WO2022075953A1 - Performing automatic analysis of heavy metals on the microfluid platform - Google Patents
Performing automatic analysis of heavy metals on the microfluid platform Download PDFInfo
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- WO2022075953A1 WO2022075953A1 PCT/TR2021/051010 TR2021051010W WO2022075953A1 WO 2022075953 A1 WO2022075953 A1 WO 2022075953A1 TR 2021051010 W TR2021051010 W TR 2021051010W WO 2022075953 A1 WO2022075953 A1 WO 2022075953A1
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- Prior art keywords
- detection
- channel
- arsenic
- control channel
- syringe pump
- Prior art date
Links
- 238000004458 analytical method Methods 0.000 title description 4
- 229910001385 heavy metal Inorganic materials 0.000 title description 4
- 238000001514 detection method Methods 0.000 claims abstract description 60
- 229910052785 arsenic Inorganic materials 0.000 claims abstract description 58
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims abstract description 58
- 238000000034 method Methods 0.000 claims abstract description 48
- 239000003651 drinking water Substances 0.000 claims abstract description 18
- 235000020188 drinking water Nutrition 0.000 claims abstract description 18
- 239000004205 dimethyl polysiloxane Substances 0.000 claims abstract description 13
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims abstract description 13
- 239000010931 gold Substances 0.000 claims description 33
- 238000002835 absorbance Methods 0.000 claims description 31
- 239000002105 nanoparticle Substances 0.000 claims description 30
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 28
- 229910052737 gold Inorganic materials 0.000 claims description 28
- 239000011521 glass Substances 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 12
- 235000013870 dimethyl polysiloxane Nutrition 0.000 claims description 11
- 239000012153 distilled water Substances 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 238000002347 injection Methods 0.000 claims description 9
- 239000007924 injection Substances 0.000 claims description 9
- 238000002444 silanisation Methods 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- PZBFGYYEXUXCOF-UHFFFAOYSA-N TCEP Chemical compound OC(=O)CCP(CCC(O)=O)CCC(O)=O PZBFGYYEXUXCOF-UHFFFAOYSA-N 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 5
- 238000011534 incubation Methods 0.000 claims description 4
- 238000001802 infusion Methods 0.000 claims 3
- CXQXSVUQTKDNFP-UHFFFAOYSA-N octamethyltrisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C CXQXSVUQTKDNFP-UHFFFAOYSA-N 0.000 claims 2
- 238000004987 plasma desorption mass spectroscopy Methods 0.000 claims 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 238000002174 soft lithography Methods 0.000 abstract description 2
- -1 Polydimethylsiloxane Polymers 0.000 abstract 1
- 238000005086 pumping Methods 0.000 abstract 1
- 230000036541 health Effects 0.000 description 4
- 238000011005 laboratory method Methods 0.000 description 3
- 230000008520 organization Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- DJHGAFSJWGLOIV-UHFFFAOYSA-K Arsenate3- Chemical compound [O-][As]([O-])([O-])=O DJHGAFSJWGLOIV-UHFFFAOYSA-K 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 229940000489 arsenate Drugs 0.000 description 2
- 238000003149 assay kit Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000021615 conjugation Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000012417 linear regression Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- WYWHKKSPHMUBEB-UHFFFAOYSA-N 6-Mercaptoguanine Natural products N1C(N)=NC(=S)C2=C1N=CN2 WYWHKKSPHMUBEB-UHFFFAOYSA-N 0.000 description 1
- 238000001391 atomic fluorescence spectroscopy Methods 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
- 238000004737 colorimetric analysis Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007306 functionalization reaction Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- MNRILEROXIRVNJ-UHFFFAOYSA-N tioguanine Chemical compound N1C(N)=NC(=S)C2=NC=N[C]21 MNRILEROXIRVNJ-UHFFFAOYSA-N 0.000 description 1
- 229960003087 tioguanine Drugs 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
- B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N2021/7756—Sensor type
- G01N2021/7763—Sample through flow
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
- G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
- G01N2021/7769—Measurement method of reaction-produced change in sensor
- G01N2021/7783—Transmission, loss
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
- G01N33/1813—Specific cations in water, e.g. heavy metals
Definitions
- the invention relates to a microfluidic platform that can detect the amount of arsenic in drinking water up to ⁇ 10 pg/L.
- the used laboratory techniques can detect up to 1 pg/L.
- the laboratory techniques mentioned in the literature are quite expensive and require well-trained technicians.
- Arsenic test kits such as NIPSOM, Merck, AAN, Hach EZ, Arsenator can have detection concentrations of up to 20-50 pg/L. Although commercial arsenic test kits are economical and portable, they are less reliable and cannot go down to the arsenic detection concentration specified by the World Health Organization.
- colorimetric measurement methods measure arsenate and phosphate concentrations. Although colorimetric analyzes are simple, fast, and inexpensive methods, the presence of arsenate and phosphate in drinking water, which have similar chemical properties, creates a disadvantage for detection.
- the present invention relates to the detection of arsenic on a microfluidic platform, which meets the above-mentioned requirements, eliminates the disadvantages, and brings some additional advantages.
- the invention offers the opportunity to analyze heavy metals in drinking water up to a level lower ( ⁇ 10 pg/L) than the maximum arsenic concentration (10 pg/L) that should be found according to the World Health Organization (WHO).
- WHO World Health Organization
- a flow is created in the PDMS-based microfluidic platform channels using the syringe pump.
- the arsenic sample and gold nanoparticles introduced into the microfluidic channel with the help of a syringe pump are bound to the -SH groups on the glass coverslip surface; agglomeration/collapse/clustering does not occur.
- the detection process is performed by looking at the absorbance difference at a certain wavelength between the detection channel and the control channel using a spectrometer device.
- Figure 1 Schematic representation of the microfluidic platform.
- Figure 2 At different concentrations; a) 1 pg/L, b) 10 pg/L, c) 100 pg/L ve d) 1 mg/L arsenic samples absorbance differences between the two channels, respectively.
- the graph shows the relationship between absorbance differences and arsenic concentration differences.
- Figure 3 Analysis of arsenic samples at different concentrations on a microfluidic platform using a flow with a syringe pump.
- arsenic detection from drinking water is performed quickly and below the desired arsenic concentration range ( ⁇ 10 pg/L) by using Poly dimethyl siloxane (PDMS) based microfluidic chip (3) produced by soft lithography method and by using a syringe pump.
- PDMS Poly dimethyl siloxane
- the invention is a microfluidic platform that can detect the amount of arsenic in drinking water; PDMS-based microfluidic chip (3), which contains the detection channel (6) and the control channel (5), spectrometer device (7) connected to the microfluidic chip (3), which enables the measurement of the absorbance difference value formed by the Au nanoparticles attached to the surface between the detection channel (6) and the control channel (5), a light source (1) that illuminates the microfluidic chip (3) for the measurement of the absorbance difference value, the glass surface (4), which is attached to the PDMS- based microfluidic chip (3), and functionalized with the surface silanization process for the attachment of As molecule and Au nanoparticles to the surface via -SH bonds.
- the PDMS-based microfluidic chip (3) is attached to the glass surface (4) by clamping it with 2 plastic layers.
- the spectrometer device (7) is connected to the microfluidic chip (3) with a fiber cable (2).
- the method of detecting the amount of arsenic in drinking water on a microfluidic platform of the invention includes;
- the surface of the channels is primarily functional with the silanization process.
- Arsenic solution is injected into the detection channel (6) and As-S bond is formed.
- the SH- bonds in the detection channel (6) are reduced and fewer gold nanoparticles are attached to the surface compared to the control channel (5).
- the absorbance value of the control channel (5) becomes higher than that of the detection channel (6). The difference in absorbance between the two channels is used to determine the arsenic content.
- the glass coverslip is cleaned in a 70% ethanol solution in a sonicator for 10 minutes at room temperature, and then quickly dried with N2 gas and subjected to oxygen plasma treatment for 4 minutes to activate the surfaces.
- 3-MPS prepared in acetone is transferred onto the cleaned glass coverslip and incubated in the dark at room temperature for 2 hours. In this way, -SH groups are formed on the glass slide surfaces.
- the glasses are dried with N2 gas.
- the method of determining the amount of arsenic in drinking water on a microfluidic platform includes;
- PDMS mixture prepared at a ratio of 10: 1 is poured into the molds obtained from the Formlabs Form2 three-dimensional (3D) printer with a clear resin, and it is cured in an oven at 68°C.
- the cured PDMS chip is carefully removed from the mold and the inlets and outlets are opened on the channels.
- the surface to be bonded on the glass coverslip is exposed to oxygen plasma for 3.5 minutes.
- the glass coverslip, the surface of which is characterized by 3-MPS, and the PDMS chip are attached on top of each other and screwed in sandwich form between the pieces produced using a clear resin.
- Each channel (a control channel (5) and a detection channel (6)) is washed with distilled water.
- TCEP tris(2-carboxyethyl)phosphine
- gold nanoparticles can also be delivered to the surface with the help of a syringe pump.
- Gold nanoparticles with a diameter of 40 nm give a maximum absorbance signal between 529-533 nm; the highest peak was observed at 530 nm wavelength in the optimization process. For this reason, the absorbance value at 530 nm wavelength was used for the measurements. This wavelength changes when gold nanoparticles of different sizes are used and are in 500-600 nm wavelength band.
- the channels are washed with distilled water and the absorbance values between the channels at 530 nm are measured using a spectrometer device (7). The arsenic value corresponding to the absorbance value is calculated from the calibration curve.
- the amount of arsenic is determined from the absorbance difference.
- the amount of -SH group decreases in the detection channel (6) and less gold nanoparticles bind to the surface compared to the control channel (5).
- the absorbance value of the control channel (5) is higher than the detection channel (6).
- the absorbance difference between the two channels is used to determine the amount of arsenic.
- Figure 3 shows the analysis of arsenic samples of different concentrations on the microfluidic platform with a flow using a syringe pump.
- LOD limit of detection
- the background absorbance value was measured using 0 pg/mL As. Linear regression was made for other As-concentrations and absorbance values corresponding to these concentrations. The As concentration, where this linear regression curve cuts the LOD absorbance value, was calculated as the LOD-As concentration value.
- the detection limit was found to be 2.22 pg/L in the tests performed on the platform using a flow with a syringe pump. This value meets to the standard range specified by the WHO.
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- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Molecular Biology (AREA)
- Biophysics (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Plasma & Fusion (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention relates to the detection of arsenic from drinking water rapidly and below the desired arsenic concentration range (<10 μg/L) using the Polydimethylsiloxane (PDMS) based microfluidic system fabricated with soft lithography method and using the push-and- pull pumping method with the syringe pump.
Description
PERFORMING AUTOMATIC ANALYSIS OF HEAVY METALS ON THE
MICROFLUID PLATFORM
Technical Field of the Invention
The invention relates to a microfluidic platform that can detect the amount of arsenic in drinking water up to <10 pg/L.
Known State of the Art (Prior Art)
Heavy metals in drinking water are a serious problem for human health. According to the World Health Organization (WHO), the maximum concentration of arsenic, which is one of these metals, in drinking water should be 10 pg/L.
Today, various laboratory techniques (atomic absorbance spectroscopy, atomic fluorescence spectroscopy, chromatography), arsenic kits, colorimetric methods and microfluidic devices are used for arsenic detection.
The used laboratory techniques can detect up to 1 pg/L. The laboratory techniques mentioned in the literature are quite expensive and require well-trained technicians.
Arsenic test kits such as NIPSOM, Merck, AAN, Hach EZ, Arsenator can have detection concentrations of up to 20-50 pg/L. Although commercial arsenic test kits are economical and portable, they are less reliable and cannot go down to the arsenic detection concentration specified by the World Health Organization.
On the other hand, colorimetric measurement methods measure arsenate and phosphate concentrations. Although colorimetric analyzes are simple, fast, and inexpensive methods, the presence of arsenate and phosphate in drinking water, which have similar chemical properties, creates a disadvantage for detection.
“Chanda N. vd., 2014, The Royal Society of Chemistry, 4, 59558-59561” study concerns a microfluidic device that can detect up to 1.0 ppb of arsenic (As3+). In the microfluidic device, the amount of arsenic is determined based on the As3+ interaction with the free -SH groups on the surface of the TG (Thioguanine) in the gold nano sensor (Au-TA-TG) and thus the clustering of the gold nanoparticles and thus the color change. In this study, the microfluidic system is paper-based, and gold nanoparticles are exposed to chemical conjugation with an
extra process and then a detection is made by forming agglomeration with arsenic.
Brief Description and Objectives of the Invention
The present invention relates to the detection of arsenic on a microfluidic platform, which meets the above-mentioned requirements, eliminates the disadvantages, and brings some additional advantages.
With the microfluidic system, the invention offers the opportunity to analyze heavy metals in drinking water up to a level lower (<10 pg/L) than the maximum arsenic concentration (10 pg/L) that should be found according to the World Health Organization (WHO).
Analyzes are made more economically and faster with this invention. It is an easier method to use than other techniques in the literature. On the other hand, gold (Au) nanoparticles used for arsenic detection offer high sensitivity and selectivity in detection. In addition, in the method of the invention, an extra process such as an extra chemical conjugation and functionalization is not applied to the gold nanoparticles, and flow is provided by applying the push-and-pull method of a syringe pump.
With the invention, by using the push-and-pull method of a syringe pump, it is possible to reach below the specified arsenic concentration value (<10 pg/L) with the use of small sample volume and small sample amount.
In the method mentioned in the invention, a flow is created in the PDMS-based microfluidic platform channels using the syringe pump. The arsenic sample and gold nanoparticles introduced into the microfluidic channel with the help of a syringe pump are bound to the -SH groups on the glass coverslip surface; agglomeration/collapse/clustering does not occur.
With the invention, the detection process is performed by looking at the absorbance difference at a certain wavelength between the detection channel and the control channel using a spectrometer device.
Definitions of Figures Explaining the Invention
Figure 1: Schematic representation of the microfluidic platform.
Figure 2: At different concentrations; a) 1 pg/L, b) 10 pg/L, c) 100 pg/L ve d) 1 mg/L arsenic samples absorbance differences between the two channels, respectively. The graph shows the relationship between absorbance differences and arsenic concentration differences.
Figure 3: Analysis of arsenic samples at different concentrations on a microfluidic platform
using a flow with a syringe pump.
Definitions of Elements/Pieces/Parts Forming the Invention
To better explain the microfluidic platform developed with this invention, the pieces/parts/elements in the figures prepared are given below.
1: Light Source
2: Fiber Cable
3: Microfluidic Chip
4: Glass Surface
5: Control Channel
6: Detection Channel
7: Spectrometer Device
Detailed Description of the Invention
In this invention, arsenic detection from drinking water is performed quickly and below the desired arsenic concentration range (<10 pg/L) by using Poly dimethyl siloxane (PDMS) based microfluidic chip (3) produced by soft lithography method and by using a syringe pump.
As shown in Figure 1, the invention is a microfluidic platform that can detect the amount of arsenic in drinking water; PDMS-based microfluidic chip (3), which contains the detection channel (6) and the control channel (5), spectrometer device (7) connected to the microfluidic chip (3), which enables the measurement of the absorbance difference value formed by the Au nanoparticles attached to the surface between the detection channel (6) and the control channel (5), a light source (1) that illuminates the microfluidic chip (3) for the measurement of the absorbance difference value, the glass surface (4), which is attached to the PDMS- based microfluidic chip (3), and functionalized with the surface silanization process for the attachment of As molecule and Au nanoparticles to the surface via -SH bonds.
The PDMS-based microfluidic chip (3) is attached to the glass surface (4) by clamping it with 2 plastic layers. The spectrometer device (7) is connected to the microfluidic chip (3) with a fiber cable (2).
The method of detecting the amount of arsenic in drinking water on a microfluidic platform of the invention includes;
• Silanization of the glass surface (4) containing the detection channel (6) and the control channel (5), and forming -SH groups on the surface,
• Ensuring incubation by giving tris(2-carboxyethyl)phosphine (TCEP) from the inlets of the glass surface (4) attached with the microfluidic chip (3), and then washing both channels with distilled water,
• Injection of arsenic solution into the detection channel (6) and drinking water into the control channel (5) with the push-and-pull method of the syringe pump or by using only the infuse method, and forming As-S bonds on the surface of the detection channel (6),
• Washing both the detection (6) and the control channels (5) with distilled water,
• Injection of gold nanoparticle solution into both the detection (6) and control channels (5) using the push-and-pull method of a syringe pump,
• Washing again both the detection (6) and the control channels (5) with distilled water,
• Detection of the difference in absorbance value between the detection (6) and the control channel (5) in the 500-600 nm wavelength band where the gold nanoparticle absorbs by the spectrometer device (7).
In the detection of arsenic with the microfluidic platform of the invention, the surface of the channels is primarily functional with the silanization process. Arsenic solution is injected into the detection channel (6) and As-S bond is formed. Thus, the SH- bonds in the detection channel (6) are reduced and fewer gold nanoparticles are attached to the surface compared to the control channel (5). Thus, the absorbance value of the control channel (5) becomes higher than that of the detection channel (6). The difference in absorbance between the two channels is used to determine the arsenic content.
In the process of modification of the glass surface (4), the glass coverslip is cleaned in a 70% ethanol solution in a sonicator for 10 minutes at room temperature, and then quickly dried with N2 gas and subjected to oxygen plasma treatment for 4 minutes to activate the surfaces. 3-MPS prepared in acetone is transferred onto the cleaned glass coverslip and incubated in the dark at room temperature for 2 hours. In this way, -SH groups are formed on the glass slide surfaces. After the procedure, the glasses are dried with N2 gas.
In one of the usages of the invention, the method of determining the amount of arsenic in drinking water on a microfluidic platform includes;
• Silanization of the glass surface (4) with 3-MPS prepared in acetone and incubation at room temperature for 2 hours in the dark and -SH groups are formed on the surface,
• Injection of 1 mL of arsenic solution to the detection channel (6) using the push-and- pull method with a syringe pump or injection of 100 mL of arsenic solution with a syringe pump using only the infuse method, and injecting of 1 mL of drinking water to the control channel (5) using the push-and-pull method with a syringe pump or injection of 100 mL of drinking water to the control channel (5) using only the infuse method with a syringe pump,
• Injecting 100 pL of gold nanoparticle solution into both the detection (6) and control channels (5) 75 times with push-and-pull method using the syringe pump,
• Detection of the difference in absorbance value in the 530 nm wavelength band, where the gold nanoparticle absorbs, between the detection (6) and the control channels (5) with the spectrometer device (7)
On the other hand, for microfluidic chip (3) fabrication, PDMS mixture prepared at a ratio of 10: 1 is poured into the molds obtained from the Formlabs Form2 three-dimensional (3D) printer with a clear resin, and it is cured in an oven at 68°C. The cured PDMS chip is carefully removed from the mold and the inlets and outlets are opened on the channels. Then, the surface to be bonded on the glass coverslip is exposed to oxygen plasma for 3.5 minutes. The glass coverslip, the surface of which is characterized by 3-MPS, and the PDMS chip are attached on top of each other and screwed in sandwich form between the pieces produced using a clear resin. Each channel (a control channel (5) and a detection channel (6)) is washed with distilled water. Then, tris(2-carboxyethyl)phosphine (TCEP), a reducing agent, is introduced into each channel and incubated for 10 minutes in the light and at room temperature. After the procedure, an arsenic-containing sample (detection channel (6)) and an arsenic-free sample (control channel (5)) are given to one of the 2 separate channels on the PDMS-based microfluidic chip for 10 minutes using the push-and-pull method with a syringe pump. After the channels are cleaned with distilled water, the gold nanoparticle solution is given to both channels with the syringe pump and push-and-pull method for 10 minutes and incubated for 2 hours at room temperature in the dark. In order to make the process shorter, gold nanoparticles can also be delivered to the surface with the help of a syringe pump. Gold
nanoparticles with a diameter of 40 nm give a maximum absorbance signal between 529-533 nm; the highest peak was observed at 530 nm wavelength in the optimization process. For this reason, the absorbance value at 530 nm wavelength was used for the measurements. This wavelength changes when gold nanoparticles of different sizes are used and are in 500-600 nm wavelength band. After the process, the channels are washed with distilled water and the absorbance values between the channels at 530 nm are measured using a spectrometer device (7). The arsenic value corresponding to the absorbance value is calculated from the calibration curve. Thus, the amount of arsenic is determined from the absorbance difference. As arsenic binds to the -SH group because of the protocol, the amount of -SH group decreases in the detection channel (6) and less gold nanoparticles bind to the surface compared to the control channel (5). Thus, the absorbance value of the control channel (5) is higher than the detection channel (6). The absorbance difference between the two channels is used to determine the amount of arsenic.
In the invention, 100 mL of arsenic sample was used and injected into the channel with a syringe pump and could reach the detection limit of 2.2 pg/mL. In addition, the push-and-pull method was applied 50 times for 1 mL of arsenic sample with the help of a syringe pump. In this case, 10 pg/mL could be detected. Without flow, the detection limit of 1.3 mg/L was reached for low volume arsenic sample (100 pL). In the invention, increasing the amount of sample and applying the flow caused better adhesion of arsenic molecules to the surface, which improved the detection limit. After arsenic was bound, 100 pL of gold nanoparticles were injected 75 -times into the channel with a push-and-pull method using a syringe pump. This process enabled the gold particles to be attached to the surface in a very short time, in just 10 minutes. On the other hand, the time required for 100 pL of gold nanoparticles to be attached to the surface was observed as 2 hours. Thus, with this invention, arsenic detection can be done in about 30 minutes. The push-and-pull method applied in the invention allowed arsenic molecules and gold nanoparticles to bind to the -SH groups on the surface more quickly. After the arsenic sample was introduced into the channel, there was a decrease in the -SH groups on the channel surface. Then, the gold nanoparticles introduced into the channel were bound to the -SH groups remaining on the surface. In this bonding process, the surface of the gold nanoparticles was not modified by any treatment. As a result, as the amount of arsenic increased, the amount of gold nanoparticles bound to the surface decreased. This caused the absorbance value of the arsenic-containing channel to be lower than the absorbance value of the arsenic-free channel. The amount of arsenic could be detected from the changes in the absorbance value of the channel.
Figure 2 shows the relationship between absorbance differences and arsenic concentration differences. It is observed that the difference between the arsenic absorbance value in the detection channel (6) and the distilled water absorbance value in the control channel (5) increases as the arsenic concentration increases. Increasing the arsenic concentration in the detection channel (6) allows more arsenic to adhere to the surface. Thus, the number of free - SH groups in the detection channel (6) will be reduced and the gold nanoparticles will be adhered to less. This ensures that the absorbance value measured in the detection channel (6) is lower than the value in the control channel (5).
Figure 3 shows the analysis of arsenic samples of different concentrations on the microfluidic platform with a flow using a syringe pump. For determination of the limit of detection (LOD); the formula of LOD= 3x,standard deviation of the background signal)+average of the background signal was used. The background absorbance value was measured using 0 pg/mL As. Linear regression was made for other As-concentrations and absorbance values corresponding to these concentrations. The As concentration, where this linear regression curve cuts the LOD absorbance value, was calculated as the LOD-As concentration value.
The detection limit was found to be 2.22 pg/L in the tests performed on the platform using a flow with a syringe pump. This value meets to the standard range specified by the WHO.
Claims
CLAIMS A microfluidic platform that can detect the amount of arsenic in drinking water comprising;
• PDMS-based microfluidic chip (3) containing the detection channel (6) and the control channel (5),
• Spectrometer device (7) connected to the microfluidic chip (3), which enables the measurement of the absorbance difference value formed by the Au nanoparticles attached to the surface between the detection channel (6) and the control channel (5),
• The light source (1), which illuminates the microfluidic chip (3) for the measurement of the aforementioned absorbance difference value,
• The glass surface (4), which is attached to the PDMS-based microfluidic chip (3), is functionalized with the surface silanization process for the adhesion of As molecule and Au nanoparticles to the surface via -SH bonds. A method of detecting the amount of arsenic in drinking water with a microfluidic platform according to Claim 1, comprising following steps;
• Silanization of the glass surface (4) containing the detection channel (6) and the control channel (5) and forming -SH groups on the surface,
• Ensuring incubation by introducing tris(2-carboxyethyl)phosphine (TCEP) from the inlets of the glass surface (4) attached to the microfluidic chip (3), and then washing both channels with distilled water,
• Injection of arsenic solution into the detection channel (6) and drinking water into the control channel (5) with a syringe pump using the push-and-pull method or only the infusion method, and the formation of As-S bonds on the surface of the detection channel (6),
• Washing both the detection (6) and the control channel (5) with distilled water,
• Injection of gold nanoparticle solution into both the detection (6) and control channels (5) using the push-and-pull method with a syringe pump,
• Washing both the detection (6) and the control channel (5) again with distilled water,
8
Detection of the difference in absorbance value between the detection (6) and the control channel (5) in the 500-600 nm wavelength band, where the gold nanoparticle absorbs, by the spectrometer device (7). he detection method according to Claim 2 , comprising following steps;
• Silanization of the glass surface (4) with 3 -MPS prepared in acetone and incubation at room temperature for 2 hours in the dark and -SH groups are formed on the surface,
• Injection of 1 mL of arsenic solution in the syringe into the detection channel (6) using the push-and-pull method with a syringe pump or 100 mL of arsenic solution using the infusion method with a syringe pump, and injection of 1 mL of drinking water in the syringe into the control channel (6) using the push-and-pull method with a syringe pump or 100 mL drinking water using the infusion method with a syringe pump,
• Injecting 100 pL of gold nanoparticle solution into the channel 75 times using the push-and-pull method with a syringe pump to both the detection (6) and control channels (5),
• Detection of the difference in absorbance value in the 530 nm wavelength, where the gold nanoparticle absorbs, between the detection (6) and the control channel (5) with the spectrometer device (7).
9
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WO2007081635A2 (en) * | 2005-12-14 | 2007-07-19 | Texas Tech University | Method and apparatus for analyzing arsenic concentrations using gas phase ozone chemiluminescence |
US20090225310A1 (en) * | 2003-07-28 | 2009-09-10 | The Regents Of The University Of California | Surface-enhanced raman spectroscopy substrate for arsenic sensing in groundwater |
CN104764892A (en) * | 2015-04-08 | 2015-07-08 | 三峡大学 | Water quality heavy metal multi-parameter online monitoring instrument |
CN111007038A (en) * | 2019-11-29 | 2020-04-14 | 太原理工大学 | Device and method for quantitatively detecting arsenic ions in water based on laser photo-thermal interference |
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US20090225310A1 (en) * | 2003-07-28 | 2009-09-10 | The Regents Of The University Of California | Surface-enhanced raman spectroscopy substrate for arsenic sensing in groundwater |
WO2007081635A2 (en) * | 2005-12-14 | 2007-07-19 | Texas Tech University | Method and apparatus for analyzing arsenic concentrations using gas phase ozone chemiluminescence |
CN104764892A (en) * | 2015-04-08 | 2015-07-08 | 三峡大学 | Water quality heavy metal multi-parameter online monitoring instrument |
CN111007038A (en) * | 2019-11-29 | 2020-04-14 | 太原理工大学 | Device and method for quantitatively detecting arsenic ions in water based on laser photo-thermal interference |
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