Fabrication of a Dipole-assisted Solid Phase Extraction Microchip for Trace Metal Analysis in Water Samples

The fabrication protocol of a dipole-assisted solid phase extraction microchip for the trace metal analysis is presented.

The overall goal of this protocol is to fabricate an innovative solid phase extraction microchip for the determination of trace metal ions in water samples by virtue of the dipole ion interactions. This method provides an interactive working strategy for chip solid effects nutrition techniques for the analysis of trace metal ion. The developed chips retains metal ions only by the dipole electrode static force.

Those majors to do in general on chips solely fast instruction procedures. Such is conditioning for the activation of the stationary phase and regeneration for the maintenance of a structure media avoided. Demonstrating the procedure will be Yu-Chen Chuang and Pei-Chun Chao, grad students from Dr.Soon's laboratory.

To begin use a cad program to draw the network pattern of the chip as shown here. Focus the laser source and then mount a 2 mm thick sheet of PMMA on the working table of the laser micro machining system. Select print in the cad software and then use the control panel of the micro machining system to set the power to 45%or 4.5 watts, the speed to 13%or 99.06 mm per second and the pen mode to VECT.

Machine the PMMA sheet using the laser micro machining system according to the manufacturer's protocol. A cross section of the machine to plate is shown here. Next drill three holes into the patterned plate that are one sixteenth inch in diameter that will be used as an access for a sample inlet, a buffer inlet and an LU inlet on the bottom plate.

Then drill one hole for a confluent outlet on the cover plate. Immerse the machined plates into one liter of 0.1%SDS and expose the parts to ultrasonic agitation via an oscillator for ten minutes. Then replace the SDS solution with deionized water.

An agitate via an ultrasonic oscillator for ten minutes. Replace the residual deionized water with one liter of fresh deionized water and then immerse the machined plates with ultrasonic agitation for ten minutes for the third time. Afterward dry each of the cleaned plates using a gentle stream of nitrogen for two minutes.

Once dry, align the two machined plates with the naked eye and then place the two plates in compression between two glass boards using binder clips. Because of the modification to the chip channel by photosynthesis reaction in the subsequent session, the substrate should be handled with extreme care to prevent damages to the surface. That may hamper if it lights the radiation.

Next bond the two plates under compression at 105 degrees Celsius for 30 minutes. Then cool the sandwich to ambient temperature and remove the binder clips and glass boards. Insert 1/16 inch outer diameter polyether ether ketone tubes into the access holes.

Then mix two component of epoxy based adhesives properly and secure the conduits with a two component epoxy based adhesive. Allow the epoxy to cure at ambient temperature for twelve hours. Place the tubing through a peristaltic pump and into a solution of saturated sodium hydroxide.

Deliver the sodium hydroxide solution to the channel at a flow rate of 100 microliters per minute for 12 hours. Remove the residual sodium hydroxide solution and then rinse the channel interior with deionized water. Then remove the residual deionized water and deliver a 0.5 nitric acid solution into the microchip.

Remove the residual nitric acid solution and then set up the system to deliver a 50%acrylamide solution into the microchip in the dark. Flow the acrylamide solution into the microchip at a flow rate of 100 microliters per minute for eight hours. Next remove the residual acrylamide solution and then rinse the channel interior with deionized water.

When the rinse is finished pump air through the microchip to remove the remaining deionized water then cover the microchip with an inhouse built photo mask which allows the desired region of the extraction channel to be exposed to light. Next take an inhibitor removal solid phase extraction cartridge and use a pump to flush the cartridge with at least three cartridge volumes of ethanol. Then flush the cartridge with three cartridge volumes of 1:1 dichloroethene.

Because 1:1 dichloroethene becomes unstable once the inhibit is removed. The chlorine containing solid phase extraction formation should be used as soon as possible. Next pass 1 mL of 1:1 dichlorethene through the treated cartridge and then collect the fraction in a 20 mL sample vial wrapped in aluminum foil.

Then transfer 491 microliters of the 1:1 dichloroethene sample into a solution containing 12 mg of AIBN, 3.18 mL of ethanol and 1.65 mL of hexanes in a 100 mL glass bottle. Use a syringe to inject the chip's channel with approximately 200 microliters of the chlorine containing SPE formation solution. Then expose the microchip to ultraviolet radiation with a maximum emission wavelength of 365 nm for 10 minutes.

Replace the residual solution by injecting 200 microliters of fresh chlorine containing SPE formation solution into the channel and again expose the microchip to UV radiation for 10 minutes. Repeat this process a total of 18 times. Lastly use the peristaltic pump to rinse the channel interior with ethanol at a flow rate of 100 microliters per minute for 30 minutes.

When the rinse is finished pump air through the microchip to remove the remaining ethanol. After removing the residual solution with the peristaltic pump store the fabricated microchip in a zipper bag for subsequent use. During the stepwise growth contact angle measurements were used to monitor the surface changes.

The variations in the contact angle clearly indicated that surface changes occurred during the modification procedures. A contact angle of 80.3 degrees was measured for the final product. The existence of the carbon chlorine moeities on the modified PMMA was confirmed via laser ablation inductively coupled plasma mass spectrometry analysis.

Compared with the results obtained by ablating the native PMMA distinct signals for chlorine were observed expectedly by ablating the PMMA modified with the carbon chlorine moeities. The Rama spectra were collected for further validating the attachment of the carbon chlorine moeities to the PMMA. Demonstrating successful attachment two characteristic peaks associated with the carbon chlorine asymmetric stretching vibration were observed at 682 inverse cm and 718 inverse cm in the spectrum of the modified PMMA.

The dipole electrostatic interactions important for on chip extraction for trace metal analyses were measured here using X-ray absorption near edge structures. It shows that the modified surface has strong interactions with manganese 2+After watching this video you should have a good understanding of how to fabricate a dipole assisted SPE micro chip. This technique paved the way researchers in environmental science to determine the presence of metal ions which cause serious pollution and the toxicology compartment in nature water.

Once mastered this technique can be applied to environmental management and contamination prevention.