma 55 has pulses with the energy of 150 μJ each, the repetition rate of 1 kHz, and the duration of 500 pS. The lenses 24a of the optical head 24 includes an aspheric lens and the focal length of the lenses 24a is 20 mm.

Figs. 4 to 8 show typical LIBS spectra for Mg (Mg II, bivalent magnesium), Ca (Ca II, bivalent calcium), Na (Na I, monovalent sodium), K (K I, monovalent potassium), and Cl (Cl I, monovalent chlorine) respectively. Mineral salts dissolved in deionized water (NaCl, KCl, Na2HPO4, MgCl2-6H2O, and CaCl2) were prepared as the samples of the liquid bodies and measured by using an experimental system that had the laser light source 21 with the fiber laser 21a and the optical head 24 with lenses 24a specified above. The sample liquids (target fluids) 5 were held in the transparent cuvette (holder) 11. A spectrometer for detecting wide band was applied as the detector 22 in the experimental system. The specification of the spectrometer is followings.
Focal length: 80.8 mm,
Aperture: f/4,
Wavelength range: 220 - 1100 nm,
1024 x 256 CCD camera, with UV coatings,
Integrated delay generator (10 ns accuracy),
1200 g/mm blaze @300 nm,
1200 g/mm blaze @550 nm, and
0.22 nm/pixel spectral resolution.

Figs. 9 to 11 show LIBS spectra of Na (Na I, monovalent sodium) at varying concentrations. Fig. 9 depicts LIBS spectra for Na with concentrations 100 mg/dL, 50 mg/dL, 25 mg/dL, 12.5 mg/dL, 6 mg/dL, 3 mg/dL, and 1.5 mg/dL. Fig. 10 depicts results of pseudo-Voigt profile (function) fittings. Fig. 11 depicts the calibration curve between the Na concentrations and the Na I peak areas obtained by Fig. 10. According to the results, concentrations of atoms in the liquid body 5 can be measured with high accuracy by using the LIBS analyzer 20. That is, by collecting the LIBS spectra from the liquid (water, solutions, target fluid) 5 held in the holder 11 having the transparent wall 13, the materials (solutes) in the liquid 5 can be monitored quantitatively. That is, the system 20 with the high RR lasers will be applicable for monitoring (detection and quantification) of alkali and alkali earth metals (Na, K, and Ca) and nonmetals such as Cl and/or P in the liquids using a fiber laser 21a. This new LIBS-based sensor system 20 for continuous monitoring of solutes in the liquid 5 including a fluid of a human body such as blood, urine, etc., a dialysate to/from the human body, and a drainage from a dialysis equipment.

Fig. 12 shows another type of the detector (detection system) 22 of the LIBS analyzer 20. In this detection system 22, the optical path 26 for conveying the emitted light 52 including filters 261 - 264 for dividing the emitted light 52 into a plurality of wavelength bands and paths 265 - 269 for conveying divided lights 52a - 52e to the corresponding detectors 231 - 235 that include spectrometer devices and/or photosensors. The filters 261 - 264 may include diffract gratings, dichroic optical elements (mirrors and/or prisms) for dividing the emitted light 52 into a plurality of wavelengths corresponding to the materials such as the light 52a for K (above 760 nm), the light 52b for Cl (620-760 nm), the light 52c for Na (500-620 nm), the light 52d for Ca (350-500 nm), and the light 52e for Mg (below 350 nm) respectively. The emitted light 52a with the wavelength above 760 nm may be used other optical modalities such as imaging, CARS analysis and others. By dividing the emitted light 52 to the wavelengths corresponding to the materials, it becomes possible to use the photosensors such as photodiodes for detecting the divided light such as the detectors 233 - 235 for the lights 52c - 52e. For detecting the spectra of the emitted light 52 by using the spectrometer, the light is forced to pass through the slit and grating and received at limited areas that reduces the intensities of the wavelength components of the emitted light 52. On the contrary, the photosensor such as photodiodes can gather the divided lights. This increases light-receiving intensities of the detection system 22 and enables more accurate measurements.

Fig. 13 depicts a method including a step of monitoring substances in a liquid using a flowchart. In step 71, the conditions for measuring liquids are set up by holding (receiving, filling) or flowing a liquid body 5 to be monitored in the holder 11 that has the transparent wall 13 and making or forming the liquid surface 15 along and in contact (in touch, in physical connection, covered) with the inner surface 14 of the transparent wall 13. The liquid body 5 to be monitored or analyzed (the target fluid) may be a fluid of a human body, a dialysate to/from the human body, a drainage from a dialysis equipment 2 or others that should be transparent enough to transmit the laser light, flow well, and be able to form the surface 15 in contact with the wall 13 without gaps. In step 72, the optical head 24 of the LIBS analyzer 20 focuses (irradiates, concentrates) the excitation light 51 from the laser source 21 on the liquid body 5 in the holder 11 through the transparent wall 13 in a vicinity of the transparent wall 13 to generate a plasma 55 under the liquid body5. In step 73, the detector 22 of the LIBS analyzer 20 detects the emitted light 52 due to the plasma 55 received through the transparent wall 13 via the optical head 24. In step 72, the optical head 24 may focus the excitation light 51 within 10 mm from the transparent wall 13.

In this specification, a system for monitoring a material contained in a subject that includes liquid medium is disclosed. The system comprises: one or more light sources configured to provide an excitation light; an optical probe (optical head) configured to focus the excitation light onto a subsurface of the liquid medium to generate a plasma under the liquid medium and receive an emitted light due to the plasma; and an optical path configured to convey the emitted light to one or more spectrometer devices. The optical probe may include one or more optical lenses for focusing the excitation light within 10 mm from a surface of the liquid medium. The optical probe may include one or more optical lenses for focusing the excitation light within 10 mm from an outermost surface of the one or more optical lenses. The one or more light sources may include a pulsed laser light source that has a repetition rate of greater than or equal to 100 Hz. The one or more light sources may include a pulsed laser light source that has a repetition rate of greater than 1 kHz. The one or more light sources may include a pulsed laser light source that emits pulses with an energy below 10 mJ per each. The one or more light sources may include a pulsed laser light source that emits pulses with an energy below 1 mJ per each. The one or more light sources may include a pulsed laser light source that emits pulses with an energy below 0.5 mJ per each. The one or more light sources may include a fiber laser.

The optical path may include one or more filters for dividing the emitted light into a plurality of wavelength bands and one or more paths for conveying divided lights to corresponding spectrometer devices. The one or more filters may include one or more diffract gratings and/or dichroic optical elements. The liquid medium may include a fluid of a body or a dialysate to/from the body included in a transparent vessel or flowing in a transparent pipe that makes a surface of the liquid medium through which the excitation light and the emitted light pass. The one or more light sources may provide the excitation light commonly used in multiple optical modalities.

In this specification, a method including monitoring a material contained in a subject that includes liquid medium is disclosed. The monitoring step comprises: focusing an excitation light onto a subsurface of the liquid medium to generate a plasma under the liquid medium; receiving an emitted light due to the plasma; and detecting the emitted light by one or more spectrometer devices. The focusing step may include focusing the excitation light within 10 mm from a surface of the liquid medium. The focusing step may include focusing the excitation light within 10 mm from an outermost surface of one or more optical lenses. The focusing step may include focusing, as the excitation light, a pulsed laser light that has a repetition rate of greater than or equal to 100 Hz. The focusing step may include focusing, as the excitation light, a pulsed laser light with an energy below 10 mJ per each.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

Claims

A system for monitoring substances in a liquid including:
a light source configured to provide an excitation light;
an optical head configured to focus the excitation light on a liquid body through a transparent wall that makes a surface of the liquid body and in a vicinity of the transparent wall to generate a plasma under the liquid body; and
an optical path configured to convey an emitted light due to the plasma received through the transparent wall to one or more detectors.
The system according to claim 1, wherein the optical head includes one or more optical lenses for focusing the excitation light within 10 mm from the transparent wall.
The system according to claim 1 or 2, wherein the optical head receives the emitted light from the plasma.
The system according to any one of claims 1 to 3, wherein the light source includes a pulsed laser light source that provides the excitation light with a repetition rate at least 100 Hz, an energy at most 10 mJ per each, and a duration at most 5 ns per each.
The system according to claim 4, wherein the pulsed laser light source provides the excitation light with the repetition rate at least 1 kHz.
The system according to claim 4 or 5, wherein the pulsed laser light source provides the excitation light with the energy at most 1 mJ per each.
The system according to claim 4 or 5, wherein the pulsed laser light source provides the excitation light with the energy at most 0.5 mJ per each.
The system according to any one of claims 4 to 7, wherein the pulsed laser light source provides the excitation light with the duration at most 1 ns per each.
The system according to any one of claims 1 to 8, wherein the light source includes a fiber laser.
The system according to any one of claims 1 to 9, wherein the optical path includes one or more filters for dividing the received emitted light to a plurality of wavelength bands and one or more paths for conveying divided lights to corresponding detectors.
The system according to claim 10, wherein the one or more filters include one or more diffract gratings and/or dichroic optical elements.
The system according to any one of claims 1 to 11, further comprising a non-plasma type optical analyzer that includes a laser irradiation apparatus for irradiating the liquid body with one or more laser lights through the transparent wall and a detector for detecting a generated light from the liquid body.
The system according to any one of claims 1 to 12, wherein the transparent wall is a part of a holder, and the optical head is configured to focus the excitation light on the liquid body held in or flowing in the holder.
The system according to claim 13, further comprising the holder that includes a transparent vessel and a transparent pipe through which a target fluid is allowed to pass as the liquid body.
The system according to claim 14, wherein the target fluid includes one of a fluid of a human body, a dialysate to/from the human body, and a drainage from a dialysis equipment.
A system for analyzing a liquid including:
a light source configured to provide an excitation light;
an optical head configured to focus the excitation light on a liquid body held in or flowing in a holder through a transparent wall of the holder and in a vicinity of the transparent wall to generate a plasma under the liquid body; and
an optical path configured to convey an emitted light due to the plasma received through the transparent wall to one or more detectors.
A method including monitoring substances in a liquid, wherein the monitoring comprises:
holding or flowing a liquid body to be monitored in a holder having a transparent wall;
focusing an excitation light on the liquid body in the holder through the transparent wall in a vicinity of the transparent wall to generate a plasma under the liquid body; and
detecting an emitted light due to the plasma received through the transparent wall.
The method according to claim 17, wherein the focusing includes focusing the excitation light within 10 mm from the transparent wall.
The method according to claim 18, further comprising receiving the emitted light from the plasma through the transparent wall via an optical head for focusing the excitation light on the liquid body in the holder.
The method according to any one of claims 17 to 19, wherein the focusing includes providing the excitation light with a repetition rate at least 100 Hz, an energy at most 10 mJ per each, and a duration at most 5 ns per each.