Rapid determination hexavalent chromium in tap water by using a microfluidic dilution chip

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY TA THI VIET NGA RAPID DETERMINATION HEXAVALENT CHROMIUM IN TAP WATER BY USING A MICROFLUIDIC DILUTION CHIP BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : Internatinonal Training and Development Center Batch : 2011-2015 Thai Nguyen, September, 2015 THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY TA THI VIET NGA Topic title: RAPID DETERMINATION HEXAVALENT CHROMIUM IN TAP WATER BY USING A MICROFLUIDIC DILUTION CHIP BACHELOR THESIS Study Mode : Full-time Major : Environmental Science and Management Faculty : Internatinonal Training and Development Center Batch : 2011-2015 Superviors : Prof Yuh-Chang Sun Ph.D Nguyen Huu Tho Thai Nguyen, September, 2015 DOCUMENTATION PAGE WITH ABSTRACT Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student name Ta Thi Viet Nga Student ID DTN 1153180061 Thesis Title Rapid determination Hexavalent Chromium in tap water by using a Microfluidic dilution chip Prof Yuh-Chang Sun Supervisor (s) Ph.D Nguyen HuuTho Abstract: This study introduces about assessing the risk of tap water containing Chromium residuals, development a microfluidic dilution chip for rapid determination of Cr 6+ without the need of time-consuming and complex sample preparation procedures Based on the obtained result, it is good research with the other conventional methods Because the chemical instrumentation or analytical methods require expensive equipment and troublesome manipulation, which is not suitable for detection in house The study described a methodology of using a model of CO2-Laser Engraver to ablation in poly(methyl methacrylate) - PMMA based on the effects of laser power and processing speed on the depth and width of microchannels Furthermore, successfully application Hexavalent Chromium in water – Colorimetric Method which can sense Cr6+ in stock solution of tap water with (R2 =0.9809) and determination Hexavalent Chromium in tap water was confirmed with 108 % (Spike 50 ppb) and 105 % ( Spike 100 ppb) showed that both of two volumes followed a positive direction for this research i Keywords Microfluidic dilution chip, dilution chip, Gradients, determination Hexavalent Chromium, tap water Number of pages 46 Date of Submision September 30th, 2015 Supervisor’s Signature ii ACKNOWLEDGEMENT This thesis has been greatly conducted from the support as well as assistance of many people whom I would sincerely like to give deep thanks here First of all, I would like to express sincere thanks to the school board Thai Nguyen University of Agriculture and Forestry, Faculty of International Training and Development; Advanced Education Program, thank the teachers that have imparted to me the knowledge and valuable experience during the process of learning and researching here In the process of implementing and completing thesis, I am deeply grateful to my supervisor, Prof Yuh-Chang Sun at Department of Biomedical Engineering and Environmental Science, National Tsing Hua University (NTHU), Taiwan who has spent a lot of time, created favorable conditions, take care, generous and enthusiastic to guide me In addition, I would like to say thanks to Ph.D Nguyen Huu Tho for his enthusiasm in guiding and correcting my report writing I sincerely thank Ph.D Tsung-Ting Shih, an enthusiastic guider, he was the one who has had a very positive influence on me and my orientation from the beginning on suggesting and assisting me this interesting topic during implementation of the study I would gratefully like to thank Ping-Hung Chen, I couldn't gain new research experiences and noticeably involve in a variety of fantastic work by practicing in several new scientific instruments and chemically professional devices without him He continued to inspire along the way as well as his enthusiastic and responsibility iii I also want to thank Louise, Betty, Yuting-Luo and lovely friends in NTHU, all of your presences would help my little heart experience the second home with unforgettable memories and events I would like to express my deep gratitude and motivation to my parents, my family and my all friends for their encouragement throughout my studies Ultimately, in the process of implementing the project, due my time and research levels are limited so this project is inevitable shortcomings So, I would like to receive the attention and feedback from teachers and friends to this thesis is more complete I sincerely thank you! Thai Nguyen, September 30th, 2015 Signature of Student: Ta Thi Viet Nga iv TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES LIST OF ABBRIVIATIONS I INTRODUCTION 1.1 Research rationale 1.2 Research’s objectives .4 1.3 Research questions 1.4 Limitations of the study 1.5 Definitions 1.5.1 Microfluidic 1.5.2 Microfluidic dilution chip II LITERATURE REVIEW 2.1 Microfluidic dilution chip .7 2.2 Hexavalent Chromium in water – Colorimetric Method 11 III METHOD 15 3.1 Materials 15 3.1.1 Raw materials 15 3.1.2 The chemicals 16 3.1.3 Equipments 16 3.2 Method 19 3.2.1 Design microchannel on AutoCAD software for Engraving on PMMA sheet 19 v 3.2.2 Inspection of the channel 22 3.2.3 Creating the input on chip 25 3.2.4 Chip transplantation 25 3.2.5 NanoPort connections with microfluidic dilution chip 29 3.2.6 Verify of Microfluidic dilution chip operation with Rhodamine solution 30 3.2.7 Determination HexavalentChromium in tap water 32 IV RESULTS 35 4.1 Fabrication microchannels on PMMA by CO2-Laser Engraver 35 4.2 Effect of Speed and Power of CO2 laser on microchannels of chip .36 4.3 Verify of Microfluidic dilution chip’s Channel .37 4.4 Determination Hexavalent Chromium in tap water .39 V DISCUSSION AND CONCLUSION 41 5.1 Discussion .41 5.2 Conclusion 42 REFERENCES 44 vi LIST OF FIGURES Figure 2.1 Diagram of a dilution chip sample Figure 2.2 Schematic demonstrating the application of the formulas Figure 2.3 Outlet Vertical Channel 10 Figure 3.1 Design microchannels on AutoCAD 2004 software 20 Figure 3.2 The complete designing microchannels on a PMMA sheet .20 Figure 3.3 Measuring channel by Power Image Analysis (PIA) systems 24 Figure 3.4 Schematic illustration of image’s result of SS-50 lens .24 Figure 3.5 Checking distance between countersink and point on the chip 25 Figure 3.6 Schematic illustration of all of layers is submerged by 26 Figure 3.7 Schematic illustration .26 Figure 3.8 Chip transplantation 28 Figure 3.9 Transplantation chip’s layers for placing into 28 Figure 3.10 Temperature control in Hot air circulation oven 29 Figure 3.11 NanoPort connections with microfluidic dilution chip of process 30 Figure 3.12 Verify of Microfluidic dilution chip’s Channel operation with 32 Figure 4.1 Schematic diagram of the photothermal ablation process 35 Figure 4.2 Microchannels in PMMA have been engraved 35 Figure 4.3 Effect of the laser power on depth and width 36 Figure 4.4 Size microchannels with the constant power 95 (%) and 37 Figure 4.5 Microfluidic dilution chip's channel was examined 38 LIST OF TABLES Table 3.1: Items with the their Speed and Power number of percentage 21 Table 3.2: The Speed and Power numbers of percentage of channel 22 Table 4.1: Examination of tap water concentration 40 Table 4.2: Determination Hexavalent Chromium in tap water .40 Figure 3.12 Verify of Microfluidic dilution chip’s Channel operation with Rhodamine solution 3.2.7 Determination HexavalentChromium in tap water To validate the possibility of Microfluidic dilution chip's channel by tap water was prepared in advance as follows:  DI water: 30 mL  syringes with size: mL  segment of PEEK tubings with length: 20 cm  Banknote  Syringe pump  Microplate Spectrophotometers  Tap water ( Rm 701, BMES Bldg., 101, Sec 2, Kuang Fu Road Hsinchu 30013, Taiwan ): 9.4 mL  H3PO4 ( 66.6 % ): 3.52.8 µL for each syringe 32  [H2SO4]: 50 µL for each syringe  [Cr6+] solution Firstly, surface of chip, syringes and segmentsof PEEK tubingsare washed by DI water, HNO3 (0.5%) Prepared as follow:  Syringe1 (4mL) from solution: 9.4 mL Tap Water (solution has 100 ppb [Cr6+]) + 352.8 µL H3PO4 + 50 µL molarH2SO4 (This syringe would be wrapped by banknoteto avoid causing agents to chemical reactions such as light)  Syringe (4mL) from solution: 9.4 mL DI Water + 352.8 µL H3PO4 + 50 µL molar H2SO4 Placing syringes on the syringe pump, connecting segment of PEEK tubings between chip and syringes and setting up for program with Rate: 30 µl/minute, Vol: mL When solution flowed continuously, which has not been interrupted ( by factors such as dust, air) in the channels, took this solution samples (it called solution A) in outlets to small bottles and prepared solution B to add solution A with ratio: 500 µL solution A : 10 µL solution B Solution B: 0.25 g (1.5-Diphenylcarbazide) + 50 mL Acetone Thereafter, solution A and solution B were mixed together and to take each sample to analysisin Microplate Spectrophotometers 33 Note: Analyzed the original tap water before determination of Hexavalent Chromium in tap water by microfluidic dilution chip 34 IV RESULTS 4.1 Fabrication microchannels on PMMA by CO2-Laser Engraver A photothermal ablation process has happened during the CO2 laser cutting process When the laser beam with certain power and cutting speed focuses on the surface of PMMA substrate, the temperature of the irradiated spot would be increased rapidly, inducing melting and decomposition (Figure 4.1) CO2 laser had rapid fabrication microchanels on PMMA substrate during some short minute Microchannels had structure as picture on AutoCAD With clean machine system, there was no sign of dust on microchannels or bad smell for laboratory’s environment (Figure 4.2) Figure 4.1 Schematic diagram of the photothermal ablation process of Figure 4.2 Microchannels in PMMA have been engraved CO2 laser on PMMA substrate 35 4.2 Effect of Speed and Power of CO2 laser on microchannels of chip In terms of carbon dioxide laser processing system for the production of microflow channel, the flow of microchannel's size by the laser scan speed (Speed) and outlet power (Power) of the effect was quite significant There was the certainty of its processing result, thereby providing designed the good microfluidic dilution chip 0.6 Channel Size (mm) 0.5 0.4 0.3 Width Depth 0.2 0.1 10 11 12 13 14 15 Speed (%) Figure 4.3 Effect of the laser power on depth and width at a constant Power of 95% on PMMA The figure 4.3 illustrated the dependence of the channel depth and width on the laser speed at a constant laser power of 95 % on PMMA It was clear that the values of scanning speeds affect to the scanning speed of the channel's flow After keeping a constant laser power, changed the value of the scanning speed from 10-14 (%) causes the value of the width and depth of the uneven with correlation coefficient (Figure 4.3) 36 (Depth: 0.8285; Width: 0.2514) Just by the depth, at laser power of 95 (%), ascending values and alter more, with the scanning speed beam is increased specifically at the most of the width changing increased from 0.45088 mm to 0.41986 mm when the scanning speed achieved from 10.7 (%) to 11 (%) Values of scanning speed have been adjusted for with laser power at 95 (%) for suitable target of research At laser power 95 (%) scanning speed 10.7 (%) made the best result with cross section: 0.066080973 mm2, while at scanning speed 14 (%) had just cross section: 0.04117068 mm2 or 13 (%)0.049847 mm2or 12 (%) 0.055768 mm2 (Figure 4.4) Figure 4.4 Size microchannels with the constant power 95 (%) and a Scanning speed 10.7 (%) b Scanning speed 12 (%) c Scanning speed 13 (%) d Scanning speed 14 (%) 4.3 Verify of Microfluidic dilution chip’s Channel The inspection of chip flow was very important, hence the need to test a compound flowed through the microchannels in the chip, which worked well or not for the certainty In this step, used the Rhodamine solution 37 0.07 0.06 Absorbance 0.05 y = 0.000x + 0.035 R² = 0.980 0.04 0.03 0.02 0.01 0 10 20 30 40 50 60 70 80 90 100 Concentration, ppb Figure 4.5 Microfluidic dilution chip's channel was examined by Rhodamine solution The figure 4.5 described the concentration of Rhodamine solution in each outlet on the microfluidic dilution chip There were outlets on the chip, each outlet corresponds each percent value such as (%), 20 (%), 40 (%), 60 (%), 80 (%), 100 (%) of Rhodamine concentration First of all, the results is situated approximately a regressionline Particularly, the output of 100 (%) belongs the regressionline, which of concentration of Rhodamine was accurate There was 0.027066 from the first value (0 %) to value (100 %), the results were different and ascending trend The values SD gradually fluctuate distance with regression line which are shorter Besides, at the output (0%) SD = 0.037766668 and (20%) SD = 0.0399 were the biggest values than others Secondly, metrics run with equations: y = 0.0003x + 0.0359 and R2 = 0.9809 38 The closer R2 is to 1.00 (R2 = 0.9809) - The better the fit The result came up with the evidence that microchannels of chip were acted well, the size of channel was designed suitable It meaned scanning speed: 10.7 (%) and laser power: 95 (%) which was perfect design, so that application for next step which would determine Hexavalent Chromium in tap water 4.4 Determination Hexavalent Chromium in tap water First of all, check quality of tap water before determination Hexavalent Chromium in experiment (Table 4.1) Table 4.1 Examination of tap water concentration Tap Water Time Time Time Results 0.0379 0.0379 0.0383 AVG SD 0.038033 0.000231 RSD (%) The concentration of tap water 7.111113 The Table 4.1 showed the tap water which was analyzed by Microplate Spectrophotometers In times for examination, tap water was not infected Chromium (Hexavalent Chromium) Standard Deviation - SD = 0.000231 and Relative Standard Deviation – RSD = (%), that were very small so the difference was not significant By 7.1111113, the concentration of tap water was steady After that Hexavalent Chromium would be added into tap water sample 39 Table 4.2 Determination Hexavalent Chromium in tap water Tap Water Time Time Time AVG SD RSD Spike Recovery Spike (50 ppb) 0.052 0.052 0.052 0.052 0.000 0% 108% Spike (100 ppb) 0.067 0.067 0.067 0.067 0.000 0% 105% Assessing the effectiveness of the chip from the actual analysis of tap water, specially, the results analyzed of chromium concentration in tap water have types, which were the volumes of the tap water sample There were 50 ppb and 100 ppb (Table 4.2) The results were analyzed by Microplate Spectrophotometersto confirm again Standard Deviation from 0.000115 (Spike 1) to 0.000153 (Spike 2) is 0.000038, the Relative Standard Deviation achieved (%), those number were so teeny like target of research In addition, the difference between the volumes was insignificantly, it did not affect the quality of the samples Stability of equipment was appreciated well, so determination Hexavalent Chromium in tap water was confirmed with 108 % (Spike 1) and 105 % (Spike 2) showed that both of two volumes followed a positive direction and remain application this model of microfluidic dilution chip in life 40 V DISCUSSION AND CONCLUSION 5.1 Discussion The assessment of capability of microfluidic dilution chip which was hopefully able to substitute in future, there was shown positive prospects about microfluidic dilution chip In this case, there was been clearly demonstrated, to research and create a concentration Gradient which did not need to be complicated by concept of operations (George et al, 2001) Aimed to design a simple dilution of the operation sequence of the wafer, the chip was made of two layers of poly (methyl methacrylate) - PMMA substrate, PMMA was chosen to be the wafer because its cost was lower than the other wafers such as glass, quartz, silicon or polymer Furthermore, PMMA was easy to use and convenient purchase By changing the inlet to solve the solution flowed in channel system, completion of the calculation of the theoretical concentration Gradient, and draw out the wafer shape There were many factors influence the effectiveness of dilution (Hayat et al, 2008) Firstly, the fluid would be directly depended on the flow depth, width of channel, we tried to create a different channel size with laser power of 95 (%) and scanning speed from 10-14 (%) According to the experimental results (Figure 4.3), change of channel's scanning speeds so concentration gradient obtained linear correlation coefficient which is also improved In addition, mixed principally by molecular diffusion to reach between different fluids, sufficient contact time between the fluids was also expected to provide a solution to be mixed in the diffusion of molecules were intact Thus, there was achieved the purposes of effective dilution Based on a fixed flowed channel dimensions, at the laser power of 95 (%) and scanning speed 10.7 (%) was the best 41 value with cross section 0.066081(mm2) Secondly, the analysis followed by assessment of the effectiveness of the system by Rhodamine solution The microfluidic dilution chip of the calibration curve established quite credible, with the real measurement of this sample values was R2 = 0.9809, we decide to apply for determination Hexavalent Chromium in tap water This investigation has marked an accessible development of microfluidic dilution chip in the near future According the results, spike recoveries of Spike (50 ppb): 108 (%) and Spike (100 ppb): 105 (%) after confirmed by Microplate Spectrophotometers It meaned that this model of chip would be applied potential quickly to determination Hexavalent Chromium in tap water Nevertheless, the using of Microplate Spectrophotometers was a limitation of the study, which was expensive machine After successfully applying microfluidic dilution chip, samples have been checked by Microplate Spectrophotometers Finally, topic of wafer and shape of channel focused upon for future researchers They could be found by new materials for not only environment science, but also other areas 5.2 Conclusion This study successfully produced and combined the theories of microfluidic dilution chip It showed that this method of the wafer has been in improving the accuracy of wafer manufacturing from PMMA In addition, successfully application Hexavalent Chromium in tap water – Colorimetric Method which could sense Cr6+ in stock solution of tap water with (R2 = 0.9809) and determination hexavalent Chromium in tap water was confirmed with 108 (%) (Spike 50 ppb) and 105 (%) 42 (Spike 100 ppb) showed that both of two volumes followed a positive direction for this research As expected, model of microfluidic dilution chip opened a new bright future for manufacturing scientific equipment to reduce costs and expenses in scientific researches It could be used at home, company to determination Hexavalent Chromium in tap water which was also an appropriate and convenience analytical method By the short of time, we only stopped at the detection Hexavalent Chromium in tap water from applying gradient theories for chip and Hexavalent Chromium in water – Colorimetric Method In addition, the using of Microplate Spectrophotometers was a limitation of the study, which was expensive machine After successfully applying microfluidic dilution chip, samples have been checked by Microplate Spectrophotometers In the future, scientists won’t only using the microfluidic dilution chip to 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determination of Hexavalent Chromium in tap water by microfluidic dilution chip 34... industrial waste water and toxic waste water untreated or treatment is not satisfactory The phenomenon of water has been contaminated heavy metals in the water basin near industrial areas, big