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Grasselli G, Arigò A, Palma P, Famiglini G, Cappiello A. Latest Developments in Direct and Non-Direct LC-MS Methods Based on Liquid Electron Ionization (LEI). Crit Rev Anal Chem 2024:1-18. [PMID: 39046707 DOI: 10.1080/10408347.2024.2381543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
Mass spectrometry (MS) enables precise identification and quantification of molecules, particularly when combined with chromatography. The advent of atmospheric pressure ionization (API) techniques allowed the efficient coupling of liquid chromatography with MS (LC-MS), extending analyses to nonvolatile and thermolabile compounds. API techniques present limitations such as low informative capacity and reproducibility of mass spectra, increasing instrument complexity and costs. Other challenges include analyzing poorly polar molecules and matrix effects (ME), which negatively impact quantitative analyses, necessitating extensive sample purification or using expensive labeled standards. These limitations prompted the exploration of alternative solutions, leading to the development of the Liquid Electron Ionization (LEI) interface. The system has demonstrated excellent robustness and reproducibility. LEI has been employed to analyze various compounds, including pesticides, drugs of abuse, phenols, polycyclic aromatic hydrocarbons (PAHs), phthalates, and many others. Its versatility has been validated with single quadrupole, triple quadrupole, and QToF detectors, operating in electron ionization (EI) or chemical ionization (CI) modes and with both reverse phase liquid chromatography (RPLC) and normal phase liquid chromatography (NPLC). LEI has also been successfully integrated with the Microfluidic Open Interface (MOI), Membrane Introduction Mass Spectrometry (MIMS), and Microfluidic Water-Assisted Trap Focusing (M-WATF), broadening its application scope and consistently demonstrating promising results in terms of sensitivity and identification power. The most recent advancement is the development of Extractive-Liquid Sampling Electron Ionization-Mass Spectrometry (E-LEI-MS), a surface sampling and real-time analysis technique based on the LEI concept. This review article offers a comprehensive and up-to-date picture of the potential of LEI.
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Affiliation(s)
- Genny Grasselli
- Department of Pure and Applied Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Adriana Arigò
- Department of Pure and Applied Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Pierangela Palma
- Department of Pure and Applied Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Giorgio Famiglini
- Department of Pure and Applied Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Achille Cappiello
- Department of Pure and Applied Sciences, University of Urbino Carlo Bo, Urbino, Italy
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Pua A, Huang Y, Goh RMV, Ee KH, Tan LP, Cornuz M, Liu SQ, Lassabliere B, Yu B. Combination of solid phase microextraction and low energy electron ionisation gas chromatography-quadrupole time-of-flight mass spectrometry to meet the challenges of flavour analysis. Talanta 2021; 235:122793. [PMID: 34517651 DOI: 10.1016/j.talanta.2021.122793] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 08/05/2021] [Accepted: 08/05/2021] [Indexed: 10/20/2022]
Abstract
The flavour analysis of volatile compounds remains challenging not only because of their diversity in properties and dynamic range, but also due to the high background noise from food matrix constituents. To improve sensitivity and specificity for a multiclass range of compounds, a combination of solid phase micro-extraction (SPME) devices and low energy electron ionisation (LE-EI) was proposed for the analysis of 36 volatile compounds, using coffee as a model matrix. From a pre-evaluation of devices and extraction modes, the combined use of direct immersion-stir bar sorptive extraction and headspace-thin-film SPME (SBSE-TFSPME) was selected to increase compound recovery, and further optimised for extraction temperature (88 °C) and time (110 min). Furthermore, to complement sample preparation by improving method specificity, a LE-EI technique was developed by evaluating the effect of ionisation energy, source temperature, and emission current on the formation of the diagnostic molecular ions and their preservation. This LE-EI method (15 eV, 150 °C, 0.3 μA) was validated with SBSE-TFSPME as a complete workflow in coffee matrices, and was found to possess good repeatability (intra-day RSD: 1.6-7.3 %), intermediate precision (inter-day RSD: 4.1-12.2 %), and linearity (R2 > 0.98). Even for complex coffee samples, the method detection limit reached the pg/mL range (e.g. 2,4,5-trimethylthiazole was detected at 15 pg/mL). In conclusion, this study provided insights on the potential of SPME and LE-EI to improve the sensitivity and specificity of analysis for a range of volatile compounds from food and other complex matrices.
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Affiliation(s)
- Aileen Pua
- Mane SEA Pte Ltd, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623; Department of Food Science and Technology, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542
| | - Yunle Huang
- Mane SEA Pte Ltd, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623; Department of Food Science and Technology, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542
| | - Rui Min Vivian Goh
- Department of Food Science and Technology, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542
| | - Kim-Huey Ee
- Mane SEA Pte Ltd, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623
| | - Lay Peng Tan
- Agilent Technologies Singapore (Sales) Pte Ltd, 1 Yishun Avenue 7, Singapore 768923
| | - Maurin Cornuz
- Mane SEA Pte Ltd, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623
| | - Shao Quan Liu
- Department of Food Science and Technology, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542.
| | | | - Bin Yu
- Mane SEA Pte Ltd, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623.
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Page MK, Goniewicz ML. New Analytical Method for Quantifying Flavoring Chemicals of Potential Respiratory Health Risk Concerns in e-Cigarette Liquids. Front Chem 2021; 9:763940. [PMID: 34778213 PMCID: PMC8581464 DOI: 10.3389/fchem.2021.763940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/11/2021] [Indexed: 11/29/2022] Open
Abstract
Numerous flavoring chemicals are added to e-cigarette liquids to create various flavors. Flavorings provide sensory experience to users and increase product appeal; however, concerns have been raised about their potential inhalation toxicity. Estimating potential health risk of inhaling these chemicals has been challenging since little is known about their actual concentrations in e-cigarette products. To date, a limited number of analytical methods exist to measure the concentrations of flavoring chemicals in e-cigarette products. We have developed an analytical method that accurately and precisely measures the concentrations of 20 flavoring chemicals of potential inhalation risk concerns: 2,3,5-trimethylpyrazine, acetoin, benzaldehyde, benzyl alcohol, butanoic acid, dl-limonene, ethyl maltol, ethyl salicylate, ethyl vanillin, eucalyptol, eugenol, furaneol, isovanillin, l-menthol, maltol, methyl salicylate, pulegone, trans-cinnamaldehyde, triacetin, and vanillin. Calibration and QC solutions were prepared in 50:50 propylene glycol (PG):vegetable glycerin (VG) and 5% H2O and flavoring concentrations ranging from 0.02 to 10.00 mg/ml. Samples of commercial e-cigarette liquids, calibration and QC solutions were combined with 30 µL of an internal standard mix (benzene-d6, pyridine-d5, chlorobenzene-d5, naphthalene-d8 and acenaphthene-d10; 1 mg/ml each) and were diluted 100-fold into methanol. Analysis was performed on an Agilent 7890B/7250 GC/Q-TOF using a DB-624UI column (30 m x 0.25 mmID x 1.4 μm film thickness), with a total runtime of 13.5 min. Calibration curves were fit using a weighted quadratic model and correlations of determination (r2) values exceeded 0.990 for all chemicals. Bias and precision tests yielded values less than 20% and lower limits of quantitation (LLOQ) ranged from 0.02 to 0.63 mg/ml. Over 200 commercially available products, purchased or collected from adult e-cigarette users and spanning a range of flavor categories, were evaluated with this method. Concentrations of pulegone, a suspected carcinogen, varied from below limit of quantitation (BLOQ) to 0.32 mg/ml, while acetoin and vanillin, known precursors to more cytotoxic byproducts, ranged from BLOQ to 1.52 mg/ml and from BLOQ to 16.22 mg/ml, respectively. This method features a wide dynamic working range and allows for a rapid routine analysis of flavoring additives in commercial e-cigarette liquids.
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Affiliation(s)
- Michelle K Page
- Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, NY, United States
| | - Maciej L Goniewicz
- Department of Health Behavior, Roswell Park Comprehensive Cancer Center, Buffalo, NY, United States
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Glineur A, Beccaria M, Purcaro G. Exploring 20 eV electron impact ionization in gas chromatography-tandem mass spectrometry for the determination of estrogenic compounds. J Chromatogr A 2021; 1652:462359. [PMID: 34261020 DOI: 10.1016/j.chroma.2021.462359] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/31/2021] [Accepted: 06/18/2021] [Indexed: 10/21/2022]
Abstract
In electron ionization mass spectrometry (MS), the generation of characteristic fragmentation patterns allows reliable and sensitive identification of compounds. However, loss or a less intense signal of the molecular ion (or more diagnostic ions) can often be observed, which can be detrimental for identification and/or sensitivity, even when MS/MS approaches are applied for quantification. The benefits of applying lower ionization energy (i.e., 20 eV compared to 70 eV) using a gas chromatography (GC) - tandem MS (MS/MS) instrument were investigated in the detection of three estrogenic compounds, namely estrone (E1), 17β-estradiol (E2), and 17α-ethynylestradiol (EE2), emerging aquatic pollutants included in the European Commission Watch List. As expected, the relative intensity of molecular ions (M+.) or high-mass fragments closely related (M+.-CH3) increased significantly at 20 eV compared to 70 eV (from 4.6 % to 35.0 % for EE2, from 22.5 % to 87.3 % for E2, and from 76 % to 100 % for E1). This change in the spectrum profile led to an overall increase in the sensitivity of the compounds when detected using the multiple reaction monitoring mode. These results were compared with the instrumental limit of quantification obtained in liquid chromatography - MS/MS showing a limit of quantification of about 100-folds lower for GC-MS/MS and a completely neglectable matrix effect, thus posing the base for the development of a miniaturized sample preparation method (with an overall lower concentration factor) to achieve the challenging low limits of detection required by the EU regulation for estrogenic compounds.
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Affiliation(s)
- Alex Glineur
- Laboratory of Analytical Chemistry, Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés 2, 5030 Gembloux, Belgium
| | - Marco Beccaria
- Organic and Biological Analytical Chemistry Group, MolSys Research Unit, University of Liège, 4000 Liège, Belgium; Currently at: University of Ferrara, Department of Chemical, Pharmaceutical, and Agricultural Sciences,via L. Borsari 46, Ferrara, Italy.
| | - Giorgia Purcaro
- Laboratory of Analytical Chemistry, Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés 2, 5030 Gembloux, Belgium.
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PENG Z, SUN M, LI L, GUO T, MO T, HUANG ZX, GAO W, CHENG P, ZHOU Z. An Improved Design of Electron Ionization Time-of-Fight Mass Spectrometry with Collisional Focusing Ion Guiding. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2021. [DOI: 10.1016/s1872-2040(21)60088-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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He M, Zhou Y. How to identify “Material basis–Quality markers” more accurately in Chinese herbal medicines from modern chromatography-mass spectrometry data-sets: Opportunities and challenges of chemometric tools. CHINESE HERBAL MEDICINES 2021; 13:2-16. [PMID: 36117762 PMCID: PMC9476807 DOI: 10.1016/j.chmed.2020.05.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 03/26/2020] [Accepted: 05/25/2020] [Indexed: 12/20/2022] Open
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Caban M, Stepnowski P. The application of isotopically labeled analogues for the determination of small organic compounds by GC/MS with selected ion monitoring. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2020; 12:3854-3864. [PMID: 32699873 DOI: 10.1039/d0ay00723d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The study aimed to show the limitations and advantages of the use of stable isotope labeled internal standards (SILISs) for the quantification of small polar compounds (ibuprofen, diclofenac, metoprolol, bisphenol A, 17β-estradiol) in water samples by GC/MS with selected ion monitoring (SIM). The selection of SIM ions shows that for some of the analytes, in the form of trimethylsilylated derivatives, it is problematic to have a minimum of two qualifiers because of the poor mass spectra, high impact of the background or overlapping of the peaks from the analytes and SILISs. The "isotope effect" was observed on GC chromatograms. During the development of the SIM method, special attention was given to the qualifier/quantifier ratio, for which a variety of acceptance criteria can be found in the official guidelines. The values of the solid-phase extraction efficiency, as well as the matrix effect and absolute recovery were the same for the analytes and their corresponding SILISs. The developed method was used for the quantification of analytes in wastewaters.
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Affiliation(s)
- Magda Caban
- Department of Environmental Analysis, Faculty of Chemistry, University of Gdansk, Ul. Wita Stwosza 63, 80-308 Gdańsk, Poland.
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Revealing hidden information in GC–MS spectra from isomeric drugs: Chemometrics based identification from 15 eV and 70 eV EI mass spectra. Forensic Chem 2020. [DOI: 10.1016/j.forc.2020.100225] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Hong L, Li Y, He M, Zhao C, Li M. An algorithm to calibrate ionic isotopes using data mining strategy in hyphenated chromatographic datasets from herbal samples. J Chromatogr A 2020; 1613:460668. [PMID: 31706580 DOI: 10.1016/j.chroma.2019.460668] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 11/25/2022]
Abstract
The bottleneck of analytical instrument itself and non-ideal instrumental performance will produce a certain degree of drifts between the measured isotopes and the true values. An AAID-IC algorithm was thereby proposed to keep the isotopic distributions more accurate in hyphenated instruments, e.g. Gas Chromatography (GC)/ Liquid Chromatography (LC) - Mass Spectrometry (MS). During this data mining process, chemical information will be fully used from dozens of data points in retention time (rt) dimension: the target isotopes were firstly re-constructed in mass charge ratio (m/z) dimension; their re-calculation values were then averaged from an interesting rt zone; the calibration functions were followed established based on a well-defined series of calibration ions. It is worth mentioning that natural metabolites in complex samples can be identified as reference materials to amend the target isotopes. Next, the corrected mass axes (m/z values)/isotope abundances were transformed into an ionic isotopic curve using Gaussian box. Taking herbal sample as an example, AAID-IC can better reduce the systematic and random errors of the m/z ions in one run environment, whether it's profile or bar graph from any type of MS and any ionization method employed. Finally, the calibrated values can be utilized to deduce the elemental compositions of molecular (fragment) ions in GC/LC-MS determination.
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Affiliation(s)
- Liang Hong
- Department of Pharmaceutical Engineering, School of Chemical Engineering, Xiangtan University, Xiangtan 411105, PR China
| | - Yaping Li
- Xiangtan Central Hospital, Xiangtan 411100, PR China
| | - Min He
- Department of Pharmaceutical Engineering, School of Chemical Engineering, Xiangtan University, Xiangtan 411105, PR China.
| | - Chenxi Zhao
- College of Biological and Environmental Engineering, Changsha University, Changsha, Hunan, PR China
| | - Minghui Li
- Department of Pharmaceutical Engineering, School of Chemical Engineering, Xiangtan University, Xiangtan 411105, PR China
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Qi G, Tian D, Gao G, Liu G, Qiu C, Long T. Numerical Simulations and the Design of Magnetic Field-Enhanced Electron Impact Ion Source with Hollow Cylinder Structure. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2020; 2020:2809485. [PMID: 32399307 PMCID: PMC7204179 DOI: 10.1155/2020/2809485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 01/07/2020] [Indexed: 06/11/2023]
Abstract
An electron impact ion source-adopted magnetic field-enhanced technology has been designed for enhancing the electron intensity and the ionization efficiency. Based on the ion optic focus mechanism, an electron impact ionization source was designed, and the electron entrance into the ionization chamber was designed with a hollow cylinder structure to improve the ion extraction efficiency. Numerical simulation and optimal geometry were optimized by SIMION 8.0 to provide higher electron intensity and ion transmission efficiency. To improve the electron intensity, the influence of the filament potential and magnetic intensity was investigated, and the values of 70 eV and 150 Gs were chosen in our apparatus. Based on the optimal parameters, the air in the lab and oxygen gas was detected by the homemade apparatus, and the ion intensity was detected in the positive and negative ion modes, respectively. The homemade electron impact ion source apparatus has the potential to enhance ionization efficiency applied in the mass spectrometer ionization source.
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Affiliation(s)
- Guochen Qi
- College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China
| | - Di Tian
- College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China
| | - Guolun Gao
- College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China
| | - Guangda Liu
- College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China
| | - Chunling Qiu
- College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China
| | - Tao Long
- Beijing SHRIMP Center, Institute of Geology Chinese Academy of Geological Sciences, Beijing 100037, China
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Pua A, Lau H, Liu SQ, Tan LP, Goh RMV, Lassabliere B, Leong KC, Sun J, Cornuz M, Yu B. Improved detection of key odourants in Arabica coffee using gas chromatography-olfactometry in combination with low energy electron ionisation gas chromatography-quadrupole time-of-flight mass spectrometry. Food Chem 2019; 302:125370. [PMID: 31442699 DOI: 10.1016/j.foodchem.2019.125370] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/24/2019] [Accepted: 08/13/2019] [Indexed: 11/28/2022]
Abstract
Four Arabica coffees (Brazil, Colombia, Ethiopia, and Guatemala) yield highly variant odours, attesting to the complexities of coffee aroma that command advanced analytical tools. In this study, their volatiles were extracted using solvent-assisted flavour evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME). Due to matrix complexity, some trace odourants were detected in SAFE extracts by aroma extract dilution analysis (AEDA) but remained difficult to quantify by gas chromatography-mass spectrometry (GC-MS). This prompted the application of low energy electron ionisation (EI) coupled with GC-quadrupole time-of-flight (GC-QTOF). Optimal low EI GC-QTOF parameters (EI energy: 15 eV, acquisition rate: 3 Hz) were applied to achieve improved molecular ion signal intensity and reproducibility (relative standard deviation < 10%) across five compounds, which resulted in good linearity (R2 ≥ 0.999) and lowered detection levels (e.g. 0.025 ± 0.005 ng/mL for 4-hydroxy-5-methyl-3(2H)-furanone). Therefore, this method potentially improves the measurement of trace odourants in complex matrices by increasing specificity and sensitivity.
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Affiliation(s)
- Aileen Pua
- Food Science and Technology Programme, Department of Chemistry, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542, Singapore
| | - Hazel Lau
- Food Science and Technology Programme, Department of Chemistry, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542, Singapore
| | - Shao Quan Liu
- Food Science and Technology Programme, Department of Chemistry, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542, Singapore.
| | - Lay Peng Tan
- Agilent Technologies Singapore (Sales) Pte Ltd, 1 Yishun Avenue 7, Singapore 768923, Singapore
| | - Rui Min Vivian Goh
- Food Science and Technology Programme, Department of Chemistry, National University of Singapore, S14 Level 5, Science Drive 2, Singapore 117542, Singapore
| | - Benjamin Lassabliere
- Mane SEA PTE LTD, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623, Singapore
| | - Kwong-Chee Leong
- Mane SEA PTE LTD, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623, Singapore
| | - Jingcan Sun
- Mane SEA PTE LTD, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623, Singapore
| | - Maurin Cornuz
- Mane SEA PTE LTD, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623, Singapore
| | - Bin Yu
- Mane SEA PTE LTD, 3 Biopolis Drive, #07-17/18/19 Synapse, Singapore 138623, Singapore.
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